WorldWideScience

Sample records for cubic fcc structure

  1. Stability of the fcc structure in block copolymer systems.

    Science.gov (United States)

    Nonomura, Makiko

    2008-11-19

    The stability of the face-centered cubic (fcc) structure in microphase separated copolymers is investigated by a coarse-grained approach. Direct simulations of the equation for the microphase separation in three dimensions indicate that there is a narrow area above a certain degree of segregation in the phase diagram, where the fcc structure is the most stable structure. By employing the mode expansion, we have confirmed that the fcc structure can form as a metastable structure even in the weak segregation regime.

  2. Geometric structure, electronic structure and optical absorption properties of one-dimensional thiolate-protected gold clusters containing a quasi-face-centered-cubic (quasi-fcc) Au-core: a density-functional theoretical study.

    Science.gov (United States)

    Ma, Zhongyun; Wang, Pu; Pei, Yong

    2016-09-29

    Based on the recently reported atomic structures of thiolate-protected Au28(SR)20, Au36(SR)24, Au44(SR)28, and Au52(SR)32 clusters, a family of homogeneous, linear, thiolate-protected gold superstructures containing novel quasi-face-centered-cubic (quasi-fcc) Au-cores is theoretically envisioned, denoted as the Au20+8N(SR)16+4N cluster. By means of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, a unified view of the geometric structure, electronic structure, magic stable size and size-dependent NIR absorption properties of Au20+8N(SR)16+4N clusters is provided. We find that the Au20+8N(SR)16+4N clusters demonstrate oscillating transformation energies dependent on N. The odd-N clusters show more favorable (negative) reaction energies than the even-N clusters. The magic stability of recently reported Au28(SR)20, Au36(SR)24, Au44(SR)28, Au52(SR)32 and Au76(SR)44 clusters can be addressed from the relative reaction energies and geometric distortion of Au-cores. A novel 4N + 4 magic electron-number is suggested for the Au20+8N(SR)16+4N cluster. Using the polyhedral skeletal electron pair theory (PSEPT) and the extended Hückel molecular orbital (EHMO) calculations, we suggest that the magic 4N + 4 electron number is correlated with the quasi-fcc Au-cores, which can be viewed as double helical tetrahedron-Au4 chains. The size-dependent optical absorption properties of Au20+8N(SR)16+4N clusters are revealed based on TD-DFT calculations. We propose that these clusters are potential candidates for the experimental synthesis of atomically precise one-dimensional ligand protected gold superstructures with tunable NIR absorption properties.

  3. Effects of PEO-PPO diblock impurities on the cubic structure of aqueous PEO-PPO-PEO pluronics micelles: fcc and bcc ordered structures in F127

    DEFF Research Database (Denmark)

    Mortensen, Kell; Pedersen, Walther Batsberg; Hvidt, S.

    2008-01-01

    We report on structural properties of PEO-PPO-PEO type of triblock block copolymers (Pluronics F127) with special emphasis on the effect of diblock PEO-PPO impurities on the ordered gel phase. Commercial F127 polymers contain as received roughly 20% PEO-PPO diblock and 80% PEO-PPO-PEO triblock...... copolymers. Aqueous solutions of F127 copolymers used as received form fee ordered micellar structure. Copolymers depleted with respect to the diblock impurity, resulting in a pure PEO-PPO-PEO triblock copolymer system, form bcc ordered micelles within the major parts of the gel phase. However, close...

  4. Ferromagnetic Fe on Cu(001) throughout the fcc-like phase: arguing from the viewpoint of the electronic structure.

    Science.gov (United States)

    Donath, M; Pickel, M; Schmidt, A B; Weinelt, M

    2009-04-01

    The scientific enthusiasm for ultrathin Fe films on Cu(001) has now lasted for more than 20 years. Is there ferromagnetic iron with a face-centred cubic (fcc) structure? Does ferromagnetism in Fe hinge on the body-centred cubic (bcc) structure? In this contribution, we try to establish that the electron system gives evidence of ferromagnetic behaviour with fcc-like electronic bands. We examine a crystal-induced surface state, which is characteristic of fcc surface order. Furthermore, we compare electronic signatures of fcc and bcc: the d-band exchange splitting, image-potential-state energies and the work function. We conclude that, from the viewpoint of the electronic structure, Fe on Cu(001) is found to be ferromagnetic throughout the fcc-like phase. This result raises a new question: how much deviation from the relaxed fcc order is acceptable without losing the electronic signature of fcc?

  5. Use of the Primitive Unit Cell in Understanding Subtle Features of the Cubic Closest-Packed Structure

    Science.gov (United States)

    Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.

    2008-01-01

    One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…

  6. Ru Nanoframes with an fcc Structure and Enhanced Catalytic Properties.

    Science.gov (United States)

    Ye, Haihang; Wang, Qingxiao; Catalano, Massimo; Lu, Ning; Vermeylen, Joseph; Kim, Moon J; Liu, Yuzi; Sun, Yugang; Xia, Xiaohu

    2016-04-13

    Noble-metal nanoframes are of great interest to many applications due to their unique open structures. Among various noble metals, Ru has never been made into nanoframes. In this study, we report for the first time an effective method based on seeded growth and chemical etching for the facile synthesis of Ru nanoframes with high purity. The essence of this approach is to induce the preferential growth of Ru on the corners and edges of Pd truncated octahedra as the seeds by kinetic control. The resultant Pd-Ru core-frame octahedra could be easily converted to Ru octahedral nanoframes of ∼2 nm in thickness by selectively removing the Pd cores through chemical etching. Most importantly, in this approach the face-centered cubic (fcc) crystal structure of Pd seeds was faithfully replicated by Ru that usually takes an hcp structure. The fcc Ru nanoframes showed higher catalytic activities toward the reduction of p-nitrophenol by NaBH4 and the dehydrogenation of ammonia borane compared with hcp Ru nanowires with roughly the same thickness.

  7. Mixed structural face-centered cubic and body-centered cubic orders in near stoichiometric Fe2MnGa alloys

    Science.gov (United States)

    Kudryavtsev, Y. V.; Perekos, A. E.; Uvarov, N. V.; Kolchiba, M. R.; Synoradzki, K.; Dubowik, J.

    2016-05-01

    Magnetic and transport properties of near stoichiometric metastable FexMnyGaz alloys (46 ≤ x ≤ 52, 17 ≤ y ≤ 25, 26 ≤ z ≤ 30) with face-centered cubic (FCC), body-centered cubic (BCC), and two-phase (FCC + BCC) structures are investigated. The experimental results are analyzed in terms of first-principles calculations of stoichiometric Fe2MnGa alloy with the L21, L12, and the tetragonally distorted L21 structural orderings. It is shown that the pure BCC and FCC phases have distinct magnetic and transport properties. Two-phase Fe2MnGa alloys have magnetic and transport properties typical of the mixed BCC and FCC phases. Among the investigated alloys, Fe46Mn24Ga30 has a martensitic transformation accompanied with significant changes of its magnetic and transport properties.

  8. Comparing the structural stability of PbS nanocrystals assembled in fcc and bcc superlattice allotropes.

    Science.gov (United States)

    Bian, Kaifu; Wang, Zhongwu; Hanrath, Tobias

    2012-07-04

    We investigated the structural stability of colloidal PbS nanocrystals (NCs) self-assembled into superlattice (SL) allotropes of either face-centered cubic (fcc) or body-centered cubic (bcc) symmetry. Small-angle X-ray scattering analysis showed that the NC packing density is higher in the bcc than in the fcc SL; this is a manifestation of the cuboctahedral shape of the NC building block. Using the high-pressure rock-salt/orthorhombic phase transition as a stability indicator, we discovered that the transition pressure for NCs in a bcc SL occurs at 8.5 GPa, which is 1.5 GPa higher than the transition pressure (7.0 GPa) observed for a fcc SL. The higher structural stability in the bcc SL is attributed primarily to the effective absorption of loading force in specific SL symmetry and to a lesser extent to the surface energy of the NCs. The experimental results provide new insights into the fundamental relationship between the symmetry of the self-assembled SL and the structural stability of the constituent NCs.

  9. Interface effect of magnetic properties in Ni nanoparticles with a hcp core and fcc shell structure.

    Science.gov (United States)

    Choo, Seongmin; Lee, Kyujoon; Jo, Younghun; Yoon, Seon-Mi; Choi, Jae-Young; Kim, Jea-Young; Park, Jea-Hoon; Lee, Kyung-Jin; Lee, Jong-Heun; Jung, Myung-Hwa

    2011-07-01

    We have fabricated hexagonal close-packed (hcp) Ni nanoparticles covered by a face-centered cubic (fcc) Ni surface layer by polyol method. The magnetic properties have been investigated as a function of temperature and applied magnetic field. The magnetic behavior reveals that the system should be divided magnetically into three distinct phases with different origins. The fcc Ni phase on the shell contributes to the superparamagnetism through a wide temperature range up to 360 K. The hcp Ni phase at the core is associated with antiferromagnetic nature below 12 K. These observations are in good agreement with the X-ray absorption spectroscopy and magnetic circular dichroism measurements. In our particular case, the unique hcp core and fcc shell structure gives rise to an additional anomaly at 20 K in the zero-field-cooled magnetization curve. Its position is barely affected by the magnetic field but its structure disappears above 30 kOe, showing a metamagnetic transition in the magnetization versus magnetic field curve. This new phase originates from the magnetic exchange at the interface between the hcp and fcc Ni sublattices.

  10. DISLOCATION STRUCTURE OF FCC COPPER/BCC IRON INTERPHASE INTERFACES

    OpenAIRE

    C Forwood

    1990-01-01

    The Burgers vectors and geometry of the interfacial dislocation structure in fcc/bcc interfaces in a Cu+25 wt.% Fe alloy are analysed using TEM and the technique of image matching. The Burgers vectors are shown to be differences of the Cu and Fe lattice vectors and the interfacial structure is interpreted in terms of a CSL/DSC model.

  11. Superhard BC(3) in cubic diamond structure.

    Science.gov (United States)

    Zhang, Miao; Liu, Hanyu; Li, Quan; Gao, Bo; Wang, Yanchao; Li, Hongdong; Chen, Changfeng; Ma, Yanming

    2015-01-01

    We solve the crystal structure of recently synthesized cubic BC(3) using an unbiased swarm structure search, which identifies a highly symmetric BC(3) phase in the cubic diamond structure (d-BC(3)) that contains a distinct B-B bonding network along the body diagonals of a large 64-atom unit cell. Simulated x-ray diffraction and Raman peaks of d-BC(3) are in excellent agreement with experimental data. Calculated stress-strain relations of d-BC(3) demonstrate its intrinsic superhard nature and reveal intriguing sequential bond-breaking modes that produce superior ductility and extended elasticity, which are unique among superhard solids. The present results establish the first boron carbide in the cubic diamond structure with remarkable properties, and these new findings also provide insights for exploring other covalent solids with complex bonding configurations.

  12. The special symplectic structure of binary cubics

    CERN Document Server

    Slupinski, Marcus

    2009-01-01

    Let $k$ be a field of characteristic not 2 or 3. Let $V$ be the $k$-space of binary cubic polynomials. The natural symplectic structure on $k^2$ promotes to a symplectic structure $\\omega$ on $V$ and from the natural symplectic action of $\\textrm{Sl}(2,k)$ one obtains the symplectic module $(V,\\omega)$. We give a complete analysis of this symplectic module from the point of view of the associated moment map, its norm square $Q$ (essentially the classical discriminant) and the symplectic gradient of $Q$. Among the results are a symplectic derivation of the Cardano-Tartaglia formulas for the roots of a cubic, detailed parameters for all $\\textrm{Sl}(2,k)$ and $\\textrm{Gl}(2,k)$-orbits, in particular identifying a group structure on the set of $\\textrm{Sl}(2,k)$-orbits of fixed nonzero discriminant, and a purely symplectic generalization of the classical Eisenstein syzygy for the covariants of a binary cubic. Such fine symplectic analysis is due to the special symplectic nature inherited from the ambient excepti...

  13. Use of Pom Pons to Illustrate Cubic Crystal Structures.

    Science.gov (United States)

    Cady, Susan G.

    1997-01-01

    Describes a method that uses olefin pom pons to illustrate cubic crystal structure. Facilitates hands-on examination of different packing arrangements such as hexagonal close-packed and cubic close-packed structures. (JRH)

  14. Local atomic structure in cubic stabilized zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Villella, P.; Conradson, S. D.; Espinosa-Faller, F. J.; Foltyn, S. R.; Sickafus, K. E.; Valdez, J. A.; Degueldre, C. A.

    2001-09-01

    X-ray-absorption fine structure measurements have been used to elucidate the local atomic structure of quaternary Zr, Y, Er, Ce/U cubic stabilized zirconia. These compounds display more complicated local environments than those reported for simpler binary systems. While the shortest cation-O distances are similar to those found in the binary cubic stabilized compounds, responding to the different sizes of the cations, we have identified large distortions in the first-shell oxygen distribution involving long, 2.8--3.2 {angstrom} cation-O distances that are similar to those found in the amorphous phase of zirconium. The cation-cation distributions are also found to be quite complicated (non-Gaussian) and element specific. The U-near neighbor distances are expanded relative to the Ce ions for which it substitutes, consistent with the larger size of the actinide, and the U-cation distribution is also more complicated. In terms of the effects of this substitution on the other cation sites, the local environment around Y is altered while the Zr and Er local environments remain unchanged. These results point out the importance of collective and correlated interactions between the different pairs of cations and the host lattice that are mediated by the local strain fields generated by the different cations. The presence of pair-specific couplings has not been commonly included in previous analyses and may have implications for the stabilization mechanisms of cubic zirconia.

  15. Structural transformation between bcc and fcc in Fe-Ni nanoparticle during heating process

    Science.gov (United States)

    Li, Guojian; Sui, Xudong; Qin, Xuesi; Ma, Yonghui; Wang, Kai; Wang, Qiang

    2016-10-01

    Phase transformation between bcc and fcc in Fe-Ni nanoparticle has been studied by using molecular dynamics simulation with an embedded atom method. The transformation has been explored by designing the nanoparticles with different initial structures, sizes and elemental distributions at various Ni concentrations. The results show that the structural transformation is strongly related to the Ni content and elemental distribution. Initial fcc structure transforms to bcc for a lower Ni content and bcc transforms to fcc for a higher Ni content. The transformation is accompanied with a sharp reduction in energy even for the nanoparticle with a large size. Furthermore, lattice distortion first occurs before the transformation. The transformation from fcc to bcc is occurred by elongating fcc (100) to bcc (110) and that from bcc to fcc by compressing bcc (110) to fcc (100). The reason is that the nanoparticle has a low energy state for bcc structure with a lower Ni content and also for fcc structure with a higher Ni content. The coexistence of bcc and fcc phases appears with the change of elemental distribution.

  16. On the Convergence of the Electronic Structure Properties of the FCC Americium (001) Surface

    OpenAIRE

    Gao, Da; Ray, Asok K.

    2006-01-01

    Electronic and magnetic properties of the fcc Americium (001) surface have been investigated via full-potential all-electron density-functional electronic structure calculations at both scalar and fully relativistic levels. Effects of various theoretical approximations on the fcc Am (001) surface properties have been thoroughly examined. The ground state of fcc Am (001) surface is found to be anti-ferromagnetic with spin-orbit coupling included (AFM-SO). At the ground state, the magnetic mome...

  17. 典型晶格结构FCC/BCC钢的剧烈塑性变形研究现状%Research progress on severe plastic deformation of steels with BCC/FCC crystal structures

    Institute of Scientific and Technical Information of China (English)

    马明; 蔡明晖; 唐正友; 丁桦

    2015-01-01

    晶格结构(体心立方BCC、面心立方FCC及其复合形式)类型对金属材料剧烈塑性变形过程中的晶粒细化机制产生重要影响。本文以不同晶格结构的钢铁材料为对象,重点阐述和总结了不同晶格结构类型及其变形模式差异对剧烈塑性变形过程中晶粒细化理论、组织形貌和力学性能的影响规律,其结果有望为探索剧烈塑性变形工艺过程中的组织细化理论提供一个新途径。%The crystal-structure types of metallic materials such as face-centered cubic ( FCC) and body-centered cubic ( BCC) play a crucial role on ultra-grain refinement during severe plastic deformation ( SPD) . This work will focus on three different types of steels with BCC, FCC, and BCC/FCC crystal structures, and comprehensively discuss and summarize the influence of different crystal - structure types on deformation modes, ultra - grain refinement, microstructure and properties, which will provide a new route to apply and develop this theory to ultra - grain refinement of metallic materials through SPD processing.

  18. Simulation for F.C.C. deformation texture by modified pencil glide theory[Face Centered Cubic

    Energy Technology Data Exchange (ETDEWEB)

    Masui, H.

    1999-11-26

    Inspired by the pencil glide theory for b.c.c. metal, modified pencil glide theory for f.c.c. metal was proposed, dividing the 12 glide systems of f.c.c. metal into three groups individually composed of eight {l{underscore}brace}111{r{underscore}brace}{l{underscore}angle}110{r{underscore}angle} glide systems around the principal axes X[100], Y[010] and Z[001]. These assumptions yielded two mathematical solutions {Omega}(3) and {Omega}(1). In {Omega}(3), from the three groups with four complete conjugated glide systems composed of, respectively, two glide systems of common {l{underscore}angle}110{r{underscore}angle} direction, only one group with the maximum plastic work may operate if the requirements are satisfied, otherwise glide systems in {Omega}(1) where one of the four conjugated glide systems is zero are activated. The model considering the 12 glide systems of f.c.c. as a whole explained many experimentally stable orientations in axisymmetric and rolling deformation. The differences between the two pencil glide theories for b.c.c. and f.c.c. are also discussed with data.

  19. Size dependence of structural parameters in fcc and hcp Ru nanoparticles, revealed by Rietveld refinement analysis of high-energy X-ray diffraction data.

    Science.gov (United States)

    Song, Chulho; Sakata, Osami; Kumara, Loku Singgappulige Rosantha; Kohara, Shinji; Yang, Anli; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi

    2016-08-10

    To reveal the origin of the CO oxidation activity of Ruthenium nanoparticles (Ru NPs), we structurally characterized Ru NPs through Rietveld refinement analysis of high-energy X-ray diffraction data. For hexagonal close-packed (hcp) Ru NPs, the CO oxidation activity decreased with decreasing domain surface area. However, for face-centered cubic (fcc) Ru NPs, the CO oxidation activity became stronger with decreasing domain surface area. In comparing fcc Ru NPs with hcp Ru NPs, we found that the hcp Ru NPs of approximately 2 nm, which had a smaller domain surface area and smaller atomic displacement, showed a higher catalytic activity than that of fcc Ru NPs of the same size. In contrast, fcc Ru NPs larger than 3.5 nm, which had a larger domain surface area, lattice distortion, and larger atomic displacement, exhibited higher catalytic activity than that of hcp Ru NPs of the same size. In addition, the fcc Ru NPs had larger atomic displacements than hcp Ru NPs for diameters ranging from 2.2 to 5.4 nm. Enhancement of the CO oxidation activity in fcc Ru NPs may be caused by an increase in imperfections due to lattice distortions of close-packed planes and static atomic displacements.

  20. Ytterbium: Transition at High Pressure from Face-Centered Cubic to Body-Centered Cubic Structure.

    Science.gov (United States)

    Hall, H T; Barnett, J D; Merrill, L

    1963-01-11

    Pressure of 40,000 atmospheres at 25 degrees C induces a phase transformation in ytterbium metal; the face-centered cubic structure changes to body-centered cubic. The radius of the atom changes from 1.82 to 1.75 A. At the same time the atom's volume decreases by 11 percent and the volume, observed macroscopically, decreases 3.2 percent.

  1. Origin of the catalytic activity of face-centered-cubic ruthenium nanoparticles determined from an atomic-scale structure.

    Science.gov (United States)

    Kumara, L S R; Sakata, Osami; Kohara, Shinji; Yang, Anli; Song, Chulho; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi

    2016-11-09

    The 3-dimensional (3D) atomic-scale structure of newly discovered face-centered cubic (fcc) and conventional hexagonal close packed (hcp) type ruthenium (Ru) nanoparticles (NPs) of 2.2 to 5.4 nm diameter were studied using X-ray pair distribution function (PDF) analysis and reverse Monte Carlo (RMC) modeling. Atomic PDF based high-energy X-ray diffraction measurements show highly diffuse X-ray diffraction patterns for fcc- and hcp-type Ru NPs. We here report the atomic-scale structure of Ru NPs in terms of the total structure factor and Fourier-transformed PDF. It is found that the respective NPs have substantial structural disorder over short- to medium-range order atomic distances from the PDF analysis. The first-nearest-neighbor peak analyses show a significant size dependence for the fcc-type Ru NPs demonstrating the increase in the peak height due to an increase in the number density as a function of particle size. The bond angle and coordination number (CN) distribution for the RMC-simulated fcc- and hcp-type Ru NP models indicated inherited structural features from their bulk counterparts. The CN analysis of the whole NP and surface of each RMC model of Ru NPs show the low activation energy packing sites on the fcc-type Ru NP surface atoms. Finally, our newly defined order parameters for RMC simulated Ru NP models suggested that the enhancement of the CO oxidation activity of fcc-type NPs was due to a decrease in the close packing ordering that resulted from the increased NP size. These structural findings could be positively supported for synthesized low-cost and high performance nano-sized catalysts and have potential application in fuel-cell systems and organic synthesis.

  2. Can the Lennard-Jones solid be expected to be fcc?

    NARCIS (Netherlands)

    Waal, van de Benjamin W.

    1991-01-01

    The structure of the Lennard-Jones solid, obtained by molecular-dynamics simulation of crystallization in the supercooled liquid, may be fcc, although the hcp structure is energetically more favorable. This could derive from the cubic symmetry of the fcc lattice, allowing lattice defects that are no

  3. Can the Lennard-Jones solid be expected to be fcc?

    OpenAIRE

    Waal, de, SAJ Bas

    1991-01-01

    The structure of the Lennard-Jones solid, obtained by molecular-dynamics simulation of crystallization in the supercooled liquid, may be fcc, although the hcp structure is energetically more favorable. This could derive from the cubic symmetry of the fcc lattice, allowing lattice defects that are not possible in the hcp arrangement, but are essential to crystal growth in the simulated liquid. Two crossing stacking faults in a small fcc crystallite can produce nonvanishing, growth-promoting, b...

  4. Competing structural instabilities in cubic perovskites

    CERN Document Server

    Vanderbilt, D

    1994-01-01

    We study the antiferrodistortive instability and its interaction with ferroelectricity in cubic perovskite compounds. Our first-principles calculations show that coexistence of both instabilities is very common. We develop a first-principles scheme to study the thermodynamics of these compounds when both instabilities are present, and apply it to SrTiO$_3$. We find that increased pressure enhances the antiferrodistortive instability while suppressing the ferroelectric one. Moreover, the presence of one instability tends to suppress the other. A very rich $P$--$T$ phase diagram results.

  5. Electronic Structure of Crystalline Buckyballs: fcc-C60

    Science.gov (United States)

    Jalali-Asadabadi, Saeid; Ghasemikhah, E.; Ouahrani, T.; Nourozi, B.; Bayat-Bayatani, M.; Javanbakht, S.; Aliabad, H. A. Rahnamaye; Ahmad, Iftikhar; Nematollahi, J.; Yazdani-Kachoei, M.

    2016-01-01

    The electronic properties of pristine fcc-C60 are calculated by utilizing a variety of density functional theory (DFT) approaches including the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA), PBE-GGA+DFT-D3(vdW), Engel and Vosko GGA (EV-GGA), GGA plus Hubbard U parameter (GGA+U), hybrids Becke-Perdew-Wang hybrid functional (B3PW91), Becke-Lee-Yang-Parr hybrid functional (B3LYP), the PBE exchange-correlation functional (PBE0), and Tran and Blaha regular and non-regular modified Becke and Johnson (TB-mBJ) potential within a DFT frame work using augmented plane waves plus local orbital method. The comparison of the calculated results with the experimental values shows that the non-regular TB-mBJ method reproduces a correct experimental direct band gap of 2.12 eV at X symmetry for this compound. The effectiveness of this theoretical approach in the reproduction of the experimental band gap is due to the proper treatment of the electrons in the interstitial region of the crystal. Our results show that the C60 clusters are weakly interacting with each other in the fcc crystal. This study also reveals that the five-fold degeneracies of the isolated C60 molecule due to its icosahedral symmetry are completely lifted at an X symmetry point by the crystal field.

  6. Optical studies of cubic III-nitride structures

    OpenAIRE

    Powell, Ross E L

    2014-01-01

    The properties of cubic nitrides grown by molecular beam epitaxy (MBE) on GaAs (001) have been studied using optical and electrical techniques. The aim of these studies was the improvement of the growth techniques in order to improve the quality of grown nitrides intended for bulk substrate and optoelectronic device applications. We have also characterised hexagonal nanocolumn structures incorporating indium. Firstly, bulk films of cubic AlxGa1-xN with aluminium fractions (x) spanning the ...

  7. Frustrated fcc antiferromagnet Ba2YOsO6 : Structural characterization, magnetic properties, and neutron scattering studies

    Science.gov (United States)

    Kermarrec, E.; Marjerrison, C. A.; Thompson, C. M.; Maharaj, D. D.; Levin, K.; Kroeker, S.; Granroth, G. E.; Flacau, R.; Yamani, Z.; Greedan, J. E.; Gaulin, B. D.

    2015-02-01

    We report the crystal structure, magnetization, and neutron scattering measurements on the double perovskite Ba2YOsO6 . The F m 3 ¯m space group is found both at 290 K and 3.5 K with cell constants a0=8.3541 (4 ) Å and 8.3435 (4 ) Å, respectively. Os5 + (5 d3 ) ions occupy a nondistorted, geometrically frustrated face-centered-cubic (fcc) lattice. A Curie-Weiss temperature θ ˜-700 K suggests the presence of a large antiferromagnetic interaction and a high degree of magnetic frustration. A magnetic transition to long-range antiferromagnetic order, consistent with a type-I fcc state below TN˜69 K, is revealed by magnetization, Fisher heat capacity, and elastic neutron scattering, with an ordered moment of 1.65(6) μB on Os5 +. The ordered moment is much reduced from either the expected spin-only value of ˜3 μB or the value appropriate to 4 d3 Ru5 + in isostructural Ba2YRuO6 of 2.2(1) μB, suggesting a role for spin-orbit coupling (SOC). Triple-axis neutron scattering measurements of the order parameter suggest an additional first-order transition at T =67.45 K, and the existence of a second-ordered state. Time-of-flight inelastic neutron results reveal a large spin gap Δ ˜17 meV, unexpected for an orbitally quenched, d3 electronic configuration. We discuss this in the context of the ˜5 meV spin gap observed in the related Ru5 +,4 d3 cubic double perovskite Ba2YRuO6 , and attribute the ˜3 times larger gap to stronger SOC present in this heavier, 5 d , osmate system.

  8. Band structure of fcc-C60 solid state crystal study

    Directory of Open Access Journals (Sweden)

    S Javanbakht

    2009-09-01

    Full Text Available We studied the architecture of the C60 cluster to drive its atomic positions which can be seen at room temperature. We then used the obtained carbon positions as a basis set for the fcc structure to construct the fcc-C60 compound. Self consistent calculations were performed based on the density functional theory (DFT utilizing the accurate WIEN2K code to solve the single-particle Kohen-Sham equation within the augmented plane waves plus local orbital (APW+lo method. The cohesive energy has been found to be 1.537 eV for the fcc-C60 . The calculated small cohesive energy that results from the weak Van der Waals-London interactions among a C60 cluster with its nearest neighbors is in good agreement with experiment. The electron densities of states (DOSs were calculated for a C60 macromolecule as well as the fcc-C60 compound and the results were compared with each other. The band gap from DOS calculations has been found to be 0.7 eV. Band structures were also calculated within the generalized gradient approximation (GGA. The band structure calculation results in 1.04 eV for the direct band gap. Two kinds of σ and π bonds were determined in the band structure. Our results are in good agreement with experiment and pseudopotential calculations.

  9. Rheological Modeling with Hookean Bead-Spring Cubes (SC, BBC and FCC)

    NARCIS (Netherlands)

    Denneman, A.I.M.; Jongschaap, R.J.J.; Mellema, J.

    1998-01-01

    In this study a general bead-spring model is used for predicting some rheological properties of a cubic bead-spring structure of arbitrary size immersed in a Newtonian solvent. The topology of this bead-spring structure is based upon the well-known cubic crystals (SC, BCC or FCC) and it consists of

  10. Synthesis of 4H/fcc-Au@Metal Sulfide Core-Shell Nanoribbons.

    Science.gov (United States)

    Fan, Zhanxi; Zhang, Xiao; Yang, Jian; Wu, Xue-Jun; Liu, Zhengdong; Huang, Wei; Zhang, Hua

    2015-09-02

    Although great advances on the synthesis of Au-semiconductor heteronanostructures have been achieved, the crystal structure of Au components is limited to the common face-centered cubic (fcc) phase. Herein, we report the synthesis of 4H/fcc-Au@Ag2S core-shell nanoribbon (NRB) heterostructures from the 4H/fcc Au@Ag NRBs via the sulfurization of Ag. Remarkably, the obtained 4H/fcc-Au@Ag2S NRBs can be further converted to a novel class of 4H/fcc-Au@metal sulfide core-shell NRB heterostructures, referred to as 4H/fcc-Au@MS (M = Cd, Pb or Zn), through the cation exchange. We believe that these novel 4H/fcc-Au@metal sulfide NRB heteronanostructures may show some promising applications in catalysis, surface enhanced Raman scattering, solar cells, photothermal therapy, etc.

  11. Realizing high magnetic moments in fcc Fe nanoparticles through atomic structure stretch.

    Science.gov (United States)

    Baker, S H; Roy, M; Thornton, S C; Binns, C

    2012-05-02

    We describe the realization of a high moment state in fcc Fe nanoparticles through a controlled change in their atomic structure. Embedding Fe nanoparticles in a Cu(1-x)Au(x) matrix causes their atomic structure to switch from bcc to fcc. Extended x-ray absorption fine structure (EXAFS) measurements show that the structure in both the matrix and the Fe nanoparticles expands as the amount of Au in the matrix is increased, with the data indicating a tetragonal stretch in the Fe nanoparticles. The samples were prepared directly from the gas phase by co-deposition, using a gas aggregation source and MBE-type sources respectively for the nanoparticle and matrix materials. The structure change in the Fe nanoparticles is accompanied by a sharp increase in atomic magnetic moment, ultimately to values of ~2.5 ± 0.3 μ(B)/atom .

  12. Two Types of Novel Feedstock Injection Structures of the FCC Riser Reactor

    Institute of Scientific and Technical Information of China (English)

    范怡平; 蔡飞鹏; 时铭显; 徐春明

    2004-01-01

    Based on the analysis of flow characteristics of the FCC riser feedstock injection zone, two novel feedstock injection structures are put forward. By investigating three flow parameters in the feedstock injection zone under the three different structures (the traditional and the novel No. 1, No. 2 structures): the local density, the particle backmixng ratio, and the jet eigen-concentration, the flow feature under three structures were obtained. The experimental results demonstrate that the flow features under both proposed structures are obviously improved comparing with those under the traditional structure. Especially, the performance of the deflector-structured No. 2 is more desirable than that of No. 1.

  13. Orientation dependence of structural transition in fcc Al driven under uniaxial compression by atomistic simulations

    Institute of Scientific and Technical Information of China (English)

    Li Li; Shao Jian-Li; Duan Su-Qing; Liang Jiu-Qing

    2011-01-01

    By molecular dynamics simulations employing an embedded atom method potential, we have investigated structural transformations in single crystal Al caused by uniaxial strain loading along the[001],[011]and[111]directions.We find that the structural transition is strongly dependent on the crystal orientations. The entire structure phase transition only occurs when loading along the[001]direction, and the increased amplitude of temperature for[001]loading is evidently lower than that for other orientations. The morphology evolutions of the structural transition for [011]and[111]loadings are analysed in detail. The results indicate that only 20% of atoms transit to the hcp phase for[011]and[111]loadings, and the appearance of the hcp phase is due to the partial dislocation moving forward on {111}fcc family. For[011]loading, the hcp phase grows to form laminar morphology in four planes, which belong to the{111}fcc family;while for[111]loading, the hcp phase grows into a laminar structure in three planes, which belong to the {111}fcc family except for the(111)plane. In addition, the phase transition is evaluated by using the radial distribution functions.

  14. Synthesis and the Structural Transformation of fcc to hcp in Ni-Graphene Nanocomposite by Simple Chemical Route via Sonication

    Directory of Open Access Journals (Sweden)

    N. K. Mahale

    2014-01-01

    Full Text Available We report the synthesis and structural transformation of fcc to hcp in Ni-graphene (Ni-Gr composite by simple chemical route via sonication. The syntheses of Ni-Gr composite by simultaneous reduction method, and the effect of different composition ratio on morphology and crystal structure were examined in our present study. The results indicated that the graphene ratio played an important role in crystal structure and d-spacing in nickel crystals. Different compositions have shown different behavior. The nanonickel clusters of various shapes with coated graphene and decorated as nickel on graphene sheets are observed. The synthesized composites were characterized using X-ray diffraction (XRD, field emission scanning electron microscopy (FE-SEM, and transmission electron microscope (TEM. The XRD patterns indicated crystal lattice modifications in some composites while composites with a higher graphene ratio produced very small crystals with uniform lattice parameter and d-spacing. FE-SEM images indicated the growth of Datura fruit like shapes of nickel clusters in higher composition of nickel while the composites with least concentration of nickel were composed of cubical nanoparticles grown on graphene sheets. TEM analysis revealed many Ni nanoparticles surrounding the smooth petals like surface of graphene, with average diameters of spiky nickel nanoparticles being about 50 nm and 124 nm, respectively, on 200 nm of scale.

  15. Discovery of face-centered-cubic ruthenium nanoparticles: facile size-controlled synthesis using the chemical reduction method.

    Science.gov (United States)

    Kusada, Kohei; Kobayashi, Hirokazu; Yamamoto, Tomokazu; Matsumura, Syo; Sumi, Naoya; Sato, Katsutoshi; Nagaoka, Katsutoshi; Kubota, Yoshiki; Kitagawa, Hiroshi

    2013-04-17

    We report the first discovery of pure face-centered-cubic (fcc) Ru nanoparticles. Although the fcc structure does not exist in the bulk Ru phase diagram, fcc Ru was obtained at room temperature because of the nanosize effect. We succeeded in separately synthesizing uniformly sized nanoparticles of both fcc and hcp Ru having diameters of 2-5.5 nm by simple chemical reduction methods with different metal precursors. The prepared fcc and hcp nanoparticles were both supported on γ-Al2O3, and their catalytic activities in CO oxidation were investigated and found to depend on their structure and size.

  16. Transition-sized Au92 nanoparticle bridging non-fcc-structured gold nanoclusters and fcc-structured gold nanocrystals.

    Science.gov (United States)

    Liao, Lingwen; Chen, Jishi; Wang, Chengming; Zhuang, Shengli; Yan, Nan; Yao, Chuanhao; Xia, Nan; Li, Lingling; Bao, Xiaoli; Wu, Zhikun

    2016-10-04

    Herein, we report the intriguing structure, optical absorption and electrochemical properties of the transition-sized Au92(TBBT)44 (Au92 for short, TBBT = 4-tert-butylbenzenethiolate) nanoparticle. An interesting observation is the 4H phase array of Au92 nanoparticles in the unit cells of single crystals.

  17. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    KAUST Repository

    Suteewong, Teeraporn

    2011-01-19

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.

  18. Theoretical study of the structural stability for fcc-CHx phases using density functional theory

    Directory of Open Access Journals (Sweden)

    M Dadsetani

    2011-09-01

    Full Text Available  Recently, a new carbon modification, namly n-diamond, have been reported, whose structure is still a matter of debate. It is important to note that the synthesis of n-diamond was carried out in the presence of hydrogen or methan. In this work we evaluate the structural stability of five fcc-CHx phases by means of first-principle calculation. The total energy is obtained as a function of the isotropic, tetragonal and rhombohedral deformations for the bulk structures. First, we analyze the C2H (cuprite, CH (zincblende, CH (rocksalt and CH2 (fluorite structures.It is found that the four systems show a minimum in the total energy for the isotropic and rhombohedral deformations, but are unstable against tetragonal deformation. In the second part, we explore the structural stability of CH2 in the pyrite structure. We find that CH2 (pyrite with the hydrogen atoms defined by the internal parameter u=0.35 and a lattice parameter of 3.766 Å is elastically stable, providing a possible explanation for the experimental observation of fcc-carbon in materials prepared in the presence of hydrogen or methan. In final, we calculate density of states, band structure and EELS spectrum of CH2 (pyrite and compare them with n-diamond.

  19. Three-Dimensional Structure of a Simple Liquid at a Face-Centered-Cubic (001) Solid Surface Interface.

    Science.gov (United States)

    Bao, Luyao; Hu, Haibao; Wen, Jun; Sepri, Paavo; Luo, Kai

    2016-07-19

    A liquid in the vicinity of a solid-liquid interface (SLI) may exhibit complex structures. In this study, we used molecular dynamics simulations demonstrating for the first time that the liquid adjacent to the SLI can have a two-level structure in some cases: a major structure and a minor structure. Through a time-averaging process of molecular motions, we identified the type of the liquid structure by calculating positions of the maximum liquid density in three spatial dimensions, and these positions were found to distribute in many dispersed zones (called high-density zones (HDZs)). The major structure appears throughout the SLI, while the minor structure only occurs significantly within the third layer. Instead of the previously reported body-centered cubic (BCC) or face-centered-cubic (FCC) types, the major structure was found to show a body-centered tetragonal (BCT) type. The adjacent HDZs are connected by specific junctions, demonstrating that atoms diffuse along some particular high probability paths from one HDZ to another. By considering the three-dimensional liquid density distribution from the continuum point of view, more complete details of the structure and diffusive behavior of liquids in the SLI are also possible to be revealed.

  20. Three-Dimensional Structure of a Simple Liquid at a Face-Centered-Cubic (001) Solid Surface Interface

    Science.gov (United States)

    Bao, Luyao; Hu, Haibao; Wen, Jun; Sepri, Paavo; Luo, Kai

    2016-07-01

    A liquid in the vicinity of a solid-liquid interface (SLI) may exhibit complex structures. In this study, we used molecular dynamics simulations demonstrating for the first time that the liquid adjacent to the SLI can have a two-level structure in some cases: a major structure and a minor structure. Through a time-averaging process of molecular motions, we identified the type of the liquid structure by calculating positions of the maximum liquid density in three spatial dimensions, and these positions were found to distribute in many dispersed zones (called high-density zones (HDZs)). The major structure appears throughout the SLI, while the minor structure only occurs significantly within the third layer. Instead of the previously reported body-centered cubic (BCC) or face-centered-cubic (FCC) types, the major structure was found to show a body-centered tetragonal (BCT) type. The adjacent HDZs are connected by specific junctions, demonstrating that atoms diffuse along some particular high probability paths from one HDZ to another. By considering the three-dimensional liquid density distribution from the continuum point of view, more complete details of the structure and diffusive behavior of liquids in the SLI are also possible to be revealed.

  1. Electronic band structure and optical properties of the cubic, Sc, Y and La hydride systems

    Energy Technology Data Exchange (ETDEWEB)

    Peterman, D.J.

    1980-01-01

    Electronic band structure calculations are used to interpret the optical spectra of the cubic Sc, Y and La hydride systems. Self-consistent band calculations of ScH/sub 2/ and YH/sub 2/ were carried out. The respective joint densities of states are computed and compared to the dielectric functions determined from the optical measurements. Additional calculations were performed in which the Fermi level or band gap energies are rigidly shifted by a small energy increment. These calculations are then used to simulate the derivative structure in thermomodulation spectra and relate the origin of experimental interband features to the calculated energy bands. While good systematic agreement is obtained for several spectral features, the origin of low-energy interband transitions in YH/sub 2/ cannot be explained by these calculated bands. A lattice-size-dependent premature occupation of octahedral sites by hydrogen atoms in the fcc metal lattice is suggested to account for this discrepancy. Various non-self-consistent calculations are used to examine the effect of such a premature occupation. Measurements of the optical absorptivity of LaH/sub x/ with 1.6 < x < 2.9 are presented which, as expected, indicate a more premature occupation of the octahedral sites in the larger LaH/sub 2/ lattice. These experimental results also suggest that, in contrast to recent calculations, LaH/sub 3/ is a small-band-gap semiconductor.

  2. Electronic Structure of the fcc Transition Metals Ir, Rh, Pt, and Pd

    DEFF Research Database (Denmark)

    Andersen, O. Krogh

    1970-01-01

    /atom)/Ry, respectively. Spin-orbit coupling is important for all four metals and the coupling parameter varies by 30% over the d bandwidth. Detailed comparisons with de Haas—van Alphen Fermi-surface dimensions have previously been presented and the agreement was very good. Comparison with measured electronic specific......We give a complete description of a relativistic augmented-plane-wave calculation of the band structures of the paramagnetic fcc transition metals Ir, Rh, Pt, and Pd. The width and position of the d band decrease in the sequence Ir, Pt, Rh, Pd; and N(EF)=13.8,23.2,18.7, and 32.7 (states...

  3. Ab initio random structure search for 13-atom clusters of fcc elements.

    Science.gov (United States)

    Chou, J P; Hsing, C R; Wei, C M; Cheng, C; Chang, C M

    2013-03-27

    The 13-atom metal clusters of fcc elements (Al, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) were studied by density functional theory calculations. The global minima were searched for by the ab initio random structure searching method. In addition to some new lowest-energy structures for Pd13 and Au13, we found that the effective coordination numbers of the lowest-energy clusters would increase with the ratio of the dimer-to-bulk bond length. This correlation, together with the electronic structures of the lowest-energy clusters, divides the 13-atom clusters of these fcc elements into two groups (except for Au13, which prefers a two-dimensional structure due to the relativistic effect). Compact-like clusters that are composed exclusively of triangular motifs are preferred for elements without d-electrons (Al) or with (nearly) filled d-band electrons (Ni, Pd, Cu, Ag). Non-compact clusters composed mainly of square motifs connected by some triangular motifs (Rh, Ir, Pt) are favored for elements with unfilled d-band electrons.

  4. Computational simulation of the CrN - FCC structure; Simulación computacional de la estructura FCC del CrN

    Directory of Open Access Journals (Sweden)

    ALEXANDER RUDEN MUÑOZ

    2013-06-01

    Full Text Available CrN thin films were synthesized via Magnetron Sputtering deposition technique on (111 oriented Silicon substrates. Coatings were analyzed by using X-ray Diffraction (XRD and Raman spectroscopy, determining the cubic phase for the ceramic compound. Computational simulation of the CrN cubic crystallographic structure, performed by using Density Functional Theory (DFT, showed stability by the sum of Mulliquen charges equal to zero and compound hybridization with characteristic sp molecular orbitals and the identification of the p molecular orbital component from the nitrogen.

  5. The elastic properties and stability of fcc-Fe and fcc-FeNi alloys at inner-core conditions

    Science.gov (United States)

    Martorell, Benjamí; Brodholt, John; Wood, Ian G.; Vočadlo, Lidunka

    2015-07-01

    The agreement between shear wave velocities for the Earth's inner core observed from seismology with those derived from mineral physics is considerably worse than for any other region of the Earth. Furthermore, there is still debate as to the phase of iron present in the inner core, particularly when alloying with nickel and light elements is taken into account. To investigate the extent to which the mismatch between seismology and mineral physics is a function of either crystal structure and/or the amount of nickel present, we have used ab initio molecular dynamics simulations to calculate the elastic constants and seismic velocities (Vp and Vs) of face centred cubic (fcc) iron at Earth's inner core pressures (360 GPa) and at temperatures up to ˜7000 K. We find that Vp for fcc iron (fcc-Fe) is very similar to that for hexagonal close packed (hcp) iron at all temperatures. In contrast, Vs for fcc-Fe is significantly higher than in hcp-Fe, with the difference increasing with increasing temperature; the difference between Vs for the core (from seismology) and Vs for fcc-Fe exceeds 40 per cent. These results are consistent with previous work at lower temperatures. We have also investigated the effect of 6.5 and 13 atm% Ni in fcc-Fe. We find that Ni only slightly reduces Vp and Vs (e.g. by 2 per cent in Vs for 13 atm% Ni at 5500 K), and cannot account for the difference between the velocities observed in the core and those of pure fcc-Fe. We also tried to examine pre-melting behaviour in fcc-Fe, as reported in hcp-Fe by extending the study to very high temperatures (at which superheating may occur). However, we find that fcc-Fe spontaneously transforms to other hcp-like structures before melting; two hcp-like structures were found, both of hexagonal symmetry, which may most easily be regarded as being derived from an hcp crystal with stacking faults. That the structure did not transform to a true hcp phase is likely as a consequence of the limited size of the

  6. Growth and micromagnetism of self-assembled epitaxial fcc(111) cobalt dots.

    Science.gov (United States)

    Fruchart, O; Masseboeuf, A; Toussaint, J C; Bayle-Guillemaud, P

    2013-12-11

    We develop the self-assembly of epitaxial submicrometer-sized face-centered-cubic (fcc) Co(111) dots using pulsed laser deposition. The dots display atomically flat facets, from which the ratios of surface and interface energies for fcc Co are deduced. Zero-field magnetic structures are investigated with magnetic force and Lorentz microscopies, revealing vortex-based flux-closure patterns. A good agreement is found with micromagnetic simulations.

  7. Nonlinear structure formation in the Cubic Galileon gravity model

    CERN Document Server

    Barreira, Alexandre; Hellwing, Wojciech A; Baugh, Carlton M; Pascoli, Silvia

    2013-01-01

    We model the linear and nonlinear growth of large scale structure in the Cubic Galileon gravity model, by running a suite of N-body cosmological simulations using the {\\tt ECOSMOG} code. Our simulations include the Vainshtein screening effect, which reconciles the Cubic Galileon model with local tests of gravity. In the linear regime, the amplitude of the matter power spectrum increases by $\\sim 25%$ with respect to the standard $\\Lambda$CDM model today. The modified expansion rate accounts for $\\sim 20%$ of this enhancement, while the fifth force is responsible for only $\\sim 5%$. This is because the effective unscreened gravitational strength deviates from standard gravity only at late times, even though it can be twice as large today. In the nonlinear regime ($k \\gtrsim 0.1 h\\rm{Mpc}^{-1}$), the fifth force leads to only a modest increase ($\\lesssim 8%$) in the clustering power on all scales due to the very efficient operation of the Vainshtein mechanism. Such a strong effect is typically not seen in other...

  8. Electronic structure and magnetism of strained bcc phases across the fcc to bcc transition in ultrathin Fe films

    Science.gov (United States)

    Calloni, Alberto; Berti, Giulia; Bussetti, Gianlorenzo; Fratesi, Guido; Finazzi, Marco; Ciccacci, Franco; Duò, Lamberto

    2016-11-01

    We investigated the electronic structure of the bcc metastable phases involved in the fcc to bcc transition of Fe. Ultrathin Fe films were grown on a 2-monolayer (ML) Ni/W(110) substrate, where a fcc lattice is stabilized at low Fe coverages and the transition proceeds through the formation of bcc nuclei showing a specific "Kurdjumov-Sachs" orientation with the substrate. A comprehensive description of the electronic structure evolution is achieved by combining spin-resolved UV photoemission spectroscopy and ab initio calculations. According to our results, an exchange-split band structure is observed starting from 2 ML of Fe, concomitant with the formation of ferromagnetic bcc nuclei. Continuous modifications are observed in the spin-resolved photoemission spectra for increasing Fe coverage, especially for what concerns the minority states, possibly indicative of the progressive relaxation of the strained bcc phase starting from the bcc/fcc interface.

  9. Why FCC

    Science.gov (United States)

    Angele, W.

    1972-01-01

    Summaries are given of design characteristics and various advantages of FCC use. The information is presented in tables that include the following headings: (1) mechanical design, (2) electrical design, (3) manufacturing advantages, (4) inspection and reliability, and (5) cost savings. In addition, the results are summarized of a Saturn 4B FCC-RWC comparison study.

  10. Structure and energetics of nanotwins in cubic boron nitrides

    Science.gov (United States)

    Zheng, Shijian; Zhang, Ruifeng; Huang, Rong; Taniguchi, Takashi; Ma, Xiuliang; Ikuhara, Yuichi; Beyerlein, Irene J.

    2016-08-01

    Recently, nanotwinned cubic boron nitrides (NT c-BN) have demonstrated extraordinary leaps in hardness. However, an understanding of the underlying mechanisms that enable nanotwins to give orders of magnitude increases in material hardness is still lacking. Here, using transmission electron microscopy, we report that the defect density of twin boundaries depends on nanotwin thickness, becoming defect-free, and hence more stable, as it decreases below 5 nm. Using ab initio density functional theory calculations, we reveal that the Shockley partials, which may dominate plastic deformation in c-BNs, show a high energetic barrier. We also report that the c-BN twin boundary has an asymmetrically charged electronic structure that would resist migration of the twin boundary under stress. These results provide important insight into possible nanotwin hardening mechanisms in c-BN, as well as how to design these nanostructured materials to reach their full potential in hardness and strength.

  11. Structure and energetics of nanotwins in cubic boron nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Shijian, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn; Ma, Xiuliang [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, Ruifeng, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn [School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191 (China); Huang, Rong [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062 (China); Taniguchi, Takashi [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Ikuhara, Yuichi [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656 (Japan); Beyerlein, Irene J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-08-22

    Recently, nanotwinned cubic boron nitrides (NT c-BN) have demonstrated extraordinary leaps in hardness. However, an understanding of the underlying mechanisms that enable nanotwins to give orders of magnitude increases in material hardness is still lacking. Here, using transmission electron microscopy, we report that the defect density of twin boundaries depends on nanotwin thickness, becoming defect-free, and hence more stable, as it decreases below 5 nm. Using ab initio density functional theory calculations, we reveal that the Shockley partials, which may dominate plastic deformation in c-BNs, show a high energetic barrier. We also report that the c-BN twin boundary has an asymmetrically charged electronic structure that would resist migration of the twin boundary under stress. These results provide important insight into possible nanotwin hardening mechanisms in c-BN, as well as how to design these nanostructured materials to reach their full potential in hardness and strength.

  12. New cubic structure compounds as actinide host phases

    Energy Technology Data Exchange (ETDEWEB)

    Stefanovsky, S V [SIA Radon, 7th Rostovskii lane 2/14, Moscow 119121 (Russian Federation); Yudintsev, S V; Livshits, T S, E-mail: profstef@mtu-net.ru [Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry RAS, Staromonetny lane 35, Moscow 119017 (Russian Federation)

    2010-03-15

    Various compounds with fluorite (cubic zirconia) and fluorite-derived (pyrochlore, zirconolite) structures are considered as promising actinide host phases at immobilization of actinide-bearing nuclear wastes. Recently some new cubic compounds - stannate and stannate-zirconate pyrochlores, murataite and related phases, and actinide-bearing garnet structure compounds were proposed as perspective matrices for complex actinide wastes. Zirconate pyrochlore (ideally Gd{sub 2}Zr{sub 2}O{sub 7}) has excellent radiation resistance and high chemical durability but requires high temperatures (at least 1500 deg. C) to be produced by hot-pressing from sol-gel derived precursor. Partial Sn{sup 4+} substitution for Zr{sup 4+} reduces production temperature and the compounds REE{sub 2}ZrSnO{sub 7} may be hot-pressed or cold pressed and sintered at {approx}1400 deg. C. Pyrochlore, A{sub 2}B{sub 2}O{sub 7-x} (two-fold elementary fluorite unit cell), and murataite, A{sub 3}B{sub 6}C{sub 2}O{sub 20-y} (three-fold fluorite unit cell), are end-members of the polysomatic series consisting of the phases whose structures are built from alternating pyrochlore and murataite blocks (nano-sized modules) with seven- (2C/3C/2C), five- (2C/3C), eight- (3C/2C/3C) and three-fold (3C - murataite) fluorite unit cells. Actinide content in this series reduces in the row: 2C (pyrochlore) > 7C > 5C > 8C > 3C (murataite). Due to congruent melting murataite-based ceramics may be produced by melting and the firstly segregated phase at melt crystallization is that with the highest fraction of the pyrochlore modules in its structure. The melts containing up to 10 wt. % AnO{sub 2} (An = Th, U, Np, Pu) or REE/An fraction of HLW form at crystallization zoned grains composed sequentially of the 5C {yields} 8C {yields} 3C phases with the highest actinide concentration in the core and the lowest - in the rim of the grains. Radiation resistance of the 'murataite' is comparable to titanate pyrochlores. One

  13. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  14. The Structure of the Cubic Coincident Site Lattice Rotation Group

    Energy Technology Data Exchange (ETDEWEB)

    Reed, B W; Minich, R W; Rudd, R E; Kumar, M

    2004-01-13

    This work is intended to be a mathematical underpinning for the field of grain boundary engineering and its relatives. The interrelationships within the set of rotations producing coincident site lattices in cubic crystals are examined in detail. Besides combining previously established but widely scattered results into a unified context, the present work details newly developed representations of the group structure in terms of strings of generators (based on quaternionic number theory, and including uniqueness proofs and rules for algebraic manipulation) as well as an easily visualized topological network model. Important results that were previously obscure or not universally understood (e.g. the {Sigma} combination rule governing triple junctions) are clarified in these frameworks. The methods also facilitate several general observations, including the very different natures of twin-limited structures in two and three dimensions, the inadequacy of the {Sigma} combination rule to determine valid quadruple nodes, and a curious link between allowable grain boundary assignments and the four-color map theorem. This kind of understanding is essential to the generation of realistic statistical models of grain boundary networks (particularly in twin-dominated systems) and is especially applicable to the field of grain boundary engineering.

  15. Deformation-induced structural transition in body-centred cubic molybdenum.

    Science.gov (United States)

    Wang, S J; Wang, H; Du, K; Zhang, W; Sui, M L; Mao, S X

    2014-03-07

    Molybdenum is a refractory metal that is stable in a body-centred cubic structure at all temperatures before melting. Plastic deformation via structural transitions has never been reported for pure molybdenum, while transformation coupled with plasticity is well known for many alloys and ceramics. Here we demonstrate a structural transformation accompanied by shear deformation from an original -oriented body-centred cubic structure to a -oriented face-centred cubic lattice, captured at crack tips during the straining of molybdenum inside a transmission electron microscope at room temperature. The face-centred cubic domains then revert into -oriented body-centred cubic domains, equivalent to a lattice rotation of 54.7°, and ~15.4% tensile strain is reached. The face-centred cubic structure appears to be a well-defined metastable state, as evidenced by scanning transmission electron microscopy and nanodiffraction, the Nishiyama-Wassermann and Kurdjumov-Sachs relationships between the face-centred cubic and body-centred cubic structures and molecular dynamics simulations. Our findings reveal a deformation mechanism for elemental metals under high-stress deformation conditions.

  16. Deformation-induced structural transition in body-centred cubic molybdenum

    Science.gov (United States)

    Wang, S. J.; Wang, H.; Du, K.; Zhang, W.; Sui, M. L.; Mao, S. X.

    2014-03-01

    Molybdenum is a refractory metal that is stable in a body-centred cubic structure at all temperatures before melting. Plastic deformation via structural transitions has never been reported for pure molybdenum, while transformation coupled with plasticity is well known for many alloys and ceramics. Here we demonstrate a structural transformation accompanied by shear deformation from an original -oriented body-centred cubic structure to a -oriented face-centred cubic lattice, captured at crack tips during the straining of molybdenum inside a transmission electron microscope at room temperature. The face-centred cubic domains then revert into -oriented body-centred cubic domains, equivalent to a lattice rotation of 54.7°, and ~15.4% tensile strain is reached. The face-centred cubic structure appears to be a well-defined metastable state, as evidenced by scanning transmission electron microscopy and nanodiffraction, the Nishiyama-Wassermann and Kurdjumov-Sachs relationships between the face-centred cubic and body-centred cubic structures and molecular dynamics simulations. Our findings reveal a deformation mechanism for elemental metals under high-stress deformation conditions.

  17. FCC Fe2NiSi prepared by mechanical alloying and stabilization effect of L21B disorder on BCC Heusler structure

    Science.gov (United States)

    Luo, Hongzhi; Xin, Yuepeng; Ma, Yuexing; Liu, Bohua; Meng, Fanbin; Liu, Heyan; Liu, Enke; Wu, Guangheng

    2016-12-01

    Fe2NiSi FCC phase has been prepared by ball-milling successfully, which is different from the BCC Heusler phase prepared by arc-melting in previous literatures. The FCC Fe2NiSi is a ferromagnet with a lattice constant of 3.58 Å. The phase stability of the FCC and BCC Fe2NiSi has been compared by first-principles calculations. It has been found that the FCC structure has a lower total energy compared with the highly-ordered Heusler structures XA and L21, that is the reason why the FCC phase can be prepared by ball-milling. However, the Fe (A)-Ni (C) disorder in the BCC XA structure can lower its total energy further and make it smaller than the FCC phase. So the most stable structure in Fe2NiSi is L21B, as has been observed in the arc-melting sample. This can be explained from their DOS structures. The calculated total moments for the FCC and BCC phases agree with their Ms at 5 K quite well.

  18. Relative stability of the FCC and HCP polymorphs with interacting polymers.

    Science.gov (United States)

    Mahynski, Nathan A; Kumar, Sanat K; Panagiotopoulos, Athanassios Z

    2015-01-14

    Recent work [Mahynski et al., Nat. Commun., 2014, 5, 4472] has demonstrated that the addition of long linear homopolymers thermodynamically biases crystallizing hard-sphere colloids to produce the hexagonal close-packed (HCP) polymorph over the closely related face-centered cubic (FCC) structure when the polymers and colloids are purely repulsive. In this report, we investigate the effects of thermal interactions on each crystal polymorph to explore the possibility of stabilizing the FCC crystal structure over the HCP. We find that the HCP polymorph remains at least as stable as its FCC counterpart across the entire range of interactions we explored, where interactions were quantified by the reduced second virial coefficient, -1.50 0, its tetrahedral voids produce a similar effect when B FCC crystals are elusive in these binary mixtures.

  19. Electronic structure of FCC-Fe{sub n}X (X=C, N; n=4, 8) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Peltzer y Bianca, E.L. [Grupo de Estudio de Materiales y Dispositivos Electronicos (GEMyDE), Facultad de Ingenieria, UNLP, IFLYSIB-CONICET, C.C. No 565, 1900 La Plata (Argentina)]. E-mail: eitel@iflysib.unlp.edu.ar; Desimoni, J. [Departamento de Fisica, Facultad de Ciencias. Exactas, UNLP, IFLP-CONICET, C.C.No 67, 1900 La Plata (Argentina); Christensen, N.E. [Department of Physics and Astronomy, Aarhus University, Ny Munkegade, Bld. 520, DK-8000 Aarhus C (Denmark)

    2004-12-31

    To obtain a picture of the FCC-FeX (X=C, N) austenite solid solution, we compare the hyperfine parameters obtained by Moessbauer spectroscopy and those obtained by the full-potential linear augmented-plane wave (FLAPW) method. We have focused the study on the magnetic moments, isomer shifts, and hyperfine magnetic fields obtained by FLAPW assuming an Fe{sub 4}X structure to sketch the austenite.

  20. Perfect cubic texture, structure, and mechanical properties of nonmagnetic copper-based alloy ribbon substrates

    Science.gov (United States)

    Khlebnikova, Yu. V.; Rodionov, D. P.; Gervas'eva, I. V.; Egorova, L. Yu.; Suaridze, T. R.

    2015-03-01

    A sharp cubic texture is formed in a number of copper alloys subjected to cold deformation by rolling by 98.6-99% followed by recrystallization annealing, which opens up fresh opportunities for long thin ribbons made of these alloys to be used as substrates in the production of second-generation high- T c superconductor (2G HTSC) cables. The possibility of creating ternary alloys based on a binary Cu-30 at % Ni alloy with additional elements that harden its fcc matrix (iron, chromium) is shown. The measurements of the mechanical properties of textured ribbons made of these alloys demonstrate that their yield strength is higher than that of a textured ribbon made of pure copper by a factor of 2.5-4.5.

  1. Structure and magnetic properties of hcp and fcc nanocrystalline thin Ni films and nanoparticles produced by radio frequency magnetron sputtering.

    Science.gov (United States)

    Kapaklis, Vassilios; Pappas, Spiridon D; Poulopoulos, Panagiotis; Trachylis, Dimitrios; Schweiss, Peter; Politis, Constantin

    2010-09-01

    We report on the growth of thin Ni films by radio frequency magnetron sputtering in Ar-plasma. The growth temperature was about 350 K and the films were deposited on various substrates such as glass, silicon, sapphire and alumina. The thickness of the thinnest films was estimated by the appearance of Kiessig fringes up to about 2theta = 8 degrees in the small-angle X-ray diffraction pattern, as expected for high-quality atomically-flat thin films. With the help of this, a quartz balance system was calibrated and used for measuring the thickness of thicker samples with an accuracy of better than 5%. Structural characterization via X-ray diffraction and high resolution transmission electron microscopy revealed an Ar-gas pressure window, where single phase hcp Ni films may be grown. The magnetic response of the Ni films was checked at room temperature via a newly established and fully automatic polar magneto-optic Kerr effect magnetometer. The hcp films show no magnetic response. Interestingly, the magnetic saturation field of fcc films deposited at low Ar pressure is comparable to the one of bulk Ni, while the one of fcc films deposited at high Ar pressures is decreased, revealing the presence of residual strain in the films. Finally, it is shown that it is possible to form films which contain magnetic Ni fcc nanoparticles in a non-magnetic hcp matrix, i.e., a system interesting for technological applications demanding a single Ni target for its production.

  2. Body-centered-cubic Ni and its magnetic properties.

    Science.gov (United States)

    Tian, C S; Qian, D; Wu, D; He, R H; Wu, Y Z; Tang, W X; Yin, L F; Shi, Y S; Dong, G S; Jin, X F; Jiang, X M; Liu, F Q; Qian, H J; Sun, K; Wang, L M; Rossi, G; Qiu, Z Q; Shi, J

    2005-04-08

    The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52+/-0.08 micro(B)/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0x10(5) ergs x cm(-3), as opposed to -5.7x10(4) ergs x cm(-3) for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.

  3. Observation of the fcc-to-hcp transition in ensembles of argon nanoclusters.

    Science.gov (United States)

    Krainyukova, N V; Boltnev, R E; Bernard, E P; Khmelenko, V V; Lee, D M; Kiryukhin, V

    2012-12-14

    Macroscopic ensembles of weakly interacting argon nanoclusters are studied using x-ray diffraction in low vacuum. As the clusters grow by fusion with increasing temperature, their structure transforms from essentially face-centered cubic (fcc) to hexagonal close packed as the cluster size approaches ~10(5) atoms. The transformation involves intermediate orthorhombic phases. These data confirm extant theoretical predictions. They also indicate that growth kinetics and spatial constraints might play an important role in the formation of the fcc structure of bulk rare-gas solids, which still remains puzzling.

  4. Structure of the body-centered cubic phase of lipid systems.

    Science.gov (United States)

    Saludjian, P; Reiss-Husson, F

    1980-12-01

    A new model is proposed for the structure of the body-centered cubic phase of lipid systems. Infinite rods of polar groups (and water) are arranged with axes parallel to the four cubic [unk]1 1 1[unk] directions. The hydrocarbon chains fill the space between the rods to form a continuous matrix. With this unified topology, the model explains satisfactorily the x-ray diffraction patterns of strontium soaps, lecithin, galactolipids, potassium soaps, and hexadecyltrimethylammonium bromide and explains the transition between cubic/H(II) phases. The paradoxical thermal effects on the lipid cubic phase, in particular the decrease of unit cell dimensions with increasing temperature, can be explained with the proposed model by mechanisms similar to those used for the monodimensional and bidimensional (mesomorphic) phases.

  5. Competition among fcc-like, double-layered flat, tubular cage, and close-packed structural motifs for medium-sized Au n (n = 21-28) clusters.

    Science.gov (United States)

    Tian, Dongxu; Zhao, Jijun

    2008-04-10

    Using density functional theory calculations, we compared four kinds of possible structural motifs of the medium-sized Aun (n = 21-28) clusters, i.e., fcc-like, double-layered flat, tubular cage, and close-packed. Our results show strong competition between those structural motifs in the medium-sized gold clusters. Aun (n = 21-23) adopt fcc-like structure owing to the high stability of tetrahedral Au20. A structural transition from fcc-like to tubular occurs at Au24, and the tubular motif continues at Au27 and Au28. Meanwhile, a double-layered flat structure was found at Au25, and a pyramid-based structure at Au26. The relationship between electronic properties and cluster geometry was also discussed.

  6. THE DEVELOPMENT OF FCC STRIPPING TECHNOLOGY

    Institute of Scientific and Technical Information of China (English)

    ZHANGZhen-qian

    2003-01-01

    This article briefly describes the major patents domestic and the abroad,and the current situation and achievements of FCC stripping technology in China.The develping trend of FCC stripping technology is presented,including further developments of FCC stripper to improve unit performance,combination of the stripper and pre-stripper within disengager to from a complete high-efficiency FCC stripping system.In addition to high efficiency,simple structure and easiness of installation and maintenance for a new FCC stripper are all of consideration.

  7. Formation Mechanism and Binding Energy for Body-Centered Cubic Structure of He+9 Cluster

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian-Ping; GOU Qing-Quan; LI Ping

    2004-01-01

    The formation mechanism for the body-centered cubic structure of He+9 cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between the nuclei at the center and an apex of the body-centered cubic structure. The result of the calculation shows that the curve has a minimal energy -25.6669 (a.u.) at R = 2.550ao. The binding energy of He+9 with respect to He+ + 8He was calculated to be 0.8857 a.u. This means that the cluster of He+9 may be formed in the body-centered cubic structure of R = 2.55a0.

  8. Synthesis of 4H/fcc Noble Multimetallic Nanoribbons for Electrocatalytic Hydrogen Evolution Reaction.

    Science.gov (United States)

    Fan, Zhanxi; Luo, Zhimin; Huang, Xiao; Li, Bing; Chen, Ye; Wang, Jie; Hu, Yanling; Zhang, Hua

    2016-02-03

    Noble multimetallic nanomaterials, if only consisting of Au, Ag, Pt, and Pd, typically adopt the high-symmetry face-centered cubic (fcc) structure. Here for the first time, by using the 4H/fcc Au@Ag nanoribbons (NRBs) as seeds, we report the synthesis of 4H/fcc trimetallic Au@PdAg core-shell NRBs via the galvanic reaction method under ambient conditions. Moreover, this strategy can also be used to synthesize 4H/fcc trimetallic Au@PtAg and quatermetallic Au@PtPdAg core-shell NRBs. Impressively, for the first time, these alloy shells, i.e., PdAg, PtAg, and PtPdAg, epitaxially grown on the 4H/fcc Au core with novel 4H hexagonal phase were successfully synthesized. Remarkably, the obtained 4H/fcc Au@PdAg NRBs exhibit excellent electrocatalytic activity toward the hydrogen evolution reaction, which is even quite close to that of the commercial Pt black. We believe that our findings here may provide a novel strategy for the crystal-structure-controlled synthesis of advanced functional noble multimetallic nanomaterials with various promising applications.

  9. Accurate Monte Carlo simulations on FCC and HCP Lennard-Jones solids at very low temperatures and high reduced densities up to 1.30.

    Science.gov (United States)

    Adidharma, Hertanto; Tan, Sugata P

    2016-07-07

    Canonical Monte Carlo simulations on face-centered cubic (FCC) and hexagonal closed packed (HCP) Lennard-Jones (LJ) solids are conducted at very low temperatures (0.10 ≤ T(∗) ≤ 1.20) and high densities (0.96 ≤ ρ(∗) ≤ 1.30). A simple and robust method is introduced to determine whether or not the cutoff distance used in the simulation is large enough to provide accurate thermodynamic properties, which enables us to distinguish the properties of FCC from that of HCP LJ solids with confidence, despite their close similarities. Free-energy expressions derived from the simulation results are also proposed, not only to describe the properties of those individual structures but also the FCC-liquid, FCC-vapor, and FCC-HCP solid phase equilibria.

  10. Crystallographic dependence of CO activation on cobalt catalysts: HCP versus FCC.

    Science.gov (United States)

    Liu, Jin-Xun; Su, Hai-Yan; Sun, Da-Peng; Zhang, Bing-Yan; Li, Wei-Xue

    2013-11-06

    Identifying the structure sensitivity of catalysts in reactions, such as Fischer-Tropsch synthesis from CO and H2 over cobalt catalysts, is an important yet challenging issue in heterogeneous catalysis. Based on a first-principles kinetic study, we find for the first time that CO activation on hexagonal close-packed (HCP) Co not only has much higher intrinsic activity than that of face centered-cubic (FCC) Co but also prefers a different reaction route, i.e., direct dissociation with HCP Co but H-assisted dissociation on the FCC Co. The origin is identified from the formation of various denser yet favorable active sites on HCP Co not available for FCC Co, due to their distinct crystallographic structure and morphology. The great dependence of the activity on the crystallographic structure and morphology of the catalysts revealed here may open a new avenue for better, stable catalysts with maximum mass-specific reactivity.

  11. Isolation of mitochondria with cubic membrane morphology reveals specific ionic requirements for the preservation of membrane structure.

    Science.gov (United States)

    Chong, Ketpin; Tan, Olivia Li Ling; Almsherqi, Zakaria A; Lin, Qingsong; Kohlwein, Sepp D; Deng, Yuru

    2015-03-01

    Biological membranes with cubic symmetry are a hallmark of virus-infected or diseased cells. The mechanisms of formation and specific cellular functions of cubic membranes, however, are unclear. The best-documented cubic membrane formation occurs in the free-living giant amoeba Chaos carolinense. In that system, mitochondrial inner membranes undergo a reversible structural change from tubular to cubic membrane organization upon starvation of the organism. As a prerequisite to further analyze the structural and functional features of cubic membranes, we adapted protocols for the isolation of mitochondria from starved amoeba and have identified buffer conditions that preserve cubic membrane morphology in vitro. The requirement for high concentration of ion-chelating agents in the isolation media supports the importance of a balanced ion milieu in establishing and maintaining cubic membranes in vivo.

  12. Structural Characterization of Cubic GaN Grown on GaAs(001) Substrates

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xinhe; QU Bo; WANG Yutian; YANG Hui; LIANGJunwu; HAN Jingyi

    2001-01-01

    Structural characteristics of cubic GaN epilayers grown on GaAs(001) were studied using X-ray double-crystal diffraction technique. The structure factors of cubic GaN(002) and (004) components are approximately identical. However, the integrated intensities of the rocking curve for cubic (002) components are over five times as those of (004)components. The discrepancy has been interpreted in detail considering other factors. In the conventional double crystal rocking curve, the peak broadening includes such information caused by the orientation distribution (mosaicity) and the distribution of lattice spacing. These two kinds of distributions can be distinguished by the triple-axis diffraction in which an analyzer crystal is placed in front of the detector.Moreover, the peak broadening was analyzed by reciprocal lattice construction and Eward sphere. By using triple-axis diffraction of cubic (002) and (113)components, domain size and dislocation density were estimated. The fully relaxed lattice parameter of cubic GaN was determined to be about 0.451 ± 0.001nm.

  13. Boron fullerenes B(32+8k) with four-membered rings and B32 solid phases: geometrical structures and electronic properties.

    Science.gov (United States)

    Sheng, Xian-Lei; Yan, Qing-Bo; Zheng, Qing-Rong; Su, Gang

    2009-11-14

    Based on ab initio calculations, we have studied the geometrical, electronic properties and chemical bonding of boron fullerenes B(32+8k) (0 cubic (sc), face-centered cubic (fcc), body-centered cubic (bcc), and body-centered tetragonal (bct) structures, where the bct phase is observed to be the most stable. Electronic structure calculations reveal that the sc, fcc and bcc phases of B(32) solids are metallic, but the bct phase is a semimetal.

  14. On structural transitions in a discontinuous micellar cubic phase loaded with sodium diclofenac.

    Science.gov (United States)

    Efrat, R; Aserin, A; Garti, N

    2008-05-01

    An intermediate mesophase of lyotropic liquid crystalline structure from the ternary mixtures of glycerol monooleate, water, and ethanol was recently characterized in our lab. This mesophase, termed Q(L), consists of discrete discontinuous micelles arranged in a cubic array. The Q(L) phase can solubilize very significant loads of water-insoluble anti-inflamatory drug sodium diclofenac (Na-DFC). Close examination of the internal structures of the lyotropic liquid structure upon increasing the solubilization loads reveals the existence of three structural transitions controlled by the Na-DFC levels. Up to 0.4 wt% Na-DFC, the Q(L) structure remains intact with some influence on the hydration of the headgroups and on the intermicellar forces. However, at 0.8 to 1.2 wt% Na-DFC, the discontinuous micellar cubic phase is transformed into a more condensed mesophase of a bicontinuous cubic phase. At > or =1.2 wt% Na-DFC, the cubic phase is converted into a lamellar phase (L(alpha)). Within 5.5 to 7.3 wt% Na-DFC the mesophase is progressively transformed into a less ordered lamellar structure. At 12 wt% Na-DFC crystals tend to precipitate out. At low Na-DFC concentrations the drug behaves like a lyotropic or kosmotropic salt and can salt-out the surfactant from its water layer, but at higher levels it behaves like a hydrotropic, chaotropic salt and can salt-in the surfactant. The Na-DFC location and position within the interface as well as its polarization and partial ionization are strongly affected by its solubilization contents and the structure that it is inducing. In the cubic phase the drug is located less close to the hydration layer while once transition occurs it is exposed more to the water layer and the surfactant headgroups.

  15. A note on the prolongation structure of the cubically nonlinear integrable Camassa-Holm type equation

    Energy Technology Data Exchange (ETDEWEB)

    Stalin, S. [Centre for Nonlinear Dynamics, School of Physics, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu (India); Senthilvelan, M., E-mail: velan@cnld.bdu.ac.in [Centre for Nonlinear Dynamics, School of Physics, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu (India)

    2011-10-17

    In this Letter, we formulate an exterior differential system for the newly discovered cubically nonlinear integrable Camassa-Holm type equation. From the exterior differential system we establish the integrability of this equation. We then study Cartan prolongation structure of this equation. We also discuss the method of identifying conservation laws and Baecklund transformation for this equation from the identified exterior differential system. -- Highlights: → An exterior differential system for a cubic nonlinear integrable equation is given. → The conservation laws from the exterior differential system is derived. → The Baecklund transformation from the Cartan-Ehresmann connection is obtained.

  16. Numerical evidence for bcc ordering at the surface of a critical fcc nucleus

    OpenAIRE

    Wolde, P.R. ten; Ruiz-Montero, M. J.; Frenkel, D.

    1995-01-01

    We report a computer-simulation study of the crystal nucleation barrier and the structure of crystal nuclei in a Lennard-Jones system at moderate supercooling. The stable structure of the Lennard-Jones solid is known to be face-centered cubic. We find that the precritical nuclei are predominantly body-centered cubic ordered. But, as the nucleus grows to its critical size, the core becomes fcc ordered. Surprisingly, however, the interface of the critical nucleus retains a high degree of bcc-li...

  17. The structure model of a cubic aperiodic phase ('quasicrystal without forbidden symmetry axes').

    Science.gov (United States)

    Kraposhin, V S; Talis, A L; Thanh Lam, Ha

    2008-03-19

    A model structure of the aperiodic cubic phase (a cubic quasicrystal) has been constructed as a periodical packing of hierarchical octahedral clusters which were composed of truncated tetrahedra (Friauf-Laves polyhedra) and chains of Frank-Kasper polyhedra with 14 vertices. The construction of the hierarchical model for the cubic aperiodic phase became possible due to the discovery of a new space subdivision with equal edges and with vertices belonging to two orbits of the space group Fm3m. The subdivision is characterized by unique values and unique relations between the coordinates of the starting points of two orbits. Calculated x-ray diffraction patterns for the proposed hierarchical model are in qualitative agreement with published experimental x-ray patterns for aperiodical phases observed in melt-quenched Mg-Al and Fe-Nb-B-Si alloys.

  18. Unique Bonding Properties of the Au36(SR)24 Nanocluster with FCC-Like Core.

    Science.gov (United States)

    Chevrier, Daniel M; Chatt, Amares; Zhang, Peng; Zeng, Chenjie; Jin, Rongchao

    2013-10-03

    The recent discovery on the total structure of Au36(SR)24, which was converted from biicosahedral Au38(SR)24, represents a surprising finding of a face-centered cubic (FCC)-like core structure in small gold-thiolate nanoclusters. Prior to this finding, the FCC feature was only expected for larger (nano)crystalline gold. Herein, we report results on the unique bonding properties of Au36(SR)24 that are associated with its FCC-like core structure. Temperature-dependent X-ray absorption spectroscopy (XAS) measurements at the Au L3-edge, in association with ab initio calculations, show that the local structure and electronic behavior of Au36(SR)24 are of more molecule-like nature, whereas its icosahedral counterparts such as Au38(SR)24 and Au25(SR)18 are more metal-like. Moreover, site-specific S K-edge XAS studies indicate that the bridging motif for Au36(SR)24 has different bonding behavior from the staple motif from Au38(SR)24. Our findings highlight the important role of "pseudo"-Au4 units within the FCC-like Au28 core in interpreting the bonding properties of Au36(SR)24 and suggest that FCC-like structure in gold thiolate nanoclusters should be treated differently from its bulk counterpart.

  19. Applications of Cubic MgZnO Thin Films in Metal-Insulator-Silicon Structures

    Institute of Scientific and Technical Information of China (English)

    LIANG Jun; WU Hui-Zhen; LAO Yan-Feng; QIU Dong-Jiang; CHEN Nai-Bo; XU Tian-Ning

    2004-01-01

    @@ Cubic Mgo.55Zno.45O thin film alloys have been deposited on Si substrates at low growth temperature. The topography of the cross section of the epitaxial film by scanning electronic microscope demonstrates good mor phology and high interfacial quality. The high (001) orientation and wide band-gap (Eg > 5.5 eV) of the cubic Mgo.55Zno.45 O thin films accord with the guidelines for metal-insulator-silicon (MIS) device applications. Using the cubic ternary thin films as insulators, MIS structures have been fabricated. The capacitance-voltage measurements show the flat band voltage shift VFB of11.8 V and mobile ion density Dmc of 5.57 × 1010 cm-2 for the MIS structure. Leakage current density as low as ~ 10-7 A/cm2 is obtained at E = 700 kV/cm by the currentvoltage measurements. These unique structural and electrical properties of the fabricated MIS devices indicate that cubic MgZnO materials could become a new candidate for high-κ dielectrics used in silicon integrated circuit technologies.

  20. FCC-HCP coexistence in dense thermo-responsive microgel crystals

    Science.gov (United States)

    Karthickeyan, D.; Joshi, R. G.; Tata, B. V. R.

    2017-06-01

    Analogous to hard-sphere suspensions, monodisperse thermo-responsive poly (N-isopropyl acrylamide) (PNIPAM) microgel particles beyond a volume fraction (ϕ) of 0.5 freeze into face centered cubic (FCC)-hexagonal close packed (HCP) coexistence under as prepared conditions and into an FCC structure upon annealing. We report here FCC-HCP coexistence to be stable in dense PNIPAM microgel crystals (ϕ > 0.74) with particles in their deswollen state (referred to as osmotically compressed microgel crystals) and the FCC structure with particles in their swollen state by performing annealing studies with different cooling rates. The structure of PNIPAM microgel crystals is characterized using static light scattering technique and UV-Visible spectroscopy and dynamics by dynamic light scattering (DLS). DLS studies reveal that the particle motion is diffusive at short times in crystals with ϕ 0.74. The observed sub-diffusive behavior at short times is due to the overlap (interpenetration) of the dangling polymer chains between the shells of neighbouring PNIPAM microgel particles. Overlap is found to disappear upon heating the crystals well above their melting temperature, Tm due to reduction in the particle size. Annealing studies confirm that the overlap of dangling polymer chains between the shells of neighbouring PNIPAM spheres is responsible for the stability of FCC-HCP coexistence observed in osmotically compressed PNIPAM microgel crystals. Results are discussed in the light of recent reports of stabilizing the HCP structure in hard sphere crystals by adding interacting polymer chains.

  1. Face-Centered-Cubic Nanostructured Polymer Foams

    Science.gov (United States)

    Cui, C.; Baughman, R. H.; Liu, L. M.; Zakhidov, A. A.; Khayrullin, I. I.

    1998-03-01

    Beautifully iridescent polymer foams having Fm-3m cubic symmetry and periodicities on the scale of the wavelength of light have been synthesized by the templating of porous synthetic opals. These fabrication processes involve the filling of porous SiO2 opals (with typical cubic lattice parameters of 250 nm) with either polymers or polymer precursors, polymerization of the precursors if necessary, and removal of the fcc array of SiO2 balls to provide an all-polymer structure. The structures of these foams are similar to periodic minimal surfaces, although the Gaussian curvature can have both positive and negative values. Depending upon whether the internal surfaces of the opal are polymer filled or polymer coated, the polymer replica has either one or two sets of independent channels. We fill these channels with semiconductors, metals, or superconductors to provide electronic and optical materials with novel properties dependent on the nanoscale periodicity.

  2. Fabrications of Photonic Bandgap Structures in Si and Ge Substrates Using Laser-Assisted Nanoimprinting of Self-Assembled Nanoparticles

    Science.gov (United States)

    2006-09-01

    and FDTD. The PBG structures were modeled as face center cubic ( FCC ) structure , illustrated in Fig. 19, with different geometry and refractive index...normal incidence to (111) plane of FCC structure (indicated as red arrows in Fig. 23) is labeled in the diagram as red band. When the incident angle is

  3. Crystal structure and optical properties of the [Ag62S12(SBu(t))32](2+) nanocluster with a complete face-centered cubic kernel.

    Science.gov (United States)

    Jin, Shan; Wang, Shuxin; Song, Yongbo; Zhou, Meng; Zhong, Juan; Zhang, Jun; Xia, Andong; Pei, Yong; Chen, Man; Li, Peng; Zhu, Manzhou

    2014-11-05

    The crystal structure of the [Ag62S12(SBu(t))32](2+) nanocluster (denoted as NC-I) has been successfully determined, and it shows a complete face-centered-cubic (FCC) Ag14 core structure with a Ag48(SBu(t))32 shell configuration interconnected by 12 sulfide ions, which is similar to the [Ag62S13(SBu(t))32](4+) structure (denoted as NC-II for short) reported by Wang. Interestingly, NC-I exhibits prominent differences in the optical properties in comparison with the case of the NC-II nanocluster. We employed femtosecond transient absorption spectroscopy to further identify the differences between the two nanoclusters. The results show that the quenching of photoluminescence in NC-I in comparison to that of NC-II is caused by the free valence electrons, which dramatically change the ligand to metal charge transfer (LMCT, S 3p → Ag 5s). To get further insight into these, we carried out time-dependent density functional theory (TDDFT) calculations on the electronic structure and optical absorption spectra of NC-I and NC-II. These findings offer a new insight into the structure and property evolution of silver cluster materials.

  4. Structure and Luminescence Properties of Eu3+-Doped Cubic Mesoporous Silica Thin Films

    Directory of Open Access Journals (Sweden)

    Lu Qingshan

    2010-01-01

    Full Text Available Abstract Eu3+ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol–gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu3+ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of5D0-7F1 and 5D0-7F2 of Eu3+ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu3+ ions-doped mesoporous silica thin films increases linearly with increasing Eu3+ concentration.

  5. Structure and luminescence properties of eu3+-doped cubic mesoporous silica thin films.

    Science.gov (United States)

    Lu, Qingshan; Wang, Zhongying; Wang, Peiyu; Li, Jiangong

    2010-02-11

    Eu3+ ions-doped cubic mesoporous silica thin films with a thickness of about 205 nm were prepared on silicon and glass substrates using triblock copolymer as a structure-directing agent using sol-gel spin-coating and calcination processes. X-ray diffraction and transmission electron microscopy analysis show that the mesoporous silica thin films have a highly ordered body-centered cubic mesoporous structure. High Eu3+ ion loading and high temperature calcination do not destroy the ordered cubic mesoporous structure of the mesoporous silica thin films. Photoluminescence spectra show two characteristic emission peaks corresponding to the transitions of5D0-7F1 and 5D0-7F2 of Eu3+ ions located in low symmetry sites in mesoporous silica thin films. With the Eu/Si molar ratio increasing to 3.41%, the luminescence intensity of the Eu3+ ions-doped mesoporous silica thin films increases linearly with increasing Eu3+ concentration.

  6. Oxidation of Membrane Curvature-Regulating Phosphatidylethanolamine Lipid Results in Formation of Bilayer and Cubic Structures.

    Science.gov (United States)

    Sankhagowit, Shalene; Lee, Ernest Y; Wong, Gerard C L; Malmstadt, Noah

    2016-03-15

    Oxidation is associated with conditions related to chronic inflammations and aging. Cubic structures have been observed in the smooth endoplasmic reticulum and mitochondrial membranes of cells under oxidative stress (e.g., tumor cells and virus-infected cells). It has been previously suspected that oxidation can result in the rearrangement of lipids from a fluid lamellar phase to a cubic structure in organelles containing membranes enriched with amphiphiles that have nonzero intrinsic curvature, such as phosphatidylethanolamine (PE) and cardiolipin. This study focuses on the oxidation of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), a lipid that natively forms an inverted hexagonal phase at physiological conditions. The oxidized samples contain an approximately 3:2 molar ratio of nonoxidized to oxidized DOPE. Optical microscopy images collected during the hydration of this mixture from a dried film suggest that the system evolves into a coexistence of a stable fluid lamellar phase and transient square lattice structures with unit cell sizes of 500-600 nm. Small-angle X-ray scattering of the same lipid mixture yielded a body-centered Im3m cubic phase with the lattice parameter of 14.04 nm. On average, the effective packing parameter of the oxidized DOPE species was estimated to be 0.657 ± 0.069 (standard deviation). This suggests that the oxidation of PE leads to a group of species with inverted molecular intrinsic curvature. Oxidation can create amphiphilic subpopulations that potently impact the integrity of the membrane, since negative Gaussian curvature intrinsic to cubic phases can enable membrane destabilization processes.

  7. Modulating fcc and hcp Ruthenium on the Surface of Palladium-Copper Alloy through Tunable Lattice Mismatch.

    Science.gov (United States)

    Yao, Yancai; He, Dong Sheng; Lin, Yue; Feng, Xiaoqian; Wang, Xin; Yin, Peiqun; Hong, Xun; Zhou, Gang; Wu, Yuen; Li, Yadong

    2016-04-25

    Herein, we report an epitaxial-growth-mediated method to grow face-centered cubic (fcc) Ru, which is thermodynamically unfavorable in the bulk form, on the surface of Pd-Cu alloy. Induced by the galvanic replacement between Ru and Pd-Cu alloy, a shape transformation from a Pd-Cu@Ru core-shell to a yolk-shell structure was observed during the epitaxial growth. The successful coating of the unconventional crystallographic structure is critically dependent on the moderate lattice mismatch between the fcc Ru overlayer and PdCu3 alloy substrate. Further, both fcc and hexagonal close packed (hcp) Ru can be selectively grown through varying the lattice spacing of the Pd-Cu substrate. The presented findings provide a new synthetic pathway to control the crystallographic structure of metal nanomaterials.

  8. Structure analyses of Cu nanoclusters in the soft magnetic Fe85.2Si1B9P4Cu0.8 alloy by XAFS and fcc cluster model

    Science.gov (United States)

    Matsuura, M.; Nishijima, M.; Konno, K.; Ofuchi, H.; Takenaka, K.; Makino, A.

    2016-05-01

    Size of the clusters and structure details of fcc Cu clusters in nanocrystalline soft magnetic alloy of Fe85-86Si1-2B8P4Cu1 (NANOMET) are investigated. A linear combination fitting of XAFS data indicates that about 30% of Cu atoms are partitioned in the fcc clusters and the rest in the amorphous matrix. EXAFS of the fcc Cu nanocluster embedded in amorphous matrix is calculated on the basis of a simple fcc structure model using FEFF9. Surface effect of the nanoclusters is considered by counting a fraction of the nearest neighbour atoms in amorphous matrix. Good agreement with the experimental result is obtained for the fcc nanocluster with 9 coordination shells which consists of total 177 atoms within 1.5 nm in a diameter.

  9. C atom endohedral doping effect on the bond lengths in the crystal structure of fcc-C60

    Directory of Open Access Journals (Sweden)

    S Javanbakht

    2011-03-01

    Full Text Available Single and double equilibrium bond lengths of the fcc-C60 crystal were calculated in the absence and presence of the endohedral C atom as an impurity doped into each C60 cluster, i.e., fcc-C@C60, by means of fully-relaxed self-consistent calculations within the density functtional theory (DFT employing the full potential-augmented plane waves plus local orbital (FP-APW+lo method. The result shows that the single and double bond lengths were decreased for the doped case of fcc-C@C60 when compared with the pure fcc-C60. The reduction in the bond lengths by the carbon impurity doping is attributed to the bond alternation effect and reduction of the symmetry in the C60 molecule. The result shows that the impurity injection gives rise to change in the electron charge distribution and as a result to change in electronic properties.

  10. Magnetic properties of cubic FeCo nanoparticles with anisotropic long chain structure

    Science.gov (United States)

    Liu, Jinming; Wu, Kai; Wang, Jian-Ping

    2016-05-01

    Cubic FeCo alloy nanoparticles (NPs) with body-centered cubic (bcc) phase were prepared using sputter based gas-condensation method. When the NPs formed long chain assemblies, the magnetic properties were quite different from that of well-dispersed NPs. Most of the well-dispersed NPs were superparamagnetic at room temperature while the long chain NP assemblies were ferromagnetic with coercivities around 765 Oe, which displayed quite different magnetic properties. The ferromagnetism of long chain NPs was from the exchange coupling between NPs, which eventually led to the transition from superparamagnetism (SPM) to superferromagetism (SFM). Zero-field-cooled (ZFC) and field-cooled (FC) curves were obtained and long chain NP assemblies displayed ferromagnetism at the temperature ranging from 10 K to 400 K. Time-dependent remanent magnetic moment curves also indicated that the long chain structure had better thermal stability due to the strong exchange coupling.

  11. Magnetic properties of cubic FeCo nanoparticles with anisotropic long chain structure

    Directory of Open Access Journals (Sweden)

    Jinming Liu

    2016-05-01

    Full Text Available Cubic FeCo alloy nanoparticles (NPs with body-centered cubic (bcc phase were prepared using sputter based gas-condensation method. When the NPs formed long chain assemblies, the magnetic properties were quite different from that of well-dispersed NPs. Most of the well-dispersed NPs were superparamagnetic at room temperature while the long chain NP assemblies were ferromagnetic with coercivities around 765 Oe, which displayed quite different magnetic properties. The ferromagnetism of long chain NPs was from the exchange coupling between NPs, which eventually led to the transition from superparamagnetism (SPM to superferromagetism (SFM. Zero-field-cooled (ZFC and field-cooled (FC curves were obtained and long chain NP assemblies displayed ferromagnetism at the temperature ranging from 10 K to 400 K. Time-dependent remanent magnetic moment curves also indicated that the long chain structure had better thermal stability due to the strong exchange coupling.

  12. Synthesis, characterization, and nanoindentation response of single crystal Fe–Cr–Ni alloys with FCC and BCC structures

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Y.Z. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Bei, H., E-mail: beih@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Gao, Y.F., E-mail: ygao7@utk.edu [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Catoor, D. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); George, E.P. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

    2014-08-12

    Fe-based alloys are used extensively in many structural applications including under irradiation conditions in the nuclear industry. In this study, model Fe–Cr, Fe–Ni and Fe–Cr–Ni alloys that are the basis of many structural steels were synthesized as single crystals and characterized. The compositions investigated were Fe–15Cr, Fe–30Cr, Fe–30Ni and Fe–15Cr–15Ni (at%). Several key mechanical properties were determined which will be useful in further studies of irradiation/deformation-induced defects. Incipient plasticity and slip characteristics were investigated by nanoindentation on (001) and (1{sup ¯}10) surfaces, and hardness, modulus, pop-in behavior and theoretical strength were determined. The slip trace patterns after microindentation were imaged in a microscope. A novel slip trace analysis was developed and the underlying deformation mechanisms identified. The analysis shows that under both (001) and (1{sup ¯}10) indentations, the activated slip system for the BCC alloys is {112}〈111〉; for the FCC alloys the activated slip plane is {111}. These results were confirmed with finite element simulations using a slip-based crystal-plasticity model. Finally, the effects of heterogeneous pop-in mechanisms are discussed in the context of incipient plasticity in the four different alloys.

  13. Metal-organic pathways for anisotropic growth of a highly symmetrical crystal structure: example of the fcc Ni.

    Science.gov (United States)

    Mourdikoudis, Stefanos; Collière, Vincent; Amiens, Catherine; Fau, Pierre; Kahn, Myrtil L

    2013-11-05

    The control of the metallic nanocrystal shape is of prime importance for a wide variety of applications. We report a detailed research work on metal-organic chemical routes for the synthesis of a highly symmetrical crystal structure. In particular, this study shows the key parameters ensuring the anisotropic growth of nickel nanostructures (fcc crystal). Numerous reaction conditions are investigated (precursors, solvents, temperature, reducing agents, reaction time, and types and ratios of surfactants, such as alkyl amines, carboxylic acids, and phosphine oxides), and their effects on the size and shape of the final product are reported. The role of the growth modifiers and the structuring of the reaction media on the anisotropic growth are demonstrated. This metal-organic approach generates several novel anisotropic nanostructures in a wide size range depending on the reaction conditions. In this way, nanomaterials with reproducible size, shape, and composition are obtained with good yield. Transmission electron microscopy techniques (TEM and HRTEM) are the principal methods for monitoring the morphology.

  14. Formation of Superlattices of Gold Nanoparticles Using Ostwald Ripening in Emulsions: Transition from fcc to bcc Structure.

    Science.gov (United States)

    Schmitt, Julien; Hajiw, Stéphanie; Lecchi, Amélie; Degrouard, Jéril; Salonen, Anniina; Impéror-Clerc, Marianne; Pansu, Brigitte

    2016-06-30

    An efficient method to form 3D superlattices of gold nanoparticles inside oil emulsion droplets is presented. We demonstrate that this method relies on Ostwald ripening, a well-known phenomenon occurring during the aging of emulsions. The key point is that the nanoparticle concentration inside the smaller droplets is increasing very slowly with time, thus inducing the crystallization of the nanoparticles into superlattices. Using oil-in-water emulsions doped with hydrophobic gold nanoparticles, we demonstrate that this method is efficient for different types of oils (toluene, cyclohexane, dodecane, and hexadecane). 3D superlattices of the nanoparticles are obtained, with dimensions reaching a hundred nanometers. The kinetics of the crystallization depends on the solubility of the oil in water but also on the initial concentration of the gold nanoparticles in oil. This method also provides an innovative way to obtain the complete phase diagram of nanoparticle suspensions with concentration. Indeed, during this slow crystallization process, a transition from a disordered suspension to a fcc structure is observed, followed by a transition toward a bcc structure. This evolution with time provides key results to understand the role played by the ligands located at the surface of the nanoparticles in order to control the type of superlattices which are formed.

  15. The hcp to fcc transformation path of scandium trihydride under high pressure.

    Science.gov (United States)

    Pakornchote, T; Pinsook, U; Bovornratanaraks, T

    2014-01-15

    We used density functional theory to calculate the phase stability of the hcp (hexagonal close packed) and the fcc (face centered cubic) structures of ScH3. The hcp form is stable up to 22 GPa according to the generalized gradient approximation calculation. Then the fcc form becomes energetically more stable. In order to provide insight into the phase transition mechanism, we modeled the hcp to fcc transition by sliding the hcp basal planes, i.e. (001)h planes, in such a way that the ABABAB sequence of the hcp form is altered into the ABCABC sequence of the fcc form. This sliding was suggested by the experiment. The configurations of these sliding steps are our proposed intermediate configurations, whose symmetry group is the Cm group. By using the Cm crystallography, we can match the d-spacings from the lattice planes of the hcp and fcc forms and the intermediate planes measured from the experiment. We also calculated the enthalpy per step, from which the energy barrier between the two phases at various pressures was derived. The barrier at 35 GPa is 0.370 eV per formula or 0.093 eV/atom. The movements of the hydrogen atoms during the hcp to intermediate phase transition are consistent with the result from the Raman spectra.

  16. Cubic AlGaN/GaN structures for device application

    Energy Technology Data Exchange (ETDEWEB)

    Schoermann, Joerg

    2007-05-15

    The aim of this work was the growth and the characterization of cubic GaN, cubic AlGaN/GaN heterostructures and cubic AlN/GaN superlattice structures. Reduction of the surface and interface roughness was the key issue to show the potential for the use of cubic nitrides in futur devices. All structures were grown by plasma assisted molecular beam epitaxy on free standing 3C-SiC (001) substrates. In situ reflection high energy electron diffraction was first investigated to determine the Ga coverage of c-GaN during growth. Using the intensity of the electron beam as a probe, optimum growth conditions were found when a 1 monolayer coverage is formed at the surface. GaN samples grown under these conditions reveal excellent structural properties. On top of the c-GaN buffer c-AlGaN/GaN single and multiple quantum wells were deposited. The well widths ranged from 2.5 to 7.5 nm. During growth of Al{sub 0.15}Ga{sub 0.85}N/GaN quantum wells clear reflection high energy electron diffraction oscillations were observed indicating a two dimensional growth mode. We observed strong room-temperature, ultraviolet photoluminescence at about 3.3 eV with a minimum linewidth of 90 meV. The peak energy of the emission versus well width is reproduced by a square-well Poisson- Schroedinger model calculation. We found that piezoelectric effects are absent in c-III nitrides with a (001) growth direction. Intersubband transition in the wavelength range from 1.6 {mu}m to 2.1 {mu}m was systematically investigated in AlN/GaN superlattices (SL), grown on 100 nm thick c-GaN buffer layers. The SLs consisted of 20 periods of GaN wells with a thickness between 1.5 nm and 2.1 nm and AlN barriers with a thickness of 1.35 nm. The first intersubband transitions were observed in metastable cubic III nitride structures in the range between 1.6 {mu}m and 2.1 {mu}m. (orig.)

  17. Lattice Dynamics of fcc Ca

    DEFF Research Database (Denmark)

    Stassis, C.; Zaretsky, J.; Misemer, D. K.;;

    1983-01-01

    to the propagation of elastic waves. The frequencies of the T1[ξξ0] branch for ξ between approximately 0.5 and 0.8 are slightly above the velocity-of-sound line determined from the low-frequency measurements. Since a similar effect has been observed in FCC Yb, it is natural to assume that the anomalous dispersion......A large single crystal of FCC Ca was grown and was used to study the lattice dynamics of this divalent metal by coherent inelastic neutron scattering. The phonon dispersion curves were measured, at room temperature, along the [ξ00], [ξξ0], [ξξξ], and [0ξ1] symmetry directions. The dispersion curves...... bear a striking resemblance to those of FCC Yb, which is also a divalent metal with an electronic band structure similar to that of Ca. In particular, the shear moduli c44 and (c11-c 12)/2 differ by a factor of 3.4, which implies that FCC Ca (like FCC Yb) is very anisotropic with regard...

  18. Two Types of Novel Feedstock Injection Structures of the FCC Riser Reactor%FCC升降式反应器的两种新式进料结构

    Institute of Scientific and Technical Information of China (English)

    范怡平; 蔡飞鹏; 时铭显; 徐春明

    2004-01-01

    Based on the analysis of flow characteristics of the FCC riser feedstock injection zone, two novel feedstock injection structures are put forward. By investigating three flow parameters in the feedstock injection zone under the three different structures (the traditional and the novel No. 1, No. 2 structures): the local density, the particle backmixng ratio, and the jet eigen-concentration, the flow feature under three structures were obtained. The experimental results demonstrate that the flow features under both proposed structures are obviously improved comparing with those under the traditional structure. Especially, the performance of the deflector-structured No. 2is more desirable than that of No. 1.

  19. Atomistic study on the FCC/BCC interface structure with {112}KS orientation

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Keonwook [Los Alamos National Laboratory; Beyerlein, Irene [Los Alamos National Laboratory

    2011-09-23

    In this study, atomistic simulation is used to explore the atomic interface structure, the intrinsic defect network, and mechanism of twin formation from the {112}KS Cu-Nb interface. The interface structure of different material systems AI-Fe and AI-Nb are also compared with Cu-Nb interface.

  20. A new Bcc-Fcc orientation relationship observed between ferrite and austenite in solidification structures of steels

    Science.gov (United States)

    Headley, T. J.; Brooks, J. A.

    2002-01-01

    A new crystallographic orientation relationship (OR) between delta-ferrite and austenite has been observed in solidification microstructures of 304L and 309S austenitic stainless steels and a ternary Fe-Cr-Ni alloy. Evidence for the new OR was obtained from electron diffraction patterns in transmission electron microscopy (TEM). This relationship, (111)fcc//(110)bcc and [bar 110]_{fcc} //[bar 110]_{bcc} , has not been previously reported for bcc-fcc systems. The fcc//#x2329;110>bcc alignment is distinctive among known bcc-fcc ORs. The new OR is related to the Kurdjumov-Sachs (K-S) and Nishiyama-Wassermann (N-W) ORs by relative rotations of 35.26 and 30 deg, respectively, about the normal to the parallel close-packed planes. In 304L fabricated by laser-engineered net shaping (LENS), delta-ferrite with the new OR was found to coexist in the microstructure with both K-S and N-W oriented ferrite, but in separate austenite grains and with less frequent occurrence. In gas-tungsten arc (GTA) welds of 309S and the Fe-Cr-Ni alloy, the new OR was the only one observed within a few grains, whereas ferrite within other grains did not establish an apparent OR with the austenite matrix.

  1. Phase stability, electronic structure and equation of state of cubic TcN from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Song, T., E-mail: songting_lzjtu@yeah.net [School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070 (China); School of Material Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Ma, Q. [School of Material Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Sun, X.W., E-mail: xsun@carnegiescience.edu [School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070 (China); Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (United States); Liu, Z.J., E-mail: liuzj_lzcu@163.com [School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070 (China); Department of Physics, Lanzhou City University, Lanzhou 730070 (China); Fu, Z.J. [School of Electrical and Electronic Engineering, Chongqing University of Arts and Sciences, Chongqing 402160 (China); Wei, X.P.; Wang, T.; Tian, J.H. [School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070 (China)

    2016-09-07

    The phase transition, electronic band structure, and equation of state (EOS) of cubic TcN are investigated by first-principles pseudopotential method based on density-functional theory. The calculated enthalpies show that TcN has a transformation between zincblende and rocksalt phases and the pressure determined by the relative enthalpy is 32 GPa. The calculated band structure indicates the metallic feature and it might make cubic TcN a better candidate for hard materials. Particular attention is paid to the predictions of volume, bulk modulus and its pressure derivative which play a central role in the formulation of approximate EOSs using the quasi-harmonic Debye model. - Highlights: • The phase transition pressure and electronic band structure for cubic TcN are determined. • Particular attention is paid to investigate the equation of state parameters for cubic TcN. • The thermodynamic properties up to 80 GPa and 3000 K are successfully predicted.

  2. Nonlinearities in composition dependence of structure parameters and magnetic properties of nanocrystalline fcc/bcc-mixed Co-Ni-Fe thin films

    NARCIS (Netherlands)

    Chechenin, N. G.; Khomenko, E. V.; Vainchtein, D. I.; De Hosson, J. Th. M.

    2008-01-01

    In this report, the nonlinearities are analyzed in fcc-to-bcc (fcc/bcc) population ratio, lattice parameters (a(exp)(fcc)/a(ideal)(fcc) and a(exp)(bcc)/a(ideal)(bcc)) and saturation magnetization (I(S)(obs)/I(S)(a)) of the electrodeposited thin Co-Fe-Ni films as a function of average number of elect

  3. Size dependence of cubic to trigonal structural distortion in silver micro- and nanocrystals under high pressure

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Qixum [Los Alamos National Laboratory; Zhao, Yusheng [Los Alamos National Laboratory; Zin, Zhijun [Los Alamos National Laboratory; Wang, Zhongwu [CORNELL UNIV; Skrabalak, Sara E [INDIANA UNIV; Xia, Younan [WASHINGTON UNIV

    2008-01-01

    Silver micro- and nanocrystals with sizes of {approx}2--3.5 {mu}m and {approx}50--100 nm were uniaxially compressed under nonhydrostatic pressures (strong deviatoric stress) up to {approx}30 GPa at room temperature in a symmetric diamond-anvil cell and studied in situ using angle-dispersive synchrotron X-ray diffraction. A cubic to trigonal structural distortion along a 3-fold rotational axis was discovered by careful and comprehensive analysis of the apparent lattice parameter and full width at half-maximum, which are strongly dependent upon the Miller index and crystal size.

  4. FCC-ee Overview

    CERN Document Server

    Zimmermann, F; Benedikt, M; Burkhardt, H; Cerutti, F; Ferrari, A; Gutleber, J; Haerer, B; Holzer, B; Jensen, E; Kersevan, R; Lebrun, P; Martin, R; Mereghetti, A; Osborne, J; Papaphilippou, Y; Schulte, D; Tomas, R; Wenninger, J; Blondel, A; Koratzinos, M; Boscolo, M; Lari, L; Furukawa, K; Ohmi, K; Oide, K; White, S; Bogomyagkov, A; Koop, I; Levichev, E; Muchnoi, N; Nikitin, S; Shatilov, D; Wienands, U; Gianfelice, E; Medina, L

    2015-01-01

    The FCC-ee is a proposed circular e+e- collider installed in a new 100 km tunnel delivering high luminosity to four experiments at centre-of-mass energies ranging from 91 GeV (Z pole) over 160 GeV (W threshold) and 240 GeV (H production) to 350 GeV (t physics). The FCC-ee design is pursued as part of the global Future Circular Collider (FCC) study, which regards the FCC-ee as a potential intermediate step towards a 100-TeV hadron collider, called FCC-hh, sharing the same tunnel infrastructure. We here report the FCC-ee design status.

  5. Use of Shape Memory Alloys in the Robust Control of Smart Structures

    Science.gov (United States)

    1993-08-01

    o.W w’,. Xi) 18 2.3.4 Phase Transformation and Shape Recovery In-TI alloys in a certain composition range have a FCC structure as a parent phase and...Alloy Films Alloys in the composition range of 15-30 at% thallium are known to have a face centered cubic( FCC ) structure as a parent phase which...24 Structure of as-deposited alloys In-TI alloys in a certain composition range have a face centered cubic( FCC ) structure as a parent phase and

  6. Graphene oxide-templated synthesis of ultrathin or tadpole-shaped au nanowires with alternating hcp and fcc domains.

    Science.gov (United States)

    Huang, Xiao; Li, Shaozhou; Wu, Shixin; Huang, Yizhong; Boey, Freddy; Gan, Chee Lip; Zhang, Hua

    2012-02-14

    Ultrathin Au nanowires (AuNWs) and tadpole-shaped nanowires are synthesized on graphene oxide (GO) sheet templates. For the first time, 1.6 nm-diameter AuNWs are shown to contain hexagonal close-packed (hcp) crystal domains, and the tadpole-shaped nanowires exhibit alternating sets of hcp and face-centered cubic (fcc) structures, associated with variation in wire thickness.

  7. EXTENDED CORE STRUCTURE OF DISSOCIATED EDGE DISLOCATIONS IN FCC CRYSTALS WITH CONSIDERATION OF DISCRETENESS

    Institute of Scientific and Technical Information of China (English)

    Xiaozhi Wu; Shaofeng Wang; Huili Zhang

    2008-01-01

    The extended core structure of the dissociated edge dislocation in Al,Au,Ag,Cu and Ni is determined within lattice theory of dislocation.The 2D dislocation equation governing the displacements is coupled by the restoring forces that are determined by the parameterization of the generalized stacking fault energies.The Ritz variational method is presented to solve the dislocation equation and the trial solution is constituted by two arctan-type functions with two undetermined parameters.The core widths of partial dislocations are wider than that obtained in generalized Peierls-Nabarro model due to the consideration of discreteness of crystal.

  8. Shear moduli in bcc-fcc structure transition of colloidal crystals.

    Science.gov (United States)

    Zhou, Hongwei; Xu, Shenghua; Sun, Zhiwei; Zhu, Ruzeng

    2015-10-14

    Shear moduli variation in the metastable-stable structure transition of charged colloidal crystals was investigated by the combination techniques of torsional resonance spectroscopy and reflection spectrometer. Modulus of the system increases with the proceeding of the transition process and it finally reaches the maximum value at the end of the transition. For colloidal crystals in stable state, the experimental moduli show good consistence with theoretical expectations. However, in the transition process, the moduli are much smaller than theoretical ones and this can be chalked up to crystalline imperfection in the transition state.

  9. Shear moduli in bcc-fcc structure transition of colloidal crystals

    Science.gov (United States)

    Zhou, Hongwei; Xu, Shenghua; Sun, Zhiwei; Zhu, Ruzeng

    2015-10-01

    Shear moduli variation in the metastable-stable structure transition of charged colloidal crystals was investigated by the combination techniques of torsional resonance spectroscopy and reflection spectrometer. Modulus of the system increases with the proceeding of the transition process and it finally reaches the maximum value at the end of the transition. For colloidal crystals in stable state, the experimental moduli show good consistence with theoretical expectations. However, in the transition process, the moduli are much smaller than theoretical ones and this can be chalked up to crystalline imperfection in the transition state.

  10. Is inner core seismic anisotropy a marker of plastic flow of cubic iron?

    CERN Document Server

    Lincot, A; Cardin, Philippe

    2015-01-01

    This paper investigates whether observations of seismic anisotropy are compatible with a cubic structure of the inner core Fe alloy. We assume that anisotropy is the result of plastic deformation within a large scale flow induced by preferred growth at the inner core equator. Based on elastic moduli from the literature, bcc- or fcc-Fe produce seismic anisotropy well below seismic observations ($\\textless{}0.4\\%$). A Monte-Carlo approach allows us to generalize this result to any form of elastic anisotropy in a cubic system. Within our model, inner core global anisotropy is not compatible with a cubic structure of Fe alloy. Hence, if the inner core material is indeed cubic, large scale coherent anisotropic structures, incompatible with plastic deformation induced by large scale flow, must be present.

  11. Structural and optoelectronic properties of cubic perovskite RbPbF3

    Indian Academy of Sciences (India)

    K Ephraim Babu; N Murali; D Tirupathi Swamy; V Veeraiah

    2014-04-01

    The structural and optoelectronic properties of cubic perovskite RbPbF 3 are calculated using all electrons full potential linearized augmented plane wave (FP-LAPW) method. The calculated lattice constant is in good agreement with the experimental result. The calculated band structure shows a direct band gap of 3.07 eV. The contribution of different bands is analysed from the total and partial density of state curves. We identified hybridization of Pb , Pb states with F states in the valence bonding region. Calculations of the optical spectra, viz., the dielectric function, optical reflectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss are performed for the energy range of 0-30 eV. Based on the direct bandgap, as well as other optical properties of the compound, it is predicted that this material is useful for vacuum-ultraviolet-transparent (VUV-transparent) applications.

  12. Systematic study of grain boundary atomistic structures and related properties in cubic zirconia bicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Shibata, N.; Ikuhara, Y. [Inst. of Engineering Innovation, Univ. of Tokyo, Tokyo (Japan); Oba, F. [Dept. of Materials Science and Engineering, Graduate School of Engineering, Kyoto Univ., Kyoto (Japan); Yamamoto, T. [Dept. of Advanced Materials Science, Graduate School of Frontier Science, Univ. of Tokyo, Kashiwa, Chiba (Japan)

    2005-02-01

    Systematic grain boundary study of cubic zirconia has been conducted by using bicrystals. It is clearly demonstrated that grain boundary atomistic structures dramatically change according to the misorientations and plane orientations of the boundaries, resulting in a dramatic change of excess energies and solute segregation behaviors. Combining with theoretical calculations, it is found that grain boundaries possess unique coordination-deficient cation sites at the cores, and their densities have a clear correlation with these properties in high-angle grain boundaries. This result indicates that grain boundary properties in ceramics are possibly determined by the accumulation of coordination-deficient sites. Thus, systematic grain boundary study using bicrystal offers fundamental understandings of the relationship between atomistic structures and properties in ceramic grain boundaries. (orig.)

  13. Phase transition from fcc to bcc structure of the Cu-clusters during nanocrystallization of Fe85.2Si1B9P4Cu0.8 soft magnetic alloy

    Directory of Open Access Journals (Sweden)

    Masahiko Nishijima

    2014-05-01

    Full Text Available A role of Cu on the nanocrystallization of an Fe85.2Si1B9P4Cu0.8 alloy was investigated by X-ray absorption fine structure (XAFS and transmission electron microscopy (TEM. The Cu K-edge XAFS results show that local structure around Cu is disordered for the as-quenched sample whereas it changes to fcc-like structure at 613 K. The fcc Cu-clusters are, however, thermodynamically unstable and begin to transform into bcc structure at 638 K. An explicit bcc structure is observed for the sample annealed at 693 K for 600 s in which TEM observation shows that precipitated bcc-Fe crystallites with ∼12 nm are homogeneously distributed. The bcc structure of the Cu-clusters transforms into the fcc-type again at 973 K, which can be explained by the TEM observations; Cu segregates at grain boundaries between bcc-Fe crystallites and Fe3(B,P compounds. Combining the XAFS results with the TEM observations, the structure transition of the Cu-clusters from fcc to bcc is highly correlated with the preliminary precipitation of the bcc-Fe which takes place prior to the onset of the first crystallization temperature, Tx1 = 707 K. Thermodynamic analysis suggests that an interfacial energy density γ between an fcc-Cu cluster and bcc-Fe matrix dominates at a certain case over the structural energy between fcc and bcc Cu, ΔGfcc − bcc, which causes phase transition of the Cu clusters from fcc to bcc structure.

  14. Effect of shear on cubic phases in gels of a diblock copolymer

    DEFF Research Database (Denmark)

    Hamley, I.W.; Pople, J.A.; Fairclough, J.P.A.;

    1998-01-01

    The effect of shear on the orientation of cubic micellar phases formed by a poly(oxyethylene)poly(oxybutylene) diblock copolymer in aqueous solution has been investigated using small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS). SAXS was performed on samples oriented in...... to form a macroscopically oriented domain. Shear only homogenized the sample, producing a powder SAXS pattern from a fcc structure....

  15. Weyl points and topological nodal superfluids in a face-centered-cubic optical lattice

    Science.gov (United States)

    Lang, Li-Jun; Zhang, Shao-Liang; Law, K. T.; Zhou, Qi

    2017-07-01

    We point out that a face-centered-cubic (fcc) optical lattice, which can be realized by a simple scheme using three lasers, provides one a highly controllable platform for creating Weyl points and topological nodal superfluids in ultracold atoms. In noninteracting systems, Weyl points automatically arise in the Floquet band structure when shaking such fcc lattices, and sophisticated design of the tunneling is not required. More interestingly, in the presence of attractive interaction between two hyperfine spin states, which experience the same shaken fcc lattice, a three-dimensional topological nodal superfluid emerges, and Weyl points show up as the gapless points in the quasiparticle spectrum. One could either create a double Weyl point of charge 2, or split it into two Weyl points of charge 1, which can be moved in the momentum space by tuning the interactions. Correspondingly, the Fermi arcs at the surface may be linked with each other or separated as individual ones.

  16. Ferromagnetic properties of fcc Gd thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bertelli, T. P., E-mail: tambauh@gmail.com; Passamani, E. C.; Larica, C.; Nascimento, V. P.; Takeuchi, A. Y. [Universidade Federal do Espírito Santo, Departamento de Física, Vitória/ES 29075-910 (Brazil); Pessoa, M. S. [Universidade Federal do Espírito Santo, Departamento de Ciências Naturais, São Mateus/ES 29932-540 (Brazil)

    2015-05-28

    Magnetic properties of sputtered Gd thin films grown on Si (100) substrates kept at two different temperatures were investigated using X-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements. The obtained Gd thin films have a mixture of hcp and fcc structures, but with their fractions depending on the substrate temperature T{sub S} and film thickness x. Gd fcc samples were obtained when T{sub S} = 763 K and x = 10 nm, while the hcp structure was stabilized for lower T{sub S} (300 K) and thicker film (20 nm). The fcc structure is formed on the Ta buffer layer, while the hcp phase grows on the fcc Gd layer as a consequence of the lattice relaxation process. Spin reorientation phenomenon, commonly found in bulk Gd species, was also observed in the hcp Gd thin film. This phenomenon is assumed to cause the magnetization anomalous increase observed below 50 K in stressed Gd films. Magnetic properties of fcc Gd thin films are: Curie temperature above 300 K, saturation magnetization value of about 175 emu/cm{sup 3}, and coercive field of about 100 Oe at 300 K; features that allow us to classify Gd thin films, with fcc structure, as a soft ferromagnetic material.

  17. Structure imaging and vanadium substitution in cubic TiCr2 Laves phase

    Science.gov (United States)

    Ghosh, Chanchal; Sharma, Vinit; Basu, Joysurya; Ramachandran, Divakar; Mohandas, E.

    2015-08-01

    Properties of Laves phase compounds can be tailored by alloying and microstructural engineering. V-substituted cubic TiCr2 Laves phase has been studied to understand the location of V atoms in the lattice, by structural imaging and first-principle computations. Even though Ti, V and Cr appear next to each other in the periodic table, V preferentially replaces the Ti lattice producing anti-site defects. The defect formation energy for V substitution in Ti and in Cr lattice is 0.29 and 0.40 eV, respectively. V replacement in the Ti lattice generates atomic scale strain. Atomic numbers of V, Ti and Cr being very close, this phase is not quite suitable for incoherent imaging for understanding the structure and the chemistry. Instead, difference in channelling behaviour of electron waves along the Ti columns and along the Cr columns could be exploited to preferentially image the individual atom columns. Nature of the exit phase wave, phase and amplitude has been used to understand the contrast qualitatively. The intensity distribution of any particular atom column that is disturbed by the presence of foreign atom has been used to detect the position of V atoms. This method could be extended to study other Laves phases and complex intermetallic structures to understand their structure, defects and interfaces.

  18. Phase transition from fcc to bcc structure of the Cu-clusters during nanocrystallization of Fe85.2Si1B9P4Cu0.8 soft magnetic alloy

    OpenAIRE

    Masahiko Nishijima; Makoto Matsuura; Kana Takenaka; Akira Takeuchi; Hironori Ofuchi; Akihiro Makino

    2014-01-01

    A role of Cu on the nanocrystallization of an Fe85.2Si1B9P4Cu0.8 alloy was investigated by X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM). The Cu K-edge XAFS results show that local structure around Cu is disordered for the as-quenched sample whereas it changes to fcc-like structure at 613 K. The fcc Cu-clusters are, however, thermodynamically unstable and begin to transform into bcc structure at 638 K. An explicit bcc structure is observed for the sample an...

  19. Jubilite: A 4-,8-connected Cubic Structural Pattern in Space Group Pm3

    Directory of Open Access Journals (Sweden)

    Eduardo A. Castro

    2005-05-01

    Full Text Available Abstract: In the course of investigating structural modifications of the 3-,4-connected net known as the Pt3O4 structure-type (waserite, a novel 4-,8-connected structure-type was discovered. This lattice is generated by replacing the 3-connected trigonal planar vertices of the Pt3O4 structure-type with 4-connected tetrahedral vertices, to achieve a structure which possesses a generic empirical formula of JK6L8. In such a topological modification, the four 3-fold axes of the parent cubic, Pm3n, Pt3O4 structure-type are retained. Thus the 4-connected tetrahedral vertices are oriented so as to preserve cubic symmetry in the resulting Pm3, JK6L8 (jubilite lattice. The unit cell contains a single 8-connected cubecentered vertex, six 4-connected distorted square planar vertices and eight 4-connected distorted tetrahedral vertices. It is a Wellsean structure with a Wells point symbol given by (4166484(42826(43838 and a Schläfli symbol of (53/4, 4.2667. This latter index reveals a decrease in the lattice’s polygonality and concomitant increase in the connectivity through the transformation from waserite to jubilite. The topology of the parent waserite lattice (Pt3O4 corresponds to that of the Catalan structures with the Wells point symbol (843(834, which has the Schläfli symbol (8, 3.4285. Finally, it can be seen that a sequence of structure-types starting with waserite (Pt3O4 and moving to jubilite (JK6L8 and finally to fluorite (CaF2 represents a continuous crystallographic structural transformation in which the symmetry and topology undergo concomitant changes from one structure-type (waserite to the other structure-types. The topology of the fluorite lattice, represented by the Wells point symbol (424(462, and the Schläfli symbol (4, 51/3, indicates a discontinuous topological transformation from the intermediate jubilite lattice; like the discontinuous topological transformation from Pt3O4 to JK6L8; in which the

  20. Observation of Body-Centered Cubic Gold Nanocluster.

    Science.gov (United States)

    Liu, Chao; Li, Tao; Li, Gao; Nobusada, Katsuyuki; Zeng, Chenjie; Pang, Guangsheng; Rosi, Nathaniel L; Jin, Rongchao

    2015-08-17

    The structure of nanoparticles plays a critical role in dictating their material properties. Gold is well known to adopt face-centered cubic (fcc) structure. Herein we report the first observation of a body-centered cubic (bcc) gold nanocluster composed of 38 gold atoms protected by 20 adamantanethiolate ligands and two sulfido atoms ([Au38S2(SR)20], where R=C10H15) as revealed by single-crystal X-ray crystallography. This bcc structure is in striking contrast with the fcc structure of bulk gold and conventional Au nanoparticles, as well as the bi-icosahedral structure of [Au38(SCH2CH2Ph)24]. The bcc nanocluster has a distinct HOMO-LUMO gap of ca. 1.5 eV, much larger than the gap (0.9 eV) of the bi-icosahedral [Au38(SCH2CH2Ph)24]. The unique structure of the bcc gold nanocluster may be promising in catalytic applications.

  1. The Relationship Between Atomic Structure and Strain Distribution of Misfit Dislocation Cores at Cubic Heteroepitaxial Interfaces.

    Science.gov (United States)

    Wen, Cai

    2017-03-09

    The atomic reconstruction of a misfit dislocation (MD) core causes change in the strain distribution around the core. Several MD cores at the AlSb/GaAs (001) cubic zincblende interface, including a symmetrical glide set Lomer dislocation (LD), a left-displaced glide set LD, a glide set LD with an atomic step, a symmetrical shuffle set LD, and a 60° dislocation pair, were studied using simulated projected potential and aberration-corrected transmission electron microscope images. Image deconvolution was also used to restore structure images from nonoptimum-defocus images. The corresponding biaxial strain maps, ε xx (in-plane) and ε yy (out-of-plane), were obtained by geometric phase analysis using the GaAs substrate as the reference lattice. The results show that atomic structure characteristics of MD cores can be revealed by the strain maps. The strain maps should be measured from optimum-defocus images or restored structure images. Furthermore, the ε xx strain map has been found more accurate than the ε yy strain map for MD cores, and the specimen thickness should be below the critical thickness due to the influence of dynamical scattering.

  2. Thickness dependencies of structural and magnetic properties of cubic and tetragonal Heusler alloy bilayer films

    Science.gov (United States)

    Ranjbar, R.; Suzuki, K. Z.; Sugihara, A.; Ando, Y.; Miyazaki, T.; Mizukami, S.

    2017-07-01

    The thickness dependencies of the structural and magnetic properties for bilayers of cubic Co-based Heusler alloys (CCHAs: Co2FeAl (CFA), Co2FeSi (CFS), Co2MnAl (CMA), and Co2MnSi (CMS)) and D022-MnGa were investigated. Epitaxy of the B2 structure of CCHAs on a MnGa film was achieved; the smallest thickness with the B2 structure was found for 3-nm-thick CMS and CFS. The interfacial exchange coupling (Jex) was antiferromagnetic (AFM) for all of the CCHAs/MnGa bilayers except for unannealed CFA/MnGa samples. A critical thickness (tcrit) at which perpendicular magnetization appears of approximately 4-10 nm for the CMA/MnGa and CMS/MnGa bilayers was observed, whereas this thickness was 1-3 nm for the CFA/MnGa and CFS/MnGa films. The critical thickness for different CCHAs materials is discussed in terms of saturation magnetization (Ms) and the Jex .

  3. The structure, thermal properties and phase transformations of the cubic polymorph of magnesium tetrahydroborate.

    Science.gov (United States)

    David, W I F; Callear, S K; Jones, M O; Aeberhard, P C; Culligan, S D; Pohl, A H; Johnson, S R; Ryan, K R; Parker, J E; Edwards, P P; Nuttall, C J; Amieiro-Fonseca, A

    2012-09-07

    The structure of the cubic polymorph of magnesium tetrahydroborate (γ-Mg(BH(4))(2)) has been determined in space group Ia3d from a structural database of the isoelectronic compound SiO(2); this has been corroborated by DFT calculations. The structure is found to concur with that recently determined by Filinchuk et al. (Y. Filinchuk, B. Richter, T. R. Jensen, V. Dmitriev, D. Chernyshov and H. Hagemann, Angew. Chem. Int. Ed., 2011, DOI: 10.1002/anie.201100675). The phase transformations and subsequent decomposition of γ-Mg(BH(4))(2) on heating have been ascertained from variable-temperature synchrotron X-ray diffraction data combined with thermogravimetric and mass spectrometry measurements. At ~160 °C, conversion to a disordered variant of the β-Mg(BH(4))(2) phase (denoted as β') is observed along with a further unidentified polymorph. There is evidence of amorphous phases during decomposition but there is no direct crystallographic indication of the existence of Mg(B(12)H(12)) or other intermediate Mg-B-H compounds. MgH(2) and finally Mg are observed in the X-ray diffraction data after decomposition.

  4. Diffusion of interstitial Dumbell in FCC concentrated alloys: connection with the percolation; Diffusion du defaut interstitiel dans un alliage concentre de structure CFC: lien avec la percolation

    Energy Technology Data Exchange (ETDEWEB)

    Bocquet, J.L.

    1993-12-31

    The migration mechanism of the interstitial dumbbell in a FCC (face centered cubic) lattice constrains its path on a sublattice with a coordination number of 8. In a random binary alloy AB, in which only species B has a noticeable mobility, the long range migration of the dumbbell defect is possible only if the concentration of B is larger than the percolation threshold {rho}{sub c} on the sublattice. Standard techniques have been employed to get a first evaluation of this threshold: the cluster density n(s) is obtained after an automatic counting of the clusters up to a size of 15 and a d-Log Pade approximants analysis of the various moments of this density function is performed. The use of a recent conjecture concerning the critical behaviour of the moments of n(s) in the neighbourhood of {rho}{sub c} helps us to extract simultaneously from our data reasonable values of the critical exponents {beta} and {alpha}, together with a value of {rho}{sub c} = 0.2780 + 0.0005. (Author). 16 refs., 15 figs., 7 tabs.

  5. Phase field theory of interfaces and crystal nucleation in a eutectic system of fcc structure: I. Transitions in the one-phase liquid region.

    Science.gov (United States)

    Tóth, Gyula I; Gránásy, László

    2007-08-21

    The phase field theory (PFT) has been applied to predict equilibrium interfacial properties and nucleation barrier in the binary eutectic system Ag-Cu using double well and interpolation functions deduced from a Ginzburg-Landau expansion that considers fcc (face centered cubic) crystal symmetries. The temperature and composition dependent free energies of the liquid and solid phases are taken from CALculation of PHAse Diagrams-type calculations. The model parameters of PFT are fixed so as to recover an interface thickness of approximately 1 nm from molecular dynamics simulations and the interfacial free energies from the experimental dihedral angles available for the pure components. A nontrivial temperature and composition dependence for the equilibrium interfacial free energy is observed. Mapping the possible nucleation pathways, we find that the Ag and Cu rich critical fluctuations compete against each other in the neighborhood of the eutectic composition. The Tolman length is positive and shows a maximum as a function of undercooling. The PFT predictions for the critical undercooling are found to be consistent with experimental results. These results support the view that heterogeneous nucleation took place in the undercooling experiments available at present. We also present calculations using the classical droplet model [classical nucleation theory (CNT)] and a phenomenological diffuse interface theory (DIT). While the predictions of the CNT with a purely entropic interfacial free energy underestimate the critical undercooling, the DIT results appear to be in a reasonable agreement with the PFT predictions.

  6. Design of new face-centered cubic high entropy alloys by thermodynamic calculation

    Science.gov (United States)

    Choi, Won-Mi; Jung, Seungmun; Jo, Yong Hee; Lee, Sunghak; Lee, Byeong-Joo

    2017-09-01

    A new face-centered cubic (fcc) high entropy alloy system with non-equiatomic compositions has been designed by utilizing a CALculation of PHAse Diagram (CALPHAD) - type thermodynamic calculation technique. The new alloy system is based on the representative fcc high entropy alloy, the Cantor alloy which is an equiatomic Co- Cr-Fe-Mn-Ni five-component alloy, but fully or partly replace the cobalt by vanadium and is of non-equiatomic compositions. Alloy compositions expected to have an fcc single-phase structure between 700 °C and melting temperatures are proposed. All the proposed alloys are experimentally confirmed to have the fcc single-phase during materials processes (> 800 °C), through an X-ray diffraction analysis. It is shown that there are more chances to find fcc single-phase high entropy alloys if paying attention to non-equiatomic composition regions and that the CALPHAD thermodynamic calculation can be an efficient tool for it. An alloy design technique based on thermodynamic calculation is demonstrated and the applicability and limitation of the approach as a design tool for high entropy alloys is discussed.

  7. Wang-Landau sampling in face-centered-cubic hydrophobic-hydrophilic lattice model proteins.

    Science.gov (United States)

    Liu, Jingfa; Song, Beibei; Yao, Yonglei; Xue, Yu; Liu, Wenjie; Liu, Zhaoxia

    2014-10-01

    Finding the global minimum-energy structure is one of the main problems of protein structure prediction. The face-centered-cubic (fcc) hydrophobic-hydrophilic (HP) lattice model can reach high approximation ratios of real protein structures, so the fcc lattice model is a good choice to predict the protein structures. The lacking of an effective global optimization method is the key obstacle in solving this problem. The Wang-Landau sampling method is especially useful for complex systems with a rough energy landscape and has been successfully applied to solving many optimization problems. We apply the improved Wang-Landau (IWL) sampling method, which incorporates the generation of an initial conformation based on the greedy strategy and the neighborhood strategy based on pull moves into the Wang-Landau sampling method to predict the protein structures on the fcc HP lattice model. Unlike conventional Monte Carlo simulations that generate a probability distribution at a given temperature, the Wang-Landau sampling method can estimate the density of states accurately via a random walk, which produces a flat histogram in energy space. We test 12 general benchmark instances on both two-dimensional and three-dimensional (3D) fcc HP lattice models. The lowest energies by the IWL sampling method are as good as or better than those of other methods in the literature for all instances. We then test five sets of larger-scale instances, denoted by the S, R, F90, F180, and CASP target instances on the 3D fcc HP lattice model. The numerical results show that our algorithm performs better than the other five methods in the literature on both the lowest energies and the average lowest energies in all runs. The IWL sampling method turns out to be a powerful tool to study the structure prediction of the fcc HP lattice model proteins.

  8. First-principles prediction of structural, elastic, electronic and thermodynamic properties of the cubic SrUO{sub 3}-Perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Sahli, B. [Laboratoire de Génie Physique, Université Ibn Khaldoun, Tiaret, 14000 (Algeria); Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria); Bouafia, H., E-mail: hamza.tssm@gmail.com [Laboratoire de Génie Physique, Université Ibn Khaldoun, Tiaret, 14000 (Algeria); Abidri, B.; Abdellaoui, A. [Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria); Hiadsi, S.; Akriche, A. [Laboratoire de Microscope Electronique et Sciences des Matériaux, Université des Sciences et de la Technologie Mohamed Boudiaf, département de Génie Physique, BP1505 El m’naouar, Oran (Algeria); Benkhettou, N.; Rached, D. [Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria)

    2015-06-25

    Highlights: • The ground state properties of SrUO{sub 3}-Perovskite were investigated. • Elastic constants and their related parameters were calculated. • Electronic properties are treated using GGA-PBEsol + U approach. - Abstract: In this paper, we investigate bulk properties of the cubic SrUO{sub 3}-Perovskite in their nonmagnetic (NM), antiferromagnetic (AFM) and ferromagnetic (FM) states using all-electron self consistent Full Potential Augmented Plane Waves plus local orbital (FP-(L)APW + lo) method within PBEsol Generalized Gradiant density approximations. Our calculation allowed us to predict that the more stable magnetic state of the cubic SrUO{sub 3}-Perovskite is that of the ferromagnetic (FM). This work is the first prediction of elastic constants and their related parameters (Young modulus, shear modulus, Poisson ratio, Zener anisotropy and the Debye temperature) for this cubic compound using Mehl method. We have employed the GGA(PBEsol) and GGA(PBEsol) + U to investigate the electronic band structure, density of states and electronic charge density of SrUO{sub 3}-Perovskite. The electronic band structure calculations revealed that SrUO{sub 3} exhibits metallic behavior. On the other hand the charge density plots for [1 1 0] direction indicates a strong ionic character along the Sr–O bond while the U–O bond has strong covalent character. Finally, we have analyzed the thermodynamic properties using the quasi-harmonic Debye model to complete the fundamental characterization of cubic SrUO{sub 3}-Perovskite.

  9. Epitaxially stabilized TiN/(Ti,Fe,Co)N multilayer thin films in (pseudo-)fcc crystal structure by sequential magnetron sputter deposition

    Energy Technology Data Exchange (ETDEWEB)

    Klever, C; Seemann, K; Stueber, M; Ulrich, S; Leiste, H [Karlsruhe Institute of Technology (KIT), Institute for Materials Research I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Brunken, H; Ludwig, A, E-mail: christian.klever@kit.ed [Ruhr-University Bochum, Institute of Materials, Universitaetsstr. 150, 44780 Bochum (Germany)

    2010-10-06

    Multilayer thin films were grown by non-reactive sequential magnetron sputter deposition from ceramic TiN and metallic FeCo targets addressing a combination of wear resistance and sensoric functionality. Coatings with bilayer period values ranging from 449 nm down to 2.6 nm were grown with the total amount of either material maintained constant. The multilayer thin films were post-annealed ex situ at 600 {sup 0}C for 60 min in vacuum. X-ray diffraction results imply the multilayer thin films undergo significant changes in their crystalline structure when the bilayer period is decreased. Using high-resolution transmission electron microscopy as well as selected-area electron diffraction it is shown that in the case of multilayer thin films with bilayer periods of several tens of nanometres and higher, FeCo layers and TiN layers in their respective common CsCl- and NaCl-type crystal structures alternate. In contrast, in the multilayer thin films with bilayer periods of only a few nanometres, grain growth across the interfaces between the individual layers takes place and a strongly textured microstructure is formed which features columns in (pseudo-)fcc crystal structure grown in heteroepitaxial growth mode. It is suggested that the experimental findings imply the latter multilayer thin films to be alternately composed of TiN layers and (Ti,Fe,Co)N solid solution layers which have been formed by a solid-state reaction during the deposition process. As a consequence, heteroepitaxially stabilized columnar grains in strongly textured (pseudo-)fcc crystal structure are formed. This crystal structure is preserved after the annealing procedure which qualifies these coatings for use in applications where temperatures of up to 600 {sup 0}C are reached.

  10. Virus-mediated FCC iron nanoparticle induced synthesis of uranium dioxide nanocrystals.

    Science.gov (United States)

    Ling, Tao; Yu, Huimin; Shen, Zhongyao; Wang, Hui; Zhu, Jing

    2008-03-19

    A reducing system involving M13 virus-mediated FCC Fe nanoparticles was employed to achieve uranium reduction and synthesize uranium dioxide nanocrystals. Here we show that metastable face-centered cubic (FCC) Fe nanoparticles were fabricated around the surface of the M13 virus during the specific adsorption of the virus towards Fe ions under a reduced environment. The FCC phase of these Fe nanoparticles was confirmed by careful TEM characterization. Moreover, this virus-mediated FCC Fe nanoparticle system successfully reduced contaminable U(VI) into UO(2) crystals with diameters of 2-5 nm by a green and convenient route.

  11. Synthesis and photonic band calculations of NCP face-centered cubic photonic crystals of TiO2 hollow spheres.

    Science.gov (United States)

    Zhu, Yong-zheng; Cao, Yan-ling; Li, Zhi-hui; Ding, Juan; Liu, Jun-song; Chi, Yuan-bin

    2007-02-01

    With the help of self-assembly, thermal sintering, selective etching techniques and sol-gel process, the non-close packed (ncp) face-centered cubic (fcc) photonic crystals of titanium dioxide (TiO2) hollow spheres connected by TiO2 cylindrical tubes have been fabricated using silica template. The photonic bandgap calculations indicate that the ncp structure of TiO2 hollow spheres was easier to open the pseudogaps than close packed system at the lowest energy.

  12. Deformed lattice states in a Zn{sub 0.9}V{sub 0.1}Se cubic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Maksimov, V. I., E-mail: kokailo@rambler.ru; Dubinin, S. F.; Surkova, T. P.; Parkhomenko, V. D. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

    2016-01-15

    Neutron scattering patterns have been recorded for a bulk Zn{sub 0.9}V{sub 0.1}Se cubic crystal at room temperature; they are indicative of macroscopic deformation in the material and its significant inhomogeneity. Specific features of the previously found state, preceding the fcc ↔ hcp structural transformation of the sphalerite lattice upon strong destabilization induced by vanadium ions in the doped ZnSe matrix, are discussed taking into account the data obtained.

  13. Performance of biotrickling filters packed with structured or cubic polyurethane sponges for VOC removal

    Institute of Scientific and Technical Information of China (English)

    Chunping Yang; Guanlong YU; Guangming Zeng; Haining Yang; Fayuan Chen; Congying Jin

    2011-01-01

    Two identical bench-scale biotrickling filters (BTFs),BTF 1 and BTF 2,were evaluated for toluene removal at various gas empty bed contact times (EBCTs) and organic loadings.BTF 1 and BTF 2 were packed with structured and cubic synthetic polyurethane sponges,respectively.At a constant toluene loading of 16 g/(m3.hr),toluene removal efficiencies decreased from 98.8% to 64.3% for BTF 1 and from 98.4% to 74.1% for BTF 2 as gas EBCT decreased from 30 to 5 see.When the toluene loading increased from 35 to 140 g/(m3·hr) at a gas EBCT of 30 see,the removal efficiencies decreased from 99.1% to 77.4% for BTF 1 and from 99.0% to 81.5% for BTF 2.The pressure drop for both BTFs increased with increased air flow rate,and did not significantly vary while the toluene loading was increased under similar operation conditions.BTF 1 and BTF 2 could start up successfully within 19 and 27 days,respectively,when packed with fresh sponge media,and the performances could be restored in 3-7 days after biomass was removed and wasted from the media.BTF 2 displayed higher removal efficiency even under shorter EBCT or higher loading rate than BTF1 when other operation conditions were similar,while it showed lower pressure drop than BTF 1 during the whole period of operation.These results demonstrated that both BTFs could treat waste gas containing toluene effectively.

  14. Correlation effects in fcc-Fe(x)Ni(1-x) alloys investigated by means of the KKR-CPA.

    Science.gov (United States)

    Minár, J; Mankovsky, S; Šipr, O; Benea, D; Ebert, H

    2014-07-09

    The electronic structure and magnetic properties of the disordered alloy system fcc-FexNi1-x (fcc: face centered cubic) have been investigated by means of the KKR-CPA (Korringa-Kohn-Rostoker coherent potential approximation) band structure method. To investigate the impact of correlation effects, the calculations have been performed on the basis of the LSDA (local spin density approximation), the LSDA + U as well as the LSDA + DMFT (dynamical mean field theory). It turned out that the inclusion of correlation effects hardly changed the spin magnetic moments and the related hyperfine fields. The spin-orbit induced orbital magnetic moments and hyperfine fields, on the other hand, show a pronounced and element-specific enhancement. These findings are in full accordance with the results of a recent experimental study.

  15. Electrical impedance of FCC

    Science.gov (United States)

    Liu, Y. S.

    1972-01-01

    The electrical characteristics of FCC are investigated in the context of multiple transmission lines theory. Analytical expressions for the coefficients of capacitance of conductors in a single cable are obtained. Numerical values calculated with these expressions are in good agreement with experimental data. Crosstalk, attenuation constants and phase angles of the current and voltage in flat conductor cable are also calculated.

  16. FCC Official Brochure - 2016

    CERN Multimedia

    Charitos, Panagiotis

    2016-01-01

    The FCC brochure describes the main scope of the study and give more information about the main scenarios explored under the study. It also highlights the R&D efforts under the study that will go into a Conceptual Design Report. Finally, it offers more information about the collaboration and a list of useful contact details.

  17. Temperature rise of installed FCC

    Science.gov (United States)

    Hankins, J. D.

    1976-01-01

    Report discusses temperature profiles of installed FCC for wood and tile surfaces. Three-conductor FCC was tested at twice nominal current-carrying capacity over bare floor and under carpet, with result indicating that temperature rise is not a linear function of current with FCC at this level.

  18. The FCC in Fiscal 1971.

    Science.gov (United States)

    Federal Communications Commission, Washington, DC.

    Fiscal 1971 saw major actions by the Federal Communications Commission (FCC) in all areas of its jurisdiction. In broadcasting, the FCC proposed new renewal rules and policies and issued a number of significant rulings on Fairness Doctrine matters. A policy statement outlining FCC cable television plans was submitted to the Congress. In the common…

  19. Reversible hydrogen storage property and structural analysis for face-centered cubic hydride Mg0.82Zr0.18H2 prepared by gigapascal hydrogen pressure method.

    Science.gov (United States)

    Takasaki, Tomoaki; Kyoi, Daisuke; Kitamura, Naoyuki; Tanase, Shigeo; Sakai, Tetsuo

    2007-12-27

    The face-centered cubic (fcc) type magnesium-zirconium hydride (Mg0.82Zr0.18Hx) was synthesized by means of the ultrahigh pressure (UHP) technique, which could generate 8 GPa of hydrogen pressure. The differential scanning calorimeter (DSC) measurements indicated that the fcc phase exhibited reversible hydrogen releasing and restoring properties under 0.5 MPa of hydrogen pressure. On the pressure-composition isotherms, the released and restored hydrogen capacities were estimated to be 3 approximately 3.5 wt %. The Rietveld analysis for synchrotron X-ray diffraction (XRD) data showed that the fcc phase had around 70 wt % mass fraction and was preserved without decomposition during hydrogen releasing and restoring cycles.

  20. Chromium removal by zeolite-rich materials obtained from an exhausted FCC catalyst: Influence of chromium incorporation on the sorbent structure.

    Science.gov (United States)

    Gonzalez, Maximiliano R; Pereyra, Andrea M; Torres Sánchez, Rosa M; Basaldella, Elena I

    2013-10-15

    A spent FCC catalyst was converted into a zeolitic mixture, and the product obtained was afterward used as trapping material for Cr(III) species frequently found in aqueous solutions. Eventual changes in the sorbent structure produced by Cr incorporation were studied by different characterization techniques such as point of zero charge determinations (PZC), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and infrared absorption (FTIR). The XRD and FTIR analyses indicated that chromium incorporation produces an amorphization of the material, and PZC measurements show no surface adsorption of charged chromium species. SEM and EDX analyses clearly show that after chromium sorption, the initial microspheroidal catalyst morphology was maintained, and the presence of chromium species was mainly detected in the outer microsphere surface, where the zeolite crystals were hydrothermally grown.

  1. Fluence dependence of the ultrafast transition from the A7 to the simple cubic structure in arsenic

    Energy Technology Data Exchange (ETDEWEB)

    Huntemann, Nils; Zijlstra, Eeuwe S.; Garcia, Martin E. [Universitaet Kassel, Theoretische Physik, Kassel (Germany)

    2009-07-15

    We extend a previous theoretical study, in which we have predicted that a solid-solid phase transition can be induced by a laser in arsenic under pressure, to higher fluences. In particular, we compute the fluence that is needed to induce an ultrafast structural transition from the A7 to the simple cubic phase as a function of the applied pressure. We further discuss the possibility of ultrafast, laser-induced melting. (orig.)

  2. Temperature-dependent EXAFS study of the local structure and lattice dynamics in cubic Y₂O₃.

    Science.gov (United States)

    Jonane, Inga; Lazdins, Karlis; Timoshenko, Janis; Kuzmin, Alexei; Purans, Juris; Vladimirov, Pavel; Gräning, Tim; Hoffmann, Jan

    2016-03-01

    The local structure and lattice dynamics in cubic Y2O3 were studied at the Y K-edge by X-ray absorption spectroscopy in the temperature range from 300 to 1273 K. The temperature dependence of the extended X-ray absorption fine structure was successfully interpreted using classical molecular dynamics and a novel reverse Monte Carlo method, coupled with the evolutionary algorithm. The obtained results allowed the temperature dependence of the yttria atomic structure to be followed up to ∼6 Å and to validate two force-field models.

  3. Synthesis, crystal structure, and bonding analysis of the hypoelectronic cubic phase Ca5Pd6Ge6.

    Science.gov (United States)

    Doverbratt, Isa; Ponou, Siméon; Wang, Fei; Lidin, Sven

    2015-09-21

    The title compound, Ca5Pd6Ge6, was obtained during a systematic investigation of the Ca-Pd-Ge ternary phase diagram. The crystal structure was determined and refined from single-crystal X-ray diffraction data. It crystallizes in a new structure variant of the Y4PdGa12-type structure (Im3̅m, a = 8.7764(4) Å) that features an arrangement of vertex-sharing body-centered cubes of calcium, Ca@Ca8, with a hierarchical bcc network, interpenetrating a second (Pd6Ge6) network consisting of Ge2 dumbbells surrounded by Pd in a strongly flattened octahedron with Pd(μ(2)-η(2),η(4)-Ge2)-like motifs. These octahedra are condensed through the Pd to form a 3D open fcc network. Theoretical band structure calculations suggested that the compound is hypoelectronic with predominantly multicenter-type interatomic interactions involving all three elements and essentially a Hume-Rothery-like regime of electronic stabilization. The similar electronegativity between germanium and palladium atoms has a decisive impact on the bonding picture of the system.

  4. Structural properties of undoped and doped cubic GaN grown on SiC(001)

    OpenAIRE

    Martínez-Guerrero, Esteban; Bellet-Amalric, E.; Martinet, L.; Feuillet, G.; Daudin, B.

    2002-01-01

    Transmission electron microscopy and x-ray diffraction measurements reveal the presence of stacking faults ~SFs! in undoped cubic GaN thin layers. We demonstrate the importance of the defects in the interfacial region of the films by showing that the SFs act as nucleation sites for precipitates of residual impurities such as C and Si present in the GaN layers grown on SiC~001! substrates. We used the imaging secondary ion mass spectroscopy technique to locate these impurities. The systemat...

  5. Peculiarities of Crystal Structure of the Cubic System Compounds with T 4 and T 5 Space Groups

    Science.gov (United States)

    Zolotarev, M. L.; Poplavnoi, A. S.

    2016-09-01

    We study symmetry peculiarities of crystalline compounds of a cubic system with the space groups T 4 and T 5 caused by the absence of point Wyckoff-sets in the unit cells of these groups. Due to the high multiplicity of the available Wyckoff positions, such compounds possess unit cells of complex composition. In these compounds, pseudosymmetry is realized with high probability when some group of atoms is located in positions close to the positions of higher-symmetry groups. We provide examples of crystalline compounds showing predicted specific structural features.

  6. Structural, elastic and electronic Properties of isotropic cubic crystals of carbon and silicon nanotubes : Density functional based tight binding calculations.

    Directory of Open Access Journals (Sweden)

    Alexander L. Ivanovskii

    2008-01-01

    Full Text Available Atomic models of cubic crystals (CC of carbon and graphene-like Si nanotubes are offered and their structural, cohesive, elastic and electronic properties are predicted by means of the DFTB method. Our main findings are that the isotropic crystals of carbon nanotubes adopt a very high elastic modulus B and low compressibility β, namely B = 650 GPa, β = 0.0015 1/GPa. In addition, these crystals preserve the initial conductivity type of their “building blocks”, i.e. isolated carbon and Si nanotubes. This feature may be important for design of materials with the selected conductivity type.

  7. Ionic and Optical Properties of Methylammonium Lead Iodide Perovskite across the Tetragonal-Cubic Structural Phase Transition

    Energy Technology Data Exchange (ETDEWEB)

    Hoque, Md Nadim Ferdous [Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock Texas 79409 USA; Islam, Nazifah [Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock Texas 79409 USA; Li, Zhen [Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden Colorado 80401 USA; Ren, Guofeng [Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock Texas 79409 USA; Zhu, Kai [Chemistry and Nanoscience Center, National Renewable Energy Laboratory, Golden Colorado 80401 USA; Fan, Zhaoyang [Department of Electrical and Computer Engineering and Nano Tech Center, Texas Tech University, Lubbock Texas 79409 USA

    2016-09-01

    Practical hybrid perovskite solar cells (PSCs) must endure temperatures above the tetragonal-cubic structural phase transition of methylammonium lead iodide (MAPbI3). However, the ionic and optical properties of MAPbI3 in such a temperature range, and particularly, dramatic changes in these properties resulting from a structural phase transition, are not well studied. Herein, we report a striking contrast at approximately 45 degrees C in the ionic/electrical properties of MAPbl3 owing to a change of the ion activation energy from 0.7 to 0.5 eV, whereas the optical properties exhibit no particular transition except for the steady increase of the bandgap with temperature. These observations can be explained by the 'continuous' nature of perovskite phase transition. We speculate that the critical temperature at which the ionic/electrical properties change, although related to crystal symmetry variation, is not necessarily the same temperature as when tetragonal-cubic structural phase transition occurs.

  8. Microstructural evolution and formation mechanism of FCC titanium during heat treatment processing

    Energy Technology Data Exchange (ETDEWEB)

    Jing, R.; Liu, C.Y.; Ma, M.Z. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Liu, R.P., E-mail: riping@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2013-03-05

    Highlights: ► The alloy with ST underwent the transformations: β → α + β + α″ + fcc phase. ► The lattice parameter “a” of the fcc phase was about 0.4385 nm. ► After aging at 450 °C, the highest strength was attained about 1740 MPa. ► The transus temperature of fcc-Ti was between 650 °C and 700 °C. -- Abstract: The phase transformation of Ti–20Zr–6.5Al–4V alloy was studied during different heat treatment processes. Due to the addition of zirconium possessing the high-stacking-fault energy, a small amount of Ti underwent allotropic transformation from hcp-Ti to face-centered cubic (fcc) Ti during heat treatment. The alloy, which was subjected to solid solution treatment at 950 °C for 60 min and subsequent water quenched, underwent the following phase transformations: β → α + β (residual) + α″ + fcc phase. The fcc phase was also found in the subsequent aging process, and when aging temperature reached 700 °C, the fcc-Ti completely decomposed into hexagonal close-packed α phase. The transus temperature of fcc-Ti was between 650 °C and 700 °C. It was found that the mechanical properties of the alloy are remarkably dependent on fcc phase content.

  9. Hydrogen absorption in uranium-based alloys with cubic γ -U structure

    Science.gov (United States)

    Havela, L.; Kim-Ngan, N.-T. H.

    2017-03-01

    UH3-type hydrides were formed by hydrogenation of splat-cooled U-based alloys upon applying high H2 pressures (>2.5 bar). Hydrogenation of U1‑x Mo x alloys (with x  ⩾  0.12 (12 at.% Mo) containing the cubic γ-U phase leads to a formation of nanocrystalline β-UH3, why those of U1‑x Zr x alloys (with x  ⩾15 at.% Zr) implies a pure α-UH3. The Curie temperature of hydride (UH3)0.85Mo0.15 reaches 200 K it may be the first U-based ferromagnet with such high T C. The results reflect the dominant U–H interaction. Invited talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8–12 November 2016, Ha Long City, Vietnam.

  10. Solution based synthesis of simple fcc Si nano-crystals under ambient conditions.

    Science.gov (United States)

    Balcı, Mustafa H; Sæterli, Ragnhild; Maria, Jerome; Lindgren, Mikael; Holmestad, Randi; Grande, Tor; Einarsrud, Mari-Ann

    2013-02-28

    We demonstrate for the first time that simple face-centered cubic (fcc) silicon nano-crystals can be produced by a solution based bottom-up synthesis route under ambient conditions. Simple fcc Si nano-crystals (2-7 nm) were prepared at room temperature by using sodium cyclopentadienide as a reducing agent for silicon tetrachloride. Photoluminescence emission at 550 nm was observed for the fcc silicon nano-crystals upon excitation at 340 nm, indicating that fcc Si nano-crystals were exhibiting direct bandgap like semiconductor properties with very fast radiative recombination rates. The new synthesis route makes possible the production and study of simple fcc polymorphs of Si nano-crystals with an easy alteration of surface termination groups.

  11. Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication of Superlattice Structures Using AIN and InN

    Science.gov (United States)

    1992-12-01

    AD-A258 804 Final Technical Report Ii Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent...Technical 6/1/86-12/31/92 4. TITLE AND SUBTITLE Growth, Nitrogen Vacancy Reduction and 5. FUNDING NUMBERS Solid Solution Formation in Cubic GaN Thin...According to the structural and chemical analyses, there is no reason to believe that a homogeneous solid solution close to this composition had

  12. The FCC: A Research Tool.

    Science.gov (United States)

    Wilson, Paul

    The numerous forms filed with the Federal Communications Commission (FCC) provide information about a variety of topics. Basic licensing information that is available concerns engineering, ownership, and equal employment opportunity. The FCC's broadcast bureau collects information about programing, the ascertainment of community needs, public…

  13. FCC Official Brochure - German version

    CERN Multimedia

    Charitos, Panagiotis

    2017-01-01

    The FCC brochure describes the main scope of the study and give more information about the main scenarios explored under the study. It also highlights the ongoing R&D efforts launched by the FCC study. Finally, it offers more information about the collaboration and a list of useful contact details.

  14. FCC Official Brochure - French Version

    CERN Multimedia

    Charitos, Panagiotis

    2017-01-01

    The FCC brochure describes the main scope of the study and give more information about the main scenarios explored under the study. It also highlights the ongoing R&D efforts launched by the FCC study. Finally, it offers more information about the collaboration and a list of useful contact details.

  15. Elastic and magnetic properties of cubic Fe$_{4}$C from first-principles

    OpenAIRE

    Rahman, Gul; Jan, Haseen Ullah

    2014-01-01

    First-principles based on density functional theory is used to study the phase stability, elastic, magnetic, and electronic properties of cubic (c)-Fe$_4$C. Our results show that c-Fe$_{4}$C has a ferromagnetic (FM) ground state structure compared with antiferromagnetic (AFM) and nonmagnetic (NM)states. To study the phase stability of c-Fe$_4$C, BCC Fe$_4$C, FCC Fe$_4$C, and BCC Fe$_{16}$C, where C is considered at tetrahedral and octahedral interstitial sites, are also considered. Although, ...

  16. Link between structural and mechanical stability of fcc- and bcc-based ordered MgeLi alloys

    CSIR Research Space (South Africa)

    Phasha, MJ

    2010-06-01

    Full Text Available The first principles pseudopotential calculations based on the PerdeweBurkeeErnzerhof (PBE) form of generalized gradient approximation (GGA) within density functional theory (DFT) have been utilized to investigate the structural and elastic...

  17. Ginzburg-Landau-type multiphase field model for competing fcc and bcc nucleation.

    Science.gov (United States)

    Tóth, G I; Morris, J R; Gránásy, L

    2011-01-28

    We address crystal nucleation and fcc-bcc phase selection in alloys using a multiphase field model that relies on Ginzburg-Landau free energies of the liquid-fcc, liquid-bcc, and fcc-bcc subsystems, and determine the properties of the nuclei as a function of composition, temperature, and structure. With a realistic choice for the free energy of the fcc-bcc interface, the model predicts well the fcc-bcc phase-selection boundary in the Fe-Ni system.

  18. The Federal Communications Commission: Current Structure and Its Role in the Changing Telecommunications Landscape

    Science.gov (United States)

    2009-05-14

    4 FCC Structure .......................................................................................................................6...for additional information on the history of the FCC. The Federal Communications Commission Congressional Research Service 6 FCC Structure The

  19. Three-dimensional periodic dielectric structures having photonic Dirac points

    Energy Technology Data Exchange (ETDEWEB)

    Bravo-Abad, Jorge; Joannopoulos, John D.; Soljacic, Marin

    2015-06-02

    The dielectric, three-dimensional photonic materials disclosed herein feature Dirac-like dispersion in quasi-two-dimensional systems. Embodiments include a face-centered cubic (fcc) structure formed by alternating layers of dielectric rods and dielectric slabs patterned with holes on respective triangular lattices. This fcc structure also includes a defect layer, which may comprise either dielectric rods or a dielectric slab with patterned with holes. This defect layer introduces Dirac cone dispersion into the fcc structure's photonic band structure. Examples of these fcc structures enable enhancement of the spontaneous emission coupling efficiency (the .beta.-factor) over large areas, contrary to the conventional wisdom that the .beta.-factor degrades as the system's size increases. These results enable large-area, low-threshold lasers; single-photon sources; quantum information processing devices; and energy harvesting systems.

  20. Phase transition from fcc to bcc structure of the Cu-clusters during nanocrystallization of Fe{sub 85.2}Si{sub 1}B{sub 9}P{sub 4}Cu{sub 0.8} soft magnetic alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nishijima, Masahiko; Matsuura, Makoto; Takenaka, Kana; Takeuchi, Akira; Makino, Akihiro [Research and Development Center for Ultra High Efficiency Nano-crystalline Soft Magnetic Material, Institute for Materials Research, Tohoku University, Sendai, Miyagi, 980 (Japan); Ofuchi, Hironori [Industrial Application Division, Japan Synchrotron Radiation Research Institute (JASRI) Kouto, Sayo, Hyogo 679-5198 (Japan)

    2014-05-15

    A role of Cu on the nanocrystallization of an Fe{sub 85.2}Si{sub 1}B{sub 9}P{sub 4}Cu{sub 0.8} alloy was investigated by X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM). The Cu K-edge XAFS results show that local structure around Cu is disordered for the as-quenched sample whereas it changes to fcc-like structure at 613 K. The fcc Cu-clusters are, however, thermodynamically unstable and begin to transform into bcc structure at 638 K. An explicit bcc structure is observed for the sample annealed at 693 K for 600 s in which TEM observation shows that precipitated bcc-Fe crystallites with ∼12 nm are homogeneously distributed. The bcc structure of the Cu-clusters transforms into the fcc-type again at 973 K, which can be explained by the TEM observations; Cu segregates at grain boundaries between bcc-Fe crystallites and Fe{sub 3}(B,P) compounds. Combining the XAFS results with the TEM observations, the structure transition of the Cu-clusters from fcc to bcc is highly correlated with the preliminary precipitation of the bcc-Fe which takes place prior to the onset of the first crystallization temperature, T{sub x1} = 707 K. Thermodynamic analysis suggests that an interfacial energy density γ between an fcc-Cu cluster and bcc-Fe matrix dominates at a certain case over the structural energy between fcc and bcc Cu, ΔG{sub fcc} {sub −} {sub bcc}, which causes phase transition of the Cu clusters from fcc to bcc structure.

  1. Electronic structure and metallization of cubic GdH3 under pressure: Ab initio many-body GW calculations

    Science.gov (United States)

    Kong, Bo; Zhang, Yachao

    2016-07-01

    The electronic structures of the cubic GdH3 are extensively investigated using the ab initio many-body GW calculations treating the Gd 4f electrons either in the core (4f-core) or in the valence states (4f-val). Different degrees of quasiparticle (QP) self-consistent calculations with the different starting points are used to correct the failures of the GGA/GGA + U/HSE03 calculations. In the 4f-core case, GGA + G0W0 calculations give a fundamental band gap of 1.72 eV, while GGA+ GW0 or GGA + GW calculations present a larger band gap. In the 4f-val case, the nonlocal exchange-correlation (xc) functional HSE03 can account much better for the strong localization of the 4f states than the semilocal or Hubbard U corrected xc functional in the Kohn-Sham equation. We show that the fundamental gap of the antiferromagnetic (AFM) or ferromagnetic (FM) GdH3 can be opened up by solving the QP equation with improved starting point of eigenvalues and wave functions given by HSE03. The HSE03 + G0W0 calculations present a fundamental band gap of 2.73 eV in the AFM configuration, and the results of the corresponding GW0 and GW calculations are 2.89 and 3.03 eV, respectively. In general, for the cubic structure, the fundamental gap from G0W0 calculations in the 4f-core case is the closest to the real result. By G0W0 calculations in the 4f-core case, we find that H or Gd defects can strongly affect the band structure, especially the H defects. We explain the mechanism in terms of the possible electron correlation on the hydrogen site. Under compression, the insulator-to-metal transition in the cubic GdH3 occurs around 40 GPa, which might be a satisfied prediction.

  2. Synthesis of Al3Fe5O12 Cubic Structure by Extremely Low Sintering Temperature of Sol Gel Technique

    Directory of Open Access Journals (Sweden)

    Noorhana Yahya

    2009-01-01

    Full Text Available Problem statement: Fabrication of nano materials particularly nano inductors at low sintering temperature remains a challenge. This study was carried out as our initial response to obtain a nano-size inductors, which is aluminium iron garnet using low sintering temperature. Approach: The aluminum iron garnet (Al3Fe5O12 nano crystals were prepared by sol-gel technique. The starting solution is a mixture of iron nitrate Fe(NO33.9H2O, yttrium nitrate Y(NO33.6H2O and aluminum nitrate Al(NO33.9H2O and were dissolved in 150 mL of citric acid, C6H8O7.H2O. The mixtures were stirred continuously, at about 250 r.p.m, in room temperature until the formation of a gel was observed. The gel was dried at 110°C in an oven to remove the unneeded water. The dried powder was calcined at 600°C, for 3 h in air and was wet crushed using a Fritsch Planetary Micromill for 6 h to obtain fine particles powder. The sample was then characterized by X-Ray Diffraction analysis (XRD to confirm the garnet phase. The sintered powder was characterized at different temperature by X-ray diffraction analysis and Raman Spectroscopy was used to study the vibration of atoms in a materials. Finally, Field Emission Scanning Electron Microscopy (FESEM was used to study the surface morphology of the sample. Results: The XRD results showed that, the best garnet cubic phase giving [1 0 4] plane of the Al3Fe5O12 crystallite appeared at 33.30 of the 2 theta. We report a clear cubic crystal structure of less than 62 nm, which was observed possible for the first time, for this type of garnet, Al3Fe5O12. The much lower sintering temperature 800°C comparing to the conventional method was attributed to the sol gel method. Conclusion: The long stirring time (one month that had allowed self assembly of the anions and cations to form the gelatin. In addition the small radius of aluminium prefers to occupy the tetrahedron and octahedron sites instead of the much larger dodecahedron site resulted to

  3. Structural Stability Driven by the Spin-Orbit Coupling and the Superconductivity in simple-cubic Polonium

    Science.gov (United States)

    Kang, Chang-Jong; Kim, Kyoo; Min, B. I.

    2013-03-01

    Polonium is the only element which has the simple-cubic (SC) structure in the periodic table. We have studied its structural stability based on the phonon dispersion calculations using the first-principles all-electron full-potential band method. We have demonstrated that the strong spin-orbit coupling (SOC) in SC-Po suppresses the Peierls instability and makes the SC structure stable. We have also discussed the structural chirality realized in beta-Po, as a consequence of the phonon instability. Further, we have investigated the possible superconductivity in SC-Po, and predicted that it becomes a superconductor with Tc ~ 4 K at ambient pressure. The transverse soft phonon mode at q ~ 2/3 R, which is greatly affected by the SOC, plays an important role both in the structural stability and the superconductivity in SC-Po. We have explored effects of the SOC and the volume variation on the phonon dispersions and superconducting properties of SC-Po.

  4. 47 CFR 2.926 - FCC identifier.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false FCC identifier. 2.926 Section 2.926... Authorizations § 2.926 FCC identifier. (a) A grant of equipment authorization issued by the Commission will list the validated FCC Identifier consisting of the grantee code assigned by the FCC pursuant to...

  5. The effects of a hydrogen pair in the electronic structure of the FCC iron containing a vacancy

    Energy Technology Data Exchange (ETDEWEB)

    Simonetti, S. [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Centro de Investigaciones en Mecanica Teorica y Aplicada, Universidad Tecnologica Nacional, 11 de Abril 461, 8000 Bahia Blanca (Argentina); Saravia, D. Rey [Departamento de Ingenieria, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Brizuela, G.; Juan, A. [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina)

    2010-06-15

    Fuel cell vehicles have been identified as the personal transportation technology of the future because of their high efficiency and very low emissions. To achieve the goal of road-ready fuel cell vehicles, great strides must be made in the development of fuel cells, hydrogen production and hydrogen storage technologies, that includes metal-H interaction studies and safety considerations. The interaction between two-hydrogen atoms and a {gamma}-Fe structure containing a vacancy has been studied using a cluster model and a theoretical method. For the study of the sequential absorption, the hydrogen atoms were positioned in their energy minima configurations, near the vacancy. The interactions mainly involve Fe 4s-H 1s atomic orbitals. The contribution of Fe 4p and Fe 3d orbitals is much less important. The Fe-Fe bond is weakened as new Fe-H-H and H-H pairs were formed. The effect of H atoms is limited to its first Fe neighbors. The Fe-Fe bond strength decreases with the introduction of the H atoms. Fe-H bonding is achieved at expense of weakening the metal-metal nearest bonds. There is not a real bond between the H atoms but some H-H interaction is observed. The detrimental effect of H atoms on the Fe-Fe bonds can be related to one of the aspect of embrittlement in {gamma}-Fe. (author)

  6. Dislocation creation and void nucleation in FCC ductile metals under tensile loading: a general microscopic picture.

    Science.gov (United States)

    Pang, Wei-Wei; Zhang, Ping; Zhang, Guang-Cai; Xu, Ai-Guo; Zhao, Xian-Geng

    2014-11-10

    Numerous theoretical and experimental efforts have been paid to describe and understand the dislocation and void nucleation processes that are fundamental for dynamic fracture modeling of strained metals. To date an essential physical picture on the self-organized atomic collective motions during dislocation creation, as well as the essential mechanisms for the void nucleation obscured by the extreme diversity in structural configurations around the void nucleation core, is still severely lacking in literature. Here, we depict the origin of dislocation creation and void nucleation during uniaxial high strain rate tensile processes in face-centered-cubic (FCC) ductile metals. We find that the dislocations are created through three distinguished stages: (i) Flattened octahedral structures (FOSs) are randomly activated by thermal fluctuations; (ii) The double-layer defect clusters are formed by self-organized stacking of FOSs on the close-packed plane; (iii) The stacking faults are formed and the Shockley partial dislocations are created from the double-layer defect clusters. Whereas, the void nucleation is shown to follow a two-stage description. We demonstrate that our findings on the origin of dislocation creation and void nucleation are universal for a variety of FCC ductile metals with low stacking fault energies.

  7. Spin-driven symmetry breaking in the frustrated fcc pyrite MnS2.

    Science.gov (United States)

    Kimber, Simon A J; Chatterji, Tapan

    2015-06-10

    We report the characterisation of natural samples of the cubic pyrite mineral MnS2 using very high resolution synchrotron x-ray diffraction techniques. At low temperatures we find a new low temperature polymorph, which results from coupling between magnetic and lattice degrees of freedom. Below the magnetic ordering temperature T(N) = 48 K, we detect a pseudo-tetragonal distortion with a tiny c/a ratio of 1.0006. The structure can be refined in the space group Pbca The symmetry lowering reduces magnetic frustration in the fcc Mn(2+) lattice and is likely responsible for the previously reported lock-in of the magnetic propagation vector. This behaviour is similar to the spin-Peierls phase transitions reported in other three-dimensional Heisenberg magnets like the chromate spinels.

  8. A simple model for large-scale simulations of fcc metals with explicit treatment of electrons

    Science.gov (United States)

    Mason, D. R.; Foulkes, W. M. C.; Sutton, A. P.

    2010-01-01

    The continuing advance in computational power is beginning to make accurate electronic structure calculations routine. Yet, where physics emerges through the dynamics of tens of thousands of atoms in metals, simplifications must be made to the electronic Hamiltonian. We present the simplest extension to a single s-band model [A.P. Sutton, T.N. Todorov, M.J. Cawkwell and J. Hoekstra, Phil. Mag. A 81 (2001) p.1833.] of metallic bonding, namely, the addition of a second s-band. We show that this addition yields a reasonable description of the density of states at the Fermi level, the cohesive energy, formation energies of point defects and elastic constants of some face-centred cubic (fcc) metals.

  9. Structural and electronic properties of non-magnetic intermetallic YAuX (X = Ge and Si) in hexagonal and cubic phases

    Indian Academy of Sciences (India)

    A Lekhal; F Z Benkhelifa; S Méçabih; B Abbar; B Bouhafs

    2016-02-01

    The structural and electronic properties of non-magnetic intermetallic YAuX (X = Ge and Si) crystallized in hexagonal phase have been investigated using the full potential linearized augmented-plane wave (FPLAPW) method based on the density functional theory (DFT), within the generalized gradient approximation (GGA). The calculated lattice parameters were in good agreement with experiment. Also, the structural and electronic properties of the non-magnetic half-Heusler YAuPb compound including the artificial YAuX (X = Ge and Si) calculated in cubic phase were determined. It was found that the half-Heusler YAuPb compound presented metallic character. The results showed that YAuGe in cubic phase is a semiconductor whereas the cubic YAuSi is an isolator.

  10. First-principles study of electronic structures and stability of body-centered cubic Ti-Mo alloys by special quasirandom structures.

    Science.gov (United States)

    Sahara, Ryoji; Emura, Satoshi; Ii, Seiichiro; Ueda, Shigenori; Tsuchiya, Koichi

    2014-06-01

    The electronic structures and structural properties of body-centered cubic Ti-Mo alloys were studied by first-principles calculations. The special quasirandom structures (SQS) model was adopted to emulate the solid solution state of the alloys. The valence band electronic structures of Ti-Mo and Ti-Mo-Fe alloys were measured by hard x-ray photoelectron spectroscopy. The structural parameters and valence band photoelectron spectra were calculated using first-principles calculations. The results obtained with the SQS models showed better agreement with the experimental results than those obtained using the conventional ordered structure models. This indicates that the SQS model is effective for predicting the various properties of solid solution alloys by means of first-principles calculations.

  11. Effects of Temperature on Structure and Mobility of the <100> Edge Dislocation in Body-Centred Cubic Iron

    Energy Technology Data Exchange (ETDEWEB)

    Terentyev, Dmitry [Belgian Nuclear Research Centre, SCK-CEN; Osetskiy, Yury N [ORNL; Bacon, David J [University of Liverpool

    2010-01-01

    Dislocation segments with Burgers vector b = <1 0 0> are formed during deformation of body-centred-cubic (bcc) metals by the interaction between dislocations with b = 1/2<1 1 1>. Such segments are also created by reactions between dislocations and dislocation loops in irradiated bcc metals. The obstacle resistance produced by these segments on gliding dislocations is controlled by their mobility, which is determined in turn by the atomic structure of their cores. The core structure of a straight <1 0 0> edge dislocation is investigated here by atomic-scale computer simulation for {alpha}-iron using three different interatomic potentials. At low temperature the dislocation has a non-planar core consisting of two 1/2<1 1 1> fractional dislocations with atomic disregistry spread on planes inclined to the main glide plane. Increasing temperature modifies this core structure and so reduces the critical applied shear stress for glide of the <1 0 0> dislocation. It is concluded that the response of the <1 0 0> edge dislocation to temperature or applied stress determines specific reaction pathways occurring between a moving dislocation and 1/2<1 1 1> dislocation loops. The implications of this for plastic flow in unirradiated and irradiated ferritic materials are discussed and demonstrated by examples.

  12. Effects of temperature on structure and mobility of the <1 0 0> edge dislocation in body-centred cubic iron

    Energy Technology Data Exchange (ETDEWEB)

    Terentyev, D.A., E-mail: dterenty@sckcen.be [Nuclear Materials Science Institute, SCK CEN, Boeretang 200, B-2400, Mol (Belgium); Osetsky, Yu. N. [Materials Sciences and Technology, ORNL, Oak Ridge, TN 37831 (United States); Bacon, D.J. [Department of Engineering, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom)

    2010-04-15

    Dislocation segments with Burgers vector b = <1 0 0> are formed during deformation of body-centred-cubic (bcc) metals by the interaction between dislocations with b = 1/2<1 1 1>. Such segments are also created by reactions between dislocations and dislocation loops in irradiated bcc metals. The obstacle resistance produced by these segments on gliding dislocations is controlled by their mobility, which is determined in turn by the atomic structure of their cores. The core structure of a straight <1 0 0> edge dislocation is investigated here by atomic-scale computer simulation for {alpha}-iron using three different interatomic potentials. At low temperature the dislocation has a non-planar core consisting of two 1/2<1 1 1> fractional dislocations with atomic disregistry spread on planes inclined to the main glide plane. Increasing temperature modifies this core structure and so reduces the critical applied shear stress for glide of the <1 0 0> dislocation. It is concluded that the response of the <1 0 0> edge dislocation to temperature or applied stress determines specific reaction pathways occurring between a moving dislocation and 1/2<1 1 1> dislocation loops. The implications of this for plastic flow in unirradiated and irradiated ferritic materials are discussed and demonstrated by examples.

  13. Sintering of Spherical Particles of Equal and Different Size Arranged in a Body Centered Cubic Structure

    DEFF Research Database (Denmark)

    Redanz, Pia; McMeeking, R. M.

    2003-01-01

    Solid-state sintering of a bcc structure of spherical particles has been studied numerically by use of simple shape parameters to describe the state of the unit cell. Both free and pressure-assisted sintering of particles of equal and different sizes for various ratios of boundary and surface...... to interact, or the next-nearest neighbours in the particle structure attain contact. Quantative measures of the density at the transition from open pore space between the particles to closed porosity as well as the density at which the next-nearest neighbours start to touch are derived. Furthermore...

  14. Self-focusing and solitonlike structures in materials with competing quadratic and cubic nonlinearities

    DEFF Research Database (Denmark)

    Bergé, L.; Bang, O.; Juul Rasmussen, J.;

    1997-01-01

    , mutually trapped waves can self-focus until collapse whenever their respective powers exceed some thresholds. On the contrary, coupled waves diffracting in a one-dimensional plane never collapse and may evolve towards stable solitonlike structures. For higher transverse dimension numbers, we investigate...

  15. Formation of bcc and fcc during the coalescence of free and supported Fe and Ni clusters.

    Science.gov (United States)

    Li, Guojian; Wang, Qiang; Sui, Xudong; Wang, Kai; Wu, Chun; He, Jicheng

    2015-09-07

    The formation of bcc and fcc during the coalescence of free and supported Fe and Ni clusters has been studied by molecular dynamics simulation using an embedded atom method. Structural evolution of the clusters, coalesced under varying temperature, Ni content and substrate conditions, was explored by interatomic energy, snapshots, pair distribution functions and bond order parameters. The results show that the formation of bcc and fcc is strongly related to Ni content, substrate and coalescence temperature. Free clusters coalesced at 1200 K form bcc at lower Ni contents with fcc forming at higher Ni concentrations and no observable coexistence of bcc and fcc. Differences in coalescence at 1000 K result from the coexistence of bcc and fcc within the Ni range of 50-70%. Free clusters supported on disordered Ni substrates were shown to transform from spherical morphology to islands of supported clusters with preferred epitaxial orientation. The Ni content required to form bcc and fcc coexistence on supported clusters at 1000 K decreased to 30-50% Ni. Free clusters possessing bcc and fcc generally stacked along the bcc (110) and fcc (111) facets, whereas supported clusters stacked along the (111) bcc and (100) fcc planes. Structural transformation was induced by clusters containing greater numbers of atoms. Spread over the substrate enhanced interatomic energy, order substrates affect the epitaxial growth direction and increase the melting points of the supported clusters. This study can be used to predict the nature of fcc and bcc formation in Fe-Ni films.

  16. Kinetics of Hexagonal Cylinders to Face-centered Cubic Spheres Transition of Triblock Copolymer in Selective Solvent: Brownian Dynamics Simulation

    CERN Document Server

    Li, Minghai; Bansil, Rama

    2010-01-01

    The kinetics of the transformation from the hexagonal packed cylinder (HEX) phase to the face-centered-cubic (FCC) phase was simulated using Brownian Dynamics for an ABA triblock copolymer in a selective solvent for the A block. The kinetics was obtained by instantaneously changing either the temperature of the system or the well-depth of the Lennard-Jones potential. Detailed analysis showed that the transformation occurred via a rippling mechanism. The simulation results indicated that the order-order transformation (OOT) was a nucleation and growth process when the temperature of the system instantly jumped from 0.8 to 0.5. The time evolution of the structure factor obtained by Fourier Transformation showed that the peak intensities of the HEX and FCC phases could be fit well by an Avrami equation.

  17. FCC riser quick separation system: a review

    Directory of Open Access Journals (Sweden)

    Zhi Li

    2016-10-01

    Full Text Available Abstract The riser reactor is the key unit in the fluid catalytic cracking (FCC process. As the FCC feedstocks become heavier, the product mixture of oil, gas and catalysts must be separated immediately at the outlet of the riser to avoid excessive coking. The quick separation system is the core equipment in the FCC unit. China University of Petroleum (Beijing has developed many kinds of separation system including the fender-stripping cyclone and circulating-stripping cyclone systems, which can increase the separation efficiency and reduce the pressure drop remarkably. For the inner riser system, a vortex quick separation system has been developed. It contains a vortex quick separator and an isolated shell. In order to reduce the separation time, a new type of separator called the short residence time separator system was developed. It can further reduce the separation time to less than 1 s. In this paper, the corresponding design principles, structure and industrial application of these different kinds of separation systems are reviewed. A system that can simultaneously realize quick oil gas separation, quick oil gas extraction and quick pre-stripping of catalysts at the end of the riser is the trend in the future.

  18. Electronic Structure Studies and Photocatalytic Properties of Cubic Bi1.5ZnNb1.5O7

    Directory of Open Access Journals (Sweden)

    Ganchimeg Perenlei

    2015-01-01

    Full Text Available The photocatalytic ability of cubic Bi1.5ZnNb1.5O7 (BZN pyrochlore for the decolorization of an acid orange 7 (AO7 azo dye in aqueous solution under ultraviolet (UV irradiation has been investigated for the first time. BZN catalyst powders prepared using low temperature sol-gel and higher temperature solid-state methods have been evaluated and their reaction rates have been compared. The experimental band gap energy has been estimated from the optical absorption edge and has been used as reference for theoretical calculations. The electronic band structure of BZN has been investigated using first-principles density functional theory (DFT calculations for random, completely and partially ordered solid solutions of Zn cations in both the A and B sites of the pyrochlore structure. The nature of the orbitals in the valence band (VB and the conduction band (CB has been identified and the theoretical band gap energy has been discussed in terms of the DFT model approximations.

  19. Structural, elastic, and electronic properties of cubic perovskite BaHfO{sub 3} obtained from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Hongsheng [Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China); Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083 (China); Graduate School of Chinese Academy of Sciences, Beijing 100049 (China); Chang Aimin, E-mail: changam@ms.xjb.ac.c [Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China); Wang Yunlan [Center for High Performance Computing, Northwestern Polytechnical University, Xi' an 710072 (China)

    2009-08-01

    We investigated the structural, elastic, and electronic properties of the cubic perovskite-type BaHfO{sub 3} using a first-principles method based on the plane-wave basis set. Analysis of the band structure shows that perovskite-type BaHfO{sub 3} is a wide gap indirect semiconductor. The band-gap is predicted to be 3.94 eV within the screened exchange local density approximation (sX-LDA). The calculated equilibrium lattice constant of this compound is in good agreement with the available experimental and theoretical data reported in the literatures. The independent elastic constants (C{sub 11}, C{sub 12}, and C{sub 44}), bulk modules B and its pressure derivatives B{sup '}, compressibility beta, shear modulus G, Young's modulus Y, Poisson's ratio nu, and Lame constants (mu,lambda) are obtained and analyzed in comparison with the available theoretical and experimental data for both the singlecrystalline and polycrystalline BaHfO{sub 3}. The bonding-charge density calculation make it clear that the covalent bonds exist between the Hf and O atoms and the ionic bonds exist between the Ba atoms and HfO{sub 3} ionic groups in BaHfO{sub 3}.

  20. DFT Study of the Electronic Structure of Cubic-SiC Nanopores with a C-Terminated Surface

    Directory of Open Access Journals (Sweden)

    M. Calvino

    2014-01-01

    Full Text Available A study of the dependence of the electronic structure and energetic stability on the chemical surface passivation of cubic porous silicon carbide (pSiC was performed using density functional theory (DFT and the supercell technique. The pores were modeled by removing atoms in the [001] direction to produce a surface chemistry composed of only carbon atoms (C-phase. Changes in the electronic states of the porous structures were studied by using different passivation schemes: one with hydrogen (H atoms and the others gradually replacing pairs of H atoms with oxygen (O atoms, fluorine (F atoms, and hydroxide (OH radicals. The results indicate that the band gap behavior of the C-phase pSiC depends on the number of passivation agents (other than H per supercell. The band gap decreased with an increasing number of F, O, or OH radical groups. Furthermore, the influence of the passivation of the pSiC on its surface relaxation and the differences in such parameters as bond lengths, bond angles, and cell volume are compared between all surfaces. The results indicate the possibility of nanostructure band gap engineering based on SiC via surface passivation agents.

  1. Structural and magnetic studies of fcc Fe films with self-organized lateral modulation on striped Cu(110)-O(2x1) substrates.

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.

    1998-09-21

    Fcc Fe wedges of 0-12 monolayer (ML) were grown by means of molecular beam epitaxy onto a novel substrate: flat Cu(110) with an oxygen-induced, long-range ordered striped phase, and studied in-situ with medium energy electron diffraction (MEED) and the surface magneto-optical Kerr effect (SMOKE). In contrast to Fe growth on either clean or oxygen-saturated Cu(110), the films on the striped substrates retain a layer-by-layer growth mode up to 6-7 ML and are fcc at least up to 12 ML. In addition, satellite peaks were observed on both sides of the MEED (0,0) streak, indicating a long-range-ordered lateral modulation of the Fe surface. We postulate that the Fe films grow conformally onto the original striped substrate. SMOKE studies show that these fcc Fe wedges are ferromagnetic with an easy axis along the original stripes for Fe thickness > 4ML and a remnant magnetization that increases linearly with thickness beyond 4 ML.

  2. First-principles study of the structural stability of cubic, tetragonal and hexagonal phases in Mn₃Z (Z=Ga, Sn and Ge) Heusler compounds.

    Science.gov (United States)

    Zhang, Delin; Yan, Binghai; Wu, Shu-Chun; Kübler, Jürgen; Kreiner, Guido; Parkin, Stuart S P; Felser, Claudia

    2013-05-22

    We investigate the structural stability and magnetic properties of the cubic, tetragonal and hexagonal phases of Mn3Z (Z=Ga, Sn and Ge) Heusler compounds using first-principles density-functional theory. We propose that the cubic phase plays an important role as an intermediate state in the phase transition from the hexagonal to the tetragonal phases. Consequently, Mn3Ga and Mn3Ge behave differently from Mn3Sn, because the relative energies of the cubic and hexagonal phases are different. This result agrees with experimental observations for these three compounds. The weak ferromagnetism of the hexagonal phase and the perpendicular magnetocrystalline anisotropy of the tetragonal phase obtained in our calculations are also consistent with experiment.

  3. First-principles study of the structural stability of cubic, tetragonal and hexagonal phases in Mn3Z (Z=Ga, Sn and Ge) Heusler compounds

    Science.gov (United States)

    Zhang, Delin; Yan, Binghai; Wu, Shu-Chun; Kübler, Jürgen; Kreiner, Guido; Parkin, Stuart S. P.; Felser, Claudia

    2013-05-01

    We investigate the structural stability and magnetic properties of the cubic, tetragonal and hexagonal phases of Mn3Z (Z=Ga, Sn and Ge) Heusler compounds using first-principles density-functional theory. We propose that the cubic phase plays an important role as an intermediate state in the phase transition from the hexagonal to the tetragonal phases. Consequently, Mn3Ga and Mn3Ge behave differently from Mn3Sn, because the relative energies of the cubic and hexagonal phases are different. This result agrees with experimental observations for these three compounds. The weak ferromagnetism of the hexagonal phase and the perpendicular magnetocrystalline anisotropy of the tetragonal phase obtained in our calculations are also consistent with experiment.

  4. FCC 5 and FCC 6 (3/4)

    CERN Document Server

    CERN. Geneva; Schulte, Daniel

    2016-01-01

    Abstract: The electron-positron collider, FCC-ee, should provide collisions over a wide range of beam energies, ranging from roughly 35 GeV to almost 200 GeV. The physics goals of the FCC-ee collider call for luminosities around 1e36 cm-2s-1 per interaction point at the Z pole and several 1e34 cm-2s-1 at the ZH production peak. The beam energy should be pushed above 175 GeV, with a total synchrotron-radiation power not exceeding 100 MW. The extremely high luminosities and resulting short beam lifetime, due to radiative Bhabha scattering, can be sustained by top-up injection. The FCC-ee acce...

  5. Structural and electronic properties of cubic KNbO{sub 3} (0 0 1) surfaces: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Bingcheng [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Wang, Xiaohui, E-mail: wxh@mail.tsinghua.edu.cn [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Tian, Enke [School of Science, China University of Geosciences, Beijing 100083 (China); Li, Guowu [Crystal Structure Laboratory, National Laboratory of Mineral Materials, China University of Geosciences, Beijing 100083 (China); Li, Longtu [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2015-10-01

    Highlights: • To the best of our knowledge, the (0 0 1) surfaces of SrTiO{sub 3}, BaTiO{sub 3}, CaTiO{sub 3} and PbTiO{sub 3} have been extensively investigated, but few ab initio calculations of structural and electronic properties of cubic KNbO{sub 3} (0 0 1) surface are reported. • The surface energy for the KO terminated was 1.21 eV, higher than the calculated surface energy of 0.75 eV for NbO{sub 2} termination, revealing that it take much less energy to cleave on the NbO{sub 2} plane than on the KO plane. • Mulliken population showed a strong increase in the K−O chemical bonding on the top surface of the KO-terminated slab, while the Nb−O chemical bonding on the top surface of the NbO{sub 2}-terminated slab decreased by 50 me. • The bond populations for K−O were much smaller than that for Nb−O, indicating significant covalency for Nb−O bonding. - Abstract: We present the calculations of the cubic perovskite KNbO{sub 3} (0 0 1) surface with NbO{sub 2} and KO terminations within the first-principles density functional theory. The electronic structure, surface energy, and charge distribution for both termination are calculated. For the case of NbO{sub 2}-terminated surfaces, the largest atomic relaxation is in the first-layer atoms, while for KO terminations in the second-layer atoms. The surface energy for the KO terminated was 1.21 eV, higher than the calculated surface energy of 0.75 eV for NbO{sub 2} termination, revealing that it takes much less energy to cleave on NbO{sub 2} plane than on a KO plane. The band gaps for KO-terminated and NbO{sub 2}-terminated surface are 1.70 and 1.30 eV, respectively. Mulliken population analysis shows the strong increase in the K−O chemical bonding on the top surface of the KO-terminated slab and significant covalency for Nb−O bonding.

  6. Effect of alloying element nickel on structural stability of FCC Fe-Cu precipitates studied by first-principles calculations%合金元素镍对FCC Fe-Cu析出相结构稳定性的影响

    Institute of Scientific and Technical Information of China (English)

    温玉锋; 孙坚

    2013-01-01

    采用基于投影缀加波赝势和广义梯度近似的第一性原理和特殊准随机结构模型计算FCC结构Fe-25Cu、Fe-31.25Cu、Fe-3.125Ni-25Cu和Fe-3.125Ni-31.25Cu无序固溶体的基态性质、弹性常数以及电子结构,其中无序固溶体晶胞结构建立在由特殊准随机结构方法所产生的结构模型基础上。计算结果表明:FCC 结构Fe-Ni-Cu无序固溶体存在无磁性与铁磁性两种状态,其中铁磁性 Fe-Cu 和 Fe-Ni-Cu 无序固溶体的能量相对较低;铁磁性Fe-25Cu和Fe-3.125Ni-25Cu无序固溶体不满足Born弹性稳定性准则,而Fe-31.25Cu和Fe-3.125Ni-31.25Cu无序固溶体满足Born弹性稳定性准则,以亚稳态形式存在,合金元素Ni的加入显著提高了铁磁性FCC结构Fe-31.25Cu无序固溶体的结构稳定性。%The first-principles method based on projector augmented wave pseudo-potential and generalized gradient approximation was employed to calculate the ground state properties, elastic constants and electronic structures of FCC structured Fe-25Cu, Fe-31.25Cu, Fe-3.125Ni-25Cu and Fe-3.125Ni-31.25Cu random solid solutions. The cells of the random solid solutions were established based on the special quasirandom structure (SQS) models. The calculated results show that nonmagnetic and ferromagnetic states exist in FCC Fe-Ni-Cu random solid solutions, and Fe-Cu and Fe-Ni-Cu random solid solutions in the ferromagnetic state have lower energy. The ferromagnetic Fe-25Cu and Fe-3.125Ni-25Cu random solid solutions do not satisfy Born criterion of elastic stability, whereas the Fe-31.25Cu and Fe-3.125Ni-31.25Cu random solid solutions satisfy Born criterion of elastic stability and can exist as a metastable phase. The addition of alloying element of nickel can significantly improve the structural stability of FCC Fe-31.25Cu random solid solution.

  7. Structural and Optoelectronic Properties of Cubic CsPbF3 for Novel Applications

    Institute of Scientific and Technical Information of China (English)

    G. Murtaza; Iftikhar Ahmad; M. Maqbool; H. A. Rahnamaye Aliabad; A. Afaq

    2011-01-01

    Chemical bonding as well as structural, electronic and optical properties of CsPbF3 are calculated using the highly accurate full potential linearized augmented plane-wave method within the framework of density functional theory (DFT). The calculated lattice constant is found to be in good agreement with the experimental results. The electron density plots reveal strong ionic bonding in Cs-F and strong covalent bonding in Pb-F. The calculations show that the material is a direct and wide bandgap semiconductor with a fundamental gap at the R-symmetry point. Optical properties such as the real and imaginary parts of the dielectric function, refractive index, extinction coefficient, reflectivity, optical conductivity and absorption coefficient are also calculated. Based on the calculated wide and direct bandgap, as well as other optical properties of the compound, it is predicted that CsPbF3 is suitable for optoelectronic devices and anti-reflecting coatings.%Chemical bonding as well as structural,electronic and optical properties of CsPbF3 are calculated using the highly accurate full potential linearized augmented plane-wave method within the framework of density functional theory (DFT).The calculated lattice constant is found to be in good agreement with the experimental results.The electron density plots reveal strong ionic bonding in Cs-F and strong covalent bonding in Pb-F.The calculations show that the material is a direct and wide bandgap semiconductor with a fundamental gap at the R-symmetry point.Optical properties such as the real and imaginary parts of the dielectric function,refractive index,extinction coefficient,reflectivity,optical conductivity and absorption coefficient are also calculated.Based on the calculated wide and direct bandgap,as well as other optical properties of the compound,it is predicted that CsPbF3 is suitable for optoelectronic devices and anti-reflecting coatings.Perovskites have gained high technological and fundamental importance

  8. Structural and electronic properties of V-doped cubic BN: A density functional theory study

    Science.gov (United States)

    Espitia R, Miguel J.; Díaz F, John H.; Rodríguez Martínez, Jairo Arbey

    2016-10-01

    The structural, electronic, and magnetic properties of c-BN compound doped with V atoms were calculated by means of the pseudopotential method, employed exactly as implemented in computational Quantum ESPRESSO code. For the description of the electron-electron interaction, generalized gradient approximation (GGA) was used. A half-metallic behavior is predicted for the concentrations B0.9375V0.0625N and B0.875V0.125N, because of the fact that the majority spins are metallic and the minority spins are semiconducting. We found magnetic moments of 2.0 and 4.0 μβ per supercell, respectively. The main contribution to the magnetic moment comes from the V atom, with local moments of 1.61 μβ/V-atom. These compounds are good candidates for potential applications in spintronics and as spin injectors.

  9. Ab initio lattice stability of fcc and hcp Fe-Mn random alloys.

    Science.gov (United States)

    Gebhardt, T; Music, D; Hallstedt, B; Ekholm, M; Abrikosov, I A; Vitos, L; Schneider, J M

    2010-07-28

    We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Néel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Néel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

  10. Structure of the body-centered cubic phase of lipid systems does not consist of indefinitely long straight rods

    OpenAIRE

    Luzzati, Vittorio; Tardieu, Annette; Gulik-Krzywicki, Tadeusz

    1981-01-01

    The observed intensities of the reflections from the body-centered cubic phase of lipid systems are shown to be incompatible with a recently reported model consisting of straight, indefinitely long rods.

  11. Ab initio density functional theory investigation of the structural, electronic and optical properties of Ca{sub 3}Sb{sub 2} in hexagonal and cubic phases

    Energy Technology Data Exchange (ETDEWEB)

    Arghavani Nia, Borhan, E-mail: b.arghavani@gmail.com [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Sedighi, Matin [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Shahrokhi, Masoud [Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Moradian, Rostam [Nano-Science and Nano-Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Computational Physics Science Research Laboratory, Department of Nano-Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-1795, Tehran (Iran, Islamic Republic of)

    2013-11-15

    A density functional theory study of structural, electronical and optical properties of Ca{sub 3}Sb{sub 2} compound in hexagonal and cubic phases is presented. In the exchange–correlation potential, generalized gradient approximation (PBE-GGA) has been used to calculate lattice parameters, bulk modulus, cohesive energy, dielectric function and energy loss spectra. The electronic band structure of this compound has been calculated using the above two approximations as well as another form of PBE-GGA, proposed by Engle and Vosko (EV-GGA). It is found that the hexagonal phase of Ca{sub 3}Sb{sub 2} has an indirect gap in the Γ→N direction; while in the cubic phase there is a direct-gap at the Γ point in the PBE-GGA and EV-GGA. Effects of applying pressure on the band structure of the system studied and optical properties of these systems were calculated. - Graphical abstract: A density functional theory study of structural, electronic and optical properties of Ca{sub 3}Sb{sub 2} compound in hexagonal and cubic phases is presented. Display Omitted - Highlights: • Physical properties of Ca{sub 3}Sb{sub 2} in hexagonal and cubic phases are investigated. • It is found that the hexagonal phase is an indirect gap semiconductor. • Ca{sub 3}Sb{sub 2} is a direct-gap semiconductor at the Γ point in the cubic phase. • By increasing pressure the semiconducting band gap and anti-symmetry gap are decreased.

  12. Synthesis of 4H/fcc-Au@M (M = Ir, Os, IrOs) Core-Shell Nanoribbons For Electrocatalytic Oxygen Evolution Reaction.

    Science.gov (United States)

    Fan, Zhanxi; Luo, Zhimin; Chen, Ye; Wang, Jie; Li, Bing; Zong, Yun; Zhang, Hua

    2016-08-01

    The high-yield synthesis of 4H/face-centered cubic (fcc)-Au@Ir core-shell nanoribbons (NRBs) is achieved via the direct growth of Ir on 4H Au NRBs under ambient conditions. Importantly, this method can be used to synthesize 4H/fcc-Au@Os and 4H/fcc-Au@IrOs core-shell NRBs. Significantly, the obtained 4H/fcc-Au@Ir core-shell NRBs demonstrate an exceptional electrocatalytic activity toward the oxygen evolution reaction under acidic condition, which is much higher than that of the commercial Ir/C catalyst.

  13. New developments in FCC catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, C.P. [BASF Corporation, Iselin, NJ (United States)

    2011-07-01

    Fluid catalytic cracking (FCC) unit is one of the primary boiling point reduction units in the refinery that converts longer chain crude oil to useful products such as distillate, gasoline and LPG. As the quality of feedstock deteriorates, while specifications on the product side are becoming more and more stringent, the FCC unit is being severely challenged. Over the past few years BASF has introduced two new platform technologies that will assist in this challenge. This paper will present an overview of those platforms and also provide a brief update on the research underway to mitigate the current REO crisis. (orig.)

  14. FCC-ee: Energy calibration

    CERN Document Server

    Koratzinos, M; Gianfelice-Wendt, E; Zimmermann, F

    2015-01-01

    The FCC-ee aims to improve on electroweak precision measurements, with goals of 100 keV on the Z mass and width, and a fraction of MeV on the W mass. Compared to LEP, this implies a much improved knowledge of the centre-of-mass energy when operating at the Z peak and WW threshold. This can be achieved by making systematic use of resonant depolarization. A number of issues have been identified, due in particular to the long polarization times. However the smaller emittance and energy spread of FCC-ee with respect to LEP should help achieve a much improved performance.

  15. FCC-ee: Energy Calibration

    Energy Technology Data Exchange (ETDEWEB)

    Koratzinos, M. [Univ. of Geneva (Switzerland); Blondel, A. [Univ. of Geneva (Switzerland); Gianfelice-Wendt, E. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Zimmermann, F. [European Organization for Nuclear Research (CERN), Geneva (Switzerland)

    2015-06-02

    The FCC-ee aims to improve on electroweak precision measurements, with goals of 100 ke V on the Z mass and width, and a fraction of MeV on the W mass. Compared to LEP, this implies a much improved knowledge of the center-of-mass energy when operating at the Z peak and WW threshold. This can be achieved by making systematic use of resonant depolarization. A number of issues have been identified, due in particular to the long polarization times. However the smaller emittance and energy spread of FCC-ee with respect to LEP should help achieve a much improved performance.

  16. LatticeLibrary and BccFccRaycaster: Software for processing and viewing 3D data on optimal sampling lattices

    Directory of Open Access Journals (Sweden)

    Elisabeth Schold Linnér

    2016-01-01

    Full Text Available In this paper, we present LatticeLibrary, a C++ library for general processing of 2D and 3D images sampled on arbitrary lattices. The current implementation supports the Cartesian Cubic (CC, Body-Centered Cubic (BCC and Face-Centered Cubic (FCC lattices, and is designed to facilitate addition of other sampling lattices. We also introduce BccFccRaycaster, a plugin for the existing volume renderer Voreen, making it possible to view CC, BCC and FCC data, using different interpolation methods, with the same application. The plugin supports nearest neighbor and trilinear interpolation at interactive frame rates. These tools will enable further studies of the possible advantages of non-Cartesian lattices in a wide range of research areas.

  17. LatticeLibrary and BccFccRaycaster: Software for processing and viewing 3D data on optimal sampling lattices

    Science.gov (United States)

    Linnér, Elisabeth Schold; Morén, Max; Smed, Karl-Oskar; Nysjö, Johan; Strand, Robin

    In this paper, we present LatticeLibrary, a C++ library for general processing of 2D and 3D images sampled on arbitrary lattices. The current implementation supports the Cartesian Cubic (CC), Body-Centered Cubic (BCC) and Face-Centered Cubic (FCC) lattices, and is designed to facilitate addition of other sampling lattices. We also introduce BccFccRaycaster, a plugin for the existing volume renderer Voreen, making it possible to view CC, BCC and FCC data, using different interpolation methods, with the same application. The plugin supports nearest neighbor and trilinear interpolation at interactive frame rates. These tools will enable further studies of the possible advantages of non-Cartesian lattices in a wide range of research areas.

  18. Cubical sets and the topological topos

    DEFF Research Database (Denmark)

    Spitters, Bas

    2016-01-01

    Coquand's cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. This paper contributes to the understanding of this model. We make three contributions...... show that it can also be a target for cubical realization by showing that Coquand's cubical sets classify the geometric theory of flat distributive lattices. As a side result, we obtain a simplicial realization of a cubical set. 2. Using the internal `interval' in the topos of cubical sets, we...... construct a Moore path model of identity types. 3. We construct a premodel structure internally in the cubical type theory and hence on the fibrant objects in cubical sets....

  19. FCC 3 and FCC 4 (2/4)

    CERN Document Server

    CERN. Geneva; Dam, Mogens

    2016-01-01

    Abstract: Owing to its specific interaction region design, the FCC-ee will be able to deliver unprecedented luminosities at centre-of-mass energies ranging from below the Z pole to the ttbar threshold and above. Operation at four energy regimes - at the Z pole, at the WW threshold, at 240 GeV for Higgs production, and at the ttbar thre...

  20. Migration mechanism for oversized solutes in cubic lattices: The case of yttrium in iron

    Science.gov (United States)

    Bocquet, Jean-Louis; Barouh, Caroline; Fu, Chu-Chun

    2017-06-01

    Substitutional solutes in metals generally diffuse by successive exchanges with vacancies, that is, via the so called vacancy mechanism. However, recent density functional theory (DFT) calculations predicted an atypical behavior for the oversized solute atoms (OSAs) in bcc and fcc iron. These solutes exhibit a very strong attraction with a nearby vacancy (V) at a first neighbor (1nn) distance. The attraction is so large that the 1nn OSA-V pair is no longer stable and relaxes spontaneously towards a new configuration where the OSA sits in the middle of the two half-vacancies (V/2). As a consequence, the diffusion of OSAs cannot be described by the standard vacancy mechanism. A new migration mechanism with a new formulation of correlation effects is required. The present study rests on a revised expression of the diffusion coefficient of the OSAs in bcc and fcc lattices, which introduces the concept of macrojumps. The formalism is applied presently to the case of yttrium (Y: a principal alloying element of advanced steels) in iron, using DFT data. But it is directly transferable to other OSAs in cubic metal lattices. At variance with the standard substitutional solutes, the Y atom is found to diffuse more rapidly than iron at all temperatures by orders of magnitude in the two cubic-Fe structures. This finding is opposite to the recent common belief that yttrium is a slow diffusing species in Fe alloys, based on experimental evidences. Several suggestions are proposed to solve this apparent inconsistency.

  1. The Role of Ligand Packing Frustration in Body-Centered Cubic (bcc) Superlattices of Colloidal Nanocrystals.

    Science.gov (United States)

    Goodfellow, Brian W; Yu, Yixuan; Bosoy, Christian A; Smilgies, Detlef-M; Korgel, Brian A

    2015-07-02

    This paper addresses the assembly of body centered-cubic (bcc) superlattices of organic ligand-coated nanocrystals. First, examples of bcc superlattices of dodecanethiol-capped Au nanocrystals and oleic acid-capped PbS and PbSe nanocrystals are presented and examined by transmission electron microscopy (TEM) and grazing incidence small-angle X-ray scattering (GISAXS). These superlattices tend to orient on their densest (110) superlattice planes and exhibit a significant amount of {112} twinning. The same nanocrystals deposit as monolayers with hexagonal packing, and these thin films can coexist with thicker bcc superlattice layers, even though there is no hexagonal plane in a bcc lattice. Both the preference of bcc in bulk films over the denser face-centered cubic (fcc) superlattice structure and the transition to hexagonal monolayers can be rationalized in terms of packing frustration of the ligands. A model is presented to calculate the difference in entropy associated with capping ligand packing frustration in bcc and fcc superlattices.

  2. Packing of crystalline structures of binary hard spheres: an analytical approach and application to amorphization.

    Science.gov (United States)

    Brouwers, H J H

    2007-10-01

    The geometrical stability of the three lattices of the cubic crystal system, viz. face-centered cubic (fcc), body-centered cubic (bcc), and simple cubic (sc), consisting of bimodal discrete hard spheres, and the transition to amorphous packing is studied. First, the random close packing (rcp) fraction of binary mixtures of amorphously packed spheres is recapitulated. Next, the packing of a binary mixture of hard spheres in randomly disordered cubic structures is analyzed, resulting in original analytical expressions for the unit cell volume and the packing fraction, and which are also valid for the other five crystal systems. The bimodal fcc lattice parameter appears to be in close agreement with empirical hard sphere data from literature, and this parameter could be used to distinguish the size mismatch effect from all other effects in distorted binary lattices of materials. Here, as a first model application, bimodal amorphous and crystalline fcc/bcc packing fractions are combined, yielding the optimum packing configuration, which depends on mixture composition and diameter ratio only. Maps of the closest packing mode are established and applied to colloidal mixtures of polydisperse spheres and to binary alloys of bcc, fcc, and hcp metals. The extensive comparison between the analytical expressions derived here and the published numerical and empirical data yields good agreement. Hence, it is seen that basic space-filling theories on "simple" noninteracting hard spheres are a valuable tool for the study of crystalline materials.

  3. Packing of crystalline structures of binary hard spheres: An analytical approach and application to amorphization

    Science.gov (United States)

    Brouwers, H. J. H.

    2007-10-01

    The geometrical stability of the three lattices of the cubic crystal system, viz. face-centered cubic (fcc), body-centered cubic (bcc), and simple cubic (sc), consisting of bimodal discrete hard spheres, and the transition to amorphous packing is studied. First, the random close packing (rcp) fraction of binary mixtures of amorphously packed spheres is recapitulated. Next, the packing of a binary mixture of hard spheres in randomly disordered cubic structures is analyzed, resulting in original analytical expressions for the unit cell volume and the packing fraction, and which are also valid for the other five crystal systems. The bimodal fcc lattice parameter appears to be in close agreement with empirical hard sphere data from literature, and this parameter could be used to distinguish the size mismatch effect from all other effects in distorted binary lattices of materials. Here, as a first model application, bimodal amorphous and crystalline fcc/bcc packing fractions are combined, yielding the optimum packing configuration, which depends on mixture composition and diameter ratio only. Maps of the closest packing mode are established and applied to colloidal mixtures of polydisperse spheres and to binary alloys of bcc, fcc, and hcp metals. The extensive comparison between the analytical expressions derived here and the published numerical and empirical data yields good agreement. Hence, it is seen that basic space-filling theories on “simple” noninteracting hard spheres are a valuable tool for the study of crystalline materials.

  4. Temperature-Induced Phase Transition of In2O3 from a Rhombohedral Structure to a Body-Centered Cubic Structure

    Institute of Scientific and Technical Information of China (English)

    YANG Lin-Hong; DONG Hong-Xing; SUN Zheng; SUN Liao-Xin; SHEN Xue-Chu; CHEN Zhang-Hai

    2011-01-01

    @@ We report an experimental study on the temperature-induced phase transition of three-dimensional nanosheetbased flower-like microspheres(NBFMs)of In2O3.Using InOOH as precursor, rhombohedral-In2O3 NBFMs are fabricated.Temperature-induced phase transition of In2O3 NBFMs from a rhombohedral(rh) structure to a body-centered cubic(bcc) structure is examined by Raman spectroscopy and x-ray diffraction.The critical phase transition temperature is found to be about 500℃.Photoluminescence(PL)spectra of In2O3 are measured before annealing and after annealing at different temperatures.The PL spectral results provide further evidence for the phase transition, confirming the fabrication of bcc-In2O3 NBFMs via a simple annealing method.

  5. Ab initio density functional theory investigation of the structural, electronic and optical properties of Ca3Sb2 in hexagonal and cubic phases

    Science.gov (United States)

    Arghavani Nia, Borhan; Sedighi, Matin; Shahrokhi, Masoud; Moradian, Rostam

    2013-11-01

    A density functional theory study of structural, electronical and optical properties of Ca3Sb2 compound in hexagonal and cubic phases is presented. In the exchange-correlation potential, generalized gradient approximation (PBE-GGA) has been used to calculate lattice parameters, bulk modulus, cohesive energy, dielectric function and energy loss spectra. The electronic band structure of this compound has been calculated using the above two approximations as well as another form of PBE-GGA, proposed by Engle and Vosko (EV-GGA). It is found that the hexagonal phase of Ca3Sb2 has an indirect gap in the Γ→N direction; while in the cubic phase there is a direct-gap at the Γ point in the PBE-GGA and EV-GGA. Effects of applying pressure on the band structure of the system studied and optical properties of these systems were calculated.

  6. 催化裂化汽提技术的发展%THE DEVELOPMENT OF FCC STRIPPING TECHNOLOGY

    Institute of Scientific and Technical Information of China (English)

    张振千

    2003-01-01

    This article briefly describes the major patents domestic and the abroad, and the current situation and achievements of FCC stripping technology in China. The developing trend of FCC stripping technology is presented, including further developments of FCC stripper to improve unit performance, combination of the stripper and pre-stripper within disengager to form a complete high-efficiency FCC stripping system. In addition to high efficiency, simple structure and easiness of installation and maintenance for a new FCC stripper are all of consideration.

  7. Cubic to tetragonal crystal lattice reconstruction during ordering or decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Byung-kl [Carnegie-Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering

    1992-09-01

    This thesis studied thermodynamic stability and morphology of product phases in diffusional phase transformations involving cubic-to-tetragonal crystal lattice reconstructions. Two different kinds of diffusional transformations were examined: L1{sub 0} ordering (fcc to fct lattice change) and decomposition of off-stoichiometric B2 ordering alloys accompanying bcc to fcc Bain transformation. In the first case, Fe-45 at.% Pd alloys were studied by TEM; in the second, the Bain strain relaxation during decomposition of hyper-eutectoid Cu-9.04 wt% Be alloy was studied. CuAu and InMg were also studied.

  8. FCC and the Sunshine Act.

    Science.gov (United States)

    Weiss, Kenneth

    The Sunshine Act, designed to encourage open meetings to increase public understanding of the governmental decision-making process, went into effect in March 1977. A total of 50 agencies, including the Federal Communications Commission (FCC), are subject to the provisions of the Sunshine Act. The act lists 10 exemptions, any of which can result in…

  9. Radiation damage in fcc metals

    NARCIS (Netherlands)

    Lindgreen, Ronald Julius Theodorus

    1984-01-01

    In dit proefschrift worden de structuurveranderingen ten gevolge van stralingsschade behandeld, in het bijzonder schade ontstaan door implantatie van zware deeltjes in fcc metalen. Gedetailleerde kennis van deze structuurveranderingen is van belang gezien de grote en soms gunstige invloed hiervan op

  10. Effect of microstructure of vacuum-deposited Fe{sub 100-x}Ni{sub x} (30 < x < 39) foils with FCC structure on their mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Ustinov, A.I. [E.O. Paton Electric Welding Institute of National Academy of Science of Ukraine, 11 Bozhenko St., 03680 Kiev (Ukraine); Polishchuk, S.S. [G.V. Kurdyumov Institute for Metal Physics of National Academy of Science of Ukraine, 36 Academician Vernadsky Blvd., 03680 Kiev (Ukraine); Demchenkov, S.A., E-mail: s_demchenkov@ukr.net [E.O. Paton Electric Welding Institute of National Academy of Science of Ukraine, 11 Bozhenko St., 03680 Kiev (Ukraine); Petrushinets, L.V. [E.O. Paton Electric Welding Institute of National Academy of Science of Ukraine, 11 Bozhenko St., 03680 Kiev (Ukraine)

    2015-02-15

    Highlights: • Nanostructured Fe-Ni foils with FCC lattice were produced by EBPVD method. • It is found that the foils microhardness increases as the grain size decreases. • The Hall-Petch’s relationship for the foils exhibits a non-linear dependence. • The non-linearity is related to the increase in both porosity and microstrains. - Abstract: The present paper considers the relation between microstructure characteristics of vacuum-deposited Fe{sub 100-x}Ni{sub x} (30 < x < 39) foils and their mechanical properties. The foils 40-100 μm thick with various microstructure characteristics were prepared using electron beam physical vapor deposition (EBPVD) onto substrates maintained at different temperatures in the 250-700 °S range. The foil microhardness increases as deposition temperature decreases and reaches the maximum value of 5 GPa for foils deposited at 300 °C. It has been shown that the crystallite size in the foils decreases monotonically from sub-micron values (over 100 nm) to nanoscaled ones (10-20 nm), while the level of microstrains of FCC lattice increases to 1% with lowering deposition temperature. The dependence of foil microhardness on the crystallite size in the Hall-Petch’s coordinates (Hμ vs d{sup -1/2}) exhibits the deviation from a linear function at microhardness of 5 GPa. Such behavior of the foil microhardness at decreasing deposition temperature correlates with an abrupt increase in both porosity and microstrains level.

  11. Towards an unbiased comparison of CC, BCC, and FCC lattices in terms of prealiasing

    KAUST Repository

    Vad, Viktor

    2014-06-01

    In the literature on optimal regular volume sampling, the Body-Centered Cubic (BCC) lattice has been proven to be optimal for sampling spherically band-limited signals above the Nyquist limit. On the other hand, if the sampling frequency is below the Nyquist limit, the Face-Centered Cubic (FCC) lattice was demonstrated to be optimal in reducing the prealiasing effect. In this paper, we confirm that the FCC lattice is indeed optimal in this sense in a certain interval of the sampling frequency. By theoretically estimating the prealiasing error in a realistic range of the sampling frequency, we show that in other frequency intervals, the BCC lattice and even the traditional Cartesian Cubic (CC) lattice are expected to minimize the prealiasing. The BCC lattice is superior over the FCC lattice if the sampling frequency is not significantly below the Nyquist limit. Interestingly, if the original signal is drastically undersampled, the CC lattice is expected to provide the lowest prealiasing error. Additionally, we give a comprehensible clarification that the sampling efficiency of the FCC lattice is lower than that of the BCC lattice. Although this is a well-known fact, the exact percentage has been erroneously reported in the literature. Furthermore, for the sake of an unbiased comparison, we propose to rotate the Marschner-Lobb test signal such that an undue advantage is not given to either lattice. © 2014 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.

  12. Cubic modification crystal structure of cesium neodymium tetrametaphosphates,. beta. -CsNd(POsub(3))sub(4) (CsNdP/sub 4/O/sub 12/)

    Energy Technology Data Exchange (ETDEWEB)

    Palkina, K.K.; Maksimova, S.I.; Chibiskova, N.T. (AN SSSR, Moscow. Inst. Obshchej i Neorganicheskoj Khimii)

    1981-01-01

    A complete X-ray structural investigation into ..beta..-CsNd (PO/sub 3/)/sub 4/ crystallites is presented. ..beta..-CsNd (PO/sub 3/)/sub 4/ is crystallized in the cubic crystal system; space group is 143 d; the parameters of the elementary cell are a=15.233 (3)A; Z=12, V=3535 4A/sup 3/, dsub(roent)=3.34 g/cm/sup 3/. Interatomic distances and valent angles of crystals are presented. It is shown that ..beta..- CsNd(NO/sub 3/)/sub 4/ noncentrosymmetric crystals are isotropic, as they belong to cubic crystal structure and must obviously combine simultaneously luminescent, optic non-linear and piezoelectric properties.

  13. First-principles study of the electronic structure of PbF{sub 2} in the cubic, orthorhombic, and hexagonal phases

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Huitian [Department of Physics, Michigan Technological University, Houghton, MI 49931 (United States); Orlando, Roberto [Dipartimento di Scienze e Tecnologie Avanzate, Universita del Piemonte Orientale, C. so Borsalino 54, I-15100 Alessandria (Italy); Blanco, Miguel A [Departamento de QuImica Fisica y Analitica, Universidad de Oviedo, 33006-Oviedo (Spain); Pandey, Ravindra [Department of Physics, Michigan Technological University, Houghton, MI 49931 (United States)

    2004-05-12

    The results of electronic structure calculations for PbF{sub 2} in ambient and high-pressure phases are reported here. We employ the linear combination of atomic orbital-density functional theory approximation using the CRYSTAL program package whose capabilities were expanded to include the so-called soft-core pseudopotentials with higher-order components (e.g. d, f, and g) of the angular momentum terms for heavier atoms in the periodic table. The band structure and density of states of the cubic, orthorhombic, and hexagonal phases were calculated. A direct band gap at X is predicted for the cubic phase, whereas an indirect band gap is predicted for the high-pressure phases. The density of states reveals hybridization features involving Pb s and F p orbitals in the upper valence band of PbF{sub 2}.

  14. Micromagnetic simulations of interacting dipoles on an fcc lattice: application to nanoparticle assemblies.

    Science.gov (United States)

    Plumer, M L; van Lierop, J; Southern, B W; Whitehead, J P

    2010-07-28

    Micromagnetic simulations are used to examine the effects of cubic and axial anisotropy, magnetostatic interactions and temperature on M-H loops for a collection of magnetic dipoles on fcc and sc lattices. We employ a simple model of interacting dipoles that represent single-domain particles in an attempt to explain recent experimental data on ordered arrays of magnetoferritin nanoparticles that demonstrate the crucial role of interactions between particles in an fcc lattice. Significant agreement between the simulation and experimental results is achieved, and the impact of intra-particle degrees of freedom and surface effects on thermal fluctuations is investigated.

  15. First principles study of the structural and electronic properties of double perovskite Ba2YTaO6 in cubic and tetragonal phases

    Science.gov (United States)

    Deluque Toro, C. E.; Rodríguez M., Jairo Arbey; Landínez Téllez, D. A.; Moreno Salazar, N. O.; Roa-Rojas, J.

    2014-12-01

    The Ba2YTaO6 double perovskite presents a transition from cubic (Fm-3m) to tetragonal structure (I4/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba2YTaO6 in space group Fm-3m and I4/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations. From the minimization of energy as a function of volume and the fitting of the Murnaghan equation some structural characteristics were determined as, for example, total energy, lattice parameter (a=8.50 Å in cubic phase and a=5.985 Å and c=8.576 Å in tetragonal), bulk modulus (135.6 GPa in cubic phase and 134.1 GPa in tetragonal phase) and its derivative. The study of the electronic characteristics was performed from the analysis of the electronic density of states (DOS). We find a non-metallic behavior for this with a direct band gap of approximately 3.5 eV and we found that the Ba2YTaO6 (I4/m) phase is the most stable one. © 2013 Elsevier Science.

  16. Reply to “Structural and magnetic behavior of the cubic oxyfluoride SrFeO{sub 2}F studied by neutron diffraction”

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, Oliver, E-mail: oliver.clemens@kit.edu [Technische Universität Darmstadt, Joint Research Laboratory Nanomaterials, Jovanka-Bontschits-Straße 2, 64287 Darmstadt (Germany); Karlsruher Institut für Technologie, Institut für Nanotechnologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Berry, Frank J.; Wright, Adrian J. [School of Chemistry, The University of Birmingham, Birmingham B15 2TT (United Kingdom); Knight, Kevin S. [ISIS Facility, Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX (United Kingdom); Perez-Mato, J.M.; Igartua, J.M. [Departamentos de Física de la Materia Condensada y Física Aplicada II, Facultad de Ciencia y Tecnología, Universidad del País Vasco (UPV/EHU), Apdo. 644, 48080 Bilbao (Spain); Slater, Peter R. [School of Chemistry, The University of Birmingham, Birmingham B15 2TT (United Kingdom)

    2015-03-15

    In this article we comment on the results published by Thompson et al. (, J. Solid State Chem. 219 (2014) 173–178) on the crystal structure of SrFeO{sub 2}F, who claim the compound to crystallize in the cubic space group Pm-3m. We give a more detailed explanation of the determination of our previously reported structural model with Imma symmetry (Clemens et al., J. Solid State Chem. 206 (2013) 158–169), with addition of variable temperature XRD measurements with high counting time to provide unambiguous evidence for the Imma model being correct for our sample. - Graphical abstract: The crystal structure of SrFeO{sub 2}F is discussed with regards to previous reports. - Highlights: • SrFeO{sub 2}F was synthesized by polymer based fluorination of SrFeO{sub 3}. • Evaluation of the diffraction data shows a pseudocubic cell metric. • Superstructure reflections at low d-spacings indicate deviation from cubic symmetry. • The phase transition temperature from orthorhombic to cubic was determined using variable temperature X-ray diffraction. • Results published by Thompson et al. are critically discussed with respect to those observations.

  17. On Groups Whose Proper Quotients Are FCc-Groups with the Maximal Condition%其真商群为满足极大条件的FCc-群的群

    Institute of Scientific and Technical Information of China (English)

    张志让; 邢世奇

    2012-01-01

    如果FCc-群满足极大条件,那么称之为(FCc) max群;如果群G的所有真商群都是(FCc) max-群,但是G本身不是(FCc) max-群,那么称群G为外(FCc)-max群.主要利用外FNc-群的结果,给出外(FCc)max群的结构描述,同时还推广了群的上下中心列的有限性条件.%A group is an (FCc )max-group if it is an FCc-group with the maximal condition. Group G is said to be a just non-(FCc )max-group if all of its proper quotients are (FCc )max-groups, but G itself is not. The main purpose of this article is to give a description of the structure of just non-(FCc )max-groups by making use of the results of just non-FNc-groups. Hall on finiteness conditions of upper and lower central series of groups is given.

  18. Phase-field-crystal model for fcc ordering.

    Science.gov (United States)

    Wu, Kuo-An; Adland, Ari; Karma, Alain

    2010-06-01

    We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to and reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free-energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a nonvanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a nonvanishing tetragonal shear modulus (C11-C12)/2. We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid-density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.

  19. Interaction in equilibrium plasmas of charged macroparticles located in nodes of cubic lattices

    Science.gov (United States)

    Filippov, A. V.

    2016-11-01

    Interaction of two charged pointlike macroparticles located at nodes of simple cubic (sc), body-centered cubic (bcc) and face-centered cubic (fcc) lattices in an equilibrium plasma is studied within the linearized Poisson-Boltzmann model. It is shown that the boundary shape has a strong influence on the electrostatic interaction between two macroparticles, which switches from repulsion at small interparticle distances to attraction as it approaches the halflength of a computational cell. It is found that in a case of dust particles arranged in the nodes of the sc, bcc and fcc lattices, the electrostatic force acting on them is equal to zero and the nature of the interaction changes from repulsion to attraction; hence, the infinite sc, bcc and fcc lattices of charged dust particles are thermodynamically stable at rather low temperatures.

  20. Impact of magnetic fluctuations on lattice excitations in fcc nickel.

    Science.gov (United States)

    Körmann, Fritz; Ma, Pui-Wai; Dudarev, Sergei L; Neugebauer, Jörg

    2016-02-24

    The spin-space averaging formalism is applied to compute atomic forces and phonon spectra for magnetically excited states of fcc nickel. Transverse and longitudinal magnetic fluctuations are taken into account by a combination of magnetic special quasi random structures and constrained spin-density-functional theory. It turns out that for fcc Ni interatomic force constants and phonon spectra are almost unaffected by both kinds of spin fluctuations. Given the computational expense to simulate coupled magnetic and atomic fluctuations, this insight facilitates computational modeling of magnetic alloys such as Ni-based superalloys.

  1. Impact of FCC regenerator design in the NOx emissions

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Hugo Borges; Sandes, Emanuel Freire; Gilbert, William Richard; Roncolatto, Rodolfo Eugenio; Gobbo, Rodrigo; Casavechia, Luiz Carlos; Candido, William Victor Carlos [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Bridi, Patricia Elaine [Possebon Engenharia, Sao Mateus do Sul, PR (Brazil)

    2012-07-01

    Fluid Catalytic Cracking (FCC) is the main point source of NOx in the refinery and it is responsible for at least 20% of the total NOx emissions from the refineries. The thermal NOx formation in the FCC regenerator is negligible. However, half of the feed nitrogen is converted to coke, and is burned in the regenerator. The majority of coke nitrogen is reduced to N2 and less than 10% is converted to NOx. This number may vary significantly with the oxygen excess in the flue gas and other operational conditions. With the purpose of evaluating the impact of different regenerator designs in NOx formation, several tests were carried out in the PETROBRAS FCC prototype unit. The test unit is equipped with adiabatic insulation and a CO boiler, allowing it to reproduce the heat balance of a commercial FCC and to operate either in full combustion or partial combustion. Two different designs of FCC regenerators were evaluated: single stage regenerator (the existing configuration) and two stage regenerator, with the catalyst bed divided into two sections by a structured packing baffle. It was observed in the tests that the combustion regime had a very strong effect on NOx formation. In full combustion, the effect of the FCC operating variables: excess oxygen, combustion promoter content in catalyst and regenerator design could be identified. The two stage configuration was capable of decreasing NOx emissions by 30%. In partial combustion, the effect of the CO-boiler variables on NOx emissions was overwhelming, but the use of the structured packing baffle was able to improve the catalyst regeneration.(author)

  2. Effect of Precursor Mechanism on CO-NO Catalytic Reaction on Body-Centred Cubic Structure: Monte Carlo Simulation

    Institute of Scientific and Technical Information of China (English)

    A. U. Qaisrani; M. Khalid; M. K.Khan

    2005-01-01

    @@ The CO-NO catalytic reaction on body-centred cubic (bcc) lattice is studied by Monte Carlo simulation. The simple Langmuir-Hinshelwood (LH) mechanism yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The effect of precursor mechanism on the phase diagram of the system is also studied. According to this mechanism, the precursor motion of CO molecules is considered only on the surface of bcc lattice. Some interesting observations are reported.

  3. Magnetic phase transformations of face-centered cubic and hexagonal close-packed Co at zero Kelvin.

    Science.gov (United States)

    Saal, James E; Shang, ShunLi; Wang, Yi; Liu, Zi-Kui

    2010-03-10

    The 0 K pressure-induced magnetic phase transformations of face-centered cubic (FCC) and hexagonal close packed (HCP) Co have been examined using first-principles calculations. Issues of fitting an equation of state to the first-principles energy versus volume data points containing a magnetic transformation and comparing to experimental phase equilibria are discussed. It is found that a fitting scheme employing only data where the magnetic moment decreases linearly with volume offers a physically meaningful behavior for the equation of state at metastable volumes. From this fitting, the ferromagnetic to nonmagnetic transformations with increasing pressure at 0 K are at 77 GPa and 123 GPa for FCC and HCP, respectively, and are first order and second order, respectively, on the basis of an unambiguous measure proposed in the paper. In addition to the HCP/FCC structure transformation at 99 GPa, another transformation at negative pressures is predicted, at - 31 GPa. These results are shown to be consistent with the extrapolations of the experimental pressure-temperature phase diagram to 0 K.

  4. Magnetic phase transformations of face-centered cubic and hexagonal close-packed Co at zero Kelvin

    Energy Technology Data Exchange (ETDEWEB)

    Saal, James E; Shang Shunli; Wang Yi; Liu Zikui, E-mail: jes531@psu.ed [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

    2010-03-10

    The 0 K pressure-induced magnetic phase transformations of face-centered cubic (FCC) and hexagonal close packed (HCP) Co have been examined using first-principles calculations. Issues of fitting an equation of state to the first-principles energy versus volume data points containing a magnetic transformation and comparing to experimental phase equilibria are discussed. It is found that a fitting scheme employing only data where the magnetic moment decreases linearly with volume offers a physically meaningful behavior for the equation of state at metastable volumes. From this fitting, the ferromagnetic to nonmagnetic transformations with increasing pressure at 0 K are at 77 GPa and 123 GPa for FCC and HCP, respectively, and are first order and second order, respectively, on the basis of an unambiguous measure proposed in the paper. In addition to the HCP/FCC structure transformation at 99 GPa, another transformation at negative pressures is predicted, at - 31 GPa. These results are shown to be consistent with the extrapolations of the experimental pressure-temperature phase diagram to 0 K.

  5. Phase transitions in antiferromagnets with a NaCl structure

    Energy Technology Data Exchange (ETDEWEB)

    Kassan-Ogly, F.A. [Institute of Metal Physics, Ural Division, Russian Academy of Sciences, ul. S.Kovalevskoi 18, Ekaterinburg 620219 (Russian Federation)]. E-mail: felix.kassan-ogly@imp.uran.ru; Filippov, B.N. [Institute of Metal Physics, Ural Division, Russian Academy of Sciences, ul. S.Kovalevskoi 18, Ekaterinburg 620219 (Russian Federation)

    2006-05-15

    A revised derivation scheme of possible magnetic structures in an FCC lattice with the nearest- and next-nearest-neighbor interactions taken into account is proposed. A model of simultaneous magnetic and structural phase transitions of the first order is developed for antiferromagnets with a NaCl structure and with a strong cubic magnetic anisotropy on the base of synthesis of magnetic modified 6-state Potts model and theoretical models of structural phase transitions in cubic crystals. It is shown that the high-temperature diffuse magnetic scattering of neutrons transforms into magnetic Bragg reflections below Neel point.

  6. Phase transitions in antiferromagnets with a NaCl structure

    Science.gov (United States)

    Kassan-Ogly, F. A.; Filippov, B. N.

    2006-05-01

    A revised derivation scheme of possible magnetic structures in an FCC lattice with the nearest- and next-nearest-neighbor interactions taken into account is proposed. A model of simultaneous magnetic and structural phase transitions of the first order is developed for antiferromagnets with a NaCl structure and with a strong cubic magnetic anisotropy on the base of synthesis of magnetic modified 6-state Potts model and theoretical models of structural phase transitions in cubic crystals. It is shown that the high-temperature diffuse magnetic scattering of neutrons transforms into magnetic Bragg reflections below Néel point.

  7. Determination of the structure of the cubic phase in high-ZrO{sub 2}Y{sub 2}O{sub 2}-ZrO{sub 2} alloys by CBED

    Energy Technology Data Exchange (ETDEWEB)

    McClellan, K.J.; Xiao, S.Q.; Lagerlof, K.P.D.; Heuer, A.H. [Case Western Reserve Univ., Cleveland, OH (United States)

    1993-06-20

    Convergent beam electron diffraction (CBED) was used to determine the space group of 9.9 and 18 mol% Y{sub 2}O{sub 3}-stabilized cubic ZrO{sub 2} (Y-CSZ) single crystals. The result (P43m space group) is different from the known tetragonal structure (P4{sub 2}/nmc space group) present in lower solute (3.2 mol% Y{sub 2}O{sub 3}) alloys, and the cubic structure (space group Fm3m) traditionally assumed for cubic ZrO{sub 2}. The oxygen sublattice of the cubic structure is distorted from Fm3m, relative to the cation sublattice, by displacements along the <111> directions. Computer simulations of the CBED patterns agree with experiment and suggest an anion displacement of {approximately}0.3 {Angstrom} from the (1/4,1/4,1/4) positions of the ideal fluorite structure.

  8. REACTION CHEMISTRY RELATED TO FCC GASOLINE QUALITY

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    About 80% of the gasoline pool as a whole in China for supplying the domestic market at current stage directly originates from FCC units. Obviously, FCC gasoline quality is critical for refiners to meet the nations more and more stringent gasoline specifications. FCC process is expected to produce gasoline with reduced contents of olefins, aromatics, benzene, sulfur, and, contradictorily, still with high octane number.   Catalytic cracking process involves a series of acid catalyzed reactions. Bronsted acid sites dominate the surface of the catalyst used for FCC process. All the reactions of hydrocarbons in FCC process are based on carbonium ions of penta-coordinated, or carbenium ions of tri-coordinated. The monomolecular beta scission mechanism for alkane cracking explains that the cracking of carbon-carbon bonding occurs at the beta position to the carbon atom bearing positive charge, and hence forms two small hydrocarbon molecules: one alkane molecule and one olefin molecule. The molar ratio of alkane to olefin for the primary cracking product will be 1 and it will be less than 1 if the cracking reaction proceeds.   However, it is proved that bimolecular reaction pathways exist between surface carbenium ions and the feed molecules. The products of this bimolecular disproportionation reaction could be an alkane molecule and a newly formed carbenium ion. The better understanding of the reaction chemistry of FCC process based on monomolecular pathways and bimolecular pathways should be the basis for searching approaches to the improvement of FCC gasoline quality. In the complicated reaction scheme of the FCC process, the isomerization reaction leading to the formation of iso-alkanes is obviously a target reaction, which favors both olefin reduction and octane enhancement.   The cracking of small paraffin molecules, due to its limited number of reaction pathways and products, has been used to investigate cracking mechanism. In the present work the

  9. The competitive growth of cubic domains in Ti(1-x)AlxN films studied by diffraction anomalous near-edge structure spectroscopy.

    Science.gov (United States)

    Pinot, Y; Tuilier, M-H; Pac, M-J; Rousselot, C; Thiaudière, D

    2015-11-01

    Titanium and aluminium nitride films deposited by magnetron sputtering generally grow as columnar domains made of oriented nanocrystallites with cubic or hexagonal symmetry depending on Al content, which are embedded in more disordered grain boundaries. The substitution of Al atoms for Ti in the cubic lattice of the films improves their resistance to wear and oxidation, allowing their use as protective coatings. Ti K-edge X-ray absorption spectroscopy, which probes both crystallized and more disordered grain boundaries, and X-ray diffraction anomalous fine structure, which is sensitive to short- and long-range order within a given crystallized domain, are carried out on a set of Ti(1-x)AlxN films deposited by magnetron sputtering on Si substrates. Attention is paid to the shape of the pre-edge region, which is sensitive to the symmetry of the site occupied by Ti atoms, either octahedral in face-centred-cubic Ti-rich (TiN, Ti0.54Al0.46N) samples or tetrahedral in hexagonal-close-packed Al-rich (Ti0.32Al0.68N) films. In order to obain information on the titanium environment in the well crystallized areas, subtraction of the smooth part of the energy-dependent structure factor for the Bragg reflections is applied to the pre-edge region of the diffraction anomalous data in order to restore their spectroscopic appearance. A flat pre-edge is related to the typical octahedral environment of Ti atoms for cubic reflections. The difference observed between pre-edge spectra associated with face-centred-cubic 200 and 111 Bragg reflections of Ti0.54Al0.46N is assigned to Ti enrichment of 111 large well ordered domains compared with the more disordered 200 ones. The sharp peak observed in the spectrum recorded from the hexagonal 002 peak of Ti0.32Al0.68N can be regarded as a standard for the pure tetrahedral Ti environment in hexagonal-close-packed nitride.

  10. Segregation and H2 transport rate control in body-centered cubic PdCu membranes.

    Science.gov (United States)

    Yuan, Lixiang; Goldbach, Andreas; Xu, Hengyong

    2007-09-20

    The H2 permeation of a supported 2 microm thick Pd48Cu52 membrane was investigated between 373 and 909 K at DeltaP=0.1 MPa. The initial H2 flux was 0.3 mol.m(-2).s(-1) at 723 K with an ideal H2/N2 selectivity better than 5000. The membrane underwent a bcc-fcc (body-centered cubic to face-centered cubic) phase transition between 723 and 873 K resulting in compositional segregation. After reannealing at 723 K the alloy layer reverted to a bcc structure although a small fcc fraction remained behind. The mixed-phase morphology was analyzed combining X-ray diffraction with scanning electron microscopy-energy-dispersive spectroscopic analysis (SEM-EDS) measurements, which revealed micrometer-scale Cu-enriched bcc and Cu-depleted fcc domains. The H2 flux JH2 of the fcc Pd48Cu52 single phase layer prevailing above 873 K could be described by an Arrhenius law with JH2=(7.6+/-4.9) mol.m(-2).s(-1) exp[(-32.9+/-4.5) kJ.mol(-1)/(RT)]. The characterization of the H2 flux in the mixed-phase region required two Arrhenius laws, i.e., JH2=(1.35+/-0.14) mol.m(-2).s(-1) exp[(-10.3+/-0.5) kJ.mol(-1)/(RT)] between 523 and ca. 700 K and JH2=(56.1+/-9.3) mol.m(-2).s(-1) exp[(-25.3+/-0.6) kJ.mol(-1)/(RT)] below 454 K. The H2 flux exhibited a square root pressure dependence above 523 K, but the pressure exponent gradually increased to 0.77 upon cooling to 373 K. The activation energy and pressure dependence in the intermediate temperature range are consistent with a diffusion-limited H2 transport, while the changes of these characteristics at lower temperatures indicate a desorption-limited H2 flux. The prevalence of desorption as the permeation rate-limiting step below 454 K is attributed to the pairing of an extraordinarily high hydrogen diffusivity with a marginal hydrogen solubility in bcc PdCu alloys. These result in an acceleration of the bulk diffusion rate and a deceleration of the desorption rate, respectively, allowing the bulk diffusion rate to surpass the desorption rate up to

  11. From Kepler's conjecture and fcc lattice to modelling of crowding in living matter.

    Science.gov (United States)

    Del Monte, Ugo; Caiani, Enrico G

    2013-01-01

    Up to now, sphere packing has been investigated without any reference to living matter. This study focuses on the void space (VS) of sphere packing to mimic the extracellular spaces of living tissues. It was inspired by the importance of the extracellular matrix, the vehicle of micro and macromolecules involved in cell metabolism, intercellular communication and drug delivery. The analysis of sphere packing evidenced that in uniform random packing VS is about 1.9 times greater than in the face centered cubic (fcc) lattice (thus being very close to the 1.9 volume ratio of the cube to the sphere). This datum is a good reference for cell packing in vivo. The disproportionate increase of VS per sphere in loose packing in vitro is analyzed having in mind the variability in volume and composition of the interstitial spaces in vivo and cell trafficking. Arrangements of lymphocytes mimicking a two-dimensional hexagonal pattern and dense packing of disks generated by numerical procedures, are described in 7 micro m-thick haematoxylin and eosin-stained histological slices from a human lymph node. In narrow tubes simulating roundish cells arranged in limited compartments of the interstice, sphere packing is characterized by noticeable increases of VS. The VS of this packing in vitro is compatible with variability in volume and composition of the interstitial spaces and with cell trafficking in vivo. This paper stresses that in mammalian tissues and organs cells can be packed quite more densely than spheres in the fcc lattice. As to pathology, attention is focused: (i) on overcrowding of cell organelles in some diseases, (ii) on shrinking or swelling of high amplitude, whose opposite effects are to concentrate or dilute intracellular structures and crowding of macromolecules, and (iii) on neoplastic tissues.

  12. Structural,Electronic and Elastic Properties of Cubic Perovskites SrSnO3 and SrZrO3 under Hydrostatic Pressure Effect

    Institute of Scientific and Technical Information of China (English)

    SHI Li-Wei; DUAN Yi-Feng; YANG Xian-Qing; QIN Li-Xia

    2010-01-01

    @@ Using the plane-wave pesudopotential(PWPP)method within the generalized gradient approximation(GGA),we investigate the hydrostatic pressure induced effect on the structural,electronic and elastic properties of cubic perovskites SrSnO3 and SrZrO3.The pressure dependence of the lattice constants,some indirect and direct band gaps,the upper valence bandwidths,the elastic stiffness constants and the aggregate elastic moduli,as well as the Debye temperature are investigated.Our calculated ground-state results are in good agreement with the available experimental and theoretical data.

  13. 47 CFR 73.878 - Station inspections by FCC; availability to FCC of station logs and records.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Station inspections by FCC; availability to FCC... (LPFM) § 73.878 Station inspections by FCC; availability to FCC of station logs and records. (a) The... FCC during the station's business hours, and at any time it is in operation. In the course of...

  14. Anisotropic cubic curvature couplings

    CERN Document Server

    Bailey, Quentin G

    2016-01-01

    To complement recent work on tests of spacetime symmetry in gravity, cubic curvature couplings are studied using an effective field theory description of spacetime-symmetry breaking. The associated mass dimension 8 coefficients for Lorentz violation studied do not result in any linearized gravity modifications and instead are revealed in the first nonlinear terms in an expansion of spacetime around a flat background. We consider effects on gravitational radiation through the energy loss of a binary system and we study two-body orbital perturbations using the post-Newtonian metric. Some effects depend on the internal structure of the source and test bodies, thereby breaking the Weak Equivalence Principle for self-gravitating bodies. These coefficients can be measured in solar-system tests, while binary-pulsar systems and short-range gravity tests are particularly sensitive.

  15. Isomorph invariance of the structure and dynamics of classical crystals

    DEFF Research Database (Denmark)

    Albrechtsen, Dan; Olsen, Andreas Elmerdahl; Pedersen, Ulf Rørbæk

    2014-01-01

    of a defective fcc crystal is also shown to be isomorph invariant. In contrast, a NaCl crystal model does not exhibit isomorph invariances. Other systems simulated, though in less detail, are the Wahnström binary Lennard-Jones crystal with the MgZn2 Laves crystal structure, monatomic fcc crystals of particles......This paper shows by computer simulations that some crystalline systems have curves in their thermodynamic phase diagrams, so-called isomorphs, along which structure and dynamics in reduced units are invariant to a good approximation. The crystals are studied in a classical-mechanical framework......, which is generally a good description except significantly below melting. The existence of isomorphs for crystals is validated by simulations of particles interacting via the Lennard-Jones pair potential arranged into a face-centered cubic (fcc) crystalline structure; the slow vacancy-jump dynamics...

  16. A DFT+U study of the structural, electronic, magnetic, and mechanical properties of cubic and orthorhombic SmCoO3

    Science.gov (United States)

    Olsson, Emilia; Aparicio-Anglès, Xavier; de Leeuw, Nora H.

    2016-12-01

    SmCoO3 is a perovskite material that has gained attention as a potential substitute for La1-xSrxMnO3-d as a solid oxide fuel cell cathode. However, a number of properties have remained unknown due to the complexity of the material. For example, we know from experimental evidence that this perovskite exists in two different crystal structures, cubic and orthorhombic, and that the cobalt ion changes its spin state at high temperatures, leading to a semiconductor-to-metal transition. However, little is known about the precise magnetic structure that causes the metallic behavior or the spin state of the Co centers at high temperature. Here, we therefore present a systematic DFT+U study of the magnetic properties of SmCoO3 in order to determine what magnetic ordering is the one exhibited by the metallic phase at different temperatures. Similarly, mechanical properties are difficult to measure experimentally, which is why there is a lack of data for the two different phases of SmCoO3. Taking advantage of our DFT calculations, we have determined the mechanical properties from our calculated elastic constants, finding that both polymorphs exhibit similar ductility and brittleness, but that the cubic structure is harder than the orthorhombic phase.

  17. Compression Stress Effect on Dislocations Movement and Crack propagation in Cubic Crystal

    CERN Document Server

    Suprijadi,; Yusfi, Meiqorry

    2012-01-01

    Fracture material is seriously problem in daily life, and it has connection with mechanical properties itself. The mechanical properties is belief depend on dislocation movement and crack propagation in the crystal. Information about this is very important to characterize the material. In FCC crystal structure the competition between crack propagation and dislocation wake is very interesting, in a ductile material like copper (Cu) dislocation can be seen in room temperature, but in a brittle material like Si only cracks can be seen observed. Different techniques were applied to material to study the mechanical properties, in this study we did compression test in one direction. Combination of simulation and experimental on cubic material are reported in this paper. We found that the deflection of crack direction in Si caused by vacancy of lattice,while compression stress on Cu cause the atoms displacement in one direction. Some evidence of dislocation wake in Si crystal under compression stress at high tempera...

  18. A Face Centered Cubic Key Agreement Mechanism for Mobile Ad Hoc Networks

    Science.gov (United States)

    Askoxylakis, Ioannis G.; Markantonakis, Konstantinos; Tryfonas, Theo; May, John; Traganitis, Apostolos

    Mobile ad hoc networking is an operating mode for rapid mobile node networking. Each node relies on adjacent nodes in order to achieve and maintain connectivity and functionality. Security is considered among the main issues for the successful deployment of mobile ad hoc networks (MANETs). In this paper we introduce a weak to strong authentication mechanism associated with a multiparty contributory key establishment method. The latter is designed for MANETs with dynamic changing topologies, due to continuous flow of incoming and departing nodes. We introduce a new cube algorithm based on the face-centered cubic (FCC) structure. The proposed architecture employs elliptic curve cryptography, which is considered more efficient for thin clients where processing power and energy consumption are significant constraints.

  19. The FCC and the Electric Church.

    Science.gov (United States)

    Abrams, Michael F.

    This newsletter focuses on the relationship between the Federal Communications Commission (FCC) and religious broadcasters. It traces the history of that relationship and discusses some of the pressures put on both. It includes a discussion of a recent avalanche of mail at the FCC supporting the church on the airways. It also summarizes some of…

  20. 47 CFR 2.936 - FCC inspection.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false FCC inspection. 2.936 Section 2.936 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL... Authorization § 2.936 FCC inspection. Upon reasonable request, each responsible party shall submit the...

  1. Average and equilibrium structures of methyl flouride studied by electron diffraction. A joint analysis with rotational constants and cubic force constants

    Science.gov (United States)

    Egawa, Toru; Yamamoto, Satoshi; Nakata, Munetaka; Kuchitsu, Kozo

    1987-02-01

    Electron diffraction intensity of methyl fluoride was measured and analyzed jointly with the rotational constants, Ao and Bo, of the normal species. The following structure was derived: rg(CF) = 1.391(1) Å, rg(CH) = 1.108(1) Å and β z(FCH) = 108.7(2)°, where the numbers in parentheses represent estimated limits of error. The effective anharmonic constants were derived using the rotational constants and the l-type doubling constants; the cubic force constants calculated by Kondo using a 6-311G** (MP2) basis set were also incorporated in the analysis. The following equilibrium structure was derived from the rz structure and the effective anharmonic constants: re(CF) = 1.383(1) Å, re(CH) = 1.086(2) Å and β e(FCH) = 108.8(3)°.

  2. Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication of Superlattice Structures Using AlN and InN

    Science.gov (United States)

    1992-06-01

    AD-A253 331 Semiannual Report Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication...Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication of Superlattice Structures Using...34 substrates, such as using a graded AlxGal-xN solid solution as a buffer layer. E. Conclusion We have shown that in the use of our modified gas source MBE

  3. Constitutive Model for an FCC Single-Crystal Material

    Institute of Scientific and Technical Information of China (English)

    DING Zhi-ping; LIU Yi-lun; YIN Ze-yong; YANG Zhi-guo; CHENG Xiao-ming

    2006-01-01

    Talking into account the effects that the components of tension stresses couple with components of torsion stresses when off-axis loads are applied to orthotropic materials.Hill's yield criterion for plastically orthotropic solids is modified by adding an invariant that is composed of the product item of quadratic components of the deviatoric siress tensor,and a new yield criteflon is put forward in terms of the characteristics of the face-centered cubic(FCC) single-crystal material.The correlation of prediction and experiments is very good.and the new criterion is used to predict the yield stresses of an intemal single-crystal,Nickel-based superalloy,DD3,which is more accurate than that Of Hill's at 760°C.Equivalent stress and strain that adapt to the new criterion are defined.Thinking of the yield function as a plastic potential function from the associated flow rule.the elastic-plastic constitutive model for the FCC single-crystal material is constructed,and the corresponding elastic-plastic matrix iseduced.The new yield criterion and its equivalent stress and strain will be reduced to Von Mises' yield criterion and corresponding equivalent stress and strain for isotropic materials.

  4. First-principles calculation of the structural, electronic, and magnetic properties of cubic perovskite RbXF3 (X = Mn, V, Co, Fe)

    Science.gov (United States)

    rehman Hashmi, Muhammad Raza ur; Zafar, Muhammad; Shakil, M.; Sattar, Atif; Ahmed, Shabbir; Ahmad, S. A.

    2016-11-01

    First-principles calculations by means of the full-potential linearized augmented plane wave method using the generalized gradient approximation with correlation effect correction (GGA+U) within the framework of spin polarized density functional theory (DFT+U) are used to study the structural, electronic, and magnetic properties of cubic perovskite compounds RbXF3 (X = Mn, V, Co, and Fe). It is found that the calculated structural parameters, i.e., lattice constant, bulk modulus, and its pressure derivative are in good agreement with the previous results. Our results reveal that the strong spin polarization of the 3d states of the X atoms is the origin of ferromagnetism in RbXF3. Cohesive energies and the magnetic moments of RbXF3 have also been calculated. The calculated electronic properties show the half-metallic nature of RbCoF3 and RbFeF3, making these materials suitable for spintronic applications.

  5. BDA: A novel method for identifying defects in body-centered cubic crystals.

    Science.gov (United States)

    Möller, Johannes J; Bitzek, Erik

    2016-01-01

    The accurate and fast identification of crystallographic defects plays a key role for the analysis of atomistic simulation output data. For face-centered cubic (fcc) metals, most existing structure analysis tools allow for the direct distinction of common defects, such as stacking faults or certain low-index surfaces. For body-centered cubic (bcc) metals, on the other hand, a robust way to identify such defects is currently not easily available. We therefore introduce a new method for analyzing atomistic configurations of bcc metals, the BCC Defect Analysis (BDA). It uses existing structure analysis algorithms and combines their results to uniquely distinguish between typical defects in bcc metals. In essence, the BDA method offers the following features:•Identification of typical defect structures in bcc metals.•Reduction of erroneously identified defects by iterative comparison to the defects in the atom's neighborhood.•Availability as ready-to-use Python script for the widespread visualization tool OVITO [http://ovito.org].

  6. Optical, structural and fluorescence properties of nanocrystalline cubic or monoclinic Eu:Lu{sub 2}O{sub 3} films prepared by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Martinet, C. [Laboratoire de Physico-Chimie des Materiaux Luminescents, CNRS-Universite Lyon1, 10, rue Andre-Marie Ampere, 69622 Villeurbanne Cedex (France)]. E-mail: martinet@pcml.univ-lyon1.fr; Pillonnet, A. [Laboratoire de Physico-Chimie des Materiaux Luminescents, CNRS-Universite Lyon1, 10, rue Andre-Marie Ampere, 69622 Villeurbanne Cedex (France); Lancok, J. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague (Czech Republic); Garapon, C. [Laboratoire de Physico-Chimie des Materiaux Luminescents, CNRS-Universite Lyon1, 10, rue Andre-Marie Ampere, 69622 Villeurbanne Cedex (France)

    2007-10-15

    Eu{sup 3+}-doped lutetium oxide (Eu:Lu{sub 2}O{sub 3}) nanocrystalline films were grown on fused-silica substrates by pulsed laser deposition. Depending on deposition conditions (oxygen pressure, temperature and laser energy), the structure of the films changed from amorphous to crystalline and the cubic or monoclinic phases were obtained with varying preferential orientation and crystallite size. The monoclinic phase could be prepared for the first time at temperatures as low as 240 deg. C and in a narrow range of parameters. Although this phase has been previously reported for powder samples, it occurs only for high pressures and high temperatures preparation conditions. The refractive indices were measured by m-lines spectroscopy for both crystalline phases and their dispersion curve fitted by the Sellmeier expression. The specific Eu{sup 3+} fluorescence properties of the different phases, monoclinic and cubic, were registered and show modifications due to the disorder induced by the nanometric size of the crystallites, emphasised in particular by quasi-selective excitation in the charge transfer band.

  7. Magnetic behaviors of a transverse spin-1/2 Ising cubic nanowire with core/shell structure

    Science.gov (United States)

    El Hamri, M.; Bouhou, S.; Essaoudi, I.; Ainane, A.; Ahuja, R.; Dujardin, F.

    2017-02-01

    The surface shell exchange coupling effect on the magnetic properties (surface shell, core, total longitudinal and total transverse magnetizations, susceptibility, phase diagram and hysteresis loops) of a transverse spin-1/2 Ising cubic nanowire is investigated, in the present work, by employing the effective-field theory based on the probability distribution technique with correlations, for both ferro- and antiferromagnetic cases. We have found that this parameter has a strong effect on the magnetic properties in both cases. In the ferromagnetic case, the total longitudinal magnetization curves display Q- and S-type behaviors and the hysteresis loop has just one loop, whereas in the antiferromagnetic case, the N-type behavior, in which one compensation temperature appears below the critical temperature, exists in the total longitudinal magnetization curve versus reduced temperature, and triple hysteresis loops are found. The effect of applied field is also investigated on the total longitudinal magnetization for the both cases, and we have found that a large applied field value can overcome the antiferromagnetic coupling leading to a ferromagnetic-like behavior.

  8. Cubic Subalgebras and Cubic Closed Ideals of B-algebras

    Directory of Open Access Journals (Sweden)

    Tapan Senapati

    2015-06-01

    Full Text Available In this paper, the concept of cubic set to subalgebras, ideals and closed ideals of B-algebras are introduced. Relations among cubic subalgebras with cubic ideals and cubic closed ideals of B-algebras investigated. The homomorphic image and inverse image of cubic subalgebras, ideals are studied and some related properties are investigated. Also, the product of cubic B-algebras are investigated.

  9. β-Mn-type Co(8+x)Zn(12-x) as a defect cubic Laves phase: site preferences, magnetism, and electronic structure.

    Science.gov (United States)

    Xie, Weiwei; Thimmaiah, Srinivasa; Lamsal, Jagat; Liu, Jing; Heitmann, Thomas W; Quirinale, Dante; Goldman, Alan I; Pecharsky, Vitalij; Miller, Gordon J

    2013-08-19

    The results of crystallographic analysis, magnetic characterization, and theoretical assessment of β-Mn-type Co-Zn intermetallics prepared using high-temperature methods are presented. These β-Mn Co-Zn phases crystallize in the space group P4(1)32 [Pearson symbol cP20; a = 6.3555(7)-6.3220(7)], and their stoichiometry may be expressed as Co(8+x)Zn(12-x) [1.7(2) phase with a Curie temperature of ∼420 K. Neutron powder diffraction and electronic structure calculations using the local spin density approximation indicate that the spontaneous magnetization of this phase arises exclusively from local moments at the Co atoms. Inspection of the atomic arrangements of Co(8+x)Zn(12-x) reveals that the β-Mn aristotype may be derived from an ordered defect, cubic Laves phase (MgCu2-type) structure. Structural optimization procedures using the Vienna ab initio simulation package (VASP) and starting from the undistorted, defect Laves phase structure achieved energy minimization at the observed β-Mn structure type, a result that offers greater insight into the β-Mn structure type and establishes a closer relationship with the corresponding α-Mn structure (cI58).

  10. Study on Commercial Application of FCC with Auxiliary Gasoline Reactor for Improving FCC Naphtha Quality

    Institute of Scientific and Technical Information of China (English)

    Wei Qiang

    2007-01-01

    This article introduces the commercial application of FCC technology equipped with a gasoline auxiliary reactor in the RFCC unit at PetroChina Harbin Petrochemical Branch Company.Test results have shown the excellent outcome for commercial application of the gasoline upgrading in the auxiliary reactor to reduce the olefin content in FCC naphtha.Application of this technology can reduce the olefin content in FCC naphtha to less than 35v%.Adjustment of the FCC operation towards more severg conditions can further reduce the olefin content in FCC naphtha to less than 20 v%.so that the FCC naphtha can meet the current standard or meet more stringent specification requirements in the future to achieve compelling economic and social benefits.

  11. Effects of Co doping on the metamagnetic states of the ferromagnetic fcc Fe-Co alloy.

    Science.gov (United States)

    Ortiz-Chi, Filiberto; Aguayo, Aarón; de Coss, Romeo

    2013-01-16

    The evolution of the metamagnetic states in the ferromagnetic face centered cubic (fcc) Fe(1-x)Co(x) alloy as a function of Co concentration has been studied by means of first-principles calculations. The ground state properties were obtained using the full-potential linear augmented plane wave method and the generalized gradient approximation for the exchange-correlation functional. The alloying was modeled using the virtual crystal approximation and the magnetic states were obtained from the calculations of the total energy as a function of the spin moment, using the fixed spin moment method. For ferromagnetic fcc Fe, the binding-energy curve shows metamagnetic behavior, with two minima corresponding to a small-volume, low-spin (LS) state and a large-volume, high-spin (HS) state, which are separated by a small energy (E(LS) ≲ E(HS)). The evolution of the magnetic moment, the exchange integral (J), and the binding-energy curve is analyzed in the whole range of Co concentrations (x). The magnetic moment corresponding to the HS state decreases monotonically from 2.6 μ(B)/atom in fcc Fe to 1.7 μ(B)/atom in fcc Co. In contrast, the exchange integral for the HS state shows a maximum at around x = 0.45. The thermal dependence of the lattice parameter is evaluated with a method based on statistical mechanics using the binding-energy curve as an effective potential. It is observed that the behavior of the lattice parameter with temperature is tuned by Co doping, from negative thermal expansion in fcc Fe to positive thermal expansion in fcc Co, through the modification of the energetics of the metamagnetic states.

  12. 47 CFR 1.8001 - FCC Registration Number (FRN).

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false FCC Registration Number (FRN). 1.8001 Section 1.8001 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL PRACTICE AND PROCEDURE FCC Registration Number § 1.8001 FCC Registration Number (FRN). (a) The FCC Registration Number (FRN) is a...

  13. 47 CFR 80.417 - FCC Rules and Regulations.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false FCC Rules and Regulations. 80.417 Section 80... STATIONS IN THE MARITIME SERVICES Station Documents § 80.417 FCC Rules and Regulations. The Commission's... available on the Commission's web site at www.fcc.gov or ftp.fcc.gov....

  14. Discussions on the Feasibility of Using FCC Offgas for Atomization of FCC Feed

    Institute of Scientific and Technical Information of China (English)

    Cao Dongxue

    2005-01-01

    The consumption of steam as a traditional means for feedstock atomization accounts for a relatively large share in the process energy use and makes up the main part of sulfur containing wastewater. This article on the basis of comprehensive analysis puts forward a proposition on using the FCC offgas as the medium for atomizing the FCC feed, which would play a realistic role for energy conservation and environmental protection of FCC process.

  15. First-principles calculations on the structural and electronic properties of cubic KCaF3 and NaCaF3 (001) surfaces

    Science.gov (United States)

    Yang, Kun; He, Yanqing; Cheng, Yi; Che, Li; Yao, Li

    2017-03-01

    First-principles density functional theory (DFT) calculations have been used to investigate the structural and electronic properties of the cubic KCaF3 and NaCaF3 (001) surfaces with MF (M = K or Na) and CaF2 terminations. For both KCaF3 and NaCaF3 (001) surfaces, the MF termination has stronger surface rumpling than the CaF2 termination. All the computed band gaps for the KCaF3 and NaCaF3 (001) surfaces are smaller than those of the bulks. Furthermore, separated bands that originate from surface layer F p states are introduced at the top of the valance band of MF-terminated surfaces, indicating the emergence of the surface states. The calculated surface energies show that the MF-terminated surface is energetically more favorable than the CaF2-terminated surface.

  16. Global Existence and Convergence of Solutions to a Cross-Diffusion Cubic Predator-Prey System with Stage Structure for the Prey

    Directory of Open Access Journals (Sweden)

    Shengmao Fu

    2010-01-01

    Full Text Available We study a cubic predator-prey system with stage structure for the prey. This system is a generalization of the two-species Lotka-Volterra predator-prey model. Firstly, we consider the asymptotical stability of equilibrium points to the system of ordinary differential equations type. Then, the global existence of solutions and the stability of equilibrium points to the system of weakly coupled reaction-diffusion type are discussed. Finally, the existence of nonnegative classical global solutions to the system of strongly coupled reaction-diffusion type is investigated when the space dimension is less than 6, and the global asymptotic stability of unique positive equilibrium point of the system is proved by constructing Lyapunov functions.

  17. Military and aerospace applications of FCC

    Science.gov (United States)

    Swanson, C.

    1972-01-01

    Military and NASA programs are discussed in which FCC were used. Included are Saturn 4, Pegasus satellites solar, array for Skylab orbital workshop, Poseidon missiles, MK 48 torpedo fire control, and Lunar Surveyor.

  18. Beam dynamics issues in the FCC

    CERN Document Server

    AUTHOR|(CDS)2067437; Benedikt, Michael; Besana, Maria Ilaria; Bruce, Roderik; Bruning, Oliver; Buffat, Xavier; Burkart, Florian; Burkhardt, Helmut; Calatroni, Sergio; Cerutti, Francesco; Fartoukh, Stephane; Fiascaris, Maria; Garion, Cedric; Goddard, Brennan; Hofle, Wolfgang; Holzer, Bernhard; Jowett, John; Kersevan, Roberto; Martin, Roman; Mether, Lotta Maria; Milanese, Attilio; Pieloni, Tatiana; Redaelli, Stefano; Rumolo, Giovanni; Salvant, Benoit; Schaumann, Michaela; Schulte, Daniel; Chapochnikova, Elena; Stoel, Linda; Tambasco, Claudia; Tomas Garcia, Rogelio; Tommasini, Davide; Zimmermann, Frank; Guillermo Canton, Gerardo; Kornilov, Vladimir; Boine-Frankenheim, Oliver; Niedermayer, Uwe; Mitsuhashi, Toshiyuki; Ohmi, Kazuhito; Chance, Antoine; Dalena, Barbara; Payet, Jacques; Bambade, Philip; Faus-Golfe, Angeles; Molson, James; Biarrotte, Jean-Luc; Lachaize, Antoine; Fox, John D; Stupakov, Gennady; Abelleira, Jose; Cruz Alaniz, Emilia; Seryi, Andrei; Appleby, Robert Barrie; Boscolo, Manuela; Collamati, Francesco; Drago, Alessandro; Barranco Garcia, Javier; Khan, Shaukat; Riemann, Bernhard

    2016-01-01

    The international Future Circular Collider (FCC) study is designing hadron, lepton and lepton-hadron colliders based on a new 100 km tunnel in the Geneva region. The main focus and ultimate goal of the study are high luminosity proton-proton collisions at a centre-of-mass energy of 100 TeV, using 16 T Nb3Sn dipole magnets. Specific FCC beam dynamics issues are related to the large circumference, the high brightness—made available by radiation damping —, the small geometric emittance, unprecedented collision energy and luminosity, the huge amount of energy stored in the beam, large synchrotron radiation power, plus the injection scenarios. In addition to the FCC-hh proper, also a High-Energy LHC (HE-LHC) is being explored, using the FCC-hh magnet technology in the existing LHC tunnel, which can yield a centre-of-mass energy around 25 TeV.

  19. Superstructures in cubic A{sup II}B{sup VI} crystals heavily doped with Ni and V ions

    Energy Technology Data Exchange (ETDEWEB)

    Maksimov, V. I., E-mail: kokailo@rambler.ru; Dubinin, S. F.; Surkova, T. P. [Russian Academy of Sciences, Institute of Metal Physics, Ural Branch (Russian Federation)

    2016-01-15

    Specific features of the crystal structure of bulk sphalerite-type Zn{sub 0.9}Ni{sub 0.1}S, Zn{sub 0.9}V{sub 0.1}Se, and Zn{sub 0.997}Ni{sub 0.003}Te crystals have been investigated in detail by thermal-neutron diffraction at room temperature. Fine effects (indicative of the existence of distortion microdomains, nucleation of long- and short-wavelength modulations, and tendencies toward local lowering of the symmetry based on the initial cubic structure) can be observed in the obtained scattering patterns. Various states preceding the fcc ↔ hcp phase transition have been revealed in these crystals. They depend on the elemental composition and are formed upon the reaction of the initial lattice to perturbations induced by foreign ions with an incomplete 3d shell.

  20. Role of five-fold twin boundary on the enhanced mechanical properties of fcc Fe nanowires.

    Science.gov (United States)

    Wu, J Y; Nagao, S; He, J Y; Zhang, Z L

    2011-12-14

    The role of 5-fold twin boundary on the structural and mechanical properties of fcc Fe nanowire under tension is explored by classical molecular dynamics. Twin-stabilized fcc nanowire with various diameters (6-24 nm) are examined by tension tests at several temperatures ranging from 0.01 to 1100 K. Significant increase in the Young's modulus of the smaller nanowires is revealed to originate from the central area of quinquefoliolate-like stress-distribution over the 5-fold twin, rather than from the surface tension that is often considered as the main source of such size-effects found in nanostructures. Because of the excess compressive stress caused by crossing twin-boundaries, the atoms in the center behave stiffer than those in bulk and even expand laterally under axial tension, providing locally negative Poisson's ratio. The yield strength of nanowire is also enhanced by the twin boundary that suppresses dislocation nucleation within a fcc twin-domain; therefore, the plasticity of nanowire is initiated by strain-induced fcc→bcc phase transformation that destroys the twin structure. After the yield, the nucleated bcc phase immediately spreads to the entire area, and forms a multigrain structure to realize ductile deformation followed by necking. As temperature elevated close to the critical temperature between bcc and fcc phases, the increased stability of fcc phase competes with the phase transformation under tension, and hence dislocation nucleations in fcc phase are observed exclusively at the highest temperature in our study.

  1. 78 FR 66357 - Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions

    Science.gov (United States)

    2013-11-05

    ... COMMISSION Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions AGENCY: Federal... annual Telecommunications Reporting Worksheet, FCC Form 499-A (Form 499-A) and accompanying instructions... Telecommunications Reporting Worksheet, FCC Form 499-Q (Form 499-Q) and accompanying instructions (Form...

  2. 78 FR 69415 - Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions.

    Science.gov (United States)

    2013-11-19

    ... COMMISSION Proposed Changes to FCC Form 499-A, FCC Form 499-Q, and Accompanying Instructions. AGENCY: Federal... to (1) the annual Telecommunications Reporting Worksheet, FCC Form 499-A (Form 499-A) and... quarterly Telecommunications Reporting Worksheet, FCC Form 499-Q (Form 499-Q) and accompanying...

  3. First-principles calculations of typical anisotropic cubic and hexagonal structures and homogenized moduli estimation based on the Y-parameter: Application to CaO, MgO, CH and Calcite CaCO3

    Science.gov (United States)

    Fu, Jia; Bernard, Fabrice; Kamali-Bernard, Siham

    2017-02-01

    X-ray method to test the material properties and to obtain elastic constants is commonly based on the Reuss model and Kroner model. Y parameter has been turned out to be an effective method to estimate elastic properties of polycrystalline material. Since Y-parameters of cubic polycrystalline material based on the certain uniform stress (Reuss model) has not been given, our work aims to complete this part of the theoretical analysis, which can effectively compare elastic constants measured by the X-ray diffraction method. The structural and the elastic properties of cubic structures (CaO and MgO) and hexagonal structures (CH and Calcite CaCO3) are investigated by the density functional theory method. And then the credibility of Y parameters for determing elastic moduli of cubic structures is proved and elastic properties in typical crystallographic planes of [100], [110] and [111] are also calculated. Meanwhile, Young's moduli of CH and Calcite structure are 58.08 GPa and 84.549 GPa, which are all close to references. Elastic properties of cubic and hexagonal structures under various pressures are calculated and the surface constructions of elastic moduli are drawn, showing the anisotropy at various directions. The crystal structure investigated in this work are typical of some primary or secondary components of Hardened Cements Pastes and their homogenized elastic properties are needed in a hierarchical multi-scale modeling, such as the one developed by some of the authors of this paper.

  4. Cubic Curves, Finite Geometry and Cryptography

    CERN Document Server

    Bruen, A A; Wehlau, D L

    2011-01-01

    Some geometry on non-singular cubic curves, mainly over finite fields, is surveyed. Such a curve has 9,3,1 or 0 points of inflexion, and cubic curves are classified accordingly. The group structure and the possible numbers of rational points are also surveyed. A possible strengthening of the security of elliptic curve cryptography is proposed using a `shared secret' related to the group law. Cubic curves are also used in a new way to construct sets of points having various combinatorial and geometric properties that are of particular interest in finite Desarguesian planes.

  5. In-depth investigation of EPR spectra of Mn(2+) ions in ZnS single crystals with pure cubic structure.

    Science.gov (United States)

    Nistor, S V; Stefan, M

    2009-04-01

    The X (9.8 GHz)-band electron paramagnetic resonance (EPR) properties of substitutional Mn(2+) ions in high quality cubic ZnS single crystals grown from PbCl(2) flux have been thoroughly investigated. Accurate spin Hamiltonian (SH) parameters: g = 2.002 25 ± 0.000 06; a = (7.987 ± 0.008) × 10(-4) cm(-1) and A = -(63.88 ± 0.02) × 10(-4) cm(-1) were obtained by simulation and fitting to the experimentally allowed transitions recorded for the magnetic field aligned within ± 0.25° along the main crystal axes. The normally forbidden hyperfine [Formula: see text], Δm = ± 1 transitions were also observed. Their position was found to be in agreement, within the experimental accuracy of ΔH = ± 0.01 mT, with calculations using the same SH parameters. The angular variation of the ratios of the intensities of the central forbidden to the allowed transitions could be accounted for only by including an additional constant contribution. The observed line broadening of the [Formula: see text] and [Formula: see text] fine structure transitions and their line width variation in a (110) plane have been quantitatively described by considering a random distribution of lattice strains at the Mn(2+) impurity ions. The influence of the forbidden transitions and line broadening on the EPR spectra line shape of the Mn(2+) ions in cubic ZnS crystalline powders is also examined.

  6. Structural properties of pure and Fe-doped Yb films prepared by vapor condensation

    Energy Technology Data Exchange (ETDEWEB)

    Rojas-Ayala, C., E-mail: chachi@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180, RJ (Brazil); Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Lima, P.O.B. 14-149, Lima 14 (Peru); Passamani, E.C. [Departamento de Física, Universidade Federal do Espírito Santo, Vitória 29075-910, ES (Brazil); Suguihiro, N.M. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180, RJ (Brazil); Litterst, F.J. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180, RJ (Brazil); Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, 38106 Braunschweig (Germany); Baggio Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180, RJ (Brazil)

    2014-10-15

    Ytterbium and iron-doped ytterbium films were prepared by vapor quenching on Kapton substrates at room temperature. Structural characterization was performed by X-ray diffraction and transmission electron microscopy. The aim was to study the microstructure of pure and iron-doped films and thereby to understand the effects induced by iron incorporation. A coexistence of face centered cubic and hexagonal close packed-like structures was observed, the cubic-type structure being the dominant contribution. There is an apparent thickness dependence of the cubic/hexagonal relative ratios in the case of pure ytterbium. Iron-clusters induce a crystalline texture effect, but do not influence the cubic/hexagonal volume fraction. A schematic model is proposed for the microstructure of un-doped and iron-doped films including the cubic- and hexagonal-like structures, as well as the iron distribution in the ytterbium matrix. - Highlights: • Pure and Fe-doped Yb films have been prepared by vapor condensation. • Coexistence of fcc- and hcp-type structures was observed. • No oxide phases have been detected. • Fe-clustering does not affect the fcc/hcp ratio, but favors a crystalline texture. • A schematic model is proposed to describe microscopically the microstructure.

  7. Crystal structure of monoclinic samarium and cubic europium sesquioxides and bound coherent neutron scattering lengths of the isotopes {sup 154}Sm and {sup 153}Eu

    Energy Technology Data Exchange (ETDEWEB)

    Kohlmann, Holger [Leipzig Univ. (Germany). Inst. of Inorganic Chemistry; Hein, Christina; Kautenburger, Ralf [Saarland Univ., Saarbruecken (Germany). Inorganic Solid State Chemistry; Hansen, Thomas C.; Ritter, Clemens [Institut Laue-Langevin, Grenoble (France); Doyle, Stephen [Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen (Germany). Inst. for Synchrotron Radiation (ISS)

    2016-11-01

    The crystal structures of monoclinic samarium and cubic europium sesquioxide, Sm{sub 2}O{sub 3} and Eu{sub 2}O{sub 3}, were reinvestigated by powder diffraction methods (laboratory X-ray, synchrotron, neutron). Rietveld analysis yields more precise structural parameters than previously known, especially for oxygen atoms. Interatomic distances d(Sm-O) in Sm{sub 2}O{sub 3} range from 226.3(4) to 275.9(2) pm [average 241.6(3) pm] for the monoclinic B type Sm{sub 2}O{sub 3} [space group C2/m, a = 1418.04(3) pm, b = 362.660(7) pm, c = 885.48(2) pm, β = 100.028(1) ], d(Eu-O) in Eu{sub 2}O{sub 3} from 229.9(2) to 238.8(2) pm for the cubic bixbyite (C) type [space group Ia anti 3, a = 1086.87(1) pm]. Neutron diffraction at 50 K and 2 K did not show any sign for magnetic ordering in Sm{sub 2}O{sub 3}. Isotopically enriched {sup 154}Sm{sub 2}O{sub 3} and {sup 153}Eu{sub 2}O{sub 3} were used for the neutron diffraction work because of the enormous absorption cross section of the natural isotopic mixtures for thermal neutrons. The isotopic purity was determined by inductively coupled plasma - mass spectrometry to be 98.9% for {sup 154}Sm and 99.8% for {sup 153}Eu. Advanced analysis of the neutron diffraction data suggest that the bound coherent scattering lengths of {sup 154}Sm and {sup 153}Eu need to be revised. We tentatively propose b{sub c}({sup 154}Sm) = 8.97(6) fm and b{sub c}({sup 153}Eu) = 8.85(3) fm for a neutron wavelength of 186.6 pm to be better values for these isotopes, showing up to 8% deviation from accepted literature values. It is shown that inaccurate scattering lengths may result in severe problems in crystal structure refinements causing erroneous structural details such as occupation parameters, which might be critically linked to physical properties like superconductivity in multinary oxides.

  8. The effects of next-to-nearest-neighbour hopping on Bose–Einstein condensation in cubic lattices

    Indian Academy of Sciences (India)

    G K Chaudhary; R Ramakumar

    2010-01-01

    In this paper, we present results of our calculations on the effects of next-to-nearest-neighbour boson hopping (′) energy on Bose–Einstein condensation in cubic lattices. We consider both non-interacting and repulsively interacting bosons moving in the lowest Bloch band. The interacting bosons are studied using Bogoliubov method. We find that the Bose condensation temperature is enhanced by increasing ′ for bosons in a simple cubic (sc) lattice and decreases for bosons in body-centred cubic (bcc) and face-centred cubic (fcc) lattices. We also find that interaction-induced depletion of the condensate is reduced for bosons in an sc lattice while it is enhanced for bosons in bcc and fcc lattices.

  9. The body-centered cubic structure of methyllithium tetramer crystal: staggered methyl conformation by electrostatic stabilization via intratetramer multipolarization.

    Science.gov (United States)

    Ohta, Yusuke; Demura, Akimitsu; Okamoto, Takuya; Hitomi, Haruko; Nagaoka, Masataka

    2006-06-29

    The methyllithium tetramer (CH3Li)4 structure in the bcc crystal has been theoretically optimized with the use of density functional theory calculations under the periodic boundary condition. The X-ray structure shows that the methyl-group conformation in tetramer in crystal takes the staggered form rather than the eclipsed form that is taken in the isolated tetramer, i.e., the crystal packing effect, and this has been reproduced for the first time. It is concluded that the staggered form is advantageous in crystal, as a whole, due to the larger electrostatic stabilization via the induced intratetramer multipolarization, although it should cause, simultaneously, smaller destabilization in intratetramer electronic energy.

  10. Semisymmetric Cubic Graphs of Order 162

    Indian Academy of Sciences (India)

    Mehdi Alaeiyan; Hamid A Tavallaee; B N Onagh

    2010-02-01

    An undirected graph without isolated vertices is said to be semisymmetric if its full automorphism group acts transitively on its edge set but not on its vertex set. In this paper, we inquire the existence of connected semisymmetric cubic graphs of order 162. It is shown that for every odd prime , there exists a semisymmetric cubic graph of order 162 and its structure is explicitly specified by giving the corresponding voltage rules generating the covering projections.

  11. Magnetism in bcc and fcc Fe with carbon and manganese

    Energy Technology Data Exchange (ETDEWEB)

    Medvedeva, N I [Institute of Solid State Chemistry, Yekaterinburg 620990 (Russian Federation); Van Aken, D [Department of Materials Science and Engineering, Missouri University of Science and Technology, Rolla, MO 65409 (United States); Medvedeva, J E [Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409 (United States)

    2010-08-11

    Density functional theory calculations were performed to study the structure and magnetic properties of bcc ({alpha}) and fcc ({gamma}) Fe with 3 at.% carbon and manganese impurities. We find that all bcc-based Fe, Fe-C and Fe-Mn-C phases exhibit a ferromagnetic (FM) ground state, while the antiferromagnetic double-layer (AFMD) state is lowest in energy within the collinear spin approach in fcc Fe, Fe-C and Fe-Mn-C phases. However, the carbon and manganese impurities affect the local magnetic interactions significantly. The states with opposite manganese magnetic moments are quasi-degenerate in bcc Fe-Mn alloy, whereas octa-site carbon stabilizes ferromagnetic coupling of the nearest manganese atom with the Fe host. We demonstrate that the antiferromagnetic (AFM) fcc Fe-C and Fe-Mn-C alloys are intrinsically inhomogeneous magnetic systems. Carbon frustrates the local magnetic order by reorientation of magnetic moments of the nearest Mn and Fe atoms, and favors their ferromagnetic coupling. The competition between ferromagnetic and antiferromagnetic Fe-Fe and Fe-Mn interactions and the local magnetovolume instability near carbon may give rise to the spin-glass-like regions observed in austenitic Fe-Mn-C alloys.

  12. Magnetism in bcc and fcc Fe with carbon and manganese.

    Science.gov (United States)

    Medvedeva, N I; Van Aken, D; Medvedeva, J E

    2010-08-11

    Density functional theory calculations were performed to study the structure and magnetic properties of bcc (α) and fcc (γ) Fe with 3 at.% carbon and manganese impurities. We find that all bcc-based Fe, Fe-C and Fe-Mn-C phases exhibit a ferromagnetic (FM) ground state, while the antiferromagnetic double-layer (AFMD) state is lowest in energy within the collinear spin approach in fcc Fe, Fe-C and Fe-Mn-C phases. However, the carbon and manganese impurities affect the local magnetic interactions significantly. The states with opposite manganese magnetic moments are quasi-degenerate in bcc Fe-Mn alloy, whereas octa-site carbon stabilizes ferromagnetic coupling of the nearest manganese atom with the Fe host. We demonstrate that the antiferromagnetic (AFM) fcc Fe-C and Fe-Mn-C alloys are intrinsically inhomogeneous magnetic systems. Carbon frustrates the local magnetic order by reorientation of magnetic moments of the nearest Mn and Fe atoms, and favors their ferromagnetic coupling. The competition between ferromagnetic and antiferromagnetic Fe-Fe and Fe-Mn interactions and the local magnetovolume instability near carbon may give rise to the spin-glass-like regions observed in austenitic Fe-Mn-C alloys.

  13. A novel potential: the interlayer potential for the fcc (111) plane family.

    Science.gov (United States)

    Tian, Fu-Yang; Chen, Nan-Xian; Shen, Jiang; Vitos, Levente

    2012-02-01

    We propose a novel interlayer potential, which is different from usual interatomic potentials. The interlayer potential represents the interaction between atomic layers in a layered material. Based on the Chen-Möbius inversion method in combination with ab initio calculations, the interlayer interactions are obtained for the face centered cubic (fcc) (111) planes. In order to check the validity of our interlayer potential, we calculate the intrinsic stacking fault energy (γ(sf)) and the surface energy (γ(s)) of five metals: Al, Ni, Cu, Ag and Au. The predicted γ(sf) and γ(s) values are compared with the theoretical results obtained from direct calculations and also with the available experimental data. Using the interlayer potentials, we also investigate the phonon dispersion and phonon density of state in the fcc (111) plane family of the considered metals.

  14. Einsteinian cubic gravity

    Science.gov (United States)

    Bueno, Pablo; Cano, Pablo A.

    2016-11-01

    We drastically simplify the problem of linearizing a general higher-order theory of gravity. We reduce it to the evaluation of its Lagrangian on a particular Riemann tensor depending on two parameters, and the computation of two derivatives with respect to one of those parameters. We use our method to construct a D -dimensional cubic theory of gravity which satisfies the following properties: (1) it shares the spectrum of Einstein gravity, i.e., it only propagates a transverse and massless graviton on a maximally symmetric background; (2) it is defined in the same way in general dimensions; (3) it is neither trivial nor topological in four dimensions. Up to cubic order in curvature, the only previously known theories satisfying the first two requirements are the Lovelock ones. We show that, up to cubic order, there exists only one additional theory satisfying requirements (1) and (2). Interestingly, this theory is, along with Einstein gravity, the only one which also satisfies (3).

  15. The influence of additions of Al and Si on the lattice stability of fcc and hcp Fe-Mn random alloys.

    Science.gov (United States)

    Gebhardt, T; Music, D; Ekholm, M; Abrikosov, I A; Vitos, L; Dick, A; Hickel, T; Neugebauer, J; Schneider, J M

    2011-06-22

    We have studied the influence of additions of Al and Si on the lattice stability of face-centred-cubic (fcc) versus hexagonal-closed-packed (hcp) Fe-Mn random alloys, considering the influence of magnetism below and above the fcc Néel temperature. Employing two different ab initio approaches with respect to basis sets and treatment of magnetic and chemical disorder, we are able to quantify the predictive power of the ab initio methods. We find that the addition of Al strongly stabilizes the fcc lattice independent of the regarded magnetic states. For Si a much stronger dependence on magnetism is observed. Compared to Al, almost no volume change is observed as Si is added to Fe-Mn, indicating that the electronic contributions are responsible for stabilization/destabilization of the fcc phase.

  16. Structure-property relationships in cubic cuprous iodide: A novel view on stability, chemical bonding, and electronic properties

    Science.gov (United States)

    Pishtshev, A.; Karazhanov, S. Zh.

    2017-02-01

    Based on the combination of density functional theory and theory-group methods, we performed systematic modeling of γ-CuI structural design at the atomistic level. Being started from the metallic copper lattice, we treated a crystal assembly as a stepwise iodination process characterized in terms of a sequence of intermediate lattice geometries. These geometries were selected and validated via screening of possible structural transformations. The genesis of chemical bonding was studied for three structural transformations by analyzing the relevant changes in the topology of valence electron densities. We determined structural trends driven by metal-ligand coupling. This allowed us to suggest the improved scenario of chemical bonding in γ-CuI. In particular, the unconventional effect of spatial separation of metallic and covalent interactions was found to be very important with respect to the preferred arrangements of valence electrons in the iodination process. We rigorously showed that useful electronic and optical properties of γ-CuI originate from the combination of two separated bonding patterns—strong covalency established in I-Cu tetrahedral connections and noncovalent interactions of copper cores is caused by the 3d10 closed-shell electron configurations. The other finding of ours is that the self-consistency of the GW calculations is crucial for correctly determining the dynamic electronic correlations in γ-CuI. Detail reinvestigation of the quasi-particle energy structure by means of the self-consistent GW approach allowed us to explain how p-type electrical conductivity can be engineered in the material.

  17. Structure-property relationships in cubic cuprous iodide: A novel view on stability, chemical bonding, and electronic properties.

    Science.gov (United States)

    Pishtshev, A; Karazhanov, S Zh

    2017-02-14

    Based on the combination of density functional theory and theory-group methods, we performed systematic modeling of γ-CuI structural design at the atomistic level. Being started from the metallic copper lattice, we treated a crystal assembly as a stepwise iodination process characterized in terms of a sequence of intermediate lattice geometries. These geometries were selected and validated via screening of possible structural transformations. The genesis of chemical bonding was studied for three structural transformations by analyzing the relevant changes in the topology of valence electron densities. We determined structural trends driven by metal-ligand coupling. This allowed us to suggest the improved scenario of chemical bonding in γ-CuI. In particular, the unconventional effect of spatial separation of metallic and covalent interactions was found to be very important with respect to the preferred arrangements of valence electrons in the iodination process. We rigorously showed that useful electronic and optical properties of γ-CuI originate from the combination of two separated bonding patterns-strong covalency established in I-Cu tetrahedral connections and noncovalent interactions of copper cores is caused by the 3d(10) closed-shell electron configurations. The other finding of ours is that the self-consistency of the GW calculations is crucial for correctly determining the dynamic electronic correlations in γ-CuI. Detail reinvestigation of the quasi-particle energy structure by means of the self-consistent GW approach allowed us to explain how p-type electrical conductivity can be engineered in the material.

  18. INCOHERENT Σ3 GRAIN BOUNDARIES IN F.C.C. METALS : THE INFLUENCE OF INCLINATION ON THE BOUNDARY STRUCTURE AND ENERGY

    OpenAIRE

    1990-01-01

    The "Embedded Atom Method" (EAM) is used to study the energy and structure of different Σ3 grain boundaries defined by the inclination angle Φ. The grain boundary energy, γb, varies with Φ, i.e. the boundary plane orientation. For copper the γb (Φ) plot shows a deep energy minimum for the coherent (111) twin boundary for inclinations around the [01(-1)] axis. A second significant energy minimum is found ∼8° away from the incoherent ((-2)11) twin plane. The location of a minimum energy configu...

  19. Study of Boundary Structures.

    Science.gov (United States)

    1982-09-01

    THEORY OF ABC-CBA STACKING BOUNDARY IN fcc STRUCTURE .......... 11 - 4 TRANSITIONS AND PHASE EQUILIBRIA AMONG GRAIN BOUNDARY STRUCTURES...19 B THEORY OF ABC-CBA STACKING BOUNDARY IN fcc STRUCTURE .......... 37 C TRANSITIONS AND PHASE EQUILIBRIA AMONG GRAIN BOUNDARY...layer structure. 10 SECTION 3 THEORY OF ABC-CBA STACKING BOUNDARY IN fcc STRUCTURE The (111) planes of the fcc structure is stacked as ABCABC... as

  20. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning with co...

  1. Photocatalytic Denitrogenation over Modiifed Waste FCC Catalyst

    Institute of Scientific and Technical Information of China (English)

    Zheng Liuping; Lin Mei; Huang Yingying; Yan Guiyang; Zheng Binquan; Li Ling

    2013-01-01

    The strontium modiifed waste FCC catalyst was prepared by magnetic stirring method and characterized by X-ray diffractometry (XRD), UV-Vis diffuse relfectance spectrometry (DRS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Meanwhile, its photocatalytic denitrogenation performance was evaluated in terms of its ability to degrade the N-containing simulation oil under visible light. A mixture of strontium nitrate solution (with a concentration of 0.5 mol/L) and waste FCC catalyst was calcined at 400℃for 5 h prior to taking part in the photocatalytic denitrogenation reaction. The test results showed that the photocatalytic degradation rate of pyridine contained in simulation oil in the presence of the strontium modiifed FCC catalyst could reach 92.0%under visible light irradiation for 2.5 h.

  2. Temperature dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La1-xSrxMnO3

    Energy Technology Data Exchange (ETDEWEB)

    Arenholz, Elke; Mannella, N.; Booth, C.H.; Rosenhahn, A.; Sell, B.C.; Nambu, A.; Marchesini, S.; Mun, B. S.; Yang, S.-H.; Watanabe, M.; Ibrahim, K.; Arenholz, E.; Young, A.; Guo, J.; Tomioka, Y.; Fadley, C.S.

    2007-12-06

    We have studied the temperature-dependent evolution of the electronic and local atomic structure in the cubic colossal magnetoresistive manganite La{sub 1-x}Sr{sub x}MnO{sub 3} (x= 0.3-0.4) with core and valence level photoemission (PE), x-ray absorption spectroscopy (XAS), x-ray emission spectroscopy (XES), resonant inelastic x-ray scattering (RIXS), extended x-ray absorption fine structure (EXAFS) spectroscopy and magnetometry. As the temperature is varied across the Curie temperature T{sub c}, our PE experiments reveal a dramatic change of the electronic structure involving an increase in the Mn spin moment from {approx} 3 {micro}B to {approx} 4 {micro}B, and a modification of the local chemical environment of the other constituent atoms indicative of electron localization on the Mn atom. These effects are reversible and exhibit a slow-timescale {approx}200 K-wide hysteresis centered at T{sub c}. Based upon the probing depths accessed in our PE measurements, these effects seem to survive for at least 35-50 {angstrom} inward from the surface, while other consistent signatures for this modification of the electronic structure are revealed by more bulk sensitive spectroscopies like XAS and XES/RIXS. We interpret these effects as spectroscopic fingerprints for polaron formation, consistent with the presence of local Jahn-Teller distortions of the MnO{sub 6} octahedra around the Mn atom, as revealed by the EXAFS data. Magnetic susceptibility measurements in addition show typical signatures of ferro-magnetic clusters formation well above the Curie temperature.

  3. Structural, electronic, optical and thermodynamic properties of cubic REGa{sub 3} (RE = Sc or Lu) compounds: Ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Murtaza, G., E-mail: murtaza@icp.edu.pk [Materials Modeling Laboratory, Department of Physics, Islamia College Peshawar (Pakistan); Gupta, S.K. [Department of Physics, Michigan Technological University, Houghton, MI 49931 (United States); Seddik, T. [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 Mascara (Algeria); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique et de Modélisation Mathématique, Université de Mascara, 29000 Mascara (Algeria); Alahmed, Z.A. [Department of Physics and Astronomy, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia); Ahmed, R. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor (Malaysia); Khachai, H. [Physics Department, Djillali Liabes University of Sidi Bel-Abbes (Algeria); Jha, P.K. [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar 364001 (India); Bin Omran, S. [Department of Physics and Astronomy, College of Science, King Saud University, Riyadh 11451 (Saudi Arabia)

    2014-06-01

    Highlights: • REGa{sub 3} (RE = Sc or Lu) compounds are mechanical stabile. • Both ScGa{sub 3} and LuGa{sub 3} exhibit metallic behavior just like other REGa{sub 3} compounds. • Melting temperature T{sub m} (K) for ScGa{sub 3} and LuGa{sub 3} are 1244.2 and 1143.8. • High absorption observed in the visible energy region. • The present study would be helpful for future experimental/theoretical explorations. - Abstract: Structural, elastic, optoelectronic and thermodynamic properties of REGa{sub 3} (RE = Sc and Lu) compounds have been studied self consistently by employing state of the art full potential (FP) linearized (L) approach of augmented plane wave (APW) plus local orbitals method. Calculations were executed at the level of Perdew–Burke and Ernzerhof (PBE) parameterized generalized gradient approximation (GGA) for exchange correlation functional in addition to modified Becke–Johnson (mBJ) potential. Our obtained results of lattice parameters show reasonable agreement to the previously reported experimental and other theoretical studies. Analysis of the calculated band structure of ScGa{sub 3} and LuGa{sub 3} compounds demonstrates their metallic character. Moreover, a positive value of calculated Cauchy pressure, in addition to reflecting their ductile nature, endorses their metallic character as well. To understand optical behavior calculations related to the important optical parameters; real and imaginary parts of the dielectric function, reflectivity R(ω), refractive index n(ω) and electron energy-loss function L(ω) have also been performed. In the present work, thermodynamically properties are also investigated by employing lattice vibrations integrated in quasi harmonic Debye model. Obtained results of volume, heat capacity and Debye temperature as a function of temperature for both compounds, at different values of pressure, are found to be consistent. The calculated value of melting temperature for both compounds (ScGa{sub 3} and Lu

  4. KBi(2-x)Pbx (0 phase evolving from a distortion of the cubic Laves-phase structure.

    Science.gov (United States)

    Ponou, Siméon; Müller, Noémi; Fässler, Thomas F; Häussermann, Ulrich

    2005-10-17

    The quasibinary system KBi(2-x)Pbx has been investigated, both experimentally and theoretically. Phases with compositions 0 Laves-phase structure MgCu2 (space group Fdm), which contains a rigid framework of corner-condensed symmetry-equivalent tetrahedra formed by randomly distributed Bi and Pb atoms. For compositions x > or = 0.6, these tetrahedra become alternately elongated and contracted. The distortion of the framework lowers the space-group symmetry to F43m (KBi(1.2)Pb(0.8), F43m, Z = 8, a = 9.572(1) A). Magnetometer measurements show that KBi2 (x = 0) is metallic and goes through a superconducting transition below 3.5 K. First principles calculations reveal that the Fd3m --> F43m distortion is largest for KBiPb (x = 1.0), which at the same time turns into a semiconductor. Thus, F43m KBiPb corresponds to a proper charge-balanced Zintl phase, K+[BiPb]-, with separated polyanionic tetrahedra, (Bi2Pb2)2-. However, it was not possible to prepare F43m KBiPb. Syntheses attempting to increase the Pb content in KBi(2-x)Pbx above x = 0.8 yielded additional, not yet characterized, ternary phases.

  5. Luminosity Targets for FCC-hh

    CERN Document Server

    Zimmermann, F.; Buffat, X.; Schulte, D.

    2016-01-01

    We discuss the choice of target values for the peak and integrated luminosity of a future high-energy frontier circular hadron collider (FCC-hh). We review the arguments on the physics reach of a hadron collider. Next we show that accelerator constraints will limit the beam current and the turnaround time. Taking these limits into account, we derive an expression for the ultimate integrated luminosity per year, depending on a possible pile-up limit imposed by the physics experiments. We finally benchmark our result against the planned two phases of FCC-hh [1, 2, 3

  6. Status and Challenges for FCC-ee

    CERN Document Server

    Benedikt, Michael; Zimmermann, Frank; Bogomyagkov, Anton; Levichev, Eugene; Migliorati, Mauro; Wienands, Uli

    2015-01-01

    We report the design status and beam dynamics challenges for the electron-positron branch of the Future Circular Collider (FCC) study, as of August 2015. After recalling motivation and physics requirements for the FCC-ee, we briefly discuss configurations and parameters, collider layout, the superconducting RF system, possible staging scenarios, final-focus optics, interaction-region (IR) issues, machine detector interface and IR synchrotron radiation, dynamic aperture, beam-beam effects, top-up injection, mono-chromatization option, impedances, instabilities, energy calibration and polarization, and SuperKEKB as a key demonstrator, before presenting conclusions and outlook.

  7. DETERMINATION OF IDEAL PARTITIONING-RATIOS AND-PARAMETERS OF SUBSTITUTIONAL ELEMENTS AND LATTICE CELL NUMBER OF TWO-PHASE ALLOYS WITH FCC,BCC AND HCP STRUCTURES%FCC,BCC和HCP结构两相合金中置换型元素理想分配比和分配系数及晶胞比的确定

    Institute of Scientific and Technical Information of China (English)

    彭志方; 任遥遥

    2001-01-01

    从原子分数及晶胞原子数的角度导出FCC,BCC及HCP结构两相合金中元素分配比和分配系数.通过对上述3种典型合金相结构的9种组合计算发现,任意两相之间存在一致的元素分配比和元素分配系数;两相各自的晶胞数及其比值与合金及其组成相成分之间存在特征关系;采用合金元素分配系数法算得的合金相成分与其观测值或采用统计回归法算得的相应值吻合程度较好.

  8. Phase stability, elastic anisotropy and electronic structure of cubic MAl2 (M = Mg, Ca, Sr and Ba) Laves phases from first-principles calculations

    Science.gov (United States)

    Kong, Yuanyuan; Duan, Yonghua; Ma, Lishi; Li, Runyue

    2016-10-01

    By performing first-principles calculations within the generalized gradient approximation, the phase stability, elastic constant and anisotropy, and density of states of cubic C15-type MAl2 (M = Mg, Ca, Sr and Ba) Laves phases have been investigated. Optimized equilibrium lattice parameters and formation enthalpies agree well with the available experimental data. Elastic constants C ij have been evaluated, and these C15-type MAl2 Laves phases are mechanically stable due to the meeting of C ij to the mechanical stability criteria. Polycrystalline elastic moduli have been deduced from elastic constants by Voigt-Reuss-Hill approximation. Plastic properties were characterized via values of B/G, Poisson’s ratio ν and Cauchy pressure (C 12-C 44). The elastic anisotropy has been considered by several anisotropy indexes (A U , A Z , A shear and A comp), anisotropy of shear modulus, and 3D surface constructions of bulk and Young’s moduli. Additionally, the sound velocity anisotropy and Debye temperature were predicted. Finally, electronic structures were carried out to reveal the underlying phase stability mechanism of these Laves phases.

  9. Structural, magnetic, and magneto-optical properties of nanocrystalline face centered cubic Co70Cr30/Pt multilayers with perpendicular magnetic anisotropy.

    Science.gov (United States)

    Papaioannou, E Th; Angelakeris, M; Poulopoulos, P; Tsiaoussis, I; Rüdt, C; Fumagalli, P; Flevaris, N K

    2007-12-01

    Co70Cr30 alloyed layers are combined with extremely thin Pt layers in order to produce novel face-centered-cubic multilayered films to be considered as a potential perpendicular magnetic recording medium. The films were grown on Si, glass and polyimide substrates by e-beam evaporation at a temperature slightly higher than room temperature. The multilayered structure of the films was verified by X-ray diffraction experiments. Plane-view transmission electron microscopy images have revealed the formation of very small grains in the range of 7-9 nm. Hysteresis loops as a function of temperature were recorded via the magneto-optic Kerr effect in the polar geometry configuration. The system exhibits perpendicular magnetic anisotropy, which enhances with decreasing temperature. Hysteresis loops with a squareness of 1 and a coercivity of 1.45 kOe were obtained at 10 K. Furthermore, complete magneto-optic spectra of the films are recorded, showing a strong magneto-optic enhancement in the ultraviolet region at around 4.5 eV.

  10. Carbon coated face-centered cubic Ru-C nanoalloys.

    Science.gov (United States)

    Zhao, Zhisheng; Meng, Chuanmin; Li, Peifang; Zhu, Wenjun; Wang, Qianqian; Ma, Yanming; Shen, Guoyin; Bai, Ligang; He, Hongliang; He, Duanwei; Yu, Dongli; He, Julong; Xu, Bo; Tian, Yongjun

    2014-09-07

    Carbon-encapsulated ruthenium-carbon (Ru-C) nanoalloys were synthesized by dynamic shocks. The Ru-C alloy shows a new fcc structure different from the original hcp structure of metal Ru. This fcc phase is assigned to a Ru32C4 solid solution with a lattice parameter of 3.868(2) Å and a bulk modulus KT0 of 272(12) GPa. The small amount of carbon in the solid solution enhances the thermodynamic and chemical stabilities with respect to pure Ru, as well as induces changes in the electronic properties, which have direct applications in improving the material's catalytic activity and selectivity.

  11. Atomistic simulation of fcc-bcc phase transition in single crystal A1 under uniform compression

    Institute of Scientific and Technical Information of China (English)

    Li Li; Shao Jian-Li; Li Yan-Fang; Duan Su-Qing; [ Liang Jiu-Qing

    2012-01-01

    By molecular dynamics simulations employing an embedded atom model potential,we investigate the fcc-to-bcc phase transition in single crystal Al,caused by uniform compression.Results show that the fec structure is unstable when the pressure is over 250 GPa,in reasonable agreement with the calculated value through the density functional theory.The morphology evolution of the structural transition and the corresponding transition mechanism are analysed in detail.The bec (011) planes are transited from the fcc (11(1)) plane and the (1(1)1) plane.We suggest that the transition mechanism consists mainly of compression,shear,slid and rotation of the lattice.In addition,our radial distribution function analysis explicitly indicates the phase transition of A1 from fcc phase to bcc structure.

  12. Structural and Magnetic Properties of Trigonal Iron

    CERN Document Server

    Fox, S

    1995-01-01

    First principles calculations of the electronic structure of trigonal iron were performed using density function theory. The results are used to predict lattice spacings, magnetic moments and elastic properties; these are in good agreement with experiment for both the bcc and fcc structures. We find however, that in extracting these quantities great care must be taken in interpreting numerical fits to the calculated total energies. In addition, the results for bulk iron give insight into the properties of thin iron films. Thin films grown on substrates with mismatched lattice constants often have non-cubic symmetry. If they are thicker than a few monolayers their electronic structure is similar to a bulk material with an appropriately distorted geometry, as in our trigonal calculations. We recast our bulk results in terms of an iron film grown on the (111) surface of an fcc substrate, and find the predicted strain energies and moments accurately reflect the trends for iron growth on a variety of substrates.

  13. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type-checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, is conjectured to have decidable type checking, and has an implemented type-checker. Our new type theory, called guarded cubical type theory, provides a computational interpretation of extensionality for guarded recursive...

  14. Guarded Cubical Type Theory

    DEFF Research Database (Denmark)

    Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald;

    2016-01-01

    This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, enjoys canonicity for the natural numbers type, and is conjectured to support decidable type-checking. Our new type theory, guarded cubical type theory (GCTT), provides a computational interpretation of extensionality...

  15. Synthesis of octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals and their structure-activity relationship for the decomposition of hydrazine in aqueous solution to hydrogen

    Science.gov (United States)

    Li, Chun; Wang, Tao; Chu, Wei; Wu, Ping; Tong, Dong Ge

    2016-03-01

    We developed a co-reduction method to synthesize octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals. The shape/size distribution, structural characteristics, and composition of the Rh2Ni nanocrystals are investigated, and their possible formation mechanism at high temperatures in margaric acid/1-aminoheptadecane solution in the presence of tetraethylgermanium and borane trimethylamine complexes is proposed. A preliminary probing of the structure-activity dependence of the surface ``clean'' Rh2Ni nanocrystals supported on carbon towards hydrazine (N2H4) in aqueous solution dehydrogenation revealed that the higher the percentage of {111} facets, the higher is the activity and H2 selectivity of the nanocrystals. This result was attributed to the {111} facets not only introducing more basic sites, but also weakening the interaction between the produced adspecies (including H2 and NHx) and surface metal atoms in comparison with those of {100} facets. Furthermore, the as-prepared Rh2Ni nanooctahedra exhibited 100% H2 selectivity and high activity at room temperature for H2 generation via N2H4 decomposition. The activation energy of the Rh2Ni nanooctahedra was 41.6 +/- 1.2 kJ mol-1. The Rh2Ni nanooctahedra were stable catalysts for the hydrolytic dehydrogenation of N2H4, providing 27 723 total turnovers in 30 h. Our work provides a new perspective concerning the possibility of constructing hydrogen-producing systems based on N2H4 and surface ``clean'' Rh2Ni nanocrystal catalysts with defined shapes supported on carbon that possess a competitive performance in comparison with NaBH4 and NH3BH3 hydrogen-producing systems for fuel cell applications.We developed a co-reduction method to synthesize octahedral, truncated octahedral, and cubic Rh2Ni nanocrystals. The shape/size distribution, structural characteristics, and composition of the Rh2Ni nanocrystals are investigated, and their possible formation mechanism at high temperatures in margaric acid/1

  16. Elastic constants of random solid solutions by SQS and CPA approaches: the case of fcc Ti-Al.

    Science.gov (United States)

    Tian, Li-Yun; Hu, Qing-Miao; Yang, Rui; Zhao, Jijun; Johansson, Börje; Vitos, Levente

    2015-08-12

    Special quasi-random structure (SQS) and coherent potential approximation (CPA) are techniques widely employed in the first-principles calculations of random alloys. Here we scrutinize these approaches by focusing on the local lattice distortion (LLD) and the crystal symmetry effects. We compare the elastic parameters obtained from SQS and CPA calculations, taking the random face-centered cubic (fcc) Ti(1-x)Al(x) (0 ≤ x ≤ 1) alloy as an example of systems with components showing different electronic structures and bonding characteristics. For the CPA and SQS calculations, we employ the Exact Muffin-Tin Orbitals (EMTO) method and the pseudopotential method as implemented in the Vienna Ab initio Simulation Package (VASP), respectively. We show that the predicted trends of the VASP-SQS and EMTO-CPA parameters against composition are in good agreement with each other. The energy associated with the LLD increases with x up to x = 0.625 ~ 0.750 and drops drastically thereafter. The influence of the LLD on the lattice constants and C12 elastic constant is negligible. C11 and C44 decrease after atomic relaxation for alloys with large LLD, however, the trends of C11 and C44 are not significantly affected. In general, the uncertainties in the elastic parameters associated with the symmetry lowering turn out to be superior to the differences between the two techniques including the effect of LLD.

  17. Defect Studies in bcc and fcc Iron

    OpenAIRE

    Ghorai, A.; Arjun Das

    2012-01-01

    Variation of vacancy formation energy (EF1v) with rc of Ashcroft's empty core model potential (AECMP) model for different exchange and correlation functions (ECFs) show almost independent nature but slight variation with ECF for both bcc α iron and fcc γ iron.

  18. Cubic spline symplectic algorithm for dynamic analysis of space truss structure%网架结构动力分析的三次样条辛算法

    Institute of Scientific and Technical Information of China (English)

    李纬华; 王堉; 罗恩

    2013-01-01

    According to the basic idea of dual-complementarity,the unconventional Hamilton-type variational principle in phase space for dynamic analysis of space truss structure was introduced,which can fully characterize this kind of dynamic initial-boundary-value problems.In addition,its Euler equation is of symplectic structure character.Based on this vairiational principle,a symplectic algorithm was presented,combining the finite element method in space domain with the time subdomain method,in which the cubic spline interpolation was applied as approximation.The results of numerical examples show that the method is a highly efficient method with better computational performance and superior ability of stability compared with Wilson-θ and Newmark-β methods.%根据对偶互补的思想,建立了网架结构动力学的相空间非传统Hamilton型变分原理.这种变分原理不仅能反映这种动力学初值-边值问题的全部特征,而且它的欧拉方程具有辛结构.基于该变分原理,空间域采用有限元法与时间子域采用三次样条函数插值的时间子域法相结合,构造了求解网架结构动力响应的一种辛算法,给出了逐步递推计算格式.数值算例结果表明,这种新方法的稳定性、计算精度和效率都明显高于Wilson-θ法和Newmark-β法.

  19. Effect of Gd3+ doping on structural, optical and frequency-dependent dielectric response properties of pseudo-cubic BaTiO3 nanostructures

    Science.gov (United States)

    Borah, Manjit; Mohanta, Dambarudhar

    2014-06-01

    We report on the structural, optical and dielectric characterization of solid state derived, pseudo-cubic nanoscale barium titanates (BTs) with gadolinium (Gd3+) as substitutional dopant. Referring to X-ray diffractograms, apart from the BT peaks related to perovskite structure, the non-existence of any additional peaks due to byproducts has revealed that Gd3+ has undergone substitutional doping into the BT host lattice. The well-separated BT nanoparticles of typical size ˜10-15 nm were observed through electron microscopy studies. Following a direct, allowed type carrier transition ( n=1/2), a reduction in the optical band gap value (from 3.28 to 3.255 eV) was observed when the Gd-doping level was varied within 0-7 %. Conversely, the Urbach energy followed an increasing trend, from a value of 0.741 to 1.879 eV. Furthermore, the dielectric constant showed a decreasing tendency with doping content and with increasing frequency. However, in the low-frequency region, the loss tangent (tan δ), which is the combined result of orientational polarization and electrical conduction, was found to be quite high in the doped samples as compared to their un-doped counterpart. The frequency-dependent electrical data were also analyzed in the framework of conductivity and impedance formalisms. In particular, the ac conductivity which varies as ˜ ω s approaches ideal Debye behavior ( s→1) for a low Gd level and a higher doping concentration did not show improved dielectric feature of the host. The incorporation of rare-earth (Gd3+) ions into the BT host system could greatly manifest dielectric relaxation and carrier conduction mechanisms, in a given frequency range, and thus can find immense scope in miniaturized nanoelectronic elements including ceramic capacitors and transducers.

  20. Academic Training Lectures | FCC | 2-5 February

    CERN Multimedia

    2016-01-01

    Please note that the next series of Academic Training Lectures will take place from 2 to 5 February 2016.   Tuesday, 2 February 2016 from 10.30 a.m. to 12.30 p.m. in the Filtration Plant (Building 222-R-001) FCC 1: Introduction to FCC by Michael Benedikt FCC 2: FCC Physics - Challenges and Potentials by Christophe Grojean, Michelangelo Mangano https://indico.cern.ch/event/472105/   Wednesday, 3 February 2016 from 10.30 a.m. to 12.30 p.m in the Filtration Plant (Building 222-R-001) FCC 3: FCC hh Detectors and Experiments by Werner Riegler FCC 4: Experimental Measurements and Detectors for the FCC-ee by Mogens Dam https://indico.cern.ch/event/472106/   Thursday, 4 February 2016 from 10.30 a.m. to 12.30 p.m in the Filtration Plant (Building 222-R-001) FCC 5: FCC Hadron Collider Design by Daniel Schulte FCC 6: FCC Lepton Collider Design by Frank Zimmermann https://indico...

  1. 78 FR 49126 - Modernizing the FCC Form 477 Data Program

    Science.gov (United States)

    2013-08-13

    ... COMMISSION 47 CFR Parts 0, 1, and 43 Modernizing the FCC Form 477 Data Program AGENCY: Federal Communications... Docket No. 11-10, FCC 13-87, released on June 27, 2013. The complete text of this document is available for public inspection during regular business hours in the FCC Reference Information Center, Room...

  2. 47 CFR 95.117 - Where to contact the FCC.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Where to contact the FCC. 95.117 Section 95.117... SERVICES General Mobile Radio Service (GMRS) § 95.117 Where to contact the FCC. Additional GMRS information may be obtained from any of the following sources: (a) FCC National Call Center at 1-888-225-5322....

  3. 47 CFR 73.1225 - Station inspections by FCC.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Station inspections by FCC. 73.1225 Section 73... BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.1225 Station inspections by FCC. (a) The... FCC during the station's business hours, or at any time it is in operation. (b) In the course of...

  4. 47 CFR 74.3 - FCC inspections of stations.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FCC inspections of stations. 74.3 Section 74.3... Services in Part 74 § 74.3 FCC inspections of stations. (a) The licensee of a station authorized under this part must make the station available for inspection by representatives of the FCC during the...

  5. 76 FR 10827 - Modernizing the FCC Form 477 Data Program

    Science.gov (United States)

    2011-02-28

    ... COMMISSION 47 CFR Parts 1, 20, and 43 Modernizing the FCC Form 477 Data Program AGENCY: Federal... submitting comments. Federal Communications Commission's Web Site: http://fjallfoss.fcc.gov/ecfs2/ . Follow the instructions for submitting comments. People with Disabilities: Contact the FCC to...

  6. Alkali cation specific adsorption onto fcc(111) transition metal electrodes.

    Science.gov (United States)

    Mills, J N; McCrum, I T; Janik, M J

    2014-07-21

    The presence of alkali cations in electrolyte solutions is known to impact the rate of electrocatalytic reactions, though the mechanism of such impact is not conclusively determined. We use density functional theory (DFT) to examine the specific adsorption of alkali cations to fcc(111) electrode surfaces, as specific adsorption may block catalyst sites or otherwise impact surface catalytic chemistry. Solvation of the cation-metal surface structure was investigated using explicit water models. Computed equilibrium potentials for alkali cation adsorption suggest that alkali and alkaline earth cations will specifically adsorb onto Pt(111) and Pd(111) surfaces in the potential range of hydrogen oxidation and hydrogen evolution catalysis in alkaline solutions.

  7. Packing of crystalline structures of binary hard spheres: An analytical approach and application to amorphization

    NARCIS (Netherlands)

    Brouwers, H.J.H.

    2007-01-01

    The geometrical stability of the three lattices of the cubic crystal system, viz. face-centered cubic (fcc), body-centered cubic (bcc), and simple cubic (sc), consisting of bimodal discrete hard spheres, and the transition to amorphous packing is studied. First, the random close packing (rcp) fracti

  8. Packing of crystalline structures of binary hard spheres: an analytical approach and application to amorphisation

    NARCIS (Netherlands)

    Brouwers, Jos

    2007-01-01

    The geometrical stability of the three lattices of the cubic crystal system, viz. face-centered cubic (fcc), body-centered cubic (bcc), and simple cubic (sc), consisting of bimodal discrete hard spheres, and the transition to amorphous packing is studied. First, the random close packing (rcp)

  9. 47 CFR 95.428 - (CB Rule 28) How do I contact the FCC?

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false (CB Rule 28) How do I contact the FCC? 95.428... (CB Rule 28) How do I contact the FCC? (a) FCC National Call Center at 1-888-225-5322. (b) FCC World Wide Web homepage: http://www.fcc.gov. (c) In writing, to FCC, Attention: CB, 1270 Fairfield...

  10. Appropriate deposition parameters for formation of fcc Co-Ni alloy nanowires during electrochemical deposition process

    Science.gov (United States)

    Mukhtar, Aiman; Shahzad Khan, Babar; Mehmood, Tahir

    2016-12-01

    The effect of deposition potential on the crystal structure and composition of Co-Ni alloy nanowires is studied by XRD, FE-SEM and EDX. The alloy nanowires deposited at -3.2 V are metastable fcc phase Co-Ni. The alloy nanowires deposited at -1.8 V are hcp phase Co-Ni. The formation of the metastable fcc alloy nanowires can be attributed to smaller critical clusters formed at the high potential as the smaller critical clusters favor fcc structure because of the significant surface energy effect. The content of Co inside nanowires increases with increasing potential. This can be understood by the polarization curves of depositing Co and Ni nanowires, which show that the current density ratio of Ni to Co at low potential has larger value than that at high potential.

  11. Kinetics study of crystallization with the disorder-bcc-fcc phase transition of charged colloidal dispersions.

    Science.gov (United States)

    Zhou, Hongwei; Xu, Shenghua; Sun, Zhiwei; Du, Xuan; Liu, Lixia

    2011-06-21

    Structure transformation (disorder-bcc-fcc) in charged colloidal dispersions, as a manifestation of the Ostwald's step rule, was confirmed by means of reflection spectrum (RS) measurements in our previous study. By taking advantage of a reflection spectrum containing plenty of information about the crystallization behaviors, time-dependent changes of parameters associated with the crystal structure and composition during the disorder-bcc-fcc transition are reported by treating the data from RS in this article. In addition, Avrami's model is adopted to analyze the transition process and investigate the transition rate. On the basis of the above investigations, associated kinetic features of crystallization with the disorder-bcc-fcc transition are described.

  12. Spinel type twins of the new cubic Er{sub 6}Zn{sub 23}Ge compound

    Energy Technology Data Exchange (ETDEWEB)

    Solokha, Pavlo; De Negri, Serena; Saccone, Adriana [Genova Univ. (Italy). Dipt. di Chimica e Chimica Industriale; Proserpio, Davide M. [Univ. degli Studi di Milano (Italy). Dipt. di Chimica; Samara State Univ. (Russian Federation). Samara Center for Theoretical Materials Science (SCTMS)

    2016-04-01

    The crystal structure of the new Er{sub 6}Zn{sub 23}Ge intermetallic compound was established by X-ray diffraction analysis on a twinned crystal (space group Fm anti 3m, Wyckoff sequence: f{sup 2}edba, cF120-Zr{sub 6}Zn{sub 23}Si, a=12.7726(6) Aa). The crystal is composed of two nearly equal size domains, whose mutual orientation is described by a 180 rotation around the cubic [111] axis, i.e. a spinel-type twinning law, not common for intermetallics. Applying the nanocluster approach, Er{sub 6}Ge octahedra and centered two-shell Zn{sub 45} clusters were found as structural building blocks, filling the crystal space in a NaCl-like arrangement. This description was adopted to interpret the twinning in terms of stacking faults in the fcc cubic close packed arrangement. Moreover, the assembly of the nanocluster units is proposed as a possible mechanism for crystal growth and twin formation, in agreement with the principle of the interface energy minimization. Experimental conditions such as supersaturation and co-formation of other phases are also considered as favorable factors for Er{sub 6}Zn{sub 23}Ge twin formation.

  13. Formation of deformation substructures in FCC crystals under the influence of point defect fluxes

    OpenAIRE

    Matveev, M. V.; Selivanikova, Olga Valerievna; Cherepanov, Dmitry Nikolaevich

    2016-01-01

    The article deals with sub-structural transformations in FCC crystals under the influence of point defect fluxes. Different relationships between accumulation of point defects in crystal and substructure transformations, in particular during the process of fragmented dislocation structure formation have been received.

  14. Insulating fcc YH3-δ stabilized by MgH2

    NARCIS (Netherlands)

    Molen, van der S.J.; Nagengast, D.G.; Gogh, van A.T.M.; Kalkman, J.; Kooij, E.S.; Rector, J.H.; Griessen, R.

    2001-01-01

    We study the structural, optical, and electrical properties of MgzY1-z switchable mirrors upon hydrogenation. It is found that the alloys disproportionate into essentially pure YH3-δ and MgH2 with the crystal structure of YH3-δ dependent on the Mg concentration z. For 0fcc YH3-δ

  15. Simulation of texture evolution during plastic deformation of FCC, BCC and HCP structured crystals with crystal plasticity based finite element method%基于耦合有限元的晶体塑性力学模型的FCC,BCC和HCP晶体织构演化的模拟

    Institute of Scientific and Technical Information of China (English)

    黄诗尧; 张少睿; 李大永; 彭颖红

    2011-01-01

    介绍单晶体模型的2种实现方法,并通过对有限元软件ABAQUS/Explicit的用户材料接口VUMAT做二次开发,实现2种单晶体模型构架和显式有限元方法的耦合.采取实体单元来存储材料信息,每个单元代表一个晶粒,在每个增量步中读取并更新晶粒取向.采用切线系数法来计算每个增量步中不同变形系统的塑性应变增量,通过硬化模型来描述硬化响应.利用编制的2种用户子程序模拟铜(FCC)单向拉伸过程、IF铁(BCC)冷轧过程和AZ31镁合金(HCP)单向压缩过程中的织构演化,模拟结果和试验结果吻合较好.%Two alternative formulations of single crystal plasticity model were introduced respectively and two schemes were implemented in the explicit FE code with software ABAQUS/Explicit by writing the user subroutine VUMAT.Meshes containing material data were created with solid elements.Each element represented an individual grain,and the grain orientations were explicitly stored and updated at each increment.Tangential modulus method was employed to calculate the plastic shear strain increment of deformation systems in combination with a hardening law to describe the hardening responses.Both two developed subroutines were applied to simulate the texture evolution during the uniaxial tension of copper (FCC),cold rolling of IF steel (BCC) and uniaxial compression of AZ31 magnesium alloy (HCP).The predicted texture distributions are in qualitative agreement with the experimental results.

  16. Phase boundary between cubic B1 and rhombohedral structures in (Mg,Fe)O magnesiowüstite determined by in situ X-ray diffraction measurements

    Science.gov (United States)

    Dymshits, Anna M.; Litasov, Konstantin D.; Shatskiy, Anton; Chanyshev, Artem D.; Podborodnikov, Ivan V.; Higo, Yuji

    2017-06-01

    The phase relations and equation of state of (Mg0.08Fe0.92)O magnesiowüstite (Mw92) have been studied using the Kawai-type high-pressure apparatus coupled with synchrotron radiation. To determine the phase boundary between the NaCl-type cubic (B1) and rhombohedral (rB1) structures in Mw92, in situ X-ray observations were carried out at pressures of 0-35 GPa and temperatures of 300-1473 K. Au and MgO were used as the internal pressure markers and metallic Fe as oxygen fugacity buffer. The phase boundary between B1 and rB1 structures was described by a linear equation P (GPa) = 1.6 + 0.033 × T (K). The Clapeyron slope (dP/dT) determined in this study is close to that obtained at pressures above 70 GPa but steeper than that obtained for FeO. An addition of MgO to FeO structure expands the stability field of the rB1 phase to lower pressures and higher temperatures. Thus, the rB1 phase may be stabilized with respect to the B1 phase at a lower pressures. The pressure-volume-temperature equation of state of B1-Mw92 was determined up to 30 GPa and 1473 K. Fitting the hydrostatic compression data up to 30 GPa with the Birch-Murnaghan equation of state (EoS) yielded: unit cell volume (V 0,T0), 79.23 ± 4 Å3; bulk modulus (K 0,T0), 183 ± 4 GPa; its pressure derivative (K' T ), 4.1 ± 0.4; (∂K 0,T /∂T) = -0.029 ± 0.005 GPa K‒1; a = 3.70 ± 0.27 × 10-5 K-1 and b = 0.47 ± 0.49 × 10-8 K-2, where α0,T = a + bT is the volumetric thermal expansion coefficient. The obtained bulk modulus of Mw92 is very close to the value expected for stoichiometric iron-rich (Mg,Fe)O. This result confirms the idea that the bulk modulus of (Mg,Fe)O is greatly affected by the actual defect structure, caused by either Mg2+ or vacancies.

  17. Regeneration of Hydrotreating and FCC Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    CM Wai; JG Frye; JL Fulton; LE Bowman; LJ Silva; MA Gerber

    1999-09-30

    Hydrotreating, hydrocracking, and fluid catalytic cracking (FCC) catalysts are important components of petroleum refining processes. Hydrotreating and hydrocracking catalysts are used to improve the yield of high-quality light oil fractions from heavier crude oil and petroleum feedstocks containing high levels of impurities. FCC catalysts improve the yield of higher octane gasoline from crude oil. Residuum hydrotreating and cracking catalysts are susceptible to irreversible deactivation caused by adsorption of sulfur and by metals impurities, such as vanadium and nickel. The gradual buildup of these impurities in a hydrotreating catalyst eventually plugs the pores and deactivates it. Nickel and vanadium adversely affect the behavior of cracking catalysts, reducing product yield and quality. Replacing deactivated catalysts represents a significant cost in petroleum refining. Equally important are the costs and potential liabilities associated with treating and disposing spent catalysts. For example, recent US Environmental Protection Agency rulings have listed spent hydrotreating and hydrorefining catalysts as hazardous wastes. FCC catalysts, though more easily disposed of as road-base or as filler in asphalt and cement, are still an economic concern mainly because of the large volumes of spent catalysts generated. New processes are being considered to increase the useful life of catalysts or for meeting more stringent disposal requirements for spent catalysts containing metals. This report discusses a collaborative effort between Pacific Northwest National Laboratory (PNNL) and Phillips Petroleum, Inc., to identify promising chemical processes for removing metals adhered to spent hydrodesulfurization (HDS, a type of hydrotreating catalyst) and FCC catalysts. This study, conducted by PNNL, was funded by the US Department of Energy's Bartlesville Project Office. Fresh and spent catalysts were provided by Phillips Petroleum. The FCC catalyst was a rare

  18. Transparent polycrystalline cubic silicon nitride

    Science.gov (United States)

    Nishiyama, Norimasa; Ishikawa, Ryo; Ohfuji, Hiroaki; Marquardt, Hauke; Kurnosov, Alexander; Taniguchi, Takashi; Kim, Byung-Nam; Yoshida, Hidehiro; Masuno, Atsunobu; Bednarcik, Jozef; Kulik, Eleonora; Ikuhara, Yuichi; Wakai, Fumihiro; Irifune, Tetsuo

    2017-01-01

    Glasses and single crystals have traditionally been used as optical windows. Recently, there has been a high demand for harder and tougher optical windows that are able to endure severe conditions. Transparent polycrystalline ceramics can fulfill this demand because of their superior mechanical properties. It is known that polycrystalline ceramics with a spinel structure in compositions of MgAl2O4 and aluminum oxynitride (γ-AlON) show high optical transparency. Here we report the synthesis of the hardest transparent spinel ceramic, i.e. polycrystalline cubic silicon nitride (c-Si3N4). This material shows an intrinsic optical transparency over a wide range of wavelengths below its band-gap energy (258 nm) and is categorized as one of the third hardest materials next to diamond and cubic boron nitride (cBN). Since the high temperature metastability of c-Si3N4 in air is superior to those of diamond and cBN, the transparent c-Si3N4 ceramic can potentially be used as a window under extremely severe conditions. PMID:28303948

  19. Nucleation of hcp and fcc phases in bcc iron under uniform compression: classical molecular dynamics simulations.

    Science.gov (United States)

    Wang, B T; Shao, J L; Zhang, G C; Li, W D; Zhang, P

    2010-11-03

    By classical molecular dynamics simulations employing an embedded atom method potential, we have simulated the bcc to hcp/fcc structural transition in single-crystal iron under uniform compression. Results showed that the transition pressure is different from uniaxial compression and shock loading. The transformation occurs on a picosecond timescale and the transition time decreases along with the increase of pressure. The nucleation and growth of the hcp and fcc phases under constant pressure and temperature are analyzed in detail. The nucleation planes, all belonging to the {110}(bcc) family and parallel to the three compression directions [100], [010], and [001], have been observed. About 20% bcc atoms have transformed to fcc phase under pressure just over the critical point, and under higher pressure the fraction of the fcc phase increases steadily to exceed that of the hcp phase. We have investigated the transition mechanism of iron from initial bcc to hcp/fcc and found that the transition mainly consists of compression, rotation, and shuffle.

  20. Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and Subsequent Fabrication of Superlattice Structures Using AlN and InN

    Science.gov (United States)

    1990-12-01

    Laboratories, Inc. 3. Structural Analysis Reflection high-energy electron diffraction performed during growth indicated that the BGaN film remained...was used (Hitachi H-800) to more closely examine the microstructural evolution of the BN/ BGaN /GaN epitaxial films. Cross-section TEM specimens were... BGaN layer to be a mixture of cubic and wurtzitic phases. This layer was heavily faulted. The latter phenomenon is to be expected given the high

  1. Exploiting the P L2,3 absorption edge for optics: spectroscopic and structural characterization of cubic boron phosphide thin films

    NARCIS (Netherlands)

    Huber, S.P.; Medvedev, V.V.; Meyer-Ilse, J.; Gullikson, E.; Padavala, B.; Edgar, J.H.; Sturm, J.M.; Kruijs, van de R.W.E.; Prendergast, D.; Bijkerk, F.

    2016-01-01

    The transmission of cubic boron phosphide (c-BP) thin films, prepared by chemical vapor deposition (CVD), was evaluated near the phosphorous L2,3 and boron K absorption edge. The c-BP films were analyzed with transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray ab

  2. Formation of fivefold axes in the FCC-metal nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Myasnichenko, Vladimir S., E-mail: virtson@gmail.com [Altai State Technical University, 46 Lenina av., Barnaul 656038 (Russian Federation); Starostenkov, Mikhail D. [Altai State Technical University, 46 Lenina av., Barnaul 656038 (Russian Federation)

    2012-11-01

    Highlights: Black-Right-Pointing-Pointer Formation of fcc-metal nanoclusters having the fivefold symmetry. Black-Right-Pointing-Pointer Formation of the cores of icosahedral symmetry in the gold, silver and copper nanoparticles. Black-Right-Pointing-Pointer Construction of bimetallic clusters with icosahedral symmetry and increased fractal dimensionality. - Abstract: Formation of atomistic structures of metallic Cu, Au, Ag clusters and bimetallic Cu-Au clusters was studied with the help of molecular dynamics using the many-body tight-binding interatomic potential. The simulation of the crystallization process of clusters with the number of atoms ranging from 300 to 1092 was carried out. The most stable configurations of atoms in the system, corresponding to the minimum of potential energy, was found during super-fast cooling from 1000 K. Atoms corresponding to fcc, hcp, and Ih phases were identified by the method of common neighbor analysis. Incomplete icosahedral core can be discovered at the intersection of one of the Ih axes with the surface of monometallic cluster. The decahedron-shaped structure of bimetallic Cu-Au cluster with seven completed icosahedral cores was obtained. The principles of the construction of small bimetallic clusters with icosahedral symmetry and increased fractal dimensionality were offered.

  3. BSM searches at FCC-ee

    CERN Document Server

    Tay, Jala

    2016-01-01

    The discovery of the Higgs boson in 2012 was a great triumph for the LHC. The challenge now is to study it’s properties. In order to that an FCC project was proposed, such that at the beginning it will be used for ee collisions which will be a great deal in studying the Higgs properties because of it’s clean experimental environment and high luminosity, and then will be used for pp collisions to explore physics at higher energies. Here we will show how to generate events and plot graphs which will show how is the FCC beneficial for the Higgs study. We used delphes, pythia and ROOT to generate and analyze the events.

  4. ADVANCE IN FCC TECHNOLOGY FOR RESID UPGRADING

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to treat residual oil in conventional FCC units, various aspects of catalyst improvement must be considered, such as how to get effective bottoms crackbility, lower selectivity of dry gas/coke or higher metals tolerance. Because residual oil contains many kinds of metals (Ni, V, Na), Conrandson carbon residue and asphaltene or basic nitrogen compunds, there are a lot of problems in FCC operation.   A new catalyst has been developed by means of modifying zeolite or matrix in our laboratory. The developed catalyst has a excellent bottoms crackbility, lower hydrogen / coke selectivity and higher metal tolerance. The features of the catalyst and the actual performance in our commercial units will be shown in this paper. The liquid product yield has been improved and the catalyst consumption has reduced.

  5. The temperature behaviour of the elastic and thermodynamic properties of fcc thorium

    Energy Technology Data Exchange (ETDEWEB)

    Jaroszewicz, S., E-mail: jaroszew@tandar.cnea.gov.ar [Gerencia de Investigacion y Aplicaciones, Comision Nacional de Energia Atomica, Av. Gral. Paz 1499, San Martin (Argentina); Instituto de Tecnologia Jorge A. Sabato, UNSAM-CNEA (Argentina); Mosca, H.O. [Gerencia de Investigacion y Aplicaciones, Comision Nacional de Energia Atomica, Av. Gral. Paz 1499, San Martin (Argentina); Instituto de Tecnologia Jorge A. Sabato, UNSAM-CNEA (Argentina); Garces, J.E. [DAEE, Centro Atomico Bariloche, Comisin Nacional de Energia Atomica, Av. Bustillo 9500, Bariloche, Rio Negro (Argentina)

    2012-10-15

    The temperature behaviour of the structural, elastical and thermal properties of fcc thorium have been calculated from a free-parameter Helmholtz free energy developed by computing the cohesive energy from first principles calculations coupled to the Chen-Moebius lattice inversion method and the Debye-Grueneisen quasiharmonic model. The elastic constants, shear modulus, Young modulus, Poisson's ratio and thermodynamic properties of fcc Th as the entropy, the harmonic specific heat, the (P, V, T) equation of state and the thermal lattice expansion are found to be in a very good agreement with experiments and ab initio phonon calculations. The results of this work show the potentiality of the Chen-Moebius method coupled to ab initio calculation of the cohesive energy to develop a free-parameter pair potential capable of giving an overall description of fcc Th properties at T = 0 K with an error similar to ab initio calculations.

  6. Reducing the formation of FIB-induced FCC layers on Cu-Zn-Al austenite.

    Science.gov (United States)

    Zelaya, Eugenia; Schryvers, Dominique

    2011-01-01

    The irradiation effects of thinning a sample of a Cu-Zn-Al shape memory alloy to electron transparency by a Ga(+) focused ion beam were investigated. This thinning method was compared with conventional electropolishing and Ar(+) ion milling. No implanted Ga was detected but surface FCC precipitation was found as a result of the focused ion beam sample preparation. Decreasing the irradiation dose by lowering the energy and current of the Ga(+) ions did not lead to a complete disappearance of the FCC structure. The latter could only be removed after gentle Ar(+) ion milling of the sample. It was further concluded that the precipitation of the FCC is independent of the crystallographic orientation of the surface.

  7. Electrical Power Budget for FCC-ee

    CERN Document Server

    Aull, S.; Bozzini, D.; Brunner, O.; Burnet, J.-P.; Butterworth, A.; Calaga, R.; Jensen, E.; Mertens, V.; Milanese, A.; Nonis, M.; Oide, K.; Schwerg, N.; Tavian, L.; Wenninger, J.; Zimmermann, F.; Rinolfi, L; Blondel, A.; Koratzinos, M.; Gorgi Zadeh, S.

    2016-01-01

    We present a first rough estimate for the electrical power consumption of the FCC-ee lepton collider. This electrical power is dominated by the RF system, which provides the motivation for the ongoing R&D on highly efficient RF power sources. Other contributions come from the warm arc magnets, the cryogenics systems, cooling, ventilation, general services, the particle-physics detectors, and the injector complex.

  8. Beam Dynamics Challenges for FCC-ee

    CERN Document Server

    AUTHOR|(SzGeCERN)442987; Benedikt, Michael; Oide, Katsunobu; Bogomyagkov, Anton; Levichev, Evgeny; Migliorati, Mauro; Wienands, Uli

    2015-01-01

    The goals of FCC-ee include reaching luminosities of up to a few 1036 cm-2s-1 per interaction point at the Z pole or some 1034 cm-2s-1 at the ZH production peak, and pushing the beam energy up to ≥175 GeV, in a ring of 100 km circumference, with a total synchrotron-radiation power not exceeding 100 MW. A parameter baseline as well as high-luminosity crab-waist options were described in [1] and [2], respectively. The extremely high luminosity and resulting short beam lifetime (due to radiative Bhabha scattering) are sustained by top-up injection. The FCC-ee design status and typical beam parameters for different modes of operation are reported in [3]. One distinct feature of the FCC-ee design is its conception as a double ring, with separate beam pipes for the two counter-rotating (electron and positron) beams, resembling, in this aspect, the high-luminosity B factories PEP-II, KEKB and SuperKEKB as well as the LHC. The two separate rings do not only permit operation with a large number of bunches, up to a f...

  9. Computer simulation of FCC riser reactors.

    Energy Technology Data Exchange (ETDEWEB)

    Chang, S. L.; Golchert, B.; Lottes, S. A.; Petrick, M.; Zhou, C. Q.

    1999-04-20

    A three-dimensional computational fluid dynamics (CFD) code, ICRKFLO, was developed to simulate the multiphase reacting flow system in a fluid catalytic cracking (FCC) riser reactor. The code solve flow properties based on fundamental conservation laws of mass, momentum, and energy for gas, liquid, and solid phases. Useful phenomenological models were developed to represent the controlling FCC processes, including droplet dispersion and evaporation, particle-solid interactions, and interfacial heat transfer between gas, droplets, and particles. Techniques were also developed to facilitate numerical calculations. These techniques include a hybrid flow-kinetic treatment to include detailed kinetic calculations, a time-integral approach to overcome numerical stiffness problems of chemical reactions, and a sectional coupling and blocked-cell technique for handling complex geometry. The copyrighted ICRKFLO software has been validated with experimental data from pilot- and commercial-scale FCC units. The code can be used to evaluate the impacts of design and operating conditions on the production of gasoline and other oil products.

  10. Synthesis, characterization and catalytic evaluation of cubic ordered mesoporous iron-silicon oxides

    Energy Technology Data Exchange (ETDEWEB)

    Martins, T.S., E-mail: tsmartins@unifesp.br [Departamento de Ciencias Exatas e da Terra, Universidade Federal de Sao Paulo, Rua Prof. Artur Riedel 275, 09972-270 Diadema, Sao Paulo (Brazil); Mahmoud, A.; Cides da Silva, L.C. [Instituto de Quimica, Universidade de Sao Paulo, 05508-900 Sao Paulo (Brazil); Cosentino, I.C. [IPEN, Av. Prof. Lineu Prestes 2242, Cidade Universitaria, 05508-900 Sao Paulo (Brazil); Tabacniks, M.H. [Instituto de Fisica, Universidade de Sao Paulo 66318, 05315-970 Sao Paulo (Brazil); Matos, J.R. [Instituto de Quimica, Universidade de Sao Paulo, 05508-900 Sao Paulo (Brazil); Freire, R.S. [CEPEMA/USP, Centro de Capacitacao e Pesquisa em Meio Ambiente, Cubatao/SP (Brazil); Instituto de Quimica, Universidade de Sao Paulo, 05508-900 Sao Paulo (Brazil); Fantini, M.C.A. [Instituto de Fisica, Universidade de Sao Paulo 66318, 05315-970 Sao Paulo (Brazil)

    2010-11-01

    Iron was successfully incorporated in FDU-1 type cubic ordered mesoporous silica by a simple direct synthesis route. The (Fe/FDU-1) samples were characterized by Rutherford back-scattering spectrometry (RBS), small angle X-ray scattering (SAXS), N{sub 2} sorption isotherm, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The resulting material presented an iron content of about 5%. Prepared at the usual acid pH of -0.3, the composite was mostly formed by amorphous silica and hematite with a quantity of Fe{sup 2+} present in the structure. The samples prepared with adjusted pH values (2 and 3.5) were amorphous. The samples' average pore diameter was around 12.0 nm and BET specific surface area was of 680 m{sup 2} g{sup -1}. Although the iron-incorporated material presented larger lattice parameter, about 25 nm compared to pure FDU-1, the Fe/FDU-1 composite still maintained its cubic ordered fcc mesoporous structure before and after the template removal at 540 deg. C. The catalytic performance of Fe/FDU-1 was investigated in the catalytic oxidation of Black Remazol B dye using a catalytic ozonation process. The results indicated that Fe/FDU-1 prepared at the usual acid pH exhibited high catalytic activity in the mineralization of this pollutant when compared to the pure FDU-1, Fe{sub 2}O{sub 3} and Fe/FDU-1 prepared with higher pH of 2 and 3.5.

  11. Low temperature formation of higher-k cubic phase HfO{sub 2} by atomic layer deposition on GeO{sub x}/Ge structures fabricated by in-situ thermal oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R., E-mail: zhang@mosfet.t.u-tokyo.ac.jp [School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Information Science and Electronic Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027 (China); Huang, P.-C.; Taoka, N.; Yokoyama, M.; Takenaka, M.; Takagi, S. [School of Engineering, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2016-02-01

    We have demonstrated a low temperature formation (300 °C) of higher-k HfO{sub 2} using atomic layer deposition (ALD) on an in-situ thermal oxidation GeO{sub x} interfacial layer. It is found that the cubic phase is dominant in the HfO{sub 2} film with an epitaxial-like growth behavior. The maximum permittivity of 42 is obtained for an ALD HfO{sub 2} film on a 1-nm-thick GeO{sub x} form by the in-situ thermal oxidation. It is suggested from physical analyses that the crystallization of cubic phase HfO{sub 2} can be induced by the formation of six-fold crystalline GeO{sub x} structures in the underlying GeO{sub x} interfacial layer.

  12. An alternative explanation for epitaxial growth. The case of fcc(111) on bcc(110)

    DEFF Research Database (Denmark)

    Grey, F.; Bohr, J.

    1993-01-01

    Starting from basic observations concerning commensurate structures, a simple explanation is given for the existence of energetically stable states of an fcc(111) adsorbate on a bcc(110) substrate, as a function of the mismatch and relative orientation of the two lattices. Numerical simulations...

  13. Large difference in the elastic properties of fcc and hcp hard-sphere crystals

    NARCIS (Netherlands)

    Pronk, S.; Frenkel, D.

    2003-01-01

    We report a numerical calculation of the elastic constants of the fcc and hcp crystal phases of monodisperse hard-sphere colloids. Surprisingly, some of these elastic constants are very different (up to 20%), even though the free-energy, pressure, and bulk compressibility of the two crystal structur

  14. Multivariable Control and Online State Estimation of an FCC Unit

    Directory of Open Access Journals (Sweden)

    A. T. Boum

    2015-10-01

    Full Text Available The purpose of this paper is to realize multivariable control , tuning and online state estimation of some parameters of the FCC unit . We implemented two control structures with the manipulated variables being the air inlet flow rate in the regenerator, the regenerated catalyst flow rate and the feed flow rate and, the controlled variable being the temperatures in the riser and in the densed bed of the regenerator. A novel four transfer function is built and used for controllability studies. Hard constraints are imposed with respect to the manipulated variables. Simulation results show that the configuration made of two inputs and two outputs is more easy to tune for control purposes. Althought there are important dynamic interactions between the components of the FCC and important nonlinearities, linear model predictive control is able to maintain a smooth multivariable control of the plant, while taking into account the different constraints. Tuning strategy is implemented to improve the tracking of the set point. Online state estimation is carried out with the use of the extended Kalman filter. The estimation gives results that can be used for monitoring purposes even in the presence of model mismatch.

  15. Iron Contamination Mechanism and Reaction Performance Research on FCC Catalyst

    Directory of Open Access Journals (Sweden)

    Zhaoyong Liu

    2015-01-01

    Full Text Available FCC (Fluid Catalytic Cracking catalyst iron poisoning would not only influence units’ product slate; when the poisoning is serious, it could also jeopardize FCC catalysts’ fluidization in reaction-regeneration system and further cause bad influences on units’ stable operation. Under catalytic cracking reaction conditions, large amount of iron nanonodules is formed on the seriously iron contaminated catalyst due to exothermic reaction. These nodules intensify the attrition between catalyst particles and generate plenty of fines which severely influence units’ smooth running. A dense layer could be formed on the catalysts’ surface after iron contamination and the dense layer stops reactants to diffuse to inner structures of catalyst. This causes extremely negative effects on catalyst’s heavy oil conversion ability and could greatly cut down gasoline yield while increasing yields of dry gas, coke, and slurry largely. Research shows that catalyst’s reaction performance would be severely deteriorated when iron content in E-cat (equilibrium catalyst exceeds 8000 μg/g.

  16. Crystal Structure of Garnet-Related Li-Ion Conductor Li7–3x Ga x La3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    OpenAIRE

    Wagner, Reinhard; Redhammer, Günther J.; Rettenwander, Daniel; Senyshyn, Anatoliy; Schmidt, Walter; Wilkening, Martin; Amthauer, Georg

    2016-01-01

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga3+ shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characteriz...

  17. Application of Zeolitic Additives in the Fluid Catalytic Cracking (FCC

    Directory of Open Access Journals (Sweden)

    A. Nemati Kharat

    2013-06-01

    Full Text Available Current article describes application of zeolites in fluid catalytic cracking (FCC. The use of several zeolitic additives for the production light olefins and reduction of pollutants is described. Application of zeolites as fluid catalytic cracking (FCC catalysts and additives due to the presence of active acid sites in the zeolite framework  increase the formation of desired cracking products (i.e., olefin and branched products  in the FCC unit.

  18. Preparation of cubic Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} solid electrolyte using a nano-sized core–shell structured precursor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yanhua; Cai, Jin [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Chen, Fei, E-mail: chenfei027@gmail.com [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Massachusetts Institute of Technology, 77 Massachusetts Avenue, W20-021 Cambridge, MA 02139-4307 (United States); Tu, Rong; Shen, Qiang; Zhang, Xulong [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Zhang, Lianmeng [State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Massachusetts Institute of Technology, 77 Massachusetts Avenue, W20-021 Cambridge, MA 02139-4307 (United States)

    2015-09-25

    Highlights: • A core–shell nano-sized precursor was synthesized by a two-step precipitation. • Cubic LLZO dense body was obtained at low temperatures by the novel precursor. • The cubic LLZO sintered body showed an extremely high Li ionic conductivity. - Abstract: Nano-sized Al-doped Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} (LLZO) precursor is successfully synthesized by a novel two-step precipitation method. Microstructure and thermal behavior of the prepared LLZO precursor powders and properties of the sintered LLZO pellets are comprehensively investigated. Results show that the obtained precursor powders have a special core–shell structure that a coating of Li{sub 2}C{sub 2}O{sub 4} covers on the surface of the lanthanum and zirconium co-precipitate products. Pure cubic LLZO powders can be obtained at a low calcination temperature of 900 °C. Sample sintered by field assisted sintering technology at 1000 °C has a high relative density of 96.5% with a total ionic conductivity of as high as 3.32 × 10{sup −4} S cm{sup −1} (corresponding to the activation energy of 0.32 eV) at room temperature. The reported method provides a simple and low-temperature synthesis of high quality LLZO solid electrolytes.

  19. Magnetism and electronic structure for RMn{sub 2} (R=Y and lanthanoids) with the cubic Laves phase (C15) structure

    Energy Technology Data Exchange (ETDEWEB)

    Terao, Kiyosi E-mail: terk005@gipac.shinshu-u.ac.jp; Yamada, Hideji

    2004-05-01

    Ab initio calculations for the electronic structure are carried out by means of LMTO-ASA with and without the GGA correction. The observed antiferromagnetic state with complicated spin configuration has slightly higher energy than that with the layered spin configuration near the observed volume and slightly lower than that for larger volume. In ferromagnetic configuration, Mn moment shows complicated dependence on volume and magnetic field.

  20. FCC DeSOx and DeNOx additive technology

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The fluid catalytic cracking(FCC) is the principal gasoline-producing process in the refinery. Considerable amounts of harmful sulfur oxides and nitrogen oxides (SOx and NOx ) are generated with the FCC operation. Impacted by strengthening environmental regulations and the current global emphasis on environmental protection and pollution abatement, refiners have been meaning to look for effective ways to control and reduce SOx and NOx emissions. FCC DeSOx and DeNOx additives is the most promising measure. The present paper reviews the developments in FCC DeSOx and DeNOx additive technology based on the respective authors' works, the future directions of the technology are also discussed.

  1. PURIFIED WASTE FCC CATALYST AS A CEMENT REPLACEMENT MATERIAL

    Directory of Open Access Journals (Sweden)

    Danute Vaiciukyniene

    2015-06-01

    Full Text Available Zeolites are commonly used in the fluid catalytic cracking process. Zeolite polluted with oil products and became waste after some time used. The quantity of this waste inevitably rises by expanding rapidly oil industry. The composition of these catalysts depends on the manufacturer and on the process that is going to be used. The main factors retarding hydration process of cement systems and modifying them strength are organic compounds impurities in the waste FCC catalyst. The present paper shows the results of using purified waste FCC catalyst (pFCC from Lithuania oil refinery, as Portland cement replacement material. For this purpose, the purification of waste FCC catalyst (FCC samples was treated with hydrogen peroxide. Hydrogen peroxide (H2O2 is one of the most powerful oxidizers known. By acting of waste with H2O2 it can eliminate the aforementioned waste deficiency, and the obtained product becomes one of the most promising ingredients, in new advanced building materials. Hardened cement paste samples with FCC or pFCC were formed. It was observed that the pFCC blended cements developed higher strength, after 28 days, compared to the samples with FCC or reference samples. Typical content of Portland cement substituting does not exceed 30 % of mass of Portland cement in samples. Reducing the consumption of Portland cement with utilizing waste materials is preferred for reasons of environmental protection.

  2. Generation and enumeration of compact conformations on the two-dimensional triangular and three-dimensional fcc lattices

    Science.gov (United States)

    Peto, Myron; Sen, Taner Z.; Jernigan, Robert L.; Kloczkowski, Andrzej

    2007-07-01

    We enumerated all compact conformations within simple geometries on the two-dimensional (2D) triangular and three-dimensional (3D) face centered cubic (fcc) lattice. These compact conformations correspond mathematically to Hamiltonian paths and Hamiltonian circuits and are frequently used as simple models of proteins. The shapes that were studied for the 2D triangular lattice included m ×n parallelograms, regular equilateral triangles, and various hexagons. On the 3D fcc lattice we generated conformations for a limited class of skewed parallelepipeds. Symmetries of the shape were exploited to reduce the number of conformations. We compared surface to volume ratios against protein length for compact conformations on the 3D cubic lattice and for a selected set of real proteins. We also show preliminary work in extending the transfer matrix method, previously developed by us for the 2D square and the 3D cubic lattices, to the 2D triangular lattice. The transfer matrix method offers a superior way of generating all conformations within a given geometry on a lattice by completely avoiding attrition and reducing this highly complicated geometrical problem to a simple algebraic problem of matrix multiplication.

  3. Generation and enumeration of compact conformations on the two-dimensional triangular and three-dimensional fcc lattices.

    Science.gov (United States)

    Peto, Myron; Sen, Taner Z; Jernigan, Robert L; Kloczkowski, Andrzej

    2007-07-28

    We enumerated all compact conformations within simple geometries on the two-dimensional (2D) triangular and three-dimensional (3D) face centered cubic (fcc) lattice. These compact conformations correspond mathematically to Hamiltonian paths and Hamiltonian circuits and are frequently used as simple models of proteins. The shapes that were studied for the 2D triangular lattice included mxn parallelograms, regular equilateral triangles, and various hexagons. On the 3D fcc lattice we generated conformations for a limited class of skewed parallelepipeds. Symmetries of the shape were exploited to reduce the number of conformations. We compared surface to volume ratios against protein length for compact conformations on the 3D cubic lattice and for a selected set of real proteins. We also show preliminary work in extending the transfer matrix method, previously developed by us for the 2D square and the 3D cubic lattices, to the 2D triangular lattice. The transfer matrix method offers a superior way of generating all conformations within a given geometry on a lattice by completely avoiding attrition and reducing this highly complicated geometrical problem to a simple algebraic problem of matrix multiplication.

  4. Reassessment of Atomic Mobilities in fcc Cu-Ag-Sn System Aiming at Establishment of an Atomic Mobility Database in Sn-Ag-Cu-In-Sb-Bi-Pb Solder Alloys

    Science.gov (United States)

    Xu, Huixia; Zhang, Lijun; Cheng, Kaiming; Chen, Weimin; Du, Yong

    2017-04-01

    To establish an accurate atomic mobility database in solder alloys, a reassessment of atomic mobilities in the fcc (face centered cubic) Cu-Ag-Sn system was performed as reported in the present work. The work entailed initial preparation of three fcc Cu-Sn diffusion couples, which were used to determine the composition-dependent interdiffusivities at 873 K, 923 K, and 973 K, to validate the literature data and provide new experimental data at low temperatures. Then, atomic mobilities in three boundary binaries, fcc Cu-Sn, fcc Ag-Sn, and fcc Cu-Ag, were updated based on the data for various experimental diffusivities obtained from the literature and the present work, together with the available thermodynamic database for solder alloys. Finally, based on the large number of interdiffusivities recently measured from the present authors, atomic mobilities in the fcc Cu-Ag-Sn ternary system were carefully evaluated. A comprehensive comparison between various calculated/model-predicted diffusion properties and the experimental data was used to validate the reliability of the obtained atomic mobilities in ternary fcc Cu-Ag-Sn alloys.

  5. Molecular dynamics simulations of hcp/fcc nucleation and growth in bcc iron driven by uniaxial compression.

    Science.gov (United States)

    Wang, B T; Shao, J L; Zhang, G C; Li, W D; Zhang, P

    2009-12-02

    Molecular dynamics simulations have been performed to study the structural transition in bcc iron under uniaxial strain loading. We found that the transition pressures are less dependent on the crystal orientations, ∼14 GPa for [001], [011], and [111] loadings. However, the pressure interval of a mixed phase for [011] loading is much shorter than loading along other orientations. In addition, the temperature increased amplitude for [001] loading is evidently lower than other orientations. The nucleation and growth of the hcp/fcc phases, and their crystal orientation dependence, were analyzed in detail, where the atom structure was presented by the topological medium-range-order analysis. For [001] compression, the hcp structure occurs first and grows into a laminar morphology in the (011)(bcc) plane with some fcc atoms as an intermediate structure. For loading along [011] and [111] directions, both hcp and fcc structure nucleation and growth along the {110}(bcc) planes are observed; their morphology is also discussed.

  6. Direct Numerical Simulation of turbulent flow in a porous, face centered cubic cell

    Science.gov (United States)

    He, Xiaoliang; Apte, Sourabh; Wood, Brian

    2014-11-01

    DNS of flow through a 3D, periodic, face centered cubic (FCC) unit cell geometry at Re = 300 , 550, and 950 based on diameter is performed. This low porosity arrangement of spheres is characterized by rapid flow expansions and contractions, and thus features an early onset to turbulence. The simulations are performed using a fictitious domain approach [Apte et al., J. Comp. Physics 2009], which uses non-body conforming Cartesian grids, with resolution up to D / Δ = 250 (3543 cells total). The results are used to investigate the structure of turbulence in the Eulerian and Lagrangian frames, the distribution and budget of turbulent kinetic energy, and the characteristics of the energy spectrum in complex packed beds and porous media. The porescale flow physics, which are important to properties such as bulk mixing performance and permeability, are investigated. Specifically, the data generated is being used to understand the important turbulence characteristics in low porosity packed beds of relevance for heat tranfer applications in chemical/nuclear reactors. Funding: NSF Project Number 1336983.

  7. High pressure-induced distortion in face-centered cubic phase of thallium

    Science.gov (United States)

    Kotmool, Komsilp; Li, Bing; Chakraborty, Sudip; Bovornratanaraks, Thiti; Luo, Wei; Mao, Ho-kwang; Ahuja, Rajeev

    2016-10-01

    The complex and unusual high-pressure phase transition of III-A (i.e. Al, Ga, and In) metals have been investigated in the last several decades because of their interesting periodic table position between the elements having metallic and covalent bonding. Our present first principles-based electronic structure calculations and experimental investigation have revealed the unusual distortion in face-centered cubic (f.c.c.) phase of the heavy element thallium (Tl) induced by the high pressure. We have predicted body-centered tetragonal (b.c.t) phase at 83 GPa using an evolutionary algorithm coupled with ab initio calculations, and this prediction has been confirmed with a slightly distorted parameter (2 × a - c)/c lowered by 1% using an angle-dispersive X-ray diffraction technique. The density functional theory (DFT)-based calculations suggest that s-p mixing states and the valence-core overlapping of 6s and 5d states play the most important roles for the phase transitions along the pathway h.c.p→b.c.t.

  8. Magnetic and structural transitions in crystals with a structure of the NaCl type

    Science.gov (United States)

    Kassan-Ogly, F. A.; Filippov, B. N.

    2009-04-01

    A model of simultaneous magnetic and structural first-order transitions in antiferromagnets with a strong cubic magnetic anisotropy has been constructed on the basis of a synthesis of magnetic modified 6-state and 8-state Potts models and the theoretical model of structural phase transitions in cubic crystals. A revised scheme has been suggested for the derivation of possible magnetic structures in the fcc lattice with allowance for competing interactions between the nearest and next-nearest neighbors. A calculation of the temperature evolution of high-temperature diffuse magnetic scattering of neutrons has been carried out to show that the mechanism of a magnetic transition at the Néel point is caused by the transformation of diffuse magnetic scattering into magnetic Bragg peaks.

  9. Synthesis of ultrathin face-centered-cubic Au@Pt and Au@Pd core-shell nanoplates from hexagonal-close-packed Au square sheets

    KAUST Repository

    Fan, Zhanxi

    2015-03-17

    The synthesis of ultrathin face-centered-cubic (fcc) Au@Pt rhombic nanoplates is reported through the epitaxial growth of Pt on hexagonal-close-packed (hcp) Au square sheets (AuSSs). The Pt-layer growth results in a hcp-to-fcc phase transformation of the AuSSs under ambient conditions. Interestingly, the obtained fcc Au@Pt rhombic nanoplates demonstrate a unique (101)f orientation with the same atomic arrangement extending from the Au core to the Pt shell. Importantly, this method can be extended to the epitaxial growth of Pd on hcp AuSSs, resulting in the unprecedented formation of fcc Au@Pd rhombic nanoplates with (101)f orientation. Additionally, a small amount of fcc (100)f-oriented Au@Pt and Au@Pd square nanoplates are obtained with the Au@Pt and Au@Pd rhombic nanoplates, respectively. We believe that these findings will shed new light on the synthesis of novel noble bimetallic nanostructures. Phase change: Ultrathin Au@Pt and Au@Pd core-shell nanoplates were prepared from Au square sheets. A phase transformation from hexagonal close-packed (hcp) to face-centered cubic (fcc) is observed upon coating the hcp Au square sheets with Pt or Pd under ambient conditions. The prepared fcc Au@Pt and Au@Pd rhombic nanoplates demonstrate unique (101)f orientation (picture shows a typical fcc Au@Pt rhombic nanoplate). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Crystal Structure of Garnet-Related Li-Ion Conductor Li7-3x Ga x La3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    Science.gov (United States)

    Wagner, Reinhard; Redhammer, Günther J; Rettenwander, Daniel; Senyshyn, Anatoliy; Schmidt, Walter; Wilkening, Martin; Amthauer, Georg

    2016-03-22

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga(3+) shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7-3x Ga x La3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga(3+). (7)Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure-property relationships for this class of materials, this study highlights the potential for new discoveries.

  11. Robust topology optimization of three-dimensional photonic-crystal band-gap structures

    CERN Document Server

    Men, Han; Freund, Robert M; Peraire, Jaime; Johnson, Steven G

    2014-01-01

    We perform full 3D topology optimization (in which "every voxel" of the unit cell is a degree of freedom) of photonic-crystal structures in order to find optimal omnidirectional band gaps for various symmetry groups, including fcc (including diamond), bcc, and simple-cubic lattices. Even without imposing the constraints of any fabrication process, the resulting optimal gaps are only slightly larger than previous hand designs, suggesting that current photonic crystals are nearly optimal in this respect. However, optimization can discover new structures, e.g. a new fcc structure with the same symmetry but slightly larger gap than the well known inverse opal, which may offer new degrees of freedom to future fabrication technologies. Furthermore, our band-gap optimization is an illustration of a computational approach to 3D dispersion engineering which is applicable to many other problems in optics, based on a novel semidefinite-program formulation for nonconvex eigenvalue optimization combined with other techniq...

  12. Stability and structure of metal clusters - Be(13) and Be(55)

    Science.gov (United States)

    Pettersson, Lars G. M.; Bauschlicher, Charles W., Jr.

    1986-01-01

    Face-centered cubic (fcc) and hexagonally close-packed (hcp) structures are compared for Be(13) and Be(55) clusters. Both Be(13) and Be(55) prefer the fcc structure over the bulk hcp structure, but the energy difference per atom decreases for Be(55) relative to Be(13). The binding energy per atom, 1.3 eV for Be(55) and 0.8-0.9 eV for Be(13), reflects the greater total number of bonds in the larger cluster rather than a difference in bonding. The energies per bond are much more similar, in the range of 0.30-0.34 eV for both clusters. The size of the p-basis set used influences both stability and ionization potentials strongly.

  13. 47 CFR 76.1714 - FCC rules and regulations.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FCC rules and regulations. 76.1714 Section 76.1714 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Documents to be Maintained for Inspection § 76.1714 FCC...

  14. 47 CFR 73.4000 - Listing of FCC policies.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Listing of FCC policies. 73.4000 Section 73... BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4000 Listing of FCC policies. The following sections list, solely for the purpose of reference and convenience, certain Policies of the...

  15. Tracking Simulation for Beam Loss Studies with Application to FCC

    CERN Document Server

    Boscolo, M

    2015-01-01

    We present first results on FCC-ee beam losses using a tracking simulation tool originally developed and successfully applied to Flav or Factories designs. After a brief description of the tool, we discuss first results obtained for FCC-ee at top energy, both for the Touschek effect and radiative Bhabha scattering.

  16. Major Technical Measures for Revamp of FCC Units in China

    Institute of Scientific and Technical Information of China (English)

    Li Wenjie

    2003-01-01

    FCC units are playing an important role at refineries, in particular at Chinese refineries. To cope with the current demand for better economic benefits, environmental protection and product slate adjustment, a host of FCC units need to be technically revamped. This article describes the practical processes, technologies and equipment to serve different revamp targets with analysis of two examples on revamp of commercial units.

  17. The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.

    Science.gov (United States)

    Francisco, E.; And Others

    1988-01-01

    Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)

  18. Lattice Green functions: the seven-dimensional face-centred cubic lattice

    Science.gov (United States)

    Zenine, N.; Hassani, S.; Maillard, J. M.

    2015-01-01

    We present a recursive method to generate the expansion of the lattice Green function of the d-dimensional face-centred cubic (fcc) lattice. We produce a long series for d = 7. Then we show (and recall) that, in order to obtain the linear differential equation annihilating such a long power series, the most economic way amounts to producing the non-minimal order differential equations. We use the method to obtain the minimal order linear differential equation of the lattice Green function of the seven-dimensional fcc lattice. We give some properties of this irreducible order-eleven differential equation. We show that the differential Galois group of the corresponding operator is included in SO(11, {C}). This order-eleven operator is non-trivially homomorphic to its adjoint, and we give a ‘decomposition’ of this order-eleven operator in terms of four order-one self-adjoint operators and one order-seven self-adjoint operator. Furthermore, using the Landau conditions on the integral, we forward the regular singularities of the differential equation of the d-dimensional lattice and show that they are all rational numbers. We evaluate the return probability in random walks in the seven-dimensional fcc lattice. We show that the return probability in the d-dimensional fcc lattice decreases as d-2 as the dimension d goes to infinity.

  19. Angular distortive matrices of phase transitions in the fcc-bcc-hcp system

    OpenAIRE

    Cayron, Cyril

    2016-01-01

    This work generalizes the one-step model previously developed on fcc-bcc martensitic transformations to the larger family of phase transitions in the fcc-bcc-hcp system. The angular distortive matrices are calculated for the bcc-fcc, bcc-hcp and fcc-hcp transitions, and for fcc-fcc mechanical twinning. The analytical expressions of the continuous atomic displacements, lattice distortion and lattice correspondence matrices result directly from the orientation relationships; the unique assumpti...

  20. 47 CFR 95.225 - (R/C Rule 25) How do I contact the FCC?

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false (R/C Rule 25) How do I contact the FCC? 95.225... (R/C Rule 25) How do I contact the FCC? (a) FCC National Call Center at 1-888-225-5322. (b) FCC World Wide Web homepage: http://www.fcc.gov. (c) In writing, to FCC, Attention: R/C, 1270 Fairfield...

  1. Atomic structure and thermal stability of Pt-Fe bimetallic nanoparticles: from alloy to core/shell architectures.

    Science.gov (United States)

    Huang, Rao; Wen, Yu-Hua; Shao, Gui-Fang; Sun, Shi-Gang

    2016-06-22

    Bimetallic nanoparticles comprising noble metal and non-noble metal have attracted intense interest over the past few decades due to their low cost and significantly enhanced catalytic performances. In this article, we have explored the atomic structure and thermal stability of Pt-Fe alloy and core-shell nanoparticles by molecular dynamics simulations. In Fe-core/Pt-shell nanoparticles, Fe with three different structures, i.e., body-centered cubic (bcc), face-centered cubic (fcc), and amorphous phases, has been considered. Our results show that Pt-Fe alloy is the most stable configuration among the four types of bimetallic nanoparticles. It has been discovered that the amorphous Fe cannot stably exist in the core and preferentially transforms into the fcc phase. The phase transition from bcc to hexagonal close packed (hcp) has also been observed in bcc-Fe-core/Pt-shell nanoparticles. In contrast, Fe with the fcc structure is the most preferred as the core component. These findings are helpful for understanding the structure-property relationships of Pt-Fe bimetallic nanoparticles, and are also of significance to the synthesis and application of noble metal based nanoparticle catalysts.

  2. Crystal Structure of Garnet-Related Li-Ion Conductor Li7–3xGaxLa3Zr2O12: Fast Li-Ion Conduction Caused by a Different Cubic Modification?

    Science.gov (United States)

    2016-01-01

    Li-oxide garnets such as Li7La3Zr2O12 (LLZO) are among the most promising candidates for solid-state electrolytes to be used in next-generation Li-ion batteries. The garnet-structured cubic modification of LLZO, showing space group Ia-3d, has to be stabilized with supervalent cations. LLZO stabilized with Ga3+ shows superior properties compared to LLZO stabilized with similar cations; however, the reason for this behavior is still unknown. In this study, a comprehensive structural characterization of Ga-stabilized LLZO is performed by means of single-crystal X-ray diffraction. Coarse-grained samples with crystal sizes of several hundred micrometers are obtained by solid-state reaction. Single-crystal X-ray diffraction results show that Li7–3xGaxLa3Zr2O12 with x > 0.07 crystallizes in the acentric cubic space group I-43d. This is the first definite record of this cubic modification for LLZO materials and might explain the superior electrochemical performance of Ga-stabilized LLZO compared to its Al-stabilized counterpart. The phase transition seems to be caused by the site preference of Ga3+. 7Li NMR spectroscopy indicates an additional Li-ion diffusion process for LLZO with space group I-43d compared to space group Ia-3d. Despite all efforts undertaken to reveal structure–property relationships for this class of materials, this study highlights the potential for new discoveries. PMID:27019548

  3. Precision measurements of the top quark couplings at the FCC

    CERN Document Server

    AUTHOR|(CDS)2051271

    2015-01-01

    The design study of the Future Circular Colliders (FCC) in a 100-km ring in the Geneva area has started at CERN at the beginning of 2014, as an option for post-LHC particle accelerators. The study has an emphasis on proton-proton and electron-positron high-energy frontier machines. In the current plans, the first step of the FCC physics programme would exploit a high-luminosity e+e- collider called FCC-ee, with centre-of-mass energies ranging from below the Z pole to the t-tbar threshold and beyond, followed by 100\\,TeV proton-proton collisions as ultimate goal. When combined, these two steps offer a large palette of complementary measurements and sensitivity for new physics. In particular, the association of the FCC-ee and the FCC-hh allows measurements of the top-quark electroweak and Yukawa couplings to be performed with unrivaled precision.

  4. A Cubic Tree Taper Model

    National Research Council Canada - National Science Library

    Goodwin, Adrian N

    2009-01-01

    A flexible tree taper model based on a cubic polynomial is described. It is algebraically invertible and integrable, and can be constrained by one or two diameters, neither of which need be diameter at breast height (DBH...

  5. Microstructure and mechanical properties of bulk highly faulted fcc/hcp nanostructured cobalt microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Barry, Aliou Hamady [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Laboratoire Chimie des Matériaux, Département de Chimie, Faculté des Sciences et Technique, Université de Nouakchott (Mauritania, Islamic Republic of); Dirras, Guy, E-mail: dirras@unv-paris13.fr [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France); Schoenstein, Frederic; Tétard, Florent; Jouini, Noureddine [Université Paris 13, Sorbonne Paris Cité, LSPM CNRS UPR 3407, 93430 Villetaneuse (France)

    2014-05-01

    Nanostructured cobalt powders with an average particle size of 50 nm were synthesized using a polyol method and subsequently consolidated by spark plasma sintering (SPS). SPS experiments performed at 650 °C with sintering times ranging from 5 to 45 min under a pressure of 100 MPa, yielded to dense bulk nanostructured cobalt (relative density greater than 97%). X-ray diffraction patterns of the as-prepared powders showed only a face centered cubic (fcc) crystalline phase, whereas the consolidated samples exhibited a mixture of both fcc and hexagonal close packed (hcp) phases. Transmission electron microscopy observations revealed a lamellar substructure with a high density of nanotwins and stacking faults in every grain of the sintered samples. Room temperature compression tests, carried out at a strain rate of 10{sup −3} s{sup −1}, yielded to highest strain to fracture values of up to 5% for sample of holding time of 15 min, which exhibited a yield strength of 1440 MPa, an ultimate strength as high as 1740 MPa and a Young's modulus of 205 GPa. The modulus of elasticity obtained from the nanoindentation tests, ranges from 181 to 218 GPa. The lowest modulus value of 181 GPa was obtained for the sample with the highest sintering time (45 min), which could be related to mass density loss as a consequence of trapped gases releasing. - Highlights: • Co nanopowder (50 nm) was prepared by reduction in polyol medium. • SPS was used to process bulk nanostructured Co specimens. • Microstructures were made of intricate fcc/hcp, along with nanotwins and SFs. • High strengths and moderate compressive ductility were obtained. • Deformation mechanisms related to complex interplay of different length scales.

  6. Adaptive GPC controller applied to FCC units; Controlador GPC adaptativo aplicado em unidades FCC

    Energy Technology Data Exchange (ETDEWEB)

    Melo Junior, Wilson S.; Rodrigues, Luiz Carlos A.; Arruda, L. Valeria R.; Neves Junior, Flavio [Centro Federal de Educacao Tecnologica do Parana, Curitiba, PR (Brazil). Programa de Pos-graduacao em Engenharia Eletrica e Informatica Industrial]. E-mail: melo, lcar, arruda, neves@cpgei.cefetpr.br

    2003-07-01

    This paper presents a predictive controller implementation applied on FCC unit. It is based on GPC (Generalized Predictive Control) algorithm and uses an adaptive model generated by real time identification using RLS (Recursive Least Squares) algorithm. A Kellogg Orthoflow F unit model is used to validate this implementation. In a FCC unit, the main reactions happen in riser and there are two regeneration stages. The controller is tuning to two manipulated variables and two controlled variables. The manipulated variables are the regenerated catalytic flow and the airflow rate to regenerator. The controlled variables are the riser temperature and the second stage regenerator temperature. The controller performance is evaluated by simulation and the obtained results assert the applicability of the proposed approach. (author)

  7. Strong screening by lattice confinement and resultant fusion reaction rates in fcc metals

    Science.gov (United States)

    Prados-Estévez, F. M.; Subashiev, A. V.; Nee, H. H.

    2017-09-01

    The effects of electronic screening on the cross sections and reactivities for the nuclear reactions between light nuclei in Pd and Ni is studied. We consider the applicability of the theory of thermonuclear burning in stars to the D-D nuclear reaction in metals. The screening model based on the mean field potential of the electron cloud in the metal plasma is used. We discuss the specifics of the screening for the H (D) atoms embedded in vacancies and divacancies. High concentration of hydrogen isotopes segregated to monovacancies and divacancies in face-centered cubic (fcc) metals such as Ni and Pd with densities of ∼ 6 ×1023atom /cm3 , makes the hydrogen cluster a favorable active site for the fusion reaction. Still the observation of a nuclear reaction requires an accumulation of energy in D nuclei of at least several eV, which is far above what can be achieved in the thermal heating experiments.

  8. Precision Electroweak Measurements at FCC-ee

    CERN Document Server

    Tenchini, Roberto

    2014-01-01

    The prospects for electroweak precision measurements at the Future Circular Collider with electron-positron beams (FCC-ee) are discussed. The Z mass and width, as well as the value of the electroweak mixing angle, can be measured with very high precision at the Z pole thanks to an instantaneous luminosity five to six order of magnitudes larger than LEP. At centre-of-mass energies around 160 GeV, corresponding to the WW production threshold, the W mass can be determined very precisely with high-statistics cross section measurements at several energy points. Similarly, a very precise determination of the top mass can be provided by an energy scan at the $\\mathrm{t \\bar t}$ production threshold, around 350 GeV.

  9. Stacking fault energy in FCC plutonium with multiple reference states in the modified embedded atom method

    Science.gov (United States)

    Valone, S. M.; Baskes, M. I.; Rudin, S. P.

    2012-03-01

    Basic concepts from the multi-reference state formalism for determining the functions for the modified embedded atom method (MEAM) are adopted to modeling elemental plutonium (Pu). In the case of elemental Pu, the focus is on the background electron density. Here we utilize a portion of the formalism that determines the structure of the background density necessary to capture correct phase ordering between fcc and ideal hcp crystal structures. The critical information comes from cold curves, that is the energy/volume relationships, for these phases. Practically speaking, the energy difference between these two phases determines the stacking fault energy of the material. At the same time, the simple monoclinic phase of elemental Pu also becomes higher in energy at the equilibrium volume of the fcc phase. The new model is based on first-principles electronic structure calculations and captures the basic phase ordering of those calculations.

  10. Electronic structure and magnetic properties of doped Al1- x Ti x N ( x = 0.03, 0.25) compositions based on cubic aluminum nitride from ab initio simulation data

    Science.gov (United States)

    Bannikov, V. V.; Beketov, A. R.; Baranov, M. V.; Elagin, A. A.; Kudyakova, V. S.; Shishkin, R. A.

    2016-05-01

    The phase stability, electronic structure, and magnetic properties of Al1- x Ti x N compositions based on the metastable aluminum nitride modification with the rock-salt structure at low ( x = 0.03) and high ( x = 0.25) concentrations of titanium in the system have been investigated using the results of ab initio band calculations. It has been shown that, at low values of x, the partial substitution is characterized by a positive enthalpy, which, however, changes sign with an increase in the titanium concentration. According to the results of the band structure calculations, the doped compositions have electronic conductivity. For x = 0.03, titanium impurity atoms have local magnetic moments (˜0.6 μB), and the electronic spectrum is characterized by a 100% spin polarization of near-Fermi states. Some of the specific features of the chemical bonding in Al1- x Ti x N cubic phases have been considered.

  11. Structure and Magnetic Properties of Nanocrystalline Fe55Pd45 Processed by Sonoelectrodeposition

    Science.gov (United States)

    Luong, Nguyen Hoang; Trung, Truong Thanh; Loan, Tran Phuong; Nam, Nguyen Hoang; Jenei, Péter; Lábár, János L.; Gubicza, JenŐ

    2017-01-01

    Fe55Pd45 nanoparticles were prepared from iron acetate and palladium acetate by sonoelectrodeposition. The as-prepared nanoparticles were annealed at various temperatures from 450°C to 700°C for 1 h in order to study the effect of heat treatment on the phase composition, particle size and magnetic properties. The phase composition and the crystallite size of the annealed samples were determined by x-ray diffraction while the particle size was studied by transmission electron microscopy. It was revealed that the magnetic properties of the samples depend on the phase composition of the material. The as-prepared nanoparticles had a disordered face-centered cubic (fcc) structure which transformed to a multi-phase material containing an ordered L10 FePd phase and a body-centered cubic Fe after annealing at 550°C; however, a disordered fcc FePd also remained in the material. The ordering in the structure yielded a significant increase in the room-temperature coercivity from 0.5 kOe to 1.1 kOe. At 700°C, the coercivity decreased due to the formation of a disordered fcc γ-FePd phase. In addition to the phase transformation, the average crystallite size grew from about 8 nm to 50-70 nm during annealing.

  12. Symmetry-Guaranteed and Accidental Nodal-Line Semimetals in FCC Lattice

    CERN Document Server

    Kawakami, Takuto

    2016-01-01

    We demonstrate theoretically that nodal-line semimetal (NLS) states can be realized in face-center-cubic (fcc) lattice with orbits belonging to one irreducible representation, such as [$p_x$, $p_y$, $p_z$] and/or [$d_{xy}$, $d_{xz}$, $d_{yz}$]. It is shown that the three orbits are subdivided with respect to the odd- and even-parity upon mirror reflection on high symmetry planes, which yields an analytic expression for the trajectory of NL in momentum space when a tight-binding (TB) model is adopted. It becomes clear that there are two kinds of NLs, a symmetry-guaranteed one around the surface of the first Brillouin zone (BZ), and an accidental one around the BZ center governed by the hopping integrals. As a realization of the idea, we analyze the fcc photonic crystal composed of dielectric spheres by solving the Maxwell's equations. Two symmetry-guaranteed and one accidental NLS photonic states are observed. This provides a good platform to confirm experimentally the existence of topological NLS state, and o...

  13. Bond-order potential for magnetic body-centered-cubic iron and its transferability

    Science.gov (United States)

    Lin, Yi-Shen; Mrovec, M.; Vitek, V.

    2016-06-01

    We derived and thoroughly tested a bond-order potential (BOP) for body-centered-cubic (bcc) magnetic iron that can be employed in atomistic calculations of a broad variety of crystal defects that control structural, mechanical, and thermodynamic properties of this technologically important metal. The constructed BOP reflects correctly the mixed nearly free electron and covalent bonding arising from the partially filled d band as well as the ferromagnetism that is actually responsible for the stability of the bcc structure of iron at low temperatures. The covalent part of the cohesive energy is determined within the tight-binding bond model with the Green's function of the Schrödinger equation determined using the method of continued fractions terminated at a sufficient level of the moments of the density of states. This makes the BOP an O (N ) method usable for very large numbers of particles. Only d d bonds are included explicitly, but the effect of s electrons on the covalent energy is included via their screening of the corresponding d d bonds. The magnetic part of the cohesive energy is included using the Stoner model of itinerant magnetism. The repulsive part of the cohesive energy is represented, as in any tight-binding scheme, by an empirical formula. Its functional form is physically justified by studies of the repulsion in face-centered-cubic (fcc) solid argon under very high pressure where the repulsion originates from overlapping s and p closed-shell electrons just as it does from closed-shell s electrons in transition metals squeezed into the ion core under the influence of the large covalent d bonding. Testing of the transferability of the developed BOP to environments significantly different from those of the ideal bcc lattice was carried out by studying crystal structures and magnetic states alternative to the ferromagnetic bcc lattice, vacancies, divacancies, self-interstitial atoms (SIAs), paths continuously transforming the bcc structure to

  14. 9th FCC-ee (TLEP) Physics Workshop

    CERN Document Server

    2015-01-01

    This is the 9th in the series of FCCee/TLEP-related workshops. It follows on from the sucessful 8th TLEP workshop that took place in Paris on 27-29 October 2014, and the FCC kick-off meeting held on 12-15 February 2014 at University of Geneva. The workshop is open to all FCC-ee /TLEP design study members, and more generally to all interested in a precision Z, W, H, top factory. The focus will be on physics and experiments at the FCC-ee, but a more general session is organized the first day (Tuesday 3 February afternoon) with presentations about the FCC design study as a whole, and on machine and physics for the FCC-ee and the FCC-hh, with synergies and complementarities. This session is aimed at a larger audience, towards improving the project visibility in Italy. It will be followed by a social dinner in the evening. The workshop starts on Tuesday at 13:30 and ends on Thursday 16:00. Registration is now open, please proceed at your earliest convenience! Please visit the FCC-ee / TLEP web site, and subscrib...

  15. FCC-ee Physics workshop | 19-21 June 2014

    CERN Multimedia

    2014-01-01

    The 7th FCC-ee/TLEP workshop, the first after the FCC kick-off in February 2014, will be focused on physics and experiments.     It will take place on 19-21 June at CERN in the TH auditorium. The registration is open and the agenda is available on the indico web page: http://indico.cern.ch/event/313708/. You are all cordially invited to attend! This will be the first in a series of workshops that will lead us to the first FCC-ee physics milestone, a document defining the physics landscape and study plans, required for March 2015. More information can be found here. FCC-ee is a high-luminosity Z, W, Higgs and top factory, to be hosted in a 100km tunnel, possibly as the first step towards a 100 TeV pp collider FCC-hh. These two machines are being studied within the FCC design study. High precision, high statistics and a clean environment are the tools available in FCC-ee to shed light on the unknown physics that underlies present mysteries: dark matter, the baryon asymmetry of th...

  16. Avalanche criticalities and elastic and calorimetric anomalies of the transition from cubic Cu-Al-Ni to a mixture of 18 R and 2 H structures

    Science.gov (United States)

    Vives, Eduard; Baró, Jordi; Gallardo, María Carmen; Martín-Olalla, José-María; Romero, Francisco Javier; Driver, Sarah L.; Carpenter, Michael A.; Salje, Ekhard K. H.; Stipcich, Marcelo; Romero, Ricardo; Planes, Antoni

    2016-07-01

    We studied the two-step martensitic transition of a Cu-Al-Ni shape-memory alloy by calorimetry, acoustic emission (AE), and resonant ultrasound spectroscopy (RUS) measurements. The transition occurs under cooling from the cubic (β , F m 3 m ) parent phase near 242 K to a mixture of orthorhombic 2 H and monoclinic 18 R phases. Heating leads first to the back transformation of small 18 R domains to β and/or 2 H near 255 K, and then to the transformation 2 H to β near 280 K. The total transformation enthalpy is Δ HT=328 ±10 J/mol and is observed as one large latent heat peak under cooling. The back-transformation entropy under heating breaks down into a large component 18 R to β at 255 K and a smaller, smeared component of the transformation 2 H to β near 280 K. The proportions inside the phase mixture depend on the thermal history of the sample. The elastic response of the sample is dominated by large elastic softening during cooling. The weakening of the elastic shear modulus shows a peak at 242 K, which is typical for the formation of complex microstructures. Cooling the sample further leads to additional changes of the microstructure and domain wall freezing, which is seen by gradual elastic hardening and increasing damping of the RUS signal. Heating from 220 K to room temperature leads to elastic anomalies due to the initial transformation, which is now shifted to high temperatures. The transition is smeared over a wider temperature interval and shows strong elastic damping. The shear modulus of the cubic phase is recovered at 280 K. The phase transformation leads to avalanches, which were recorded by AE and by time-resolved calorimetry. The cooling transition shows very extended avalanche signals in calorimetry with power-law distributions. Cooling and heating runs show AE signals over a large temperature interval above 260 K. Splitting the transformation into two martensite phases leads to power-law exponents ɛ ˜2 (β ↔ 18 R ) and ɛ ˜1.5 (β ↔ 2

  17. Microemulsion-mediated synthesis of cobalt (pure fcc and hexagonal phases) and cobalt-nickel alloy nanoparticles.

    Science.gov (United States)

    Ahmed, Jahangeer; Sharma, Shudhanshu; Ramanujachary, Kandalam V; Lofland, Samuel E; Ganguli, Ashok K

    2009-08-15

    By choosing appropriate microemulsion systems, hexagonal cobalt (Co) and cobalt-nickel (1:1) alloy nanoparticles have been obtained with cetyltrimethylammonium bromide as a cationic surfactant at 500 degrees C. This method thus stabilizes the hcp cobalt even at sizes (fcc cobalt is predicted to be stable. On annealing the hcp cobalt nanoparticles in H(2) at 700 degrees C we could transform them to fcc cobalt nanoparticles. Microscopy studies show the formation of spherical nanoparticles of hexagonal and cubic forms of cobalt and Co-Ni (1:1) alloy nanoparticles with the average size of 4, 8 and 20 nm, respectively. Electrochemical studies show that the catalytic property towards oxygen evolution is dependent on the applied voltage. At low voltage (less than 0.65 V) the Co (hexagonal) nanoparticles are superior to the alloy (Co-Ni) nanoparticles while above this voltage the alloy nanoparticles are more efficient catalysts. The nanoparticles of cobalt (hcp and fcc) and alloy (Co-Ni) nanoparticles show ferromagnetism. The saturation magnetization of Co-Ni nanoparticles is reduced compared to the bulk possibly due to surface oxidation.

  18. A Novel FCC Catalyst Based on a Porous Composite Material Synthesized via an In Situ Technique

    Directory of Open Access Journals (Sweden)

    Shu-Qin Zheng

    2015-11-01

    Full Text Available To overcome diffusion limitations and improve transport in microporous zeolite, the materials with a wide-pore structure have been developed. In this paper, composite microspheres with hierarchical porous structure were synthesized by an in situ technique using sepiolite, kaolin and pseudoboehmite as raw material. A novel fluid catalytic cracking (FCC catalyst for maximizing light oil yield was prepared based on the composite materials. The catalyst was characterized by XRD, FT-IR, SEM, nitrogen adsorption-desorption techniques and tested in a bench FCC unit. The results indicated that the catalyst had more meso- and macropores and more acid sites than the reference catalyst, and thus can increase light oil yield by 1.31 %, while exhibiting better gasoline and coke selectivity.

  19. Aprotic synthesis and structural determination of the nanosized nonprotonated nu3-octahedral [Pt6Ni38(CO)48]6- hexaanion stabilized as a cubic solvated [NMe4]+ salt.

    Science.gov (United States)

    de Silva, Namal; Dahl, Lawrence F

    2006-10-30

    The nonprotonated member, 1 (n = 6), of the previously established nanosized nu3-octahedral [H(6-n)Pt6Ni38(CO)48]n- series (n = 3-6) has been isolated from an aprotic synthetic route and stabilized as the crystal-ordered cyclohexane/acetonitrile-solvated [NMe4]+ salt. A highly precise X-ray determination (cubic; Pa3; Z = 4 with 1 possessing -3 site symmetry) has allowed a comparative analysis of the nonprotonated pseudo-D3d structure of 1 with the monoprotonated structure of 2 (n = 5), which constitutes the only previously reported complete geometry of any member of this extraordinary Pt6-encapsulated nu3-octahedral Pt6Ni38 cluster series.

  20. Similarity and Difference of Phase Transition FCC – BCC in Calcium and Strontium

    Directory of Open Access Journals (Sweden)

    V.V. Pozhivatenko

    2016-11-01

    Full Text Available Features of polymorphism in calcium and strontium from the point of view of similarity of physical processes which occur at change of pressure and temperatures are researched. The known experimental facts are added calculated (first principal and fit by results which illustrate both similarity, and difference of structural phase transitions FCC – BCC in calcium and strontium. The increase in similarity of the effects connected with polymorphism is shown, at increase both pressure, and temperatures.

  1. Ultrahard nanotwinned cubic boron nitride.

    Science.gov (United States)

    Tian, Yongjun; Xu, Bo; Yu, Dongli; Ma, Yanming; Wang, Yanbin; Jiang, Yingbing; Hu, Wentao; Tang, Chengchun; Gao, Yufei; Luo, Kun; Zhao, Zhisheng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan

    2013-01-17

    Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall-Petch effect--the tendency for hardness to increase with decreasing grain size. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ∼14 nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ∼3.8 nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100 GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (∼1,294 °C) and a large fracture toughness (>12 MPa m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ∼10 MPa m(1/2)). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall-Petch effect below a critical grain size or the twin thickness of ∼10-15 nm found in metals and alloys.

  2. Universal Reconfiguration of (Hyper-)cubic Robots

    OpenAIRE

    Abel, Zachary; Kominers, Scott D.

    2008-01-01

    We study a simple reconfigurable robot model which has not been previously examined: cubic robots comprised of three-dimensional cubic modules which can slide across each other and rotate about each others' edges. We demonstrate that the cubic robot model is universal, i.e., that an n-module cubic robot can reconfigure itself into any specified n-module configuration. Additionally, we provide an algorithm that efficiently plans and executes cubic robot motion. Our results directly extend to a...

  3. 47 CFR 95.422 - (CB Rule 22) How do I answer correspondence from the FCC?

    Science.gov (United States)

    2010-10-01

    ... from the FCC? 95.422 Section 95.422 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED... You Need to Know § 95.422 (CB Rule 22) How do I answer correspondence from the FCC? (a) If it appears to the FCC that you have violated the Communications Act or these rules, the FCC may send you...

  4. 76 FR 6473 - Sunshine Act; FCC To Hold Open Commission Meeting Tuesday, February 8, 2011

    Science.gov (United States)

    2011-02-04

    ... COMMISSION Sunshine Act; FCC To Hold Open Commission Meeting Tuesday, February 8, 2011 February 1, 2011. The... Competition Title: Reform of the FCC Form 477 Data Program (WC Docket No. 11-10); Development of Nationwide... impossible to fill. Send an e-mail to: fcc504@fcc.gov or call the Consumer & Governmental Affairs Bureau...

  5. 76 FR 20976 - Wireline Competition Bureau Releases 2011 Annual Telecommunications Reporting Worksheet (FCC Form...

    Science.gov (United States)

    2011-04-14

    ... COMMISSION Wireline Competition Bureau Releases 2011 Annual Telecommunications Reporting Worksheet (FCC Form... Reporting Worksheet (FCC Form 499-A) and accompanying instructions. Filers may now submit their FCC Form 499-A to the Universal Service Administrative Company. DATES: Filers must submit the FCC Form...

  6. Electronic properties of cubic TaC{sub x}N{sub 1-x}: A comparative study using self-consistent cluster and ab initio band-structure calculations and X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lavrentyev, A.A.; Gabrelian, B.V.; Vorzhev, V.B.; Nikiforov, I.Ya. [Department of Physics, Don State Technical University, Gagarin Sq. 1, Rostov-on-Don (Russian Federation); Khyzhun, O.Yu. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, UA-03142 Kyiv (Ukraine)], E-mail: khyzhun@ipms.kiev.ua

    2009-03-20

    To investigate the influence of substitution of carbon atoms for nitrogen atoms in the cubic TaC{sub x}N{sub 1-x} carbonitrides, total and partial densities of states were calculated for TaC, TaC{sub 0.5}N{sub 0.5} and TaN compounds (NaCl structure) using the self-consistent cluster (with the FEFF8 code) and ab initio band-structure augmented plane wave + local orbitals (APW + LO) methods. In the present work a rather good agreement of the theoretical FEFF8 and APW + LO data for electronic properties of the TaC{sub x}N{sub 1-x} system under consideration was obtained. The results indicate that a strong hybridization of the Ta 5d- and C(N) 2p-like states is characteristic for the valence band of the TaC{sub x}N{sub 1-x} carbonitrides. When going from TaC to TaN through the TaC{sub 0.5}N{sub 0.5} carbonitride, the main maxima of curves representing total and partial Ta 5d densities of states shift in the direction opposite to the position of the Fermi level. In the above sequence of compounds, an increase of occupation of the near-Fermi sub-band formed by contributions of Ta 5d(t{sub 2g}) states has been detected. The theoretical FEFF8 and APW + LO results for the electronic structure of the TaC{sub x}N{sub 1-x} carbonitrides were found to be in excellent agreement with the experimental data derived in the present work employing X-ray photoelectron, emission and absorption spectroscopy methods for cubic TaC{sub 0.98}, TaC{sub 0.52}N{sub 0.49} and TaN{sub 0.97} compounds.

  7. Study on Reduction of Sulfur Content in FCC Gasoline

    Institute of Scientific and Technical Information of China (English)

    Hou Dianguo

    2003-01-01

    Reduction of sulfur content in FCC gasoline was studied in a fixed fluid bed (FFB) unit by using metal-modified LV-23 FCC catalyst. The results showed that the sulfur content in FCC gasoline could be reduced with LV-23 catalyst modified with zinc, palladium, zinc-palladium, zinc-cobalt, and zinc-nickel. Among these metals or metal combinations, palladium-containing catalyst was the most effective. Desulfurization of the heavy fraction of FCC gasoline was more effective than full-range gasoline under the same conditions with palladium-containing catalysts. A high reaction temperature was favorable to desulfurization, but it would reduce the yield of liquid product. After desulfurization reaction, the olefin content of product gasoline decreased while the aromatic and iso-alkane contents increased. Removal of thiophene and benzothiophene is higher.

  8. FCC Catalysts to Meet Demand of New Era

    Institute of Scientific and Technical Information of China (English)

    Yu Daping

    2008-01-01

    The CGP series FCC catalysts for manufacture of clean gasoline and propylene and the catalyst RSC-2006 for processing inferior residuum with high yield of light distillates are novel catalysts jointly developed by Qilu Catalyst Branch Company of SINOPEC Corp. and the Research Institute of Petroleum Processing (RIPP). The results of commercial application of these catalysts have revealed that they can satisfactorily meet the requirements for environmental protection, good economic benefits and capability for processing inferior FCC feed under new circumstances.

  9. Spent FCC catalyst for improving early strength Portland cement

    OpenAIRE

    Borrachero Rosado, María Victoria; Monzó Balbuena, José Mª; Paya Bernabeu, Jorge Juan; Vunda, Christian; VELÁZQUEZ RODRÍGUEZ, SERGIO; Soriano Martinez, Lourdes

    2014-01-01

    Spent fluid catalytic cracking (FCC) catalyst from the petrol industry has proven to be a very active pozzolanic material. This behavior leads to an additional increase in the strength of the mortar that contains this catalyst. Pozzolanic effects tend to be considered for periods above three days, whereas in shorter times, the influence of pozzolan is usually negligible. The reactivity of FCC is so high, however, that both pozzolanic effects and acceleration of cement hydration are evident in...

  10. Selective Hydrodesulfurization of FCC Gasoline Using LH-07 Catalyst

    Institute of Scientific and Technical Information of China (English)

    Da Jianwen; Han Xinzhu; Liu Aihua; Xu Xinzhong

    2002-01-01

    @@ 1.Introduction Since the environmental regulations are increasingly strin gent than ever, the production of clean automobile fuel is a vital target in China, especially after China has become a WTO member. However, the sulfur content in gasoline pool of China is still very high. Over 95% of the sulfur in gaso line pool comes from FCC naphtha. It is necessary to remove sulfur in FCC naphtha.

  11. Study on Disproportionation Reaction of FCC Gasoline on Acid Catalyst

    Institute of Scientific and Technical Information of China (English)

    Xu Youhao; Wang Xieqing

    2004-01-01

    Based on the experimental data relating to the reaction of FCC gasoline on acid catalyst the analysis of product distribution, and composition of gasoline and diesel fractions have been analyzed. The occurrence of disproportionation reaction of FCC gasoline on acid catalyst and the network of disproportionation reaction have been identified. Study has also shown that different reaction temperatures can result in different pathways of disproportionation reactions on acid catalyst.

  12. Neutron Scattering from fcc Pr and Pr3Tl

    DEFF Research Database (Denmark)

    Birgeneau, R. J.; Als-Nielsen, Jens Aage; Bucher, E.

    1972-01-01

    Elastic-neutron-scattering measurements on the singlet-ground-state ferromagnets fcc Pr and Pr3 Tl are reported. Both exhibit magnetic phase transitions, possibly to a simple ferromagnetic state at 20 and 11.6 °K, respectively. The transitions appear to be of second order although that in fcc Pr...... is clearly anomalous. Additional information on the inelastic scattering studies of the Γ1-Γ4 excitons in these systems is presented. dhcp Pr is also briefly discussed....

  13. Nanotwinned fcc metals: Strengthening versus softening mechanisms

    Science.gov (United States)

    Stukowski, A.; Albe, K.; Farkas, D.

    2010-12-01

    The strengthening effect of twins in nanocrystalline metals has been reported both in experiment and simulation. While twins are mostly considered as effective barriers to dislocation slip transfer, they can also provide nucleation sites for dislocations or migrate during the deformation process, thereby contributing to plasticity. By comparing twinned and nontwinned samples, we study the effect of twins on the deformation behavior of nanocrystalline Cu and Pd using atomistic simulations. While Cu shows hardening due to the presence of twins, Pd shows the opposite effect. A quantitative dislocation analysis method is applied, which allows to analyze dislocation interactions with twin planes and grain boundaries and to measure dislocation, stacking fault, and twin-boundary densities as functions of strain. A statistical analysis of the occurring dislocation types provides direct evidence for the role of twin boundaries as effective sources for twinning dislocations, which are the reason for the observed softening in some fcc materials. In addition, we discuss how the orientation of the loading direction with respect to the twin planes affects the response of nanotwinned Cu and Pd.

  14. Outline and Status of the FCC-ee Design Study

    CERN Document Server

    Zimmermann, Frank

    2015-01-01

    The Update of the European Strategy for Particle Physics in 2013 [1] declared as its second highest priority that “…to propose an ambitious post-LHC accelerator project….., CERN should undertake design studies for accelerator projects in a global context,…with emphasis on proton-proton and electron-positron high-energy frontier machines…”. In response to this request, the global Future Circular Collider (FCC) study is designing a 100-TeV proton collider (FCC-hh) in a new ~100 km tunnel near Geneva, a high-luminosity electron-positron collider (FCC-ee) as a potential intermediate step, and a lepton-hadron option (FCC-he). The FCC study comprises accelerators, technology, infrastructure, detector, physics, concepts for worldwide data services, international governance models, and implementation scenarios. The FCC study is mandated to deliver a Conceptual Design Report and preliminary cost estimate by the time of the next European Strategy Update expected for 2019. As of July 2015, 58 institutes from...

  15. Dependency of deformation twinning on grain orientation in an FCC and a HCP metal

    Institute of Scientific and Technical Information of China (English)

    YANG Ping

    2007-01-01

    Twinning plays important roles in HCP metals and those FCC metals with low stacking fault energy.The structural difierence of two types of metals makes quite different contributions of twinning to plasticity The variety of grain orientation in polycrystalline metals causes the inhomogeneous occurrence of twinning and further distinct transformation kinetics of twinning as strain increases and texture develops.This changes finally the work hardening behavior and mechanical properties.This Paper reveals the dependency of twinning on grain orientation in an FCC TWIP(twinning induced plasticity)steel with high Mn content and in a magnesium alloy using electron-backscatter-difiraction(EBSD) technique,and analyzes the characteristies of twinning in the two types of metals by Schmid factor calculation.In addition,the relation of twinning and shear banding, as well as their influence on properties are discussed.

  16. Cubication of Conservative Nonlinear Oscillators

    Science.gov (United States)

    Belendez, Augusto; Alvarez, Mariela L.; Fernandez, Elena; Pascual, Immaculada

    2009-01-01

    A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear…

  17. Cryptographic Analysis in Cubic Time

    DEFF Research Database (Denmark)

    Nielson, Flemming; Nielson, Hanne Riis; Seidl, H.

    2004-01-01

    The spi-calculus is a variant of the polyadic pi-calculus that admits symmetric cryptography and that admits expressing communication protocols in a precise though still abstract way. This paper shows that context-independent control flow analysis can be calculated in cubic time despite the fact ...

  18. The diagonalization of cubic matrices

    Science.gov (United States)

    Cocolicchio, D.; Viggiano, M.

    2000-08-01

    This paper is devoted to analysing the problem of the diagonalization of cubic matrices. We extend the familiar algebraic approach which is based on the Cardano formulae. We rewrite the complex roots of the associated resolvent secular equation in terms of transcendental functions and we derive the diagonalizing matrix.

  19. An Example of Body-Centered Cubic Crystal Structure: The Atomium in Brussels as an Educative Tool for Introductory Materials Chemistry

    Science.gov (United States)

    Pinto, Gabriel

    2012-01-01

    When students are introduced to the ways in which atoms are arranged in crystal structures, transposing the textbook illustrations into three-dimensional structures is difficult for some of them. To facilitate this transition, this article describes an approach to the study of the structure of solids through a well-known monument, the Atomium in…

  20. An Example of Body-Centered Cubic Crystal Structure: The Atomium in Brussels as an Educative Tool for Introductory Materials Chemistry

    Science.gov (United States)

    Pinto, Gabriel

    2012-01-01

    When students are introduced to the ways in which atoms are arranged in crystal structures, transposing the textbook illustrations into three-dimensional structures is difficult for some of them. To facilitate this transition, this article describes an approach to the study of the structure of solids through a well-known monument, the Atomium in…

  1. Downflow - the FCC of the future; Downflow - o FCC do futuro

    Energy Technology Data Exchange (ETDEWEB)

    Pinho, Andrea de Rezende; Huziwara, Wilson Kenzo [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Tecnologias de FCC]. E-mail: gerla@cenpes.petrobras.com.br; Ramos, Jose Geraldo Furtado; Silva, Mauro [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES). Engenharia Basica de FCC, Coque e Separacao]. E-mail: jgramos@cenpes.petrobras.com.br

    2002-03-01

    Thermal cracking reactions are not selective in prime products such as naphtha and LPG, which favors the formation of coke and fuel gas in the RISER reactor of the FCC. For this reason, thermal cracking is gradually being reduced and, consequently, the participation of catalytic cracking in this process is being increased. One of the ways to minimize thermal cracking in the reactor is to promote flow the closest possible to plug flow, through downward flow reactors, more commonly known as DOWNER or DOWNFLOW. Innumerable studies already done at CENPES in hot pilot units have demonstrated the attractiveness of this technology, through the utilization of cold demonstration units and through a complete knowledge of fluidization and Engineering techniques at PETROBRAS. The DOWNFLOW presents significant conversion gains, of 2.2% wt, basically due to the increase in gasoline and LPG production, resulting in a specific profitability increase of 6.7 US$/t of feed. This is possible due to the low selectivity of the DOWNFLOW to the coke. This technology offers a promising alternative for the future, keeping in mind the gradual increase in the participation of national petroleum from the Campos Basin in the list of feeds processed at the FCC units. (author)

  2. Ab initio study of the effect of pressure on the structural and electronic properties of cubic LaAlO{sub 3} by density function theory using GGA, LDA and PBEsol exchange correlation potentials

    Energy Technology Data Exchange (ETDEWEB)

    Benam, M.R., E-mail: m_benam@pnu.ac.ir [Department of Physics, Payame Noor University, P.O. BOX 19395-3697 (Iran, Islamic Republic of); Abdoshahi, N.; Majidiyan Sarmazdeh, M. [Department of Physics, Payame Noor University, P.O. BOX 19395-3697 (Iran, Islamic Republic of)

    2014-08-01

    In this paper the effect of pressure on the structural and electronic properties of cubic-LaAlO{sub 3} including the equilibrium lattice constant, bulk modulus, derivative of bulk modulus and band structure have been calculated by density functional theory (DFT) using GGA, LDA, and PBEsol exchange correlation potentials. It is found that the change of the lattice constant with pressure has an exponential behavior: with increasing pressure, the lattice constant decreases first sharply at low pressures, and then more slowly at high pressures. Furthermore, the lattice constant calculated by the PBEsol method and the bulk modulus calculated by LDA and PBEsol methods are closer to the available experimental values than those obtained using other exchange correlation potentials. Regarding the electronic properties, it is shown that an increase in pressure increases the band gap, the change being 0.26 eV at 34.00 GPa. The total density of state (t-DOS) calculations demonstrate that increasing pressure has a significant effect on the core and conduction band, but little effect on the valence band. The band structure calculations indicate that, in this material, the band gap changes from indirect to direct at a pressure of about 25 GPa. Also, increasing pressure produces a clear curvature in the band structure near the bottom of the conduction band, a behavior consistent with the strong pressure dependence of the transport properties.

  3. Ab initio study of the effect of pressure on the structural and electronic properties of cubic LaAlO3 by density function theory using GGA, LDA and PBEsol exchange correlation potentials

    Science.gov (United States)

    Benam, M. R.; Abdoshahi, N.; Majidiyan Sarmazdeh, M.

    2014-08-01

    In this paper the effect of pressure on the structural and electronic properties of cubic-LaAlO3 including the equilibrium lattice constant, bulk modulus, derivative of bulk modulus and band structure have been calculated by density functional theory (DFT) using GGA, LDA, and PBEsol exchange correlation potentials. It is found that the change of the lattice constant with pressure has an exponential behavior: with increasing pressure, the lattice constant decreases first sharply at low pressures, and then more slowly at high pressures. Furthermore, the lattice constant calculated by the PBEsol method and the bulk modulus calculated by LDA and PBEsol methods are closer to the available experimental values than those obtained using other exchange correlation potentials. Regarding the electronic properties, it is shown that an increase in pressure increases the band gap, the change being 0.26 eV at 34.00 GPa. The total density of state (t-DOS) calculations demonstrate that increasing pressure has a significant effect on the core and conduction band, but little effect on the valence band. The band structure calculations indicate that, in this material, the band gap changes from indirect to direct at a pressure of about 25 GPa. Also, increasing pressure produces a clear curvature in the band structure near the bottom of the conduction band, a behavior consistent with the strong pressure dependence of the transport properties.

  4. Interaction of macroparticles localized in Wigner-Seitz cells of various types of cubic lattices in an equilibrium plasma

    Science.gov (United States)

    Filippov, A. V.

    2016-10-01

    The interaction of two charged point macroparticles located in Wigner-Seitz cells of simple cubic (SC), body-centered cubic (BCC), or face-centered cubic (FCC) lattices in an equilibrium plasma has been studied within the Debye approximation or, more specifically, based on the linearized Poisson-Boltzmann model. The shape of the outer boundary is shown to exert a strong influence on the pattern of electrostatic interaction between the two macroparticles, which transforms from repulsion at small interparticle distances to attraction as the interparticle distance approaches half the length of the computational cell. The macroparticle pair interaction potential in an equilibrium plasma is shown to be nevertheless the Debye one and purely repulsive for likely charged macroparticles.

  5. Exotic magnetism on the quasi-fcc lattices of the d3 double Perovskites La2NaB'O6 (B'=Ru, Os).

    Science.gov (United States)

    Aczel, A A; Baker, P J; Bugaris, D E; Yeon, J; Zur Loye, H-C; Guidi, T; Adroja, D T

    2014-03-21

    We find evidence for long-range and short-range (ζ=70 Å at 4 K) incommensurate magnetic order on the quasi-face-centered-cubic (fcc) lattices of the monoclinic double perovskites La2NaRuO6 and La2NaOsO6, respectively. Incommensurate magnetic order on the fcc lattice has not been predicted by mean field theory, but may arise via a delicate balance of inequivalent nearest neighbor and next nearest neighbor exchange interactions. In the Ru system with long-range order, inelastic neutron scattering also reveals a spin gap Δ ∼ 2.75 meV. Magnetic anisotropy is generally minimized in the more familiar octahedrally coordinated 3d3 systems, so the large gap observed for La2NaRuO6 may result from the significantly enhanced value of spin-orbit coupling in this 4d(3) material.

  6. Optimization of cubic GaN/AlGaN quantum well-based structures for intersubband absorption in the infrared spectral range

    Science.gov (United States)

    Radosavljević, Ana; Radovanović, Jelena; Milanović, Vitomir

    2014-03-01

    A method is proposed for the optimization of structural parameters of GaN/AlGaN quantum wells and Bragg-confined structures, with respect to peak intersubband absorption from the ground to the first excited electronic state in the mid and near infrared spectral range. It is based on the application of the Genetic Algorithm and delivers globally optimal structures with a preset number of embedded layers. Simple rectangular quantum well profile is investigated for the maximal Stark effect and applications to tunable mid-infrared photodetectors. In case of Bragg-confined structures, an above the barrier bound state is used to extend the range of transition energies above the values available in conventional quantum wells. The effects of band nonparabolicity are taken into account.

  7. Cubication of conservative nonlinear oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Belendez, Augusto; Alvarez, Mariela L [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, Elena; Pascual, Inmaculada [Departamento de Optica, FarmacologIa y Anatomia, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es

    2009-09-15

    A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.

  8. Cubic Matrix, Nambu Mechanics and Beyond

    OpenAIRE

    Kawamura, Y

    2002-01-01

    We propose a generalization of cubic matrix mechanics by introducing a canonical triplet and study its relation to Nambu mechanics. The generalized cubic matrix mechanics we consider can be interpreted as a “quantum” generalization of Nambu mechanics.

  9. Numbers for reducible cubic scrolls

    Directory of Open Access Journals (Sweden)

    Israel Vainsencher

    2004-12-01

    Full Text Available We show how to compute the number of reducible cubic scrolls of codimension 2 in (math blackboard symbol Pn incident to the appropriate number of linear spaces.Mostramos como calcular o número de rolos cúbicos redutíveis de codimensão 2 em (math blackboard symbol Pn incidentes a espaços lineares apropriados.

  10. 47 CFR 95.219 - (R/C Rule 19) How do I answer correspondence from the FCC?

    Science.gov (United States)

    2010-10-01

    ... from the FCC? 95.219 Section 95.219 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED... You Need to Know § 95.219 (R/C Rule 19) How do I answer correspondence from the FCC? (a) If it appears to the FCC that you have violated the Communications Act or FCC rules, the FCC may send you...

  11. Electronic structure of cubic Hf{sub x}Ta{sub 1-x}C{sub y} carbides from X-ray spectroscopy studies and cluster self-consistent calculations

    Energy Technology Data Exchange (ETDEWEB)

    Lavrentyev, A.A.; Gabrelian, B.V.; Vorzhev, V.B.; Nikiforov, I.Ya. [Department of Physics, Don State Technical University, Gagarin Sq. 1, Rostov-on-Don (Russian Federation); Khyzhun, O.Yu. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Str., UA-03142 Kyiv (Ukraine)], E-mail: khyzhun@ipms.kiev.ua; Rehr, J.J. [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States)

    2008-08-25

    X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were employed in the present work to investigate the electronic structure of almost stoichiometric cubic (NaCl structure) Hf{sub x}Ta{sub 1-x}C{sub y} carbides. The XPS valence-band and core-level spectra, the XES bands reflecting energy distributions of mainly the Ta 5d- and C 2p-like states as well as the XAS Ta L{sub III} edges (unoccupied Ta d-like states) were derived and compared on a common energy scale for cubic HfC{sub 0.95}, Hf{sub 0.5}Ta{sub 0.5}C{sub 0.94} and TaC{sub 0.98} compounds. To investigate the influence of substitution of tantalum atoms for hafnium atoms in the Hf{sub x}Ta{sub 1-x}C{sub y} carbides, cluster self-consistent calculations of total and partial densities of states were carried out with the FEFF8 code for HfC, Hf{sub 0.5}Ta{sub 0.5}C and TaC compounds possessing the NaCl-type structure. In the present work a rather good agreement of the experimental and theoretical results for the electronic structure of the Hf{sub x}Ta{sub 1-x}C{sub y} system under study was obtained. The results indicate that a strong hybridization of the Hf(Ta) 5d- and C 2p-like states is characteristic for the Hf{sub x}Ta{sub 1-x}C{sub y} carbides. It has been established that, substitution of hafnium atoms by tantalum atoms in the Hf{sub x}Ta{sub 1-x}C{sub y} system reveals increasing the half-width of the XES C K{alpha} band. When going from HfC{sub 0.95} to TaC{sub 0.98} through the carbide of intermediate composition, the main maximum of the XPS valence-band spectrum shifts in the direction opposite to the position of the Fermi level. In the above sequence of compounds the asymmetry index of the C K{alpha} bands decreases significantly.

  12. A study on the structure of AlMnNiTi alloy powders

    Science.gov (United States)

    Lijun, Wu; Lihua, Zhao; Qiaoqin, Yang; Shaolu, Li; Zhenjua, Chen; Yukun, Wu

    1996-02-01

    The structure of AlMnNiTi alloy powders has been studied by transmission electron microscope and X-ray diffraction. Two cubic phases are found and determined. One phase has a BCC lattice with a = 0.8905 nm, the other phase belongs to an FCC lattice with a = 1.1875 nm. The Al 3(Mn,Ni,Ti) phase, the Al solid solution and an unknown metastable phase are also found in the rapidly solidified sample. After annealing at 800°C for 1 h, the unknown metastable phase transforms into the decagonal quasicrystalline phase and the Al solid solution.

  13. First-principles calculations of the structural, electronic and optical properties of cubic B{sub x}Ga{sub 1-x}As alloys

    Energy Technology Data Exchange (ETDEWEB)

    Guemou, M., E-mail: guemoumhamed7@gmail.com [Engineering Physics Laboratory, University Ibn Khaldoun of Tiaret, BP 78-Zaaroura, Tiaret 14000 (Algeria); Bouhafs, B. [Modelling and Simulation in Materials Science Laboratory, Physics Department, University of Sidi Bel-Abbes, 22000 Sidi Bel-Abbes (Algeria); Abdiche, A. [Applied Materials Laboratory, Research Center, University of Sidi Bel Abbes, 22000 Sidi Bel Abbes (Algeria); Khenata, R. [Laboratoire de Physique Quantique et de Modelisation Mathematique (LPQ3M), Departement de Technologie, Universite de Mascara, 29000 Mascara (Algeria); Al Douri, Y. [Institute of Nano Electronic Engineering, Universiti Malaysia Perlis, Perlis (Malaysia); Bin Omran, S. [Department of Physics and Astronomy, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)

    2012-04-15

    Density functional calculations are performed to study the structural, electronic and optical properties of technologically important B{sub x}Ga{sub 1-x}As ternary alloys. The calculations are based on the total-energy calculations within the full-potential augmented plane-wave (FP-LAPW) method. For exchange-correlation potential, local density approximation (LDA) and the generalized gradient approximation (GGA) have been used. The structural properties, including lattice constants, bulk modulus and their pressure derivatives, are in very good agreement with the available experimental and theoretical data. The electronic band structure, density of states for the binary compounds and their ternary alloys are given. The dielectric function and the refractive index are also calculated using different models. The obtained results compare very well with previous calculations and experimental measurements.

  14. Cubic colloids : Synthesis, functionalization and applications

    NARCIS (Netherlands)

    Castillo, S.I.R.

    2015-01-01

    This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when

  15. Cubic colloids : Synthesis, functionalization and applications

    NARCIS (Netherlands)

    Castillo, S.I.R.

    2015-01-01

    This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when

  16. Solving Cubic Equations by Polynomial Decomposition

    Science.gov (United States)

    Kulkarni, Raghavendra G.

    2011-01-01

    Several mathematicians struggled to solve cubic equations, and in 1515 Scipione del Ferro reportedly solved the cubic while participating in a local mathematical contest, but did not bother to publish his method. Then it was Cardano (1539) who first published the solution to the general cubic equation in his book "The Great Art, or, The Rules of…

  17. Cubic Icosahedra? A Problem in Assigning Symmetry

    Science.gov (United States)

    Lloyd, D. R.

    2010-01-01

    There is a standard convention that the icosahedral groups are classified separately from the cubic groups, but these two symmetry types have been conflated as "cubic" in some chemistry textbooks. In this note, the connection between cubic and icosahedral symmetries is examined, using a simple pictorial model. It is shown that octahedral and…

  18. The 2:3:6 QPO structure in GRS 1915+105 and cubic subharmonics in the context of relativistic diskoseismology

    CERN Document Server

    Ortega-Rodr\\'\\iguez, Manuel; López-Barquero, Vanessa; Matamoros-Alvarado, Bryan; Venegas-Li, Ariadna

    2013-01-01

    We propose a simple toy model to explain the 2:3:6 QPO structure in GRS 1915+105 and, more generally, the 2:3 QPO structure in XTE J1550-564, GRO J1655-40, and H 1743-322. The model exploits the onset of subharmonics in the context of diskoseismology. The results include the prediction that, as better data become available, a QPO with a frequency of twice the higher twin frequency and a large quality factor will be observed in twin peak sources, as it might already have been observed in the especially active GRS 1915+105.

  19. Color Octet Electron Search Potential of the FCC Based e-p Colliders

    CERN Document Server

    Acar, Y C; Oner, B B; Sultansoy, S

    2016-01-01

    Resonant production of color octet electron, e_{8}, at the FCC based ep colliders has been analyzed. It is shown that e-FCC will cover much a wider region of e_{8} masses compared to the LHC. Moreover, with highest electron beam energy, e_{8} search potential of the e-FCC exceeds that of FCC pp collider. If e_{8} is discovered earlier by the FCC pp collider, e-FCC will give opportunity to handle very important additional information. For example, compositeness scale can be probed up to hundreds TeV region.

  20. Ion conductivity in cubically-stabilized fluorite-like structured Er5CeMoO12.5 and Yb5MMoO12.5 (M = Ce, Zr) solid solutions

    Science.gov (United States)

    Schildhammer, Daniel; Fuhrmann, Gerda; Petschnig, Lucas; Kogler, Michaela; Penner, Simon; Weinberger, Nikolaus; Schottenberger, Herwig; Huppertz, Hubert

    2016-12-01

    For the first time, the usually rhombohedral R 3 bar (no. 148) defect fluorite structured rare earth molybdenum oxides RE6MoO12 (RE = Er, Yb) could be stabilized in the cubic defect fluorite structure Fm 3 bar m (no. 225) through partial substitution of Er3+ and Yb3+ by M4+ cations with M4+ = Ce for Er6MoO12 and M4+ = Ce, Zr for Yb6MoO12. The solution combustion (SC) method and the classical solid state reaction are the synthetic approaches that were used (ambient atmosphere and temperatures of 1250 °C). The obtained oxide powders were characterized by energy dispersive X-ray (EDX) analysis, powder X-ray diffraction (PXRD), IR, and UV-Vis spectroscopy. The PXRD-data were used for Rietveld refinements. Electrochemical impedance spectroscopy (EIS) was conducted to identify oxygen vacancies in the cubic structure type, revealing oxygen ion conductivity starting at 500 °C. Additionally, the influence on ion conductivity by the cation substitutions are discussed. Calculation of the contributing activation energies for the bulk (best value for Yb5CeMoO12.5 is 119.8 kJmol-1), and the grain boundary (e.g. Er5CeMoO12.5: 152.1 kJmol-1) analyzed by means of the Arrhenius plot, shows similarities to the conventional stabilization of zirconia with yttrium (8-YSZ) (110 kJ mol-1 and 110-163 kJmol-1 respectively). The best-calculated conductivity values σ = 1.03 × 10-4 Scm-1 obtained for Er5CeMoO12.5 at 1000 °C are comparable to the values published for 8-YSZ with σ = 3.94 × 10-5 Scm-1 at similar temperatures. These promising preliminary results underline the potential of the title compounds for application in solid oxide fuel cells (SOFCs).

  1. A Monte Carlo Simulation of a Monomer Dimer CO-O2 Catalytic Reaction on the Surface and Subsurface of a Face-centered Cubic Lattice

    Institute of Scientific and Technical Information of China (English)

    K.Iqbal; A.Basit

    2011-01-01

    @@ The presence of oxygen in the subsurface in monomer-dimer reactions(CO-O2 and NO-CO)is observed experimentally.The effect of subsurface oxygen on a CO-O2 catalytic reaction on a face-centered cubic(FCC)lattice is studied using Monte Carlo simulation.The effect of adding subsurface neighbours on the phase diagram is also extensively explored.It is observed that the subsurface oxygen totally eliminates the typical second order phase transition.It is also shown that the introduction of the diffusion of O atoms and the subsurface of the FCC lattice shifts the single transition point towards the stoichiometric ratio.%The presence of oxygen in the subsurface in monomer-dimer reactions (CO-O2 and NO-CO) is observed experimentally. The effect of subsurface oxygen on a CO-O2 catalytic reaction on a face-centered cubic (FCC) lattice is studied using Monte Carlo simulation. The effect of adding subsurface neighbours on the phase diagram is also extensively explored. It is observed that the subsurface oxygen totally eliminates the typical second order phase transition. It is also shown that the introduction of the diffusion of O atoms and the subsurface of the FCC lattice shifts the single transition point towards the stoichiometric ratio.

  2. Development of FCC Naphtha Hydrodesulfurization and Aromatization Process

    Institute of Scientific and Technical Information of China (English)

    Zhu Huaxing; Zhu Jianhua; Liu Jinlong; Sun Diancheng; Gong Xuhui

    2005-01-01

    This articles refers to the development of the technology for hydrodesulfurization (HDS) and aromatization of FCC naphtha This technology adopts a catalyst with aromatization performance, which does not reduce the octane rating of gasoline in the course of HDS of FCC naphtha. Experimental results have shown that the sulfur removal rate of FCC naphtha could reach over 85%, with the RON of gasoline increased by 0.2-0.6 units, the MON increased by 1.3-1.8 units and the antiknock index of the gasoline increased by around one unit. The total C5+ liquid yield was over 95%. The activity of regenerated catalyst could be restored to be equal to that of fresh one after coke burning on the spent catalyst.

  3. Cubic metaplectic forms and theta functions

    CERN Document Server

    Proskurin, Nikolai

    1998-01-01

    The book is an introduction to the theory of cubic metaplectic forms on the 3-dimensional hyperbolic space and the author's research on cubic metaplectic forms on special linear and symplectic groups of rank 2. The topics include: Kubota and Bass-Milnor-Serre homomorphisms, cubic metaplectic Eisenstein series, cubic theta functions, Whittaker functions. A special method is developed and applied to find Fourier coefficients of the Eisenstein series and cubic theta functions. The book is intended for readers, with beginning graduate-level background, interested in further research in the theory of metaplectic forms and in possible applications.

  4. Ferromagnetic Ground States in Face-Centered Cubic Hubbard Clusters

    Science.gov (United States)

    Souza, T. X. R.; Macedo, C. A.

    2016-01-01

    In this study, the ground state energies of face-centered cubic Hubbard clusters are analyzed using the Lanczos method. Examination of the ground state energy as a function of the number of particle per site n showed an energy minimum for face-centered cubic structures. This energy minimum decreased in n with increasing coulombic interaction parameter U. We found that the ground state energy had a minimum at n = 0.6, when U = 3W, where W denotes the non-interacting energy bandwidth and the face-centered cubic structure was ferromagnetic. These results, when compared with the properties of nickel, shows strong similarity with other finite temperature analyses in the literature and supports the Hirsh’s conjecture that the interatomic direct exchange interaction dominates in driving the system into a ferromagnetic phase. PMID:27583653

  5. Structural transitions in electron beam deposited Co–carbonyl suspended nanowires at high electrical current densities

    Directory of Open Access Journals (Sweden)

    Gian Carlo Gazzadi

    2015-06-01

    Full Text Available Suspended nanowires (SNWs have been deposited from Co–carbonyl precursor (Co2(CO8 by focused electron beam induced deposition (FEBID. The SNWs dimensions are about 30–50 nm in diameter and 600–850 nm in length. The as-deposited material has a nanogranular structure of mixed face-centered cubic (FCC and hexagonal close-packed (HCP Co phases, and a composition of 80 atom % Co, 15 atom % O and 5 atom % C, as revealed by transmission electron microscopy (TEM analysis and by energy-dispersive X-ray (EDX spectroscopy, respectively. Current (I–voltage (V measurements with current densities up to 107 A/cm2 determine different structural transitions in the SNWs, depending on the I–V history. A single measurement with a sudden current burst leads to a polycrystalline FCC Co structure extended over the whole wire. Repeated measurements at increasing currents produce wires with a split structure: one half is polycrystalline FCC Co and the other half is graphitized C. The breakdown current density is found at 2.1 × 107 A/cm2. The role played by resistive heating and electromigration in these transitions is discussed.

  6. Structural transitions in electron beam deposited Co-carbonyl suspended nanowires at high electrical current densities.

    Science.gov (United States)

    Gazzadi, Gian Carlo; Frabboni, Stefano

    2015-01-01

    Suspended nanowires (SNWs) have been deposited from Co-carbonyl precursor (Co2(CO)8) by focused electron beam induced deposition (FEBID). The SNWs dimensions are about 30-50 nm in diameter and 600-850 nm in length. The as-deposited material has a nanogranular structure of mixed face-centered cubic (FCC) and hexagonal close-packed (HCP) Co phases, and a composition of 80 atom % Co, 15 atom % O and 5 atom % C, as revealed by transmission electron microscopy (TEM) analysis and by energy-dispersive X-ray (EDX) spectroscopy, respectively. Current (I)-voltage (V) measurements with current densities up to 10(7) A/cm(2) determine different structural transitions in the SNWs, depending on the I-V history. A single measurement with a sudden current burst leads to a polycrystalline FCC Co structure extended over the whole wire. Repeated measurements at increasing currents produce wires with a split structure: one half is polycrystalline FCC Co and the other half is graphitized C. The breakdown current density is found at 2.1 × 10(7) A/cm(2). The role played by resistive heating and electromigration in these transitions is discussed.

  7. Structure characteristics of cubic and orthorhombic phases of high density scintillator PbF{sub 2} from 4.2--300 K

    Energy Technology Data Exchange (ETDEWEB)

    Shmyt`ko, I.; Savchenko, I.B.; Klassen, N.V.; Bagautdinov, B.S.; Emel`chenko, G.A.; Sinitzin, V.V. [Russian Academy of Sciences, Chernogolovka (Russian Federation). Inst. of Solid State Physics

    1994-12-31

    An anomaly of the temperature dependence of the unit cell parameter has been observed for {beta}-PbF{sub 2} single crystals at 200 K that is interpreted as a phase transition to a pseudocubic lattice. Such a pseudocubic phase is observable at room temperature after uniaxial plastic deformation of the bulk single crystals. The structural aspects of the {beta}{r_arrow}{alpha} transition have been established. The as-grown crystals of {alpha}-PbF{sub 2} phase are shown to undergo a phase transition at 100 K.

  8. Structural, electronic and optical properties of cubic SrTiO{sub 3} and KTaO{sub 3}: Ab initio and GW calculations

    Energy Technology Data Exchange (ETDEWEB)

    Benrekia, A.R., E-mail: benrekia.ahmed@yahoo.com [Faculty of Science and Technology, University of Medea (Algeria); Benkhettou, N. [Laboratoire des Materiaux Magnetiques, Faculte des Sciences, Universite Djillali Liabes de Sidi Bel Abbes (Algeria); Nassour, A. [Laboratoire de Cristallographie, Resonance Magnetique et Modelisations (CRM2, UMR CNRS 7036) Institut Jean Barriol, Nancy Universite BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre-les-Nancy (France); Driz, M. [Applied Material Laboratory (AML), Electronics Department, University of Sidi bel Abbes (DZ 22000) (Algeria); Sahnoun, M. [Laboratoire de Physique Quantique de la Matiere et Modelisations Mathematique (LPQ3M), Faculty of Science and Technology,University of Mascara (Algeria); Lebegue, S. [Laboratoire de Cristallographie, Resonance Magnetique et Modelisations (CRM2, UMR CNRS 7036) Institut Jean Barriol, Nancy Universite BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre-les-Nancy (France)

    2012-07-01

    We present first-principles VASP calculations of the structural, electronic, vibrational, and optical properties of paraelectric SrTiO{sub 3} and KTaO{sub 3}. The ab initio calculations are performed in the framework of density functional theory with different exchange-correlation potentials. Our calculated lattice parameters, elastic constants, and vibrational frequencies are found to be in good agreement with the available experimental values. Then, the bandstructures are calculated with the GW approximation, and the corresponding band gap is used to obtain the optical properties of SrTiO{sub 3} and KTaO{sub 3}.

  9. Time-Resolved Diffraction Profiles and Atomic Dynamics in Short-Pulse Laser-Induced Structural Transformations: Molecular Dynamics Study

    Science.gov (United States)

    2006-05-16

    clearly reflected in the evolution of the structure function. In just 3–4 ps the peaks characteristic of the fcc structure dis- appear and the structure...apparent in the figure. The diffraction peaks from 111 and 311 atomic planes, present in the original fcc structure , shift in the direction of smaller Q...the fcc crystalline structure. Each peak in Gr corresponds to a specific interatomic distance between a pair of atoms in a perfect fcc structure . For

  10. FCC FAMILY TECHNOLOGY BRIDGING PETROLEUM REFINING WITH PETROCHEMICAL INDUSTRY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    FCC family technologies,such as DCC,MGG and CPP,take the advantages of both thermal and catalytic reactions. A zeolite containing material is acted as heat carrier and catalyst as well. Versatile objectives can be achieved through regulating the catalyst formulation and optimizing the process variables. The ethylene,propylene and isobutylene yields from these FCC family technologies can be 24.3%, 22.9% and 6.1%,respectively,with heavy feeds. The cracked naphtha is rich in toluene and xylenes.

  11. Quantitative comparison between simulated and experimental FCC rolling textures

    DEFF Research Database (Denmark)

    Wronski, M.; Wierzbanowski, K.; Leffers, Torben

    2015-01-01

    The degree of similarity between simulated and experimental fcc rolling textures is characterized by a single scalar parameter. The textures are simulated with a relatively simple and efficient 1-point model which allows us to vary the strength of the interaction between the grains and the surrou......The degree of similarity between simulated and experimental fcc rolling textures is characterized by a single scalar parameter. The textures are simulated with a relatively simple and efficient 1-point model which allows us to vary the strength of the interaction between the grains...

  12. Synthesis, Characterization, and Electronic Structure Studies of Cubic Bi1.5ZnTa1.5O7 for Photocatalytic Applications

    Directory of Open Access Journals (Sweden)

    Ganchimeg Perenlei

    2015-01-01

    Full Text Available Bi1.5ZnTa1.5O7 (BZT has been synthesized using an alkoxide based sol-gel reaction route. The evolution of the phases produced from the alkoxide precursors and their properties have been characterized as function of temperature using a combination of thermogravimetric analysis (TGA coupled with mass spectrometry (MS, infrared emission spectrometry (IES, X-ray diffraction (XRD, ultraviolet and visible (UV-Vis spectroscopy, Raman spectroscopy, and N2 adsorption/desorption isotherms. The lowest sintering temperature (600°C to obtain phase pure BZT powders with high surface area (14.5 m2/g has been determined from the thermal decomposition and phase analyses. The photocatalytic activity of the BZT powders has been tested for the decolorization of organic azo-dye and found to be photoactive under UV irradiation. The electronic band structure of the BZT has been investigated using density functional theory (DFT calculations to determine the band gap energy (3.12 eV and to compare it with experimental band gap (3.02 eV at 800°C from optical absorption measurements. An excellent match is obtained for an assumption of Zn cation substitutions at specifically ordered sites in the BZT structure.

  13. First-Principle Study of the Structural, Electronic, and Optical Properties of Cubic InNxP1-x Ternary Alloys under Hydrostatic Pressure

    Science.gov (United States)

    Hattabi, I.; Abdiche, A.; Moussa, R.; Riane, R.; Hadji, K.; Soyalp, F.; Varshney, Dinesh; Syrotyuk, S. V.; Khenata, R.

    2016-09-01

    In this article, we present results of the first-principle study of the structural, electronic, and optical properties of the InN, InP binary compounds and their related ternary alloy InNxP1-x in the zinc-blend (ZB) phase within a nonrelativistic full potential linearised augmented plan wave (FP-LAPW) method using Wien2k code based on the density functional theory (DFT). Different approximations of exchange-correlation energy were used for the calculation of the lattice constant, bulk modulus, and first-order pressure derivative of the bulk modulus. Whereas the lattice constant decreases with increasing nitride composition x. Our results present a good agreement with theoretical and experimental data. The electronic band structures calculated using Tran-Blaha-modified Becke-Johnson (TB-mBJ) approach present a direct band gap semiconductor character for InNxP1-x compounds at different x values. The electronic properties were also calculated under hydrostatic pressure for (P=0.00, 5.00, 10.0, 15.0, 20.0, 25.0 GPa) where it is found that the InP compound change from direct to indirect band gap at the pressure P≥7.80 GPa. Furthermore, the pressure effect on the dielectric function and the refractive index was carried out. Results obtained in our calculations present a good agreement with available theoretical reports and experimental data.

  14. First-principle study of the structural, electronic, and optical properties of cubic InN{sub x}P{sub 1-x} ternary alloys under hydrostatic pressure

    Energy Technology Data Exchange (ETDEWEB)

    Hattabi, I. [Ibn Khaldoun Univ. de Tiaret (Algeria). Lab. Synthese et Catalyse; Abdiche, A.; Riane, R. [Sidi-bel-Abbes Univ. (Algeria). Applied Materials Lab.; Moussa, R. [Sidi-bel-Abbes Univ. (Algeria). Physic Dept.; Hadji, K. [Ibn Khaldoun Univ. de Tiaret (Algeria). Science and Technology Dept.; Soyalp, F. [Yuezuencue Yil Univ., Van (Turkey). Dept. of Physics; Varshney, Dinesh [Devi Ahilya Univ., Indore (India). Materials Science Lab.; Syrotyuk, S.V. [National Univ. ' Lviv Polytechnic' , Lviv (Ukraine). Semiconductor Electronics Dept.; Khenata, R. [Mascara Univ. (Algeria). Lab. de Physique Quantique et de Modelisation Mathematique (LPQ3M)

    2016-07-01

    In this article, we present results of the first-principle study of the structural, electronic, and optical properties of the InN, InP binary compounds and their related ternary alloy InN{sub x}P{sub 1-x} in the zinc-blend (ZB) phase within a nonrelativistic full potential linearised augmented plan wave (FP-LAPW) method using Wien2k code based on the density functional theory (DFT). Different approximations of exchange-correlation energy were used for the calculation of the lattice constant, bulk modulus, and first-order pressure derivative of the bulk modulus. Whereas the lattice constant decreases with increasing nitride composition x. Our results present a good agreement with theoretical and experimental data. The electronic band structures calculated using Tran-Blaha-modified Becke-Johnson (TB-mBJ) approach present a direct band gap semiconductor character for InN{sub x}P{sub 1-x} compounds at different x values. The electronic properties were also calculated under hydrostatic pressure for (P=0.00, 5.00, 10.0, 15.0, 20.0, 25.0 GPa) where it is found that the InP compound change from direct to indirect band gap at the pressure P≥7.80 GPa. Furthermore, the pressure effect on the dielectric function and the refractive index was carried out. Results obtained in our calculations present a good agreement with available theoretical reports and experimental data.

  15. Numerical evidence for bcc ordering at the surface of a critical fcc nucleus

    NARCIS (Netherlands)

    Wolde, P.R. ten; Ruiz-Montero, M.J.; Frenkel, D.

    1995-01-01

    We report a computer-simulation study of the crystal nucleation barrier and the structure of crystal nuclei in a Lennard-Jones system at moderate supercooling. The stable structure of the Lennard-Jones solid is known to be face-centered cubic. We find that the precritical nuclei are predominantly

  16. Numerical evidence for bcc ordering at the surface of a critical fcc nucleus

    NARCIS (Netherlands)

    Wolde, P.R. ten; Ruiz-Montero, M.J.; Frenkel, D.

    1995-01-01

    We report a computer-simulation study of the crystal nucleation barrier and the structure of crystal nuclei in a Lennard-Jones system at moderate supercooling. The stable structure of the Lennard-Jones solid is known to be face-centered cubic. We find that the precritical nuclei are predominantly bo

  17. Weighted cubic and biharmonic splines

    Science.gov (United States)

    Kvasov, Boris; Kim, Tae-Wan

    2017-01-01

    In this paper we discuss the design of algorithms for interpolating discrete data by using weighted cubic and biharmonic splines in such a way that the monotonicity and convexity of the data are preserved. We formulate the problem as a differential multipoint boundary value problem and consider its finite-difference approximation. Two algorithms for automatic selection of shape control parameters (weights) are presented. For weighted biharmonic splines the resulting system of linear equations can be efficiently solved by combining Gaussian elimination with successive over-relaxation method or finite-difference schemes in fractional steps. We consider basic computational aspects and illustrate main features of this original approach.

  18. Rheological properties of Cubic colloidal suspensions

    Science.gov (United States)

    Boromand, Arman; Maia, Joao

    2016-11-01

    Colloidal and non-colloidal suspensions are ubiquitous in many industrial application. There are numerous studies on these systems to understand and relate their complex rheological properties to their microstructural evolution under deformation. Although most of the experimental and simulation studies are centered on spherical particles, in most of the industrial applications the geometry of the colloidal particles deviate from the simple hard sphere and more complex geometries exist. Recent advances in microfabrication paved the way to fabricate colloidal particles with complex geometries for applications in different areas such as drug delivery where the fundamental understanding of their dynamics has remained unexplored. In this study, using dissipative particle dynamics, we investigate the rheological properties of cubic (superball) particles which are modeled as the cluster of core-modified DPD particles. Explicit representation of solvent particles in the DPD scheme will conserve the full hydrodynamic interactions between colloidal particles. Rheological properties of these cubic suspensions are investigated in the dilute and semi-dilute regimes. The Einstein and Huggins coefficients for these particles with different superball exponent will be calculate which represent the effect of single particle's geometry and multibody interactions on viscosity, respectively. The response of these suspensions is investigated under simple shear and oscillatory shear where it is shown that under oscillation these particles tend to form crystalline structure giving rise to stronger shear-thinning behavior recently measured experimentally.

  19. Local structural studies of the cubic Cd1–xCaxO system through Cd K-edge extended X-ray absorption spectroscopic studies

    Science.gov (United States)

    Srihari, Velaga; Sridharan, V.; Nomura, Masaharu; Sastry, V. Sankara; Sundar, C. S

    2012-01-01

    Cd K-edge extended X-ray absorption fine-structure spectroscopic studies were carried out on Cd1–xCaxO (0 ≤ x ≤0.9) solid solutions and the first and second nearest neighbour (NN) distances and their mean square relative displacement σ2 were estimated. The first NN distance, d Cd–O(x), was found to be smaller than its expected value, a(x)/2, obtained from the X-ray diffraction measurements. It increases monotonically and non-linearly with a negative curvature, comparable with that of the a(x) value variation. The variation σ2 of the 1NN with x is consistent with a disordered solid solution model. The 2NN distances d Cd–Cd(x) and d Cd–Ca(x) are found to follow the average values obtained by X-ray diffraction with d Cd–Ca(x) > d Cd–Cd(x). From detailed analysis it is argued that the solid solution exhibits a bimodal distribution of the 1NN distances, d Cd–O(x) and d Ca–O(x), and that the system belongs to a persistent type. PMID:22713887

  20. Comparison of Dust Lattice Waves in Three-Dimensional Cubic Configurations

    Institute of Scientific and Technical Information of China (English)

    B. Farokhi; A. Hameditabar

    2012-01-01

    A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered. We calculate the interaction between particles up to distance √2a, implying the second-neighbor interactions for the simple cubic structure, the third-neighbor interactions for the body-centered cubic structure, and the forth-neighbor interactions the for face-centered cubic structure. Longitudinal and transverse dispersion relations are derived in arbitrary directions. The dispersion relations are studied in special directions, I.e. (1,0,0), (l,l,0)/√2, and (1,1, l)/√3- Study of dispersion relations with more neighbor interactions show that in some cases the results change physically.%A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered.We calculate the interaction between particles up to distance (√2)a,implying the second-neighbor interactions for the simple cubic structure,the third-neighbor interactions for the body-centered cubic structure,and the forth-neighbor interactions the for face-centered cubic structure.Longitudinal and transverse dispersion relations are derived in arbitrary directions.The dispersion relations are studied in special directions,i.e.(1,0,0),(1,1,0)/(√2),and (1,1,1)/(√3).Study of dispersion relations with more neighbor interactions show that in some cases the results change physically.

  1. Growth, Nitrogen Vacancy Reduction and Solid Solution Formation in Cubic GaN Thin Films and the Subsequent Fabrication of Superlattice Structures Using AlN and InN

    Science.gov (United States)

    1990-07-01

    that the BGaN film remained predominantly single crystal, but shows both a normal cubic [110] pattern and a second hexagonal pattern [0110]. By contrast...27 Transmission electron microscopy (iEM) was used (Hitachi H-800) to more closely examine the microstructural evolution of the BN/ BGaN /GaN epitaxial...area diffraction (SAD) also showed the BGaN layer to be a mixture of cubic and wurtzitic phases. This layer was heavily faulted. The latter phenomenon

  2. Predicting the Crystal Structure and Phase Transitions in High-Entropy Alloys

    Science.gov (United States)

    King, D. M.; Middleburgh, S. C.; Edwards, L.; Lumpkin, G. R.; Cortie, M.

    2015-06-01

    High-entropy alloys (HEAs) have advantageous properties compared with other systems as a result of their chemistry and crystal structure. The transition between a face-centered cubic (FCC) and body-centered cubic (BCC) structure in the Al x CoCrFeNi high-entropy alloy system has been investigated on the atomic scale in this work. The Al x CoCrFeNi system, as well as being a useful system itself, can also be considered a model HEA material. Ordering in the FCC structure was investigated, and an order-disorder transition was predicted at ~600 K. It was found that, at low temperatures, an ordered lattice is favored over a truly random lattice. The fully disordered BCC structure was found to be unstable. When partial ordering was imposed (lowering the symmetry), with Al and Ni limited specific sites of the BCC system, the BCC packing was stabilized. Decomposition of the ordered BCC single phase into a dual phase (Al-Ni rich and Fe-Cr rich) is also considered.

  3. Fcc-bcc transition for Yukawa interactions determined by applied strain deformation

    OpenAIRE

    Hoy, Robert S.; Robbins, Mark O.

    2004-01-01

    Calculations of the work required to transform between bcc and fcc phases yield a high-precision bcc-fcc transition line for monodisperse point Yukawa (screened-Couloumb) systems. Our results agree qualitatively but not quantitatively with previously published simulations and phenomenological criteria for the bcc-fcc transition. In particular, the bcc-fcc-fluid triple point lies at a higher inverse screening length than previously reported.

  4. Cubic surfaces and their invariants: Some memories of Raymond Stora

    Directory of Open Access Journals (Sweden)

    Michel Bauer

    2016-11-01

    I then turn to the study of the family of cubic surfaces. They depend on 20 parameters, and the action of the 15 parameter group SL4(C splits the family in orbits depending on 5 parameters. This takes us into the realm of (geometric invariant theory. I review briefly the classical theorems on the structure of the ring of polynomial invariants and illustrate its many facets by looking at a simple example, before turning to the already involved case of cubic surfaces. The invariant ring was described in the 19th century. I show how to retrieve this description via counting/generating functions and character formulae.

  5. Effect of hydrotreating FCC feedstock on product distribution

    Energy Technology Data Exchange (ETDEWEB)

    Salazar-Sotelo, D.; Maya-Yescas, R.; Mariaca-Dominguez, E.; Rodriguez-Salomon, S.; Aguilera-Lopez, M. [Programa de Tratamiento de Crudo Maya, Instituto Mexicano del Petroleo, Lazaro Cardenas 152, San Bartolo Atepehuacan, 07730 Mexico, D.F. (Mexico)

    2004-11-24

    The demand of low-sulfur fuels has been increasing during the last 20 years due to environmental concerns about SO{sub x} emissions from processing plants and engines. Due to its high contribution to the gasoline pool, hydrotreating fluid catalytic cracking (FCC) feedstock offers several advantages, such as the increase of conversion and yields of gasoline and liquid-phase gas, meanwhile sulfur content in fuels is diminished. However, there are more important factors to be considered when hydrotreating FCC feedstock.In this work, two FCC feedstocks, typical and hydrotreated, were converted in a microactivity test (MAT) reactor, as described by ASTM D-3907-92, at different severities and using two commercial catalysts. Feedstock conversion, product yields and selectivity to valuable products were compared against industrial-scale results predicted by using commercial FCC simulation software. Expected increment in conversion and yield to profitable products was observed when hydrotreated feedstock was used; simulation results follow acceptably MAT results. Some recommendations are given for looking closely at the overall behavior (riser-regenerator), using reliable kinetic models and simulation programs.

  6. QCD and $\\gamma\\,\\gamma$ studies at FCC-ee

    CERN Document Server

    Skands, Peter

    2016-01-01

    The Future Circular Collider (FCC) is a post-LHC project aiming at searches for physics beyond the SM in a new 80--100~km tunnel at CERN. Running in its first phase as a very-high-luminosity electron-positron collider (FCC-ee), it will provide unique possibilities for indirect searches of new phenomena through high-precision tests of the SM. In addition, by collecting tens of ab$^{-1}$ integrated luminosity in the range of center-of-mass energies $\\sqrt{s}$~=90--350~GeV, the FCC-ee also offers unique physics opportunities for precise measurements of QCD phenomena and of photon-photon collisions through, literally, billions of hadronic final states as well as unprecedented large fluxes of quasireal $\\gamma$'s radiated from the $\\rm e^+e^-$ beams. We succinctly summarize the FCC-ee perspectives for high-precision extractions of the QCD coupling, for detailed analyses of parton radiation and fragmentation, and for SM and BSM studies through $\\gamma\\gamma$ collisions.

  7. Cross-twinning model of fcc crystal growth

    NARCIS (Netherlands)

    Waal, van de Benjamin W.

    1996-01-01

    The theory developed in 1960 by Wagner, Hamilton and Seidensticker (WHS-theory) to explain observed crystal growth phenomena in Ge is critically reviewed and shown to be capable of explaining preservation of ABC stacking order in two dimensions in fcc crystals of effectively spherical closed shell m

  8. FCC-hh Hadron Collider - Parameter Scenarios and Staging Options

    CERN Document Server

    Benedikt, Michael; Schulte, Daniel; Zimmermann, F; Syphers, M J

    2015-01-01

    FCC-hh is a proposed future energy-frontier hadron collider, based on dipole magnets with a field around 16 T installed in a new tunnel with a circumference of about 100 km, which would provide proton collisions at a centre-of-mass energy of 100 TeV, as well as heavy-ion collisions at the equivalent energy. The FCC-hh should deliver a high integrated proton-proton luminosity at the level of several 100 fb−1 per year, or more. The challenges for operating FCC-hh with high beam current and at high luminosity include the heat load from synchrotron radiation in a cold environment, the radiation from collision debris around the interaction region, and machine protection. In this paper, starting from the FCC-hh design baseline parameters we explore different approaches for increasing the integrated luminosity, and discuss the impact of key individual pa- rameters, such as the turnaround time. We also present some injector considerations and options for early hadron-collider operation.

  9. Deformation microstructure and orientation of F.C.C. crystals

    DEFF Research Database (Denmark)

    Liu, Q.; Hansen, N.

    1995-01-01

    The effect of crystallographic orientation on the microstructural evolution in f.c.c. metals with medium to high stacking fault energy is analyzed. This analysis is based on a literature review of the behaviour of single crystals and polycrystals supplemented with an experimental study of cold...

  10. An effective packing density of binary cubic crystals

    Science.gov (United States)

    Eremin, I. E.; Eremina, V. V.; Sychev, M. S.; Moiseenko, V. G.

    2015-04-01

    The methodology of effective macroscopic calculation of numerical values of internuclear distances in binary crystals of a cubic crystal system is based on the use of coefficients of the structural packing density of the crystal lattice. The possibility of combining the reference data on the main physicochemical parameters of the substance is implemented by synthesis of the corresponding mathematical models.

  11. Trapping of cubic ZnO nanocrystallites at ambient conditions

    DEFF Research Database (Denmark)

    Decremps, F.; Pellicer-Porres, J.; Datchi, F.

    2002-01-01

    Dense powder of nanocrystalline ZnO has been recovered at ambient conditions in the metastable cubic structure after a heat treatment at high pressure (15 GPa and 550 K). Combined x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) experiments have been performed to probe both long-ra...

  12. 47 CFR 97.27 - FCC modification of station license grant.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false FCC modification of station license grant. 97... RADIO SERVICES AMATEUR RADIO SERVICE General Provisions § 97.27 FCC modification of station license grant. (a) The FCC may modify a station license grant, either for a limited time or for the duration...

  13. Congress, the FCC and Children's Television Regulation: A Shift in the Balance of Power.

    Science.gov (United States)

    Markin, Karen

    The Federal Communications Commission (FCC) of the late 1980s appeared to pursue its own agenda of broadcast deregulation, notwithstanding congressional pressures. The apparent power shift is evident in a case study of the interactions between Congress and the FCC on the subject of children's television. In the early 1970s, the FCC tended to…

  14. 47 CFR 11.21 - State and Local Area plans and FCC Mapbook.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false State and Local Area plans and FCC Mapbook. 11... (EAS) General § 11.21 State and Local Area plans and FCC Mapbook. EAS plans contain guidelines which... are consistent with national plans, FCC regulations, and EAS operation. (a) The State plan...

  15. 47 CFR 73.1226 - Availability to FCC of station logs and records.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Availability to FCC of station logs and records... Availability to FCC of station logs and records. The following shall be made available to any authorized representative of the FCC upon request: (a) Station records and logs shall be made available for inspection...

  16. 47 CFR 0.409 - Commission policy on private printing of FCC forms.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Commission policy on private printing of FCC... ORGANIZATION General Information General § 0.409 Commission policy on private printing of FCC forms. The Commission has established a policy regarding the printing of blank FCC forms by private companies if...

  17. 76 FR 12308 - Modernizing the FCC Form 477 Data Program; Correction

    Science.gov (United States)

    2011-03-07

    ... COMMISSION 47 CFR Parts 1, 20, and 43 Modernizing the FCC Form 477 Data Program; Correction AGENCY: Federal... FCC Form 477. Inadvertently the Comment Filing Procedures section of the February 28, 2011 publication... February 28, 2011 (76 FR 10827) relating to the modernization of the FCC Form 477. The document (FR...

  18. Commercial Test of Multi-functional Desulfurizing Agent TS-01 for Gasoline in FCC Process

    Institute of Scientific and Technical Information of China (English)

    Cai Zhi; Wu Yingjian; Yu Weisheng

    2003-01-01

    Experimental use of multi-functional desulfurizing agent TS-01 for FCC gasoline in the FCC unitof SINOPEC Jiujiang Company shows that the multi-functional desulfurizing agent can effectivelyremove various kinds of sulfur in FCC gasoline and diesel fuel and fulfill passivation on heavy metals.

  19. A new hypercube variant: Fractal Cubic Network Graph

    Directory of Open Access Journals (Sweden)

    Ali Karci

    2015-03-01

    Full Text Available Hypercube is a popular and more attractive interconnection networks. The attractive properties of hypercube caused the derivation of more variants of hypercube. In this paper, we have proposed two variants of hypercube which was called as “Fractal Cubic Network Graphs”, and we have investigated the Hamiltonian-like properties of Fractal Cubic Network Graphs FCNGr(n. Firstly, Fractal Cubic Network Graphs FCNGr(n are defined by a fractal structure. Further, we show the construction and characteristics analyses of FCNGr(n where r=1 or r=2. Therefore, FCNGr(n is a Hamiltonian graph which is obtained by using Gray Code for r=2 and FCNG1(n is not a Hamiltonian Graph. Furthermore, we have obtained a recursive algorithm which is used to label the nodes of FCNG2(n. Finally, we get routing algorithms on FCNG2(n by utilizing routing algorithms on the hypercubes.

  20. Tetragonal and cubic zirconia multilayered ceramic constructs created by EPD.

    Science.gov (United States)

    Mochales, Carolina; Frank, Stefan; Zehbe, Rolf; Traykova, Tania; Fleckenstein, Christine; Maerten, Anke; Fleck, Claudia; Mueller, Wolf-Dieter

    2013-02-14

    The interest in electrophoretic deposition (EPD) for nanomaterials and ceramics production has widely increased due to the versatility of this technique to effectively combine different materials in unique shapes and structures. We successfully established an EPD layering process with submicrometer sized powders of Y-TZP with different mol percentages of yttrium oxide (3 and 8%) and produced multilayers of alternating tetragonal and cubic phases with a clearly defined interface. The rationale behind the design of these multilayer constructs was to optimize the properties of the final ceramic by combining the high mechanical toughness of the tetragonal phase of zirconia together with the high ionic conductivity of its cubic phase. In this work, a preliminary study of the mechanical properties of these constructs proved the good mechanical integrity of the multilayered constructs obtained as well as crack deflection in the interface between tetragonal and cubic zirconia layers.

  1. FCC-hh final-focus for flat-beams: parameters and energy deposition studies

    CERN Document Server

    Abelleira, Jose; Seryi, Andrei; Van Riesen-Haupt, Leon; Besana, Maria Ilaria

    2017-01-01

    The international Future Circular Collider (FCC) study comprises the study of a new scientific structure in a tunnel of 100 km. This will allow the installation of two accelerators, a 45.6–175 GeV lepton collider and a 100-TeV hadron collider. An optimized design of a final-focus system for the hadron collider is presented here. The new design is more compact and enables unequal ${\\beta}$$^{∗}$ in both planes, whose choice is justified here. This is followed by energy deposition studies, where the total dose in the magnets as a consequence of the collision debris is evaluated.

  2. Energy of the Isolated Metastable Iron-Nickel FCC Nanocluster with a Carbon Atom in the Tetragonal Interstice.

    Science.gov (United States)

    Bondarenko, Natalya V; Nedolya, Anatoliy V

    2017-12-01

    The energy of the isolated iron-nickel nanocluster was calculated by molecular mechanics method using Lennard-Jones potential. The cluster included a carbon atom that drifted from an inside octahedral interstice to a tetrahedral interstice in [Formula: see text] direction and after that in direction to the surface. In addition, one of 14 iron atoms was replaced by a nickel atom, the position of which was changing during simulation.The energy of the nanocluster was estimated at the different interatomic distances. As a result of simulation, the optimal interatomic distances of Fe-Ni-C nanocluster was chosen for the simulation, in which height of the potential barrier was maximal and face-centered cubic (FCC) nanocluster was the most stable.It is shown that there were three main positions of a nickel atom that significantly affected nanocluster's energy.The calculation results indicated that position of the carbon atom in the octahedral interstice was more energetically favorable than tetrahedral interstice in the case of FCC nanocluster. On the other side, the potential barrier was smaller in the direction [Formula: see text] than in the direction .This indicates that there are two ways for carbon atom to drift to the surface of the nanocluster.

  3. Capturing dynamic cation hopping in cubic pyrochlores

    Science.gov (United States)

    Brooks Hinojosa, Beverly; Asthagiri, Aravind; Nino, Juan C.

    2011-08-01

    In direct contrast to recent reports, density functional theory predicts that the most stable structure of Bi2Ti2O7 pyrochlore is a cubic Fd3¯m space group by accounting for atomic displacements. The displaced Bi occupies the 96g(x,x,z) Wyckoff position with six equivalent sites, which create multiple local minima. Using nudged elastic band method, the transition states of Bi cation hopping between equivalent minima were investigated and an energy barrier between 0.11 and 0.21 eV was determined. Energy barriers associated with the motion of Bi between equivalent sites within the 96g Wyckoff position suggest the presence of dielectric relaxation in Bi2Ti2O7.

  4. Tame Kernels of Pure Cubic Fields

    Institute of Scientific and Technical Information of China (English)

    Xiao Yun CHENG

    2012-01-01

    In this paper,we study the p-rank of the tame kernels of pure cubic fields.In particular,we prove that for a fixed positive integer m,there exist infinitely many pure cubic fields whose 3-rank of the tame kernel equal to m.As an application,we determine the 3-rank of their tame kernels for some special pure cubic fields.

  5. Two-dimensional cubic convolution.

    Science.gov (United States)

    Reichenbach, Stephen E; Geng, Frank

    2003-01-01

    The paper develops two-dimensional (2D), nonseparable, piecewise cubic convolution (PCC) for image interpolation. Traditionally, PCC has been implemented based on a one-dimensional (1D) derivation with a separable generalization to two dimensions. However, typical scenes and imaging systems are not separable, so the traditional approach is suboptimal. We develop a closed-form derivation for a two-parameter, 2D PCC kernel with support [-2,2] x [-2,2] that is constrained for continuity, smoothness, symmetry, and flat-field response. Our analyses, using several image models, including Markov random fields, demonstrate that the 2D PCC yields small improvements in interpolation fidelity over the traditional, separable approach. The constraints on the derivation can be relaxed to provide greater flexibility and performance.

  6. The most stable mono-layers of (111)-Pt (fcc) on Graphene: A first-principles GGA study

    Science.gov (United States)

    Otalora-Acevedo, J.; Rodríguez Martínez, J. A.; Moreno-Armenta, G.; Vera, E.; Takeuchi Tan, N.

    2016-08-01

    We investigate monolayers of planes (111) of Pt in the FCC structure located on graphene. The energy of formation showed that the most stable structure is √3×√3 — Pt on 2 × 2 — graphene. This system has a mismatch in the lattice constant of 0.45. The layers are completely flat, and its band structure shows that the new structure is metallic and the Dirac's cones are displaced 0.6eV above of the Fermi level. In this work we present the dependence of the enthalpy of formation of these structures and we calculated all structural parameters of their relaxation.

  7. Pressure-induced fcc to hcp phase transition in Ni-based high entropy solid solution alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, F. X.; Zhao, Shijun; Jin, Ke; Bei, H.; Popov, D.; Park, Changyong; Neuefeind, J. C.; Weber, W. J.; Zhang, Yanwen [Tennessee-K; (ORNL); (CIW)

    2017-01-04

    A pressure-induced phase transition from the fcc to a hexagonal close-packed (hcp) structure was found in NiCoCrFe solid solution alloy starting at 13.5 GPa. The phase transition is very sluggish and the transition did not complete at ~40 GPa. The hcp structure is quenchable to ambient pressure. Only a very small amount (<5%) of hcp phase was found in the isostructural NiCoCr ternary alloy up to the pressure of 45 GPa and no obvious hcp phase was found in NiCoCrFePd system till to 74 GPa. Ab initio Gibbs free energy calculations indicated the energy differences between the fcc and the hcp phases for the three alloys are very small, but they are sensitive to temperature. The critical transition pressure in NiCoCrFe varies from ~1 GPa at room temperature to ~6 GPa at 500 K.

  8. The structure and surface energy of Ni{sub 80}Fe{sub 20} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yuan-Tsung, E-mail: ytchen@yuntech.edu.tw; Chen, Chin-Wu; Wu, Te-Ho

    2015-10-01

    Highlights: • X-ray diffraction patterns indicated NiFe thin films exhibited a face-centred cubic (FCC) structural. • NiFe films were more crystalline after postannealing treatment than they were after RT treatment. • NiFe films formed a contact angle of <90°, which indicated that the NiFe films were hydrophilic. • The surface energy was associated with the crystallinity of the thin films. • NiFe thin films exhibit low surface-energy characteristics that can produce a self-cleaning effect. - Abstract: In this study, NiFe thin films were deposited on a glass substrate at room temperature (RT) or postannealed at 150 and 250 °C for 1 h; the Ni{sub 80}Fe{sub 20} films were 300–1500 Å thick. The structure, surface energy, and average contact angle properties of the NiFe thin films were investigated. X-ray diffraction (XRD) results demonstrated that the NiFe thin films exhibited a face-centred cubic (FCC) structural state. The XRD results also revealed that the NiFe films were more crystalline after post-annealing treatment than they were after RT treatment alone, suggesting that the NiFe crystalline structure exhibited FCC (1 1 1) texturing. The NiFe films formed a contact angle of <90° with the test liquids water and diiodomethane, which indicated that the NiFe films were hydrophilic. The surface energy of the NiFe thin films decreased when post-annealing treatment was used and their thickness was increased from 60.4 to 47.9 mJ/mm{sup 2}, suggesting that the surface energy was associated with the crystallinity of the thin films. Therefore, these NiFe thin films exhibit low surface-energy characteristics that can produce a self-cleaning effect.

  9. Cubic liquid crystalline nanoparticles: optimization and evaluation for ocular delivery of tropicamide.

    Science.gov (United States)

    Verma, Purnima; Ahuja, Munish

    2016-10-01

    The purpose of this study was to investigate the potential of cubic liquid crystalline nanoparticles for ocular delivery of tropicamide. Ultrasound-assisted fragmentation of cubic liquid crystalline bulk phases resulted in cubic liquid crystalline nanoparticles employing Pluronic F127 as dispersant. The effects of process variables such as sonication time, sonication amplitude, sonication depth, and pre-mixing time on particle size and polydispersity index was investigated using central composite design. The morphology of tropicamide-loaded nanoparticles was found to be nearly cubical in shape by transmission electron microscopy observation. Further, small angle X-ray scattering experiment confirmed the presence of D and P phase cubic structures in coexistence. The optimized tropicamide-loaded cubic nanoparticles showed in vitro corneal permeation of tropicamide across isolated porcine cornea comparable to its commercial preparation, Tropicacyl®. Ocular tolerance was evaluated by Hen's egg-chorioallantoic membrane test and histological studies. The results of in vivo mydriatic response study demonstrated a remarkably higher area under mydriatic response curve (AUC0→1440 min) values of cubic nanoparticles over Tropicacyl® indicating better therapeutic value of cubic nanoparticles. Furthermore, tropicamide-loaded cubic nanoparticles exhibited prolonged mydriatic effect on rabbits as compared to commercial conventional aqueous ophthalmic solution.

  10. Reducibility, heats of re-oxidation, and structure of vanadia supported on TiO{sub 2} and TiO{sub 2}-Al{sub 2}O{sub 3} supports used as vanadium traps in FCC

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Silvia [CIEP/Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, Av. Dr. Manuel Nava 6, Zona Universitaria, CP 78210 San Luis Potosi, SLP Mexico (Mexico); Morales, Rosario [CIEP/Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, Av. Dr. Manuel Nava 6, Zona Universitaria, CP 78210 San Luis Potosi, SLP Mexico (Mexico); Cardenas-Galindo, Maria Guadalupe [CIEP/Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, Av. Dr. Manuel Nava 6, Zona Universitaria, CP 78210 San Luis Potosi, SLP Mexico (Mexico); Rodriguez, A. Gabriel [Instituto de Investigaciones en Comunicaciones y Opticas, Universidad Autonoma de San Luis Potosi, Av. Karakorum 1470, CP 78216 San Luis Potosi, SLP Mexico (Mexico); Pedraza, Francisco [Instituto Mexicano del Petroleo, Eje Centrale Lazaro Cardenas 152, Col. San Bartolo Atepehuacan, Delg. Gustavo I. Madero, Mexico DF 07730 (Mexico); Handy, Brent E. [CIEP/Facultad de Ciencias Quimicas, Universidad Autonoma de San Luis Potosi, Av. Dr. Manuel Nava 6, Zona Universitaria, CP 78210 San Luis Potosi, SLP Mexico (Mexico)]. E-mail: handy@uaslp.mx

    2005-08-15

    V/TiO{sub 2} and V/TiO{sub 2}-Al{sub 2}O{sub 3} (1:1 w/w basis) supports were characterized by TPR, Raman spectroscopy, and heats of re-oxidation of samples pre-reduced in CO at 770 K with a heat-flow calorimeter. Supports were pure anatase or rutile dispersed with hydrated aluminas (boehmite, gibbsite, bayerite) subsequently calcined at 870 K. Raman spectroscopy of fully oxidized, air-exposed samples show the presence of polymeric polyvanadate species, but not of isolated monomeric species. Sample loadings were 4 wt.% and show different reduction and structural features. During TPR, vanadia reduced to V(III) and V(IV) in V/rutile and V/anatase, respectively, and multiple reduction peaks were observed due to crystalline V{sub 2}O{sub 5} and amorphous vanadia. In V/TiO{sub 2}-Al{sub 2}O{sub 3} samples, vanadium coverages were 6-8 {mu}mol V m{sup -2} yielding well-dispersed, amorphous vanadia. Trends observed during TPR were: addition of bayerite phase to anatase or rutile increases H{sub 2} consumption by 100%, implying formation of V(III) and V(II), respectively. However, with addition of boehmite or gibbsite to either titania phase, vanadia reduces only to V(IV). Oxygen doses at 473 K of pre-reduced samples titrated about one-third of total vanadia content. Re-oxidation heat values range from 400 to 500 kJ mol{sup -1} O{sub 2} and represent oxygen-vanadium ion bond strengths within the dispersed vanadia. The heat values are higher than expected for re-oxidation of a bulk phase, and are indicative of the degree of stabilization provided by the support.

  11. Proceedings, High-Precision $\\alpha_s$ Measurements from LHC to FCC-ee

    Energy Technology Data Exchange (ETDEWEB)

    d' Enterria, David [CERN; Skands, Peter Z. [Monash U.

    2015-01-01

    This document provides a writeup of all contributions to the workshop on "High precision measurements of $\\alpha_s$: From LHC to FCC-ee" held at CERN, Oct. 12--13, 2015. The workshop explored in depth the latest developments on the determination of the QCD coupling $\\alpha_s$ from 15 methods where high precision measurements are (or will be) available. Those include low-energy observables: (i) lattice QCD, (ii) pion decay factor, (iii) quarkonia and (iv) $\\tau$ decays, (v) soft parton-to-hadron fragmentation functions, as well as high-energy observables: (vi) global fits of parton distribution functions, (vii) hard parton-to-hadron fragmentation functions, (viii) jets in $e^\\pm$p DIS and $\\gamma$-p photoproduction, (ix) photon structure function in $\\gamma$-$\\gamma$, (x) event shapes and (xi) jet cross sections in $e^+e^-$ collisions, (xii) W boson and (xiii) Z boson decays, and (xiv) jets and (xv) top-quark cross sections in proton-(anti)proton collisions. The current status of the theoretical and experimental uncertainties associated to each extraction method, the improvements expected from LHC data in the coming years, and future perspectives achievable in $e^+e^-$ collisions at the Future Circular Collider (FCC-ee) with $\\cal{O}$(1--100 ab$^{-1}$) integrated luminosities yielding 10$^{12}$ Z bosons and jets, and 10$^{8}$ W bosons and $\\tau$ leptons, are thoroughly reviewed. The current uncertainty of the (preliminary) 2015 strong coupling world-average value, $\\alpha_s(m_Z)$ = 0.1177 $\\pm$ 0.0013, is about 1\\%. Some participants believed this may be reduced by a factor of three in the near future by including novel high-precision observables, although this opinion was not universally shared. At the FCC-ee facility, a factor of ten reduction in the $\\alpha_s$ uncertainty should be possible, mostly thanks to the huge Z and W data samples available.

  12. The fcc-bcc crystallographic orientation relationship in AlxCoCrFeNi high-entropy alloys

    NARCIS (Netherlands)

    Rao, J. C.; Ocelik, V.; Vainchtein, D.; Tang, Z.; Liaw, P. K.; De Hosson, J. Th. M.

    2016-01-01

    This paper concentrates on the crystallographic-orientation relationship between the various phases in the Al-Co-Cr-Fe-Ni high-entropy alloys. Two types of orientation relationships of bcc phases (some with ordered B2 structures) and fcc matrix were observed in Al0.5CoCrFeNi and Al0.7CoCrFeNi alloys

  13. Cubic surfaces and their invariants: Some memories of Raymond Stora

    Science.gov (United States)

    Bauer, Michel

    2016-11-01

    Cubic surfaces embedded in complex projective 3-space are a classical illustration of the use of old and new methods in algebraic geometry. Recently, they made their appearance in physics, and in particular aroused the interest of Raymond Stora, to the memory of whom these notes are dedicated, and to whom I'm very much indebted. Each smooth cubic surface has a rich geometric structure, which I review briefly, with emphasis on the 27 lines and the combinatorics of their intersections. Only elementary methods are used, relying on first order perturbation/deformation theory. I then turn to the study of the family of cubic surfaces. They depend on 20 parameters, and the action of the 15 parameter group SL4 (C) splits the family in orbits depending on 5 parameters. This takes us into the realm of (geometric) invariant theory. I review briefly the classical theorems on the structure of the ring of polynomial invariants and illustrate its many facets by looking at a simple example, before turning to the already involved case of cubic surfaces. The invariant ring was described in the 19th century. I show how to retrieve this description via counting/generating functions and character formulae.

  14. Cubical local partial orders on cubically subdivided spaces - Existence and construction

    DEFF Research Database (Denmark)

    Fajstrup, Lisbeth

    2006-01-01

    The geometric models of higher dimensional automata (HDA) and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...

  15. Cubical local partial orders on cubically subdivided spaces - existence and construction

    DEFF Research Database (Denmark)

    Fajstrup, Lisbeth

    The geometric models of Higher Dimensional Automata and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...

  16. Lipidic cubic phase injector facilitates membrane protein serial femtosecond crystallography.

    Science.gov (United States)

    Weierstall, Uwe; James, Daniel; Wang, Chong; White, Thomas A; Wang, Dingjie; Liu, Wei; Spence, John C H; Bruce Doak, R; Nelson, Garrett; Fromme, Petra; Fromme, Raimund; Grotjohann, Ingo; Kupitz, Christopher; Zatsepin, Nadia A; Liu, Haiguang; Basu, Shibom; Wacker, Daniel; Han, Gye Won; Katritch, Vsevolod; Boutet, Sébastien; Messerschmidt, Marc; Williams, Garth J; Koglin, Jason E; Marvin Seibert, M; Klinker, Markus; Gati, Cornelius; Shoeman, Robert L; Barty, Anton; Chapman, Henry N; Kirian, Richard A; Beyerlein, Kenneth R; Stevens, Raymond C; Li, Dianfan; Shah, Syed T A; Howe, Nicole; Caffrey, Martin; Cherezov, Vadim

    2014-01-01

    Lipidic cubic phase (LCP) crystallization has proven successful for high-resolution structure determination of challenging membrane proteins. Here we present a technique for extruding gel-like LCP with embedded membrane protein microcrystals, providing a continuously renewed source of material for serial femtosecond crystallography. Data collected from sub-10-μm-sized crystals produced with less than 0.5 mg of purified protein yield structural insights regarding cyclopamine binding to the Smoothened receptor.

  17. CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS

    Institute of Scientific and Technical Information of China (English)

    Karnal H.Yasir; TANG Yun

    2002-01-01

    In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented. This classification is an extension of the result given by Takens to the cubic homogeneous parameterized vector fields with six parameters.

  18. CLASSIFICATION OF CUBIC PARAMETERIZED HOMOGENEOUS VECTOR FIELDS

    Institute of Scientific and Technical Information of China (English)

    KamalH.Yasir; TNAGYun

    2002-01-01

    In this paper the cubic homogeneous parameterized vector fields are studied.The classification of the phase portrait near the critical point is presented.This classification is an extension of the result given by takens to the cubic homogeneous parameterized vector fields with six parameters.

  19. The FCC-ee design study: luminosity and beam polarization

    CERN Document Server

    Koratzinos, M

    2015-01-01

    The FCC-ee accelerator is considered within the FCC design study as a possible first step towards the ultimate goal of a 100 TeV hadron collider. It is a high luminosity e+e- storage ring collider, designed to cover energies of around 90, 160, 240 and 350GeV ECM (for the Z peak, the WW threshold, the ZH and ttbar cross-section maxima respectively) leading to different operating modes. We report on the current status of the design study, on the most promising concepts and relevant challenges. The expected luminosity performance at all energies, and first studies on transverse polarization for beam energy calibrations will be presented.

  20. Martensitic transformation fcc(γ)→hcp(ε)

    Institute of Scientific and Technical Information of China (English)

    徐祖耀

    1997-01-01

    Criteria of the thermoelastic martensitic transformation are suggested, on the basis of which the martensitic transformation fcc(γ)→hcp(ε) in Fe-Mn-Si based alloys is classified as a semi-thermoelastic transformation In contrast with the martensitic transformation fcc(γ)→bct(bcc)α’ in iron-based alloys, the thermoelastic transformation in Cu-based alloys and the t→m transformation in ceramics containing ZrO2, in γ→ε of Fe-Mn-Si, the strengthening and grain size of the parent phase will not markedly affecl the Ms and the internal friction peak indicating the martensitic Transformation does not correspond to a significant lowering of the elastic modulus, implying that the nucleation of ε-martensite may occur directly through the stacking fault and may not strongly depend on soft mode. A comparison between the thermal and stress induced ε martensites is made and a brief discussion is given.

  1. Preparation of hcp and fcc Ni and Ni/NiO Nanoparticles Using a Citric Acid Assisted Pechini-Type Method

    Directory of Open Access Journals (Sweden)

    L. A. García-Cerda

    2011-01-01

    Full Text Available The preparation and characterization of hcp and fcc Ni and Ni/NiO nanoparticles is reported. Ni and Ni/NiO nanoparticles were obtained starting from a precursor material prepared using a citric assisted Pechini-type method and, then, followed by a calcination of the precursor in air at either 400 or 600°C for different times. The precursor was analyzed using thermogravimetric and differential thermal methods (TGA-DTA, and the resulting nanoparticles were characterized by X-ray diffraction (XRD, high-resolution transmission electron microscopy (HRTEM, and vibrational sample magnetometry. Nanoparticles showed a phase transformation for Ni from hcp to fcc and/or to fcc NiO structure as the calcination time increased. The influence of the phase transition and the formation of NiO on the magnetic properties of the samples are discussed.

  2. Advance on dynamic aperture at injection for FCC-hh

    CERN Document Server

    Dalena, Barbara; Chance, Antoine

    2017-01-01

    In the Hadron machine option, proposed in the context of the Future Circular Colliders (FCC) study, the first evaluation of dipole field quality, based on the Nb$_{3}$Sn technology, has shown a Dynamic Aperture at injection above the LHC target value. In this paper the effect of field imperfections on the dynamic aperture, using the updated lattice design, is presented. Tolerances on the main multipole components are evaluated including feed-down effect.

  3. FCC-ee final focus with chromaticity correction

    CERN Document Server

    Garcia, H; Tomás, R

    2014-01-01

    A 100 km circular electron-positron collider is considered as one of the possible future high energy facilities. In order to achieve a high luminosity, strong beam focusing at the Interaction Point (IP) is used requiring the correction of the chromatic aberrations. In this paper we study preliminary designs of a Final Focus System (FFS) for the FCC-ee collider with chromatic correction. Beam orbit stability and dynamic aperture calculations are also presented.

  4. Volume variation of Gruneisen parameters of fcc transition metals

    Indian Academy of Sciences (India)

    C V Pandya; P R Vyas; T C Pandya; V B Gohel

    2002-02-01

    The volume variation of the Gruneisen parameters of ten fcc transition metals, up to 40% compression, has been studied on the basis of a model approach proposed by Antonov et al. The results are reasonably good for six metals except for Rh, Ag, Au and Ni when compared with available experimental and other theoretical values. The model requires an appropriate modification for Rh, Ag, Au and Ni.

  5. Dynamic Aperture Studies for the FCC-ee

    CERN Document Server

    Medina, L; Tomas, R; Zimmermann, F

    2015-01-01

    Dynamic aperture (DA) studies have been conducted on the latest Future Circular Collider – ee (FCC-ee) lattices as a function of momentum deviation.Two different schemes for the interaction region are used, which are connected to the main arcs: the crab waist approach, developed by BINP, and an update to the CERN design where the use of crab cavities is envisioned. The results presented show an improvement in the performance of both designs.

  6. Physics Perspectives for a Future Circular Collider: FCC-ee

    CERN Document Server

    CERN. Geneva

    2017-01-01

    The lectures will briefly discuss the parameters of a Future Circular Collider, before addressing in detail the physics perspectives and the challenges for the experiments and detector systems. The main focus will be on ee and pp collisions, but opportunities for e—p physics will also be covered. The FCC physics perspectives will be presented with reference to the ongoing LHC programme, including the physics potential from future upgrades to the LHC in luminosity and possibly energy.  

  7. First results for a FCC-hh ring optics design

    CERN Document Server

    Chance, Antoine; Payet, Jacques; Alemany Fernandez, Reyes; Holzer, Bernhard; Schulte, Daniel

    2015-01-01

    The first order considerations of the optics for the FCC-hh ring are presented. The arc cell is generated taking into account some general considerations like the whole circumference, maximum gradients and lengths of the elements in the cell. The integration of the insertion regions started. Three types of Dispersion Suppressors (DIS) are studied. The sensitivity of the arc parameters to these layout considerations is studied in more detail. An alternative layout is shown as well.

  8. Highly anisotropic exchange interactions of jeff=1/2 iridium moments on the fcc lattice in La2B IrO6 (B =Mg ,Zn )

    Science.gov (United States)

    Aczel, A. A.; Cook, A. M.; Williams, T. J.; Calder, S.; Christianson, A. D.; Cao, G.-X.; Mandrus, D.; Kim, Yong-Baek; Paramekanti, A.

    2016-06-01

    We have performed inelastic neutron scattering (INS) experiments to investigate the magnetic excitations in the weakly distorted face-centered-cubic (fcc) iridate double perovskites La2ZnIrO6 and La2MgIrO6 , which are characterized by A-type antiferromagnetic ground states. The powder inelastic neutron scattering data on these geometrically frustrated jeff=1/2 Mott insulators provide clear evidence for gapped spin-wave excitations with very weak dispersion. The INS results and thermodynamic data on these materials can be reproduced by conventional Heisenberg-Ising models with significant uniaxial Ising anisotropy and sizeable second-neighbor ferromagnetic interactions. Such a uniaxial Ising exchange interaction is symmetry forbidden on the ideal fcc lattice, so that it can only arise from the weak crystal distortions away from the ideal fcc limit. This may suggest that even weak distortions in jeff=1/2 Mott insulators might lead to strong exchange anisotropies. More tantalizingly, however, we find an alternative viable explanation of the INS results in terms of spin models with a dominant Kitaev interaction. In contrast to the uniaxial Ising exchange, the highly directional Kitaev interaction is a type of exchange anisotropy which is symmetry allowed even on the ideal fcc lattice. The Kitaev model has a magnon gap induced by quantum order by disorder, while weak anisotropies of the Kitaev couplings generated by the symmetry lowering due to lattice distortions can pin the order and enhance the magnon gap. Our findings highlight how even conventional magnetic orders in heavy transition metal oxides may be driven by highly directional exchange interactions rooted in strong spin-orbit coupling.

  9. Beam Optics for FCC-ee Collider Ring

    CERN Document Server

    Oide, Katsunobu; Aumon, S; Benedikt, M; Blondel, A; Bogomyagkov, A V; Boscolo, M; Burkhardt, H; Cai, Y; Doblhammer, A; Haerer, B; Holzer, B; Koop, I; Koratzinos, M; Jowett, John M; Levichev, E B; Medina, L; Ohmi, K; Papaphilippou, Y; Piminov, P A; Shatilov, D N; Sinyatkin, S V; Sullivan, M; Wenninger, J; Wienands, U; Zhou, D; Zimmermann, F

    2017-01-01

    A beam optics scheme has been designed [ 1 ] for the Future Circular Collider- e + e − (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme [ 2 ] with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So- called “tapering" of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) [ 3 ] as clos...

  10. Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

    Energy Technology Data Exchange (ETDEWEB)

    Adeyiga, Adeyinka

    2010-02-05

    Commercial spent fluid catalytic cracking (FCC) catalysts provided by Engelhard and Albemarle were used as supports for Fe-based catalysts with the goal of improving the attrition resistance of typical F-T catalysts. Catalysts with the Ruhrchemie composition (100 Fe/5 Cu/4.2 K/25 spent FCC on mass basis) were prepared by wet impregnation. XRD and XANES analysis showed the presence of Fe{sub 2}O{sub 3} in calcined catalysts. FeC{sub x} and Fe{sub 3}O{sub 4} were present in the activated catalysts. The metal composition of the catalysts was analyzed by ICP-MS. F-T activity of the catalysts activated in situ in CO at the same conditions as used prior to the attrition tests was measured using a fixed bed reactor at T = 573 K, P = 1.38 MPa and H{sub 2}:CO ratio of 0.67. Cu and K promoted Fe supported over Engelhard provided spent FCC catalyst shows relatively good attrition resistance (8.2 wt% fines lost), high CO conversion (81%) and C{sub 5}+ hydrocarbons selectivity (18.3%).

  11. Nonlinear optical imaging of defects in cubic silicon carbide epilayers.

    Science.gov (United States)

    Hristu, Radu; Stanciu, Stefan G; Tranca, Denis E; Matei, Alecs; Stanciu, George A

    2014-06-11

    Silicon carbide is one of the most promising materials for power electronic devices capable of operating at extreme conditions. The widespread application of silicon carbide power devices is however limited by the presence of structural defects in silicon carbide epilayers. Our experiment demonstrates that optical second harmonic generation imaging represents a viable solution for characterizing structural defects such as stacking faults, dislocations and double positioning boundaries in cubic silicon carbide layers. X-ray diffraction and optical second harmonic rotational anisotropy were used to confirm the growth of the cubic polytype, atomic force microscopy was used to support the identification of silicon carbide defects based on their distinct shape, while second harmonic generation microscopy revealed the detailed structure of the defects. Our results show that this fast and noninvasive investigation method can identify defects which appear during the crystal growth and can be used to certify areas within the silicon carbide epilayer that have optimal quality.

  12. Bulk Nanostructured FCC Steels With Enhanced Radiation Tolerance

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xinghang; Hartwig, K. Ted; Allen, Todd; Yang, Yong

    2012-10-27

    The objective of this project is to increase radiation tolerance in austenitic steels through optimization of grain size and grain boundary (GB) characteristics. The focus will be on nanocrystalline austenitic Fe-Cr-Ni alloys with an fcc crystal structure. The long-term goal is to design and develop bulk nanostructured austenitic steels with enhanced void swelling resistance and substantial ductility, and to enhance their creep resistance at elevated temperatures via GB engineering. The combination of grain refinement and grain boundary engineering approaches allows us to tailor the material strength, ductility, and resistance to swelling by 1) changing the sink strength for point defects, 2) by increasing the nucleation barriers for bubble formation at GBs, and 3) by changing the precipitate distributions at boundaries. Compared to ferritic/martensitic steels, austenitic stainless steels (SS) possess good creep and fatigue resistance at elevated temperatures, and better toughness at low temperature. However, a major disadvantage of austenitic SS is that they are vulnerable to significant void swelling in nuclear reactors, especially at the temperatures and doses anticipated in the Advanced Burner Reactor. The lack of resistance to void swelling in austenitic alloys led to the switch to ferritic/martensitic steels as the preferred material for the fast reactor cladding application. Recently a type of austenitic stainless steel, HT-UPS, was developed at ORNL, and is expected to show enhanced void swelling resistance through the trapping of point defects at nanometersized carbides. Reducing the grain size and increasing the fraction of low energy grain boundaries should reduce the available radiation-produced point defects (due to the increased sink area of the grain boundaries), should make bubble nucleation at the boundaries less likely (by reducing the fraction of high-energy boundaries), and improve the strength and ductility under radiation by producing a higher

  13. Pressure Profile in the experimental area of FCC-hh and FCC-ee calculated by an analytical code

    CERN Multimedia

    Aichinger, Ida

    2017-01-01

    Ultra high vacuum in the beam pipe is a basic requirement for the Future Circular Colliders (FCC). The dimension of the FCC and the high energy of the particles will make this requirement challenging. Simulations that predict the vacuum quality due to material and beam induced effects will allow to evaluate different designs and to choose an optimal solution. The mathematical model behind the simulations will be shown. Four coupled differential equations describe the mass conservation of the residual gas particles in the beam pipe. The sinks include all kind of distributed and local pumping. The sources are caused by synchrotron radiation, electron clouds, thermal outgassing and ion-induced desorption. The equation system is solved by an analytical method. This requires a transformation to first order equations for which a general valid solution exists. Adding a particular solution and the inclusion of appropriate boundary conditions define the solution function. The big advantage here is that an analytical...

  14. The compressibility of cubic white and orthorhombic, rhombohedral, and simple cubic black phosphorus

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Simon M; Zaug, Joseph

    2010-03-10

    The effect of pressure on the crystal structure of white phosphorus has been studied up to 22.4 GPa. The ?alpha phase was found to transform into the alpha' phase at 0.87 +- 0.04 GPa with a volume change of 0.1 +- 0.3 cc/mol. A fit of a second order Birch- Murnaghan equation to the data gave Vo = 16.94 ? 0.08 cc/mol and Ko = 6.7 +- 0.5 GPa for the alpha phase and Vo = 16.4 +- 0.1 cc/mol and Ko = 9.1 +- 0.3 GPa for the alpha' phase. The alpha' phase was found to transform to the A17 phase of black phosphorus at 2.68 +- 0.34 GPa and then with increasing pressure to the A7 and then simple cubic phase of black phosphorus. A fit of a second order Birch-Murnaghan equation to our data combined with previous measurements gave Vo = 11.43 +- 0.05 cc/mol and Ko = 34.7 +- 0.5 GPa for the A17 phase, Vo = 9.62 +- 0.01 cc/mol and Ko = 65.0 +- 0.6 GPa for the A7 phase and , Vo = 9.23 +- 0.01 cc/mol and Ko = 72.5 +- 0.3 GPa for the simple cubic phase.

  15. Cubic III-nitrides: potential photonic materials

    Science.gov (United States)

    Onabe, K.; Sanorpim, S.; Kato, H.; Kakuda, M.; Nakamura, T.; Nakamura, K.; Kuboya, S.; Katayama, R.

    2011-01-01

    The growth and characterization of some cubic III-nitride films on suitable cubic substrates have been done, namely, c- GaN on GaAs by MOVPE, c-GaN and c-AlGaN on MgO by RF-MBE, and c-InN and c-InGaN (In-rich) on YSZ by RFMBE. This series of study has been much focused on the cubic-phase purity as dependent on the respective growth conditions and resulting electrical and optical properties. For c-GaN and c-InN films, a cubic-phase purity higher than 95% is attained in spite of the metastable nature of the cubic III-nitrides. However, for c-AlGaN and c-InGaN films, the cubic-phase purity is rapidly degraded with significant incorporation of the hexagonal phase through stacking faults on cubic {111} faces which may be exposed on the roughened growing or substrate surface. It has been shown that the electron mobilities in c-GaN and c-AlGaN films are much related to phase purity.

  16. Consistent Analytic Embedded Atom Potential for Face-Centered Cubic Metals and Alloys

    Institute of Scientific and Technical Information of China (English)

    Iyad A. Hijazi; Young Ho Park

    2009-01-01

    A consistent empirical embedded-atom potential that includes a long range force was developed for fcc (face-centered cubic) metals and alloys. The proposed potential for pure metals does not require modification of the initial function form when being applied to alloy systems. The potential parameters of this model were determined by fitting lattice constant, three elastic constants, cohesive energy, and vacancy formation energies of the pure metals and the heats of solution of the binary alloys via an optimization technique. Parameters for Ag, Al, Au, Cu, Ni, Pd and Pt were obtained. The obtained parameters were used to calculate the bulk modulus, divacancy formation energy, crystal stability, stacking fault energy, vacancy migration energy, and melting point for each pure metal and the heats of formation and lattice constants for binary alloys. The predicted values were in good agreement with experimental results.

  17. Evaluation of multiaxial stress in textured cubic films by x-ray diffraction

    Institute of Scientific and Technical Information of China (English)

    Zhang Jian-Min; Xu Ke-Wei

    2005-01-01

    X-ray diffraction is used extensively to determine the residual stress in bulk or thin film materials on the assumptions that the material is composed of fine crystals with random orientation and the stress state is biaxial and homogeneous through the x-ray penetrating region. The stress is calculated from the gradient of ε~ sin2 ψ linear relation. But the method cannot be used in textured films due to nonlinear relation. In this paper, a novel method is proposed for measuring the multiaxial stresses in cubic films with any [hkl] fibre texture. As an example, a detailed analysis is given for measuring three-dimensional stresses in FCC films with [111] fibre texture.

  18. Recycling polystyrene into fuels by means of FCC. Performance of various acidic catalysts

    Energy Technology Data Exchange (ETDEWEB)

    De la Puente, Gabriela; Sedran, Ulises [Instituto de Investigaciones en Catalisis y Petroquimica, INCAPE, Santiago del Estero 2654, 3000 Santa Fe (Argentina)

    1998-12-07

    In accordance with the option of recycling plastics into fuels by dissolving them in standard feedstocks for the process of catalytic cracking of hydrocarbons, FCC, various acidic catalysts (zeolites ZSM-5, mordenite, Y, and a sulfur-promoted zirconia) were tested in the conversion of polystyrene dissolved into inert benzene at 550C in a fluidized-bed batch reactor. Experiments were performed with very short contact times of up to 12s. Main products were in the gasoline range, including benzene, toluene, ethylbenzene, styrene, and minor amounts of C{sub 9-12} aromatics and light C{sub 5-} compounds. Coke was always produced in very significant amounts. All the products can be justified with basis on the properties of each catalyst and the various possible catalytic reaction pathways: cracking after protolytic attack on the polymer fragments, styrene oligomerization and subsequent cracking, or hydrogen transfer to styrene. Styrene would be mainly produced in this system from thermal cracking of the polymer as the initial step. If present, shape selectivity effects due to catalyst structure can influence significantly the prevalence of the various reactions, because they would interfere with those undergoing bulky transition states, like styrene oligomerization or hydrogen transfer. Even though sulfur-promoted zirconia is highly acidic, the low proportion of Broensted-type acid sites does not allow the occurrence of secondary styrene reactions. It was shown that most favorable product distributions (higher yields of desirable products) are obtained on equilibrium commercial FCC catalysts

  19. Deformation twinning in small-sized face-centred cubic single crystals: Experiments and modelling

    Science.gov (United States)

    Liang, Z. Y.; Huang, M. X.

    2015-12-01

    Small-sized crystals generally show deformation behaviour distinct from their bulk counterparts. In addition to dislocation slip, deformation twinning in small-sized face-centred cubic (FCC) single crystals has been reported to follow a different mechanism which involves coherent emission of partial dislocations on successive { 111 } planes from free surface. The present work employed a twinning-induced plasticity (TWIP) steel with a low stacking fault energy to systematically investigate the twin evolution in small-sized FCC single crystals. Micrometre-sized single crystal pillars of TWIP steel were fabricated by focus ion beam and then strained to different levels by compression experiments. Detailed transmission electron microscopy characterization was carried out to obtain a quantitative evaluation of the deformation twins, which contribute to most of the plastic strain. Emissions of partial dislocations from free surface (surface sources) and pre-existing perfect dislocations inside the pillar (inner sources) are found as the essential processes for the formation of deformation twins. Accordingly, a physically-based model, which integrates source introduction methods and source activation criterions for partial dislocation emission, is developed to quantitatively predict the twin evolution. The model is able to reproduce the experimental twin evolution, in terms of the total twin formation, the twin morphology and the occurrence of twinning burst.

  20. Generalized Vaidya spacetime for cubic gravity

    CERN Document Server

    Ruan, Shan-Ming

    2015-01-01

    We present a kind of generalized Vaidya solutions of a new cubic gravity in five dimensions whose field equations in spherically spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally we present the first law and second law hold in this gravity. Although all the results are analogue to those in Lovelock gravity, we in fact introduce the contribution of new cubic term in five dimensions where cubic Lovelock term is just zero.