Natural atomic orbital based energy density analysis: Implementation and applications
Baba, Takeshi; Takeuchi, Mari; Nakai, Hiromi
2006-06-01
We present an improvement of energy density analysis (EDA), which partitions the total energy obtained by Hartree-Fock and/or density functional theory calculations, with the use of the natural atomic orbital (NAO) [A.E. Reed et al., J. Chem. Phys. 83 (1985) 735] and Löwdin's symmetric-orthogonal orbital (LSO). The present NAO- and LSO-EDA schemes are applied to analyses of CO 2 and Li9+ with various basis sets. Numerical results confirm that NAO-EDA exhibits less basis-set dependence, while the conventional results are very sensitive to the adopted basis sets.
The Atomic orbitals of the topological atom
Ramos-Cordoba, Eloy; Salvador Sedano, Pedro
2013-01-01
The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These c...
The atomic orbitals of the topological atom.
Ramos-Cordoba, Eloy; Salvador, Pedro; Mayer, István
2013-06-07
The effective atomic orbitals have been realized in the framework of Bader's atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular value decomposition procedure.
Real and Hybrid Atomic Orbitals.
Cook, D. B.; Fowler, P. W.
1981-01-01
Demonstrates that the Schrodinger equation for the hydrogenlike atom separates in both spheroconal and prolate spheroidal coordinates and that these separations provide a sound theoretical basis for the real and hybrid atomic orbitals. (Author/SK)
DEFF Research Database (Denmark)
Avery, John Scales; Avery, James Emil; Aquilanti, Vincenzo;
2004-01-01
The generalized Sturmian method for atomic and molecular electronic structure calculations is a direct configuration interaction method in which the configurations are chosen to be isoenergetic solutions of an approximate N-electron Schrödinger equation with a weighted potential, $\\beta_\
Indian Academy of Sciences (India)
Heidar Raissi; Mehdi Yoosefian; Effat Moshfeghi; Farzaneh Farzad
2012-05-01
The characteristics of the intramolecular hydrogen bonding for a series of 19 different derivatives of -aminoacroleine have been systematically analysed at the B3LYP/6-31G∗∗ level of theory. The topological properties of the electron density distributions for N-H$\\cdots$O intramolecular bridges have been analysed by the Bader theory of atoms in molecules. The electron density () and Laplacian (∇2 ρ) properties at critical points of the relevant bonds, estimated by AIM calculations, showed that N-H$\\cdots$O have low and positive character (∇2 ρ > 0), consistent with electrostatic character of the hydrogen bond. The vibrational study of the hydrogen bonded systems showed negative (red) shifts for the (N−H) stretching mode. The -electron delocalization parameter () as a geometrical indicator of a local aromaticity and the geometry-based HOMA have also been calculated. Furthermore, the analysis of hydrogen bond in this molecule and its derivatives by natural bond orbital (NBO) methods support the DFT results. The results of AIM and NBO analysis as well as (N−H) were further used for estimation of the hydrogen bonding interactions and the forces driving their formation. The various correlations were found between geometrical, energetic and topological parameters. The substituent effect was also analysed and it was found that the strongest hydrogen bonds exist for N+(CH3)3 and Cl substituents while the weakest ones for COOCH3.
Holden, Alan
This monograph was written for the purpose of presenting physics to college students who are not preparing for careers in physics. It deals with the nature of atoms, and treats the following topics: (1) the atomic hypothesis, (2) the chemical elements, (3) models of an atom, (4) a particle in a one-dimensional well, (5) a particle in a central…
Electronic structure interpolation via atomic orbitals.
Chen, Mohan; Guo, G-C; He, Lixin
2011-08-17
We present an efficient scheme for accurate electronic structure interpolation based on systematically improvable optimized atomic orbitals. The atomic orbitals are generated by minimizing the spillage value between the atomic basis calculations and the converged plane wave basis calculations on some coarse k-point grid. They are then used to calculate the band structure of the full Brillouin zone using the linear combination of atomic orbitals algorithms. We find that usually 16-25 orbitals per atom can give an accuracy of about 10 meV compared to the full ab initio calculations, and the accuracy can be systematically improved by using more atomic orbitals. The scheme is easy to implement and robust, and works equally well for metallic systems and systems with complicated band structures. Furthermore, the atomic orbitals have much better transferability than Shirley's basis and Wannier functions, which is very useful for perturbation calculations.
Indian Academy of Sciences (India)
Xiqian Niu; Zhengguo Huang; Lingling Ma; Tingting Shen; Lingfei Guo
2013-07-01
The tryptophan-water (Trp-H2O) complexes formed by hydrogen bonding interactions were investigated at the B97XD/6-311++G(d,p) level. Five Trp-H2O complexes possessing various types of hydrogen bonds (H-bonds) were characterized by geometries, energies, vibrational frequencies. The nature of the H-bonds were characterized by the natural bond orbital (NBO) and the quantum theory of atoms in molecule (QTAIM) analyses as well. The intramolecular H-bond formed between the amino and carboxyl oxygen atom of tryptophan was retained in most of the complexes, and the cooperativity between the intra and intermolecular H-bonds exist in some complexes. The intramolecular H-bond and some intermolecular H-bonds are strong and have partial covalent character. The H-bonds formed between carboxyl and oxygen/nitrogen atoms are stronger than other H-bonds. The H-bonds involving methylene of tryptophan as H-donor are weak H-bonds. For all complexes,ele and ex makes major contributions to the total interaction energy (MP2), while disp is the smallest component of the interaction energy. Both hydrogen bonding interaction and structural deformation play important roles in the relative stabilities of the complexes. Regardless of strong H-bonds, the stabilities of some complexes are weakened by the serious structural deformations.
Reinhardt, William P.; Perry, Heidi
2003-01-01
The possibility, envisaged in 1925 by Einstein following the suggestion of Bose, of a dilute gas of atoms being condensed into a single quantum state was experimentally achieved in 1995 following decades of research. An avalanche of experiment and theory has followed, leading to the awarding of the 2001 Nobel Prizes in Physics to three of the pioneering experimentalists. Theory, mostly couched in the language and formalism of condensed matter physics, has developed apace. What we point out he...
Atomic Orbitals for the New Millennium
Williams, J M
1999-01-01
This very short article introduces a set of nested atomic orbitals, called MCAS, to replace the current s, p, d, and f orbitals. The simplest orbital is a tetrahedrally directed, four lobed, mono-orbital instead of the spherical s orbital. All the other orbitals, no matter what their energy (shell) level is, are nested with this one. All the electrons have the same spin and only one electron is allotted to each orbital. Electron spin pairing is accomplished through opposing orbitals instead of actual electron spin reversal. Orbital energy level is maintained by nuclear propulsion through perigee kick. Orbitals hybridize as Aufbau proceeds, in contrast to the inflexible, current building model. The inert gases have completely uniform electronic shells that contain only one orbital type per shell. Since outer completed shells have only one type of orbital, all eight outer electrons are identical rather than being of two types as occurs in the current model; hence, Lewis' electron-dot octet. Hydrogen should resi...
Téllez Soto, C. A.; Costa, A. C.; Versiane, O.; Lemma, T.; Machado, N. C. F.; Mondragón, M. A.; Martin, A. A.
2015-07-01
Theoretical and experimental bands have been assigned to the Fourier Transform Infrared (FT-IR) and FT-Raman spectra of the bis(diethyldithiocarbamate)Cd(II) complex, abbreviated as ([Cd(DDTC)2]). The calculations and spectral interpretation have been based on the DFT/B3LYP method, infrared and Raman second derivative spectra, and band deconvolution analysis to assist in the assignment of observed fundamentals. This study validated the unusual pseudo tetrahedral molecular structure formed around the Cd(II) cation. Surface-enhanced Raman scattering (SERS) was used to determine the interactions of the normal-modes of the diethyldithiocarbamate cadmium (II) complex on nano-structured silver surfaces. Natural bond orbital (NBO) analysis was also carried out to study the Cd(II) hybridization causing the pseudo tetrahedral geometry of the framework of the [Cd(DDTC)2] complex, and to confirm the charge transfer mechanisms through second order perturbation theory analysis of the Fox Matrix. In order to find out the electronic dispersion of the Mulliken atomic charges (MAC) in the normal modes, we calculated the MAC for each normal mode and correlated these values with the SERS effect. Experimental UV-Vis spectra were obtained and charge transfer bands were assigned. Good agreement between the calculated and experimental values for the vibrational and UV-Vis spectra was obtained.
Zhang, Guiqiu; Li, Xiwen; Li, Yan; Chen, Dezhan
2013-11-01
In this report, we extended the works of Rizzato et al. [Angew. Chem. Int. Ed. 49, 7440 (2010)] on the nature of O-H...Pt hydrogen bond in trans-[PtCl2(NH3)(N-glycine)].H2O(1.H2O) complex, by computational study of O-H...Pt interaction in [NBu4][Pt(C6F5)3(8-hydroxyquinaldine)], with emphasis on charge transfer effect in this interaction of platinum(II) and hydrogen atom. According to the crystallographic geometry reported by José María Casas et al., [NBu4][Pt(C6F5)3(8-hydroxyquinaldine)] possesses one O-H...Pt hydrogen bridging interaction, similar to the case in trans-[PtCl2(NH3)(N-glycine)].H2O(1.H2O) complex. On the basis of topological criteria of electron density, we characterised this O-H...Pt interaction. Charge transferred between platinum(II) and σ*O-H orbital in this complex was calculated by using NBO method. The stabilised energy associated to charge transfer was estimated using a direct proportionality, that is 2-3 eV per electron transferred. Charge transfer effects in O-H...Pt hydrogen bonds were studied for these two complexes. Our results indicate that the interaction of O-H...Pt is closed-shell in nature with significant charge transfer, and that charge transfer effect is not negligible in the interaction of O-H...Pt. The second conclusion is different from the result of Rizzato et al.
Software for Hydrogenic Atoms and Orbitals Visualization
Directory of Open Access Journals (Sweden)
Kowit KITTIWUTTHISAKDI
2005-06-01
Full Text Available A program was developed in java for hydrogenic atoms and orbitals visualization. The first 18 atoms in the periodic table were approximated with a hydrogenic wave-function. This simple hydrogenic wave-function allowed quick calculation for real-time interactive visualization. Electron cloud based models were employed and displayed by a ray-tracing technique. One or more orbitals that defined an atom could be selected and displayed. A user could zoom in, zoom out, and rotate the displayed cloud in real time. The approximation method for probability integrals was summation. The intensity of color at each point on the screen directly related to the integrated probability in finding the electron across the viewer%s eye path.
Atomic orbital self-energy and electronegativity
Ribeiro, Mauro
2016-01-01
In this work, atomic calculations were performed within the local-density and generalized-gradient approximations of exchange and correlation density functionals within density-functional theory to provide accurate periodic trends of first ionization energies and electron affinities of the atomic series from hydrogen to xenon. Electronegativities were determined directly from Mulliken's formula and were shown to be equivalently calculated rather by using Slater-Janak's transition state or by calculating the electrostatic self-energies of the orbitals involved in the transition to ions. Finally, comparisons were made with other theoretical and experimental results, including Mulliken-Jaff\\'e's electronegativity scale.
Spin-sensitive atom mirror via spin-orbit interaction
Zhou, Lu; Zheng, Ren-Fei; Zhang, Weiping
2016-11-01
Based on the spin-orbit coupling recently implemented in a neutral cold-atom gas, we propose a scheme to realize spin-dependent scattering of cold atoms. In particular we consider a matter wave packet of cold-atom gas impinging upon a step potential created by the optical light field, inside of which the atoms are subject to spin-orbit interaction. We show that the proposed system can act as a spin polarizer or spin-selective atom mirror for the incident atomic beam. The principle and the operating parameter regime of the system are carefully discussed.
Periodic Orbit Theory for Rydberg Atoms in External Fields
Dando, P. A.; Monteiro, T. S.; Owen, S. M.
1998-03-01
Although hydrogen in external fields is a paradigm for the application of periodic orbits and the Gutzwiller trace formula to a real system, the trace formula has never been applied successfully to other Rydberg atoms. We show that spectral fluctuations of general Rydberg atoms are given with remarkable precision by the addition of diffractive terms. Previously unknown features in atomic spectra are exposed: there are new modulations that are neither periodic orbits nor combinations of periodic orbits; ``core shadowing'' generally decreases primitive periodic orbit amplitudes but can also lead to increases.
Periodic Orbit Theory for Rydberg Atoms in External Fields
Dando, P A; Owen, S M
1998-01-01
Although hydrogen in external fields is a paradigm for the application of periodic orbits and the Gutzwiller trace formula to a real system, the trace formula has never been applied successfully to other Rydberg atoms. We show that spectral fluctuations of general Rydberg atoms are given with remarkable precision by the addition of diffractive terms. Previously unknown features in atomic spectra are exposed: there are new modulations that are neither periodic orbits nor combinations of periodic orbits; `core-shadowing' generally decreases primitive periodic orbit amplitudes but can also lead to increases.
Atoms in parallel fields: Analysis with diffractive periodic orbits
Owen, S. M.; Monteiro, T. S.; Dando, P. A.
2000-11-01
We show that fluctuations in the density of states of nonhydrogenic atoms in parallel fields are strongly influenced by diffractive periodic orbits. Unlike typical systems with a diffractive point scatterer, the atomic core of small atoms like lithium and helium is best understood as a combined geometric and diffractive scatterer. Each Gutzwiller (geometric) periodic orbit is paired with a diffractive orbit of the same action. We investigate, particularly, amplitudes for contributions from repetitions, and multiple scattering orbits. We find that periodic orbit repetitions are described by ``hybrid'' orbits, combining both diffractive and geometric core scatters, and that by including all possible permutations we can obtain excellent agreement between the semiclassical model and accurate fully quantal calculations. For high repetitions, we find even one-scatter diffractive contributions become of the same order as those of the geometric periodic orbit for repetition numbers n~ħ-1/2. Although the contribution of individual diffractive orbits is suppressed by O(ħ1/2) relative to the geometric periodic orbits, the proliferation of diffractive orbits with increasing period means that the diffractive effect for the atom can persist in the ħ-->0 limit.
Vortex line in spin-orbit coupled atomic Fermi gases
2012-01-01
PHYSICAL REVIEW A 85, 013622 (2012) Vortex line in spin-orbit coupled atomic Fermi gases M. Iskin Department of Physics, Koc¸ University, Rumelifeneri Yolu, TR-34450 Sariyer, Istanbul, Turkey (Received 1 December 2011; published 17 January 2012) It has recently been shown that the spin-orbit coupling gives rise to topologically nontrivial and thermodynamically stable gapless superfluid phases when the pseudospin populations of an atomic Fermi gas are imbalanced, with the ...
Orbital Feshbach Resonance in Alkali-Earth Atoms.
Zhang, Ren; Cheng, Yanting; Zhai, Hui; Zhang, Peng
2015-09-25
For a mixture of alkali-earth atomic gas in the long-lived excited state ^{3}P_{0} and the ground state ^{1}S_{0}, in addition to nuclear spin, another "orbital" index is introduced to distinguish these two internal states. In this Letter we propose a mechanism to induce Feshbach resonance between two atoms with different orbital and nuclear spin quantum numbers. Two essential ingredients are the interorbital spin-exchange process and orbital dependence of the Landé g factors. Here the orbital degrees of freedom plays a similar role as the electron spin degree of freedom in magnetic Feshbach resonance in alkali-metal atoms. This resonance is particularly accessible for the ^{173}Yb system. The BCS-BEC crossover in this system requires two fermion pairing order parameters, and displays a significant difference compared to that in an alkali-metal system.
Role of core-scattered closed orbits in nonhydrogenic atoms
Dando, P. A.; Monteiro, T. S.; Delande, D.; Taylor, K. T.
1996-07-01
While both diamagnetic and Stark spectra of hydrogen can be analyzed accurately in terms of classical orbits, in nonhydrogenic atoms the multielectron core induces additional spectral modulations that cannot be analyzed reliably in terms of standard periodic orbit-type theories. However, by extending closed-orbit theory to include core-scattered waves consistently, both diamagnetic and Stark photoabsorption spectra of nonhydrogenic Rydberg atoms at constant scaled energy can be analyzed semiclassically using only the closed orbits of the corresponding hydrogenic systems. Frequencies and amplitudes of the core-scattered modulations, as well as corrected amplitudes for contributions from repetitions of primitive hydrogenic orbits, are found to be in excellent agreement with quantum results. We consider whether these nonhydrogenic systems correspond to quantum chaos.
Hydrodynamics of Normal Atomic Gases with Spin-orbit Coupling.
Hou, Yan-Hua; Yu, Zhenhua
2015-10-20
Successful realization of spin-orbit coupling in atomic gases by the NIST scheme opens the prospect of studying the effects of spin-orbit coupling on many-body physics in an unprecedentedly controllable way. Here we derive the linearized hydrodynamic equations for the normal atomic gases of the spin-orbit coupling by the NIST scheme with zero detuning. We show that the hydrodynamics of the system crucially depends on the momentum susceptibilities which can be modified by the spin-orbit coupling. We reveal the effects of the spin-orbit coupling on the sound velocities and the dipole mode frequency of the gases by applying our formalism to the ideal Fermi gas. We also discuss the generalization of our results to other situations.
Manipulating atomic states via optical orbital angular-momentum
Institute of Scientific and Technical Information of China (English)
2008-01-01
Optical orbital angular-momentum(OAM)has more complex mechanics than the spin degree of photons,and may have a broad range of application.Manipulating atomic states via OAM has become an interesting topic.In this paper,we first review the general theory of generating adiabatic gauge field in ultracold atomic systems by coupling atoms to external optical fields with OAM,and point out the applications of the generated adiabatic gauge field.Then,we review our work in this field,including the generation of macroscopic superposition of vortex-antivortex states and spin Hall effect(SHE)in cold atoms.
Natural and artificial atoms for quantum computation
Energy Technology Data Exchange (ETDEWEB)
Buluta, Iulia; Ashhab, Sahel; Nori, Franco, E-mail: fnori@riken.jp [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan)
2011-10-15
Remarkable progress towards realizing quantum computation has been achieved using natural and artificial atoms as qubits. This paper presents a brief overview of the current status of different types of qubits. On the one hand, natural atoms (such as neutral atoms and ions) have long coherence times, and could be stored in large arrays, providing ideal 'quantum memories'. On the other hand, artificial atoms (such as superconducting circuits or semiconductor quantum dots) have the advantage of custom-designed features and could be used as 'quantum processing units'. Natural and artificial atoms can be coupled with each other and can also be interfaced with photons for long-distance communications. Hybrid devices made of natural/artificial atoms and photons may provide the next-generation design for quantum computers.
Beyond periodic orbits: An example in nonhydrogenic atoms
Energy Technology Data Exchange (ETDEWEB)
Dando, P.A.; Monteiro, T.S.; Delande, D.; Taylor, K.T. (Department of Mathematics, Royal Holloway, University of London, Egham, Surrey, TW20 0EX (United Kingdom) Laboratoire Kastler-Brossel, Universite Pierre et Marie Curie, 4 place Jussieu, F-75005 Paris (France) Department of Applied Mathematics and Theoretical Physics, Queen' s University Belfast, Belfast, BT7 1NN (United Kingdom))
1995-02-13
The spectrum of hydrogen in a magnetic field is a paradigm of quantum chaos and may be analyzed accurately by periodic-orbit-type theories. In nonhydrogenic atoms, the core induces pure quantum effects, especially additional spectral modulations, which cannot be analyzed reliably in terms of classical orbits and their stability parameters. Provided core-scattered waves are included consistently, core-scattered modulations as well as corrected amplitudes for primitive orbits are in excellent agreement with quantum results. We consider whether these systems correspond to quantum chaos.
Beyond Periodic Orbits: An Example in Nonhydrogenic Atoms
Dando, P. A.; Monteiro, T. S.; Delande, D.; Taylor, K. T.
1995-02-01
The spectrum of hydrogen in a magnetic field is a paradigm of quantum chaos and may be analyzed accurately by periodic-orbit-type theories. In nonhydrogenic atoms, the core induces pure quantum effects, especially additional spectral modulations, which cannot be analyzed reliably in terms of classical orbits and their stability parameters. Provided core-scattered waves are included consistently, core-scattered modulations as well as corrected amplitudes for primitive orbits are in excellent agreement with quantum results. We consider whether these systems correspond to quantum chaos.
Translation and integration of numerical atomic orbitals in linear molecules
Energy Technology Data Exchange (ETDEWEB)
Heinäsmäki, Sami, E-mail: sami.heinasmaki@gmail.com [Department of Physics, University of Oulu, FIN-90014, Oulu (Finland)
2014-02-14
We present algorithms for translation and integration of atomic orbitals for LCAO calculations in linear molecules. The method applies to arbitrary radial functions given on a numerical mesh. The algorithms are based on pseudospectral differentiation matrices in two dimensions and the corresponding two-dimensional Gaussian quadratures. As a result, multicenter overlap and Coulomb integrals can be evaluated effectively.
Cukrowski, Ignacy; de Lange, Jurgens H; Mitoraj, Mariusz
2014-01-23
In the present account factors determining the stability of ZnL, ZnL2, and ZnL3 complexes (L = bpy, 2,2′-bipyridyl) were characterized on the basis of various techniques: the quantum theory of atoms in molecules (QTAIM), energy decomposition schemes based on interacting quantum atoms (IQA), and extended transition state coupled with natural orbitals for chemical valence (ETS-NOCV). Finally, the noncovalent interactions (NCI) index was also applied. All methods consistently indicated that the strength of the coordination bonds, Zn–O and Zn–N, decreases from ZnL to ZnL3. Importantly, it has been identified that the strength of secondary intramolecular heteropolar hydrogen bonding interactions, CH···O and CH···N, increases when going from ZnL to ZnL3. A similar trend appeared to be valid for the π-bonding as well as electrostatic stabilization. In addition to the above leading bonding contributions, all techniques suggested the existence of very subtle, but non-negligible additional stabilization from the CH···HC electronic exchange channel; these interactions are the weakest among all considered here. From IQA it was found that the local diatomic interaction energy, Eint(H,H), amounts at HF to −2.5, −2.7, and −2.9 kcal mol(–1) for ZnL, ZnL2, and ZnL3, respectively (−2.1 kcal mol(–1) for ZnL at MP2). NOCV-based deformation density channels showed that formation of CH--HC contacts in Zn complexes causes significant polarization of σ(C–H) bonds, which accordingly leads to charge accumulation in the CH···HC bay region. Charge depletion from σ(C–H) bonds was also reflected in the calculated spin–spin (1)J(C–H) coupling constants, which decrease from 177.06 Hz (ZnL) to 173.87 Hz (ZnL3). This last result supports our findings of an increase in the local electronic CH···HC stabilization from ZnL to ZnL3 found from QTAIM, IQA, and ETS-NOCV. Finally, this work unites for the first time the results from four methods that are widely
Super-atom molecular orbital excited states of fullerenes.
Johansson, J Olof; Bohl, Elvira; Campbell, Eleanor E B
2016-09-13
Super-atom molecular orbitals are orbitals that form diffuse hydrogenic excited electronic states of fullerenes with their electron density centred at the centre of the hollow carbon cage and a significant electron density inside the cage. This is a consequence of the high symmetry and hollow structure of the molecules and distinguishes them from typical low-lying molecular Rydberg states. This review summarizes the current experimental and theoretical studies related to these exotic excited electronic states with emphasis on femtosecond photoelectron spectroscopy experiments on gas-phase fullerenes.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'.
Local pair natural orbitals for excited states.
Helmich, Benjamin; Hättig, Christof
2011-12-07
We explore how in response calculations for excitation energies with wavefunction based (e.g., coupled cluster) methods the number of double excitation amplitudes can be reduced by means of truncated pair natural orbital (PNO) expansions and localized occupied orbitals. Using the CIS(D) approximation as a test model, we find that the number of double excitation amplitudes can be reduced dramatically with minor impact on the accuracy if the excited state wavefunction is expanded in state-specific PNOs generated from an approximate first-order guess wavefunction. As for ground states, the PNO truncation error can also for excitation energies be controlled by a single threshold related to generalized natural occupation numbers. The best performance is found with occupied orbitals which are localized by the Pipek-Mezey localization. For a large test set of excited states we find with this localization that already a PNO threshold of 10(-8)-10(-7), corresponding to an average of only 40-80 PNOs per pair, is sufficient to keep the PNO truncation error for vertical excitation energies below 0.01 eV. This is a significantly more rapid convergence with the number doubles amplitudes than in domain-based local response approaches. We demonstrate that the number of significant excited state PNOs scales asymptotically linearly with the system size in the worst case of completely delocalized excitations and sub-linearly whenever the chromophore does not increase with the system size. Moreover, we observe that the flexibility of state-specific PNOs to adapt to the character of an excitation allows for an almost unbiased treatment of local, delocalized and charge transfer excited states.
Local pair natural orbitals for excited states
Helmich, Benjamin; Hättig, Christof
2011-12-01
We explore how in response calculations for excitation energies with wavefunction based (e.g., coupled cluster) methods the number of double excitation amplitudes can be reduced by means of truncated pair natural orbital (PNO) expansions and localized occupied orbitals. Using the CIS(D) approximation as a test model, we find that the number of double excitation amplitudes can be reduced dramatically with minor impact on the accuracy if the excited state wavefunction is expanded in state-specific PNOs generated from an approximate first-order guess wavefunction. As for ground states, the PNO truncation error can also for excitation energies be controlled by a single threshold related to generalized natural occupation numbers. The best performance is found with occupied orbitals which are localized by the Pipek-Mezey localization. For a large test set of excited states we find with this localization that already a PNO threshold of 10-8-10-7, corresponding to an average of only 40-80 PNOs per pair, is sufficient to keep the PNO truncation error for vertical excitation energies below 0.01 eV. This is a significantly more rapid convergence with the number doubles amplitudes than in domain-based local response approaches. We demonstrate that the number of significant excited state PNOs scales asymptotically linearly with the system size in the worst case of completely delocalized excitations and sub-linearly whenever the chromophore does not increase with the system size. Moreover, we observe that the flexibility of state-specific PNOs to adapt to the character of an excitation allows for an almost unbiased treatment of local, delocalized and charge transfer excited states.
Institute of Scientific and Technical Information of China (English)
Guseinov I. Israfil; Erturk Murat
2008-01-01
Using complete orthonormal sets of Ψα -exponential type orbitals in single exponent approximation the new approach has been suggested for construction of different kinds of functions which can be useful in the theory of linear combination of atomic orbitals. These functions can be chosen properly according to the nature of the problems under consideration. This is rather important because the choice of the basis set may be play a crucial role in applications to atomic and molecular problems. As an example of application, different atomic orbitals for the ground states of the neutral and the first ten cationic members of the isoelectronic series of He atom are constructed by the solution of Hartree-Fock Roothaan equations using Ψ1, Ψ0 and Ψ-1 basis sets. The calculated results are close to the numerical Hartree-Fock values. The total energy, expansion coefficients, orbital exponents and virial ratio for each atom are presented.
A well-scaling natural orbital theory.
Gebauer, Ralph; Cohen, Morrel H; Car, Roberto
2016-11-15
We introduce an energy functional for ground-state electronic structure calculations. Its variables are the natural spin-orbitals of singlet many-body wave functions and their joint occupation probabilities deriving from controlled approximations to the two-particle density matrix that yield algebraic scaling in general, and Hartree-Fock scaling in its seniority-zero version. Results from the latter version for small molecular systems are compared with those of highly accurate quantum-chemical computations. The energies lie above full configuration interaction calculations, close to doubly occupied configuration interaction calculations. Their accuracy is considerably greater than that obtained from current density-functional theory approximations and from current functionals of the one-particle density matrix.
A well-scaling natural orbital theory
Gebauer, Ralph; Car, Roberto
2016-01-01
We introduce an energy functional for ground-state electronic structure calculations. Its variables are the natural spin-orbitals of singlet many-body wave functions and their joint occupation probabilities deriving from controlled approximations to the two-particle density matrix that yield algebraic scaling in general, and Hartree-Fock scaling in its seniority-zero version. Results from the latter version for small molecular systems are compared with those of highly accurate quantum-chemical computations. The energies lie above full configuration interaction calculations, close to doubly occupied configuration interaction calculations. Their accuracy is considerably greater than that obtained from current density-functional theory approximations and from current functionals of the one-particle density matrix.
Transferring orbital and spin angular momenta of light to atoms
Energy Technology Data Exchange (ETDEWEB)
Picon, A; Benseny, A; Mompart, J [Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Vazquez de Aldana, J R; Plaja, L [Servicio Laser, Universidad de Salamanca, E-37008 Salamanca (Spain); Calvo, G F [Mathematics Department and IMACI-Institute of Applied Mathematics in Science and Engineering, Universidad de Castilla-La Mancha, E-13071 Ciudad Real (Spain); Roso, L, E-mail: antonio.picon@uab.ca [Centro de Laseres Pulsados, CLPU, Patio de Escuelas 1, E-37008 Salamanca (Spain)
2010-08-15
Light beams carrying orbital angular momentum (OAM), such as Laguerre-Gaussian (LG) beams, give rise to the violation of the standard dipolar selection rules during interaction with matter, yielding, in general, an exchange of angular momentum larger than {h_bar} per absorbed photon. By means of ab initio three-dimensional (3D) numerical simulations, we investigate in detail the interaction of a hydrogen atom with intense Gaussian and LG light pulses. We analyze the dependence of the angular momentum exchange with the polarization, the OAM and the carrier-envelope phase of light, as well as with the relative position between the atom and the light vortex. In addition, a quantum-trajectory approach based on the de Broglie-Bohm formulation of quantum mechanics is used to gain physical insight into the absorption of angular momentum by the hydrogen atom.
Atomic oxygen effects on POSS polyimides in low earth orbit.
Minton, Timothy K; Wright, Michael E; Tomczak, Sandra J; Marquez, Sara A; Shen, Linhan; Brunsvold, Amy L; Cooper, Russell; Zhang, Jianming; Vij, Vandana; Guenthner, Andrew J; Petteys, Brian J
2012-02-01
Kapton polyimde is extensively used in solar arrays, spacecraft thermal blankets, and space inflatable structures. Upon exposure to atomic oxygen in low Earth orbit (LEO), Kapton is severely eroded. An effective approach to prevent this erosion is to incorporate polyhedral oligomeric silsesquioxane (POSS) into the polyimide matrix by copolymerizing POSS monomers with the polyimide precursor. The copolymerization of POSS provides Si and O in the polymer matrix on the nano level. During exposure of POSS polyimide to atomic oxygen, organic material is degraded, and a silica passivation layer is formed. This silica layer protects the underlying polymer from further degradation. Laboratory and space-flight experiments have shown that POSS polyimides are highly resistant to atomic-oxygen attack, with erosion yields that may be as little as 1% those of Kapton. The results of all the studies indicate that POSS polyimide would be a space-survivable replacement for Kapton on spacecraft that operate in the LEO environment.
Natural triple excitations in local coupled cluster calculations with pair natural orbitals
Riplinger, Christoph; Sandhoefer, Barbara; Hansen, Andreas; Neese, Frank
2013-10-01
In this work, the extension of the previously developed domain based local pair-natural orbital (DLPNO) based singles- and doubles coupled cluster (DLPNO-CCSD) method to perturbatively include connected triple excitations is reported. The development is based on the concept of triples-natural orbitals that span the joint space of the three pair natural orbital (PNO) spaces of the three electron pairs that are involved in the calculation of a given triple-excitation contribution. The truncation error is very smooth and can be significantly reduced through extrapolation to the zero threshold. However, the extrapolation procedure does not improve relative energies. The overall computational effort of the method is asymptotically linear with the system size O(N). Actual linear scaling has been confirmed in test calculations on alkane chains. The accuracy of the DLPNO-CCSD(T) approximation relative to semicanonical CCSD(T0) is comparable to the previously developed DLPNO-CCSD method relative to canonical CCSD. Relative energies are predicted with an average error of approximately 0.5 kcal/mol for a challenging test set of medium sized organic molecules. The triples correction typically adds 30%-50% to the overall computation time. Thus, very large systems can be treated on the basis of the current implementation. In addition to the linear C150H302 (452 atoms, >8800 basis functions) we demonstrate the first CCSD(T) level calculation on an entire protein, Crambin with 644 atoms, and more than 6400 basis functions.
Atomic weights: no longer constants of nature
Coplen, Tyler B.; Holden, Norman E.
2011-01-01
Many of us were taught that the standard atomic weights we found in the back of our chemistry textbooks or on the Periodic Table of the Chemical Elements hanging on the wall of our chemistry classroom are constants of nature. This was common knowledge for more than a century and a half, but not anymore. The following text explains how advances in chemical instrumentation and isotopic analysis have changed the way we view atomic weights and why they are no longer constants of nature
Liguori, Lucia
2014-01-01
Atomic orbital theory is a difficult subject for many high school and beginning undergraduate students, as it includes mathematical concepts not yet covered in the school curriculum. Moreover, it requires certain ability for abstraction and imagination. A new atomic orbital model "the chocolate shop" created "by" students…
Liguori, Lucia
2014-01-01
Atomic orbital theory is a difficult subject for many high school and beginning undergraduate students, as it includes mathematical concepts not yet covered in the school curriculum. Moreover, it requires certain ability for abstraction and imagination. A new atomic orbital model "the chocolate shop" created "by" students…
Bridgeman, Adam J.; Schmidt, Timothy W.; Young, Nigel A.
2013-01-01
The stretching modes of ML[subscript "x"] complexes have the same symmetry as the atomic orbitals on M that are used to form its s bonds. In the exercise suggested here, the atomic orbitals are used to derive the form of the stretching modes without the need for formal group theory. The analogy allows students to help understand many…
Bridgeman, Adam J.; Schmidt, Timothy W.; Young, Nigel A.
2013-01-01
The stretching modes of ML[subscript "x"] complexes have the same symmetry as the atomic orbitals on M that are used to form its s bonds. In the exercise suggested here, the atomic orbitals are used to derive the form of the stretching modes without the need for formal group theory. The analogy allows students to help understand many…
DEFF Research Database (Denmark)
Ruud, Kenneth; Helgaker, Trygve; Kobayashi, Rika
1994-01-01
Nuclear shielding calculations are presented for multiconfigurational self-consistent field wave functions using London atomic orbitals (gauge invariant atomic orbitals). Calculations of nuclear shieldings for eight molecules (H2O, H2S, CH4, N2, CO, HF, F2, and SO2) are presented and compared...
Directory of Open Access Journals (Sweden)
Sri Mursiti
2010-06-01
Full Text Available The research of Computer Asissted Instruction with animation and simulation was used to misconception remediation of atomic orbital, molecular orbital, and hibridiziation concepts. The applicated instruction model was focused on concept approach with macromedia flash player and power point programme. The subject of this research were the 2nd semestre students of Chemistry Department. The data were collected by using of true-false pre-test and post- test followed by the reason of its. The analysis reveals that the Computer Asissted Instruction with animation and simulation model increased the understanding of atomic orbital, molecular orbital, and hibridiziation concepts or remediation of concepts missconception, shown by the significant score gained between before and after the implementation of Computer Asissted Instruction with animation and simulation model. The instruction model developed the students's generic skills too. Keywords: animation simulation,misconception remediation, orbital, hibridization
Spin-orbit interactions and quantum spin dynamics in cold ion-atom collisions
Tscherbul, Timur V; Buchachenko, Alexei A
2015-01-01
We present accurate ab initio and quantum scattering calculations on a prototypical hybrid ion-atom system Yb$^+$-Rb, recently suggested as a promising candidate for the experimental study of open quantum systems, quantum information processing, and quantum simulation. We identify the second-oder spin-orbit (SO) interaction as the dominant source of hyperfine relaxation and decoherence in cold Yb$^+$-Rb collisions. Our results are in good agreement with recent experimental observations [L. Ratschbacher et al., Phys. Rev. Lett. 110, 160402 (2013)] of hyperfine relaxation rates of trapped Yb$^+$ immersed in an ultracold Rb gas. The calculated rates are 4 times smaller than predicted by the Langevin capture theory and display a weak $T^{-0.3}$ temperature dependence, indicating significant deviations from statistical behavior. Our analysis underscores the deleterious nature of the SO interaction and implies that light ion-atom combinations such as Yb$^+$-Li should be used to minimize hyperfine relaxation and dec...
Non-sequential double ionization with time-dependent renormalized natural orbital theory
Brics, M; Bauer, D
2014-01-01
Recently introduced time-dependent renormalized natural orbital theory (TDRNOT) is tested on non-sequential double ionization (NSDI) of a numerically exactly solvable one-dimensional model He atom subject to few-cycle, 800-nm laser pulses. NSDI of atoms in strong laser fields is a prime example of non-perturbative, highly correlated electron dynamics. As such, NSDI is an important "worst-case" benchmark for any time-dependent few and many-body technique beyond linear response. It is found that TDRNOT reproduces the celebrated NSDI "knee," i.e., a many-order-of-magnitude enhancement of the double ionization yield (as compared to purely sequential ionization) with only the ten most significant natural orbitals (NOs) per spin. Correlated photoelectron spectra - as "more differential" observables - require more NOs.
Natural orbital description of the halo nucleus 6He
Constantinou, Ch; Vary, J P; Maris, P
2016-01-01
Ab initio calculations of nuclei face the challenge of simultaneously describing strong short-range internucleon correlations and the long-range properties of weakly-bound halo nucleons. Natural orbitals, which diagonalize the one-body density matrix, provide a basis which is better matched to the physical structure of the many-body wave function. We demonstrate that the use of natural orbitals significantly improves convergence for ab initio no-core configuration interaction calculations of the neutron halo nucleus 6He, relative to the traditional oscillator basis.
External Heavy-Atom Effect via Orbital Interactions Revealed by Single-Crystal X-ray Diffraction.
Sun, Xingxing; Zhang, Baicheng; Li, Xinyang; Trindle, Carl O; Zhang, Guoqing
2016-07-28
Enhanced spin-orbit coupling through external heavy-atom effect (EHE) has been routinely used to induce room-temperature phosphorescence (RTP) for purely organic molecular materials. Therefore, understanding the nature of EHE, i.e., the specific orbital interactions between the external heavy atom and the luminophore, is of essential importance in molecular design. For organic systems, halogens (e.g., Cl, Br, and I) are the most commonly seen heavy atoms serving to realize the EHE-related RTP. In this report, we conduct an investigation on how heavy-atom perturbers and aromatic luminophores interact on the basis of data obtained from crystallography. We synthesized two classes of molecular systems including N-haloalkyl-substituted carbazoles and quinolinium halides, where the luminescent molecules are considered as "base" or "acid" relative to the heavy-atom perturbers, respectively. We propose that electron donation from a π molecular orbital (MO) of the carbazole to the σ* MO of the C-X bond (π/σ*) and n electron donation to a π* MO of the quinolinium moiety (n/π*) are responsible for the EHE (RTP) in the solid state, respectively.
Intrinsic Atomic Orbitals: An Unbiased Bridge between Quantum Theory and Chemical Concepts.
Knizia, Gerald
2013-11-12
Modern quantum chemistry can make quantitative predictions on an immense array of chemical systems. However, the interpretation of those predictions is often complicated by the complex wave function expansions used. Here we show that an exceptionally simple algebraic construction allows for defining atomic core and valence orbitals, polarized by the molecular environment, which can exactly represent self-consistent field wave functions. This construction provides an unbiased and direct connection between quantum chemistry and empirical chemical concepts, and can be used, for example, to calculate the nature of bonding in molecules, in chemical terms, from first principles. In particular, we find consistency with electronegativities (χ), C 1s core-level shifts, resonance substituent parameters (σR), Lewis structures, and oxidation states of transition-metal complexes.
Distributed orbital state quantum cloning with atomic ensembles via quantum Zeno dynamics
Shen, Li-Tuo; Yang, Zhen-Biao
2011-01-01
We propose a scheme for distributed orbital state quantum cloning with atomic ensembles based on the quantum Zeno dynamics. These atomic ensembles which consist of identical three-level atoms are trapped in distant cavities connected by a single-mode integrated optical star coupler. These qubits can be manipulated through appropriate modulation of the coupling constants between atomic ensemble and classical field, and the cavity decay can be largely suppressed as the number of atoms in the ensemble qubits increases. The present scheme provides a new way to construct the quantum communication network.
Spin-splitting calculation for zincblende semiconductors using an atomic bond-orbital model.
Kao, Hsiu-Fen; Lo, Ikai; Chiang, Jih-Chen; Chen, Chun-Nan; Wang, Wan-Tsang; Hsu, Yu-Chi; Ren, Chung-Yuan; Lee, Meng-En; Wu, Chieh-Lung; Gau, Ming-Hong
2012-10-17
We develop a 16-band atomic bond-orbital model (16ABOM) to compute the spin splitting induced by bulk inversion asymmetry in zincblende materials. This model is derived from the linear combination of atomic-orbital (LCAO) scheme such that the characteristics of the real atomic orbitals can be preserved to calculate the spin splitting. The Hamiltonian of 16ABOM is based on a similarity transformation performed on the nearest-neighbor LCAO Hamiltonian with a second-order Taylor expansion k at the Γ point. The spin-splitting energies in bulk zincblende semiconductors, GaAs and InSb, are calculated, and the results agree with the LCAO and first-principles calculations. However, we find that the spin-orbit coupling between bonding and antibonding p-like states, evaluated by the 16ABOM, dominates the spin splitting of the lowest conduction bands in the zincblende materials.
The closed-orbit and the photoabsorption spectra of lithium atom in varyingmagnetic fields
Institute of Scientific and Technical Information of China (English)
Wang De-Hua; Ding Shi-Liang
2004-01-01
@@ Using a simple analytic formula from closed orbit theory, we have calculated the photoabsorption spectra of Li atom in different magnetic fields. Closed orbits in the corresponding classical system have also been obtained for B=5.96T. We demonstrate schematically that the closed orbits disappear gradually with the decrease of the magnitude of the magnetic field. This gives us a good method to control the closed orbits in the corresponding system by changing the magnetic field, and thus changing the peaks in the photoabaorption spectra. By comparing the photoabsorption spectra of Li atom with those of hydrogen case, we find the core-scattered effects play an important role in multi-electron Rydberg atoms.
Mapping trapped atomic gas with spin-orbit coupling to quantum Rabi-like model
Hu, Haiping; Chen, Shu
2013-01-01
We construct a connection of the ultracold atomic system in a harmonic trap with Raman-induced spin-orbit coupling to the quantum Rabi-like model. By mapping the trapped atomic system to a Rabi-like model, we can get the exact solution of the Rabi-like model following the methods to solve the quantum Rabi model. The existence of such a mapping implies that we can study the basic model in quantum optics by using trapped atomic gases with spin-orbit coupling.
QSPR modeling mineral crystal lattice energy by optimal descriptors of the graph of atomic orbitals
Toropova, A. P.; Toropov, A. A.; Maksudov, S. Kh.
2006-09-01
Models of the crystal lattice of minerals of general formula of A mC n: m, n = 1,2: A = Li, K, Na, Mg, Ca, Mn, Cu, Zn, Sr, Cd, Ba, Hg, Pb, Cs, and Rb ; C = Be, O, F, S, Cl, Br, and I; as a mathematical function of their structure have been constructed. Two elucidations of molecular structure have been used: molecular graph (vertexes are atoms, i.e., Li, Na, K, etc.) and graph of atomic orbitals, GAO (vertexes are atomic orbitals, i.e., 1s 2, 2p 5, 3d 10, etc). Statistical characteristics of the GAO-based models are better.
Orbital Battleship: A Guessing Game to Reinforce Atomic Structure
Kurushkin, Mikhail; Mikhaylenko, Maria
2016-01-01
A competitive educational guessing game "Orbital Battleship" which reinforces Madelung's and Hund's rules, values of quantum numbers, and understanding of periodicity was designed. The game develops strategic thinking, is not time-consuming, requires minimal preparation and supervision, and is an efficient and fun alternative to more…
An efficient and near linear scaling pair natural orbital based local coupled cluster method
Riplinger, Christoph; Neese, Frank
2013-01-01
In previous publications, it was shown that an efficient local coupled cluster method with single- and double excitations can be based on the concept of pair natural orbitals (PNOs) [F. Neese, A. Hansen, and D. G. Liakos, J. Chem. Phys. 131, 064103 (2009), 10.1063/1.3173827]. The resulting local pair natural orbital-coupled-cluster single double (LPNO-CCSD) method has since been proven to be highly reliable and efficient. For large molecules, the number of amplitudes to be determined is reduced by a factor of 105-106 relative to a canonical CCSD calculation on the same system with the same basis set. In the original method, the PNOs were expanded in the set of canonical virtual orbitals and single excitations were not truncated. This led to a number of fifth order scaling steps that eventually rendered the method computationally expensive for large molecules (e.g., >100 atoms). In the present work, these limitations are overcome by a complete redesign of the LPNO-CCSD method. The new method is based on the combination of the concepts of PNOs and projected atomic orbitals (PAOs). Thus, each PNO is expanded in a set of PAOs that in turn belong to a given electron pair specific domain. In this way, it is possible to fully exploit locality while maintaining the extremely high compactness of the original LPNO-CCSD wavefunction. No terms are dropped from the CCSD equations and domains are chosen conservatively. The correlation energy loss due to the domains remains below 8800 basis functions and >450 atoms. In all larger test calculations done so far, the LPNO-CCSD step took less time than the preceding Hartree-Fock calculation, provided no approximations have been introduced in the latter. Thus, based on the present development reliable CCSD calculations on large molecules with unprecedented efficiency and accuracy are realized.
van Meer, R.; Gritsenko, O. V.; Baerends, E. J.
2015-10-01
Linear response density matrix functional theory has been shown to solve the main problems of time-dependent density functional theory (deficient in case of double, charge transfer and bond breaking excitations). However, the natural orbitals preclude the description of excitations as (approximately) simple orbital-to-orbital transitions: many weakly occupied 'virtual' natural orbitals are required to describe the excitations. Kohn-Sham orbitals on the other hand afford for many excitations such a simple orbital description. In this communication we show that a transformation of the set of weakly occupied NOs can be defined such that the resulting natural excitation orbitals (NEOs) restore the single orbital transition structure for excitations generated by the linear response DMFT formalism.
Institute of Scientific and Technical Information of China (English)
YAKAR,Yusuf
2007-01-01
Ab initio calculations of the orbital and the ground state energies of some open- and closed-shell atoms over Slater type orbitals with quantum numbers integer and Slater type orbitals with quantum numbers noninteger have been performed. In order to increase the efficiency of these calculations the atomic two-electron integrals were expressed in terms of incomplete beta function. Results were observed to be in good agreement with the literature.
Strong spin-orbit interaction of light on the surface of atomically thin crystals
Liu, Mengxia; Cai, Liang; Chen, Shizhen; Liu, Yachao; Luo, Hailu; Wen, Shuangchun
2017-06-01
The photonic spin Hall effect (SHE) can be regarded as a direct optical analogy of the SHE in electronic systems where a refractive index gradient plays the role of an electric potential. However, it has been demonstrated that the effective refractive index fails to adequately explain the light-matter interaction in atomically thin crystals. In this paper, we examine the spin-orbit interaction on the surface of the freestanding atomically thin crystals. We find that it is not necessary to involve the effective refractive index to describe the spin-orbit interaction and the photonic SHE in the atomically thin crystals. The strong spin-orbit interaction and giant photonic SHE are predicted, which can be explained as the large polarization rotation of plane-wave components in order to satisfy the transversality of photon polarization.
Gangadharan, Rubarani P; Krishnan, S Sampath
2015-06-01
The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-31G(d, p) and 6-311++G(d,p) basis set by Gaussian program. The results from natural bond orbital (NBO) analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule. The electron density based local reactivity descriptors such as Fukui functions were calculated. The dipole moment (μ) and polarizability (a), anisotropy polarizability (Δα) and first order hyperpolarizability (β(tot)) of the molecule have been reported. Thermodynamic properties of the title compound were calculated at different temperatures.
Institute of Scientific and Technical Information of China (English)
Rubarani P Gangadharan; S Sampat H Krishnan
2015-01-01
The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6‐31G(d ,p) and 6‐311+ +G(d ,p) basis set by Gaussian program .The results from natural bond orbital (NBO) analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the ti‐tle molecule .The electron density based local reactivity descriptors such as Fukui functions were calculated . The dipole moment (μ) and polarizability (α) ,anisotropy polarizability (Δα) and first order hyperpolarizability (βtot ) of the molecule have been reported .Thermodynamic properties of the title compound were calculated at different temperatures .
Engineering an atom-interferometer with modulated light-induced $3 \\pi$ spin-orbit coupling
Olson, Abraham J; Blasing, David B; Niffenegger, Robert J; Chen, Yong P
2015-01-01
We have developed an experimental method to modify the single-particle dispersion using periodic modulation of Raman beams which couple two spin-states of an ultracold atomic gas. The modulation introduces a new coupling between Raman-induced spin-orbit-coupled dressed bands, creating a second generation of dressed-state eigenlevels that feature both a novel 3{\\pi} spin-orbit coupling and a pair of avoided crossings, which is used to realize an atomic interferometer. The spin polarization and energies of these eigenlevels are characterized by studying the transport of a Bose-Einstein condensate in this system, including observing a Stueckelberg interference.
Lin, Lin
2012-01-01
We describe how to apply the recently developed pole expansion plus selected inversion (PEpSI) technique to Kohn-Sham density function theory (DFT) electronic structure calculations that are based on atomic orbital discretization. We give analytic expressions for evaluating charge density, total energy, Helmholtz free energy and atomic forces without using the eigenvalues and eigenvectors of the Kohn-Sham Hamiltonian. We also show how to update the chemical potential without using Kohn-Sham...
Quantum Spectra of Hydrogen Atoms in Various Magnetic Fields with the Closed Orbit Theory
Institute of Scientific and Technical Information of China (English)
彭良友; 张现周; 饶建国
2002-01-01
The quantum spectra of hydrogen atoms in various magnetic fields have been calculated with the closed orbit theory. The magnitude of the magnetic field decreases from 5.96 T to 0.56 T with a step of 0. 6 T. We demonstrate schematically that the closed orbits disappear with the decrease of the magnitude of the magnetic field when the corresponding finite resolution of experiment is fixed. This may give us a good way to control the shape and the number of the closed orbits in the system, and thus to control where a peak should exist in the Fourier transformation of the quantum spectra.
Spin-orbit-coupled two-electron Fermi gases of ytterbium atoms
Song, Bo; He, Chengdong; Zhang, Shanchao; Hajiyev, Elnur; Huang, Wei; Liu, Xiong-Jun; Jo, Gyu-Boong
2016-12-01
We demonstrate all-optical implementation of spin-orbit coupling (SOC) in a two-electron Fermi gas of 173Yb atoms by coupling two hyperfine ground states with a narrow optical transition. Due to the SU (N ) symmetry of the S10 ground-state manifold which is insensitive to external magnetic fields, an optical ac Stark effect is applied to split the ground spin states, which exhibits a high stability compared with experiments on alkali-metal and lanthanide atoms, and separate out an effective spin-1/2 subspace from other hyperfine levels for the realization of SOC. The dephasing spin dynamics when a momentum-dependent spin-orbit gap is suddenly opened and the asymmetric momentum distribution of the spin-orbit-coupled Fermi gas are observed as a hallmark of SOC. The realization of all-optical SOC for ytterbium fermions should offer a route to a long-lived spin-orbit-coupled Fermi gas and greatly expand our capability of studying spin-orbit physics with alkaline-earth-metal-like atoms.
The Bohr Correspondence Principle: Kepler Orbits of the Electron in a Hydrogen Atom
Indian Academy of Sciences (India)
2016-06-01
We consider the quantum-mechanical non-relativistichydrogen atom. We show that for boundstates with size much larger than the Bohr radius,one can construct a wave packet that is localizedin space corresponding to a classical particlemoving in a circular orbit.
DEFF Research Database (Denmark)
Ruud, K.; Helgaker, T.; Jørgensen, Poul
1994-01-01
We report a systematic investigation of the magnetizability of a series of small molecules. The use of London atomic orbitals ensures gauge invariance and a fast basis set convergence. Good agreement is obtained with experimental magnetizabilities, both isotropic and anisotropic. The calculations...
Perturbative calculation of the Sternheimer anti-shielding factor with Hartree-Fock atomic orbitals
2012-01-01
We report a calculation of the Sternheimer anti-shielding factor, \\gamma, by means of first order perturbation theory. In quality of basis functions, we use Hartree-Fock electronic orbitals, expanded on hydrogenic atomic states. The computed \\gamma(r) for Fe^{3+} and Cu^{1+} inner electronic cores are reported and compared with literature values, obtained from alternative methodologies.
H$_4$: A Challenging System For Natural Orbital Functional Approximations
Ramos-Cordoba, Eloy; Piris, Mario; Matito, Eduard
2015-01-01
The correct description of nondynamic correlation by electronic structure methods not belonging to the multireference family is a challenging issue. The transition of $D_{2h}$ to $D_{4h}$ symmetry in H$_4$ molecule is among the most simple archetypal examples to illustrate the consequences of missing nondynamic correlation effects. The resurge of interest in density matrix functional methods has brought several new methods including the family of Piris Natural Orbital Functionals (PNOF). In this work we compare PNOF5 and PNOF6, which include nondynamic electron correlation effects to some extent, with other standard ab initio methods in the H$_4$ $D_{4h}/D_{2h}$ potential energy surface. Thus far, the wrongful behavior of single-reference methods at the $D_{2h}-D_{4h}$ transition of H$_4$ has been attributed to wrong account of nondynamic correlation effects, whereas in geminal-based approaches it has been assigned to a wrong coupling of spins and the localized nature of the orbitals. We will show that actual...
Energy Technology Data Exchange (ETDEWEB)
Thiele, Robert; Son, Sang-Kil [Center for Free-Electron Laser Science, DESY, 22607 Hamburg (Germany); Ziaja, Beata [Center for Free-Electron Laser Science, DESY, 22607 Hamburg (Germany); Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Krakow (Poland); Santra, Robin [Center for Free-Electron Laser Science, DESY, 22607 Hamburg (Germany); Department of Physics, University of Hamburg, 20355 Hamburg (Germany)
2013-07-01
X-ray free-electron lasers (XFELs) are a promising tool for the structural determination of macro- and biomolecules, using coherent diffractive imaging. During imaging, the intense XFEL pulses also efficiently ionize the molecules, so it is important to estimate how the charged environment within the molecule modifies atomic properties, in comparison to the case of an isolated atom. Here, we apply the XATOM toolkit to obtain predictions on the modified ionization thresholds and rates of some photoinduced processes in carbon. The Hartree-Fock-Slater model is extended to include the electron screening and ion correlation effects, induced by external charges. With this extended model, we obtain predictions on modifications of orbital energies, photoabsorption cross sections, Auger decay rates, fluorescence emission rates, and atomic scattering factors as a function of the density and temperature of the surrounding charges. Our results have implications for the studies of dynamics within XFEL irradiated samples, in particular for those dedicated to coherent diffraction imaging.
Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO.
Baumann, S; Donati, F; Stepanow, S; Rusponi, S; Paul, W; Gangopadhyay, S; Rau, I G; Pacchioni, G E; Gragnaniello, L; Pivetta, M; Dreiser, J; Piamonteze, C; Lutz, C P; Macfarlane, R M; Jones, B A; Gambardella, P; Heinrich, A J; Brune, H
2015-12-04
We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0±0.3 meV/atom. This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.
Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO
Baumann, S.; Donati, F.; Stepanow, S.; Rusponi, S.; Paul, W.; Gangopadhyay, S.; Rau, I. G.; Pacchioni, G. E.; Gragnaniello, L.; Pivetta, M.; Dreiser, J.; Piamonteze, C.; Lutz, C. P.; Macfarlane, R. M.; Jones, B. A.; Gambardella, P.; Heinrich, A. J.; Brune, H.
2015-12-01
We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0 ±0.3 meV /atom . This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.
The splitting of atomic orbitals with a common principal quantum number revisited: np vs. ns.
Katriel, Jacob
2012-04-14
Atomic orbitals with a common principal quantum number are degenerate, as in the hydrogen atom, in the absence of interelectronic repulsion. Due to the virial theorem, electrons in such orbitals experience equal nuclear attractions. Comparing states of several-electron atoms that differ by the occupation of orbitals with a common principal quantum number, such as 1s(2) 2s vs. 1s(2) 2p, we find that although the difference in energies, ΔE, is due to the interelectronic repulsion term in the Hamiltonian, the difference between the interelectronic repulsions, ΔC, makes a smaller contribution to ΔE than the corresponding difference between the nuclear attractions, ΔL. Analysis of spectroscopic data for atomic isoelectronic sequences allows an extensive investigation of these issues. In the low nuclear charge range of pertinent isoelectronic sequences, i.e., for neutral atoms and mildly positively charged ions, it is found that ΔC actually reverses its sign. About 96% of the nuclear attraction difference between the 6p (2)P and the 6s (2)S states of the Cs atom is cancelled by the corresponding interelectronic repulsion difference. From the monotonic increase of ΔE with Z it follows (via the Hellmann-Feynman theorem) that ΔL > 0. Upon increasing the nuclear charge along an atomic isoelectronic sequence with a single electron outside a closed shell from Z(c), the critical charge below which the outmost electron is not bound, to infinity, the ratio ΔC/ΔL increases monotonically from lim(Z→Z(c)(+))ΔC/ΔL=-1 to lim(Z→∞)ΔC/ΔL=1. These results should allow for a more nuanced discussion than is usually encountered of the crude electronic structure of many-electron atoms and the structure of the periodic table.
Zhao, Xin; Geskin, Victor; Stadler, Robert
2017-03-01
Destructive quantum interference (DQI) in single molecule electronics is a purely quantum mechanical effect and is entirely defined by the inherent properties of the molecule in the junction such as its structure and symmetry. This definition of DQI by molecular properties alone suggests its relation to other more general concepts in chemistry as well as the possibility of deriving simple models for its understanding and molecular device design. Recently, two such models have gained a wide spread attention, where one was a graphical scheme based on visually inspecting the connectivity of the carbon sites in conjugated π systems in an atomic orbital (AO) basis and the other one puts the emphasis on the amplitudes and signs of the frontier molecular orbitals (MOs). There have been discussions on the range of applicability for these schemes, but ultimately conclusions from topological molecular Hamiltonians should not depend on whether they are drawn from an AO or a MO representation, as long as all the orbitals are taken into account. In this article, we clarify the relation between both models in terms of the zeroth order Green's function and compare their predictions for a variety of systems. From this comparison, we conclude that for a correct description of DQI from a MO perspective, it is necessary to include the contributions from all MOs rather than just those from the frontier orbitals. The cases where DQI effects can be successfully predicted within a frontier orbital approximation we show them to be limited to alternant even-membered hydrocarbons, as a direct consequence of the Coulson-Rushbrooke pairing theorem in quantum chemistry.
Pardini, Lorenzo; Löffler, Stefan; Biddau, Giulio; Hambach, Ralf; Kaiser, Ute; Draxl, Claudia; Schattschneider, Peter
2016-07-15
Transmission electron microscopy has been a promising candidate for mapping atomic orbitals for a long time. Here, we explore its capabilities by a first-principles approach. For the example of defected graphene, exhibiting either an isolated vacancy or a substitutional nitrogen atom, we show that three different kinds of images are to be expected, depending on the orbital character. To judge the feasibility of visualizing orbitals in a real microscope, the effect of the optics' aberrations is simulated. We demonstrate that, by making use of energy filtering, it should indeed be possible to map atomic orbitals in a state-of-the-art transmission electron microscope.
Molecular electric moments calculated by using natural orbital functional theory
Mitxelena, Ion
2016-01-01
The molecular electric dipole, quadrupole and octupole moments of a selected set of 21 spin-compensated molecules are determined employing the extended version of the Piris natural orbital functional 6 (PNOF6), using the triple-$\\zeta$ Gaussian basis set with polarization functions developed by Sadlej, at the experimental geometries. The performance of the PNOF6 is established by carrying out a statistical analysis of the mean absolute errors with respect to the experiment. The calculated PNOF6 electric moments agree satisfactorily with the corresponding experimental data, and are in good agreement with the values obtained by accurate ab initio methods, namely, the coupled-cluster single and doubles (CCSD) and multi-reference single and double excitation configuration interaction (MRSD-CI) methods.
Efimov physics and universal trimers in spin-orbit-coupled ultracold atomic mixtures
Shi, Zhe-Yu; Zhai, Hui; Cui, Xiaoling
2015-02-01
We study the two-body and three-body bound states in ultracold atomic mixtures with one of the atoms subjected to an isotropic spin-orbit (SO) coupling. We consider a system of two identical fermions interacting with one SO-coupled atom. It is found that there can exist two types of three-body bound states, Efimov trimers and universal trimers. The Efimov trimers are energetically less favored by the SO coupling, which will finally merge into the atom-dimer threshold as increasing the SO-coupling strength. Nevertheless, these trimers exhibit a discrete scaling law incorporating the SO-coupling effect. On the other hand, the universal trimers are more favored by the SO coupling. They can be induced at negative s -wave scattering lengths and with smaller mass ratios than those without SO coupling. These results are obtained by both the Born-Oppenheimer approximation and exact solutions from three-body equations.
Controlling the Multiport Nature of Bragg Diffraction in Atom Interferometry
Parker, Richard H; Estey, Brian; Zhong, Weicheng; Huang, Eric; Müller, Holger
2016-01-01
Bragg diffraction has been used in atom interferometers because it allows signal enhancement through multiphoton momentum transfer and suppression of systematics by not changing the internal state of atoms. Its multi-port nature, however, can lead to parasitic interferometers, allows for intensity-dependent phase shifts in the primary interferometers, and distorts the ellipses used for phase extraction. We study and suppress these unwanted effects. Specifically, phase extraction by ellipse fitting and the resulting systematic phase shifts are calculated by Monte Carlo simulations. Phase shifts arising from the thermal motion of the atoms are controlled by spatial selection of atoms and an appropriate choice of Bragg intensity. In these simulations, we found that Gaussian Bragg pulse shapes yield the smallest systematic shifts. Parasitic interferometers are suppressed by a "magic" Bragg pulse duration. The sensitivity of the apparatus was improved by the addition of AC Stark shift compensation, which permits d...
Goos-H\\"anchen shifts in spin-orbit-coupled cold atoms
Zhou, Lu; Qin, Jie-Li; Lan, Zhihao; Dong, Guangjiong; Zhang, Weiping
2014-01-01
We consider a matter wave packet of cold atom gas impinging upon a step potential created by the optical light field. In the presence of spin-orbit (SO) coupling, the atomic eigenstates contain two types of evanescent states, one of which is the ordinary evanescent state with pure imaginary wave vector while the other possesses complex wave vector and is recognized as oscillating evanescent state. We show that the presence and interplay of these two types of evanescent states can give rise to...
Electron dynamics in the carbon atom induced by spin-orbit interaction
Rey, H F
2014-01-01
We use R-Matrix theory with Time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number $M_L$=0 and $M_L$=1 at a laser wavelength of 390 nm and peak intensity of 10$^{14}$ W cm$^{-2}$. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for $M_L$. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with $M_L=0$, the dynamics with respect to time delay of an ionizing probe pulse modelled using RMT theory is found to be in good agreement with available experimental data.
Rey, H. F.; van der Hart, H. W.
2014-09-01
We use R-matrix theory with time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number ML=0 and ML=1 at a laser wavelength of 390 nm and peak intensity of 1014W/cm2. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for ML. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with ML=0, the dynamics with respect to time delay of an ionizing probe pulse modeled by using RMT theory is found to be in good agreement with available experimental data.
Dynamics of atomic spin-orbit-state wave packets produced by short-pulse laser photodetachment
Law, S M K
2016-01-01
We analyse the experiment by Hultgren et al. [Phys. Rev. A {\\bf 87}, 031404 (2013)] on orbital alignment and quantum beats in coherently excited atomic fine-structure manifolds produced by short-pulse laser photodetachment of C$^-$, Si$^-$ and Ge$^-$ negative ions, and derive a formula that describes the beats. Analysis of the experimental data enables us to extract the non-coherent background contribution for each species, and indicates the need for a full density matrix treatment of the problem.
Search for Efimov trimers in ultracold atomic mixtures in the presence of spin-orbit coupling
Wang, Su-Ju; Han, Huili; Perez-Rios, Jesus; Greene, Chris
2015-05-01
Realization of synthetic gauge fields in ultracold atomic systems has attracted much attention in both few-body and many-body physics. Especially, there are extensive works on the two-body aspects of spin-orbit coupled quantum gases, which have already shown intriguing new features due to the change in the energy dispersion relation. However, there are few studies on the three-body physics in the presence of spin-orbit coupling. In this work, we apply the hyperspherical coordinate approach in the adiabatic approximation to solve the three-body system in zero total angular momentum subspace, where two of them are spin-orbit coupled, and the third one of a different species is not. Examination of the computed hyperspherical potential curves should provide the information needed to explore the possible existence of universal three-body bound states.
Thorvaldsen, Andreas J.; Ruud, Kenneth; Rizzo, Antonio; Coriani, Sonia
2008-10-01
We present the first gauge-origin-independent, frequency-dependent calculations of the hypermagnetizability anisotropy, which determines the temperature-independent contribution to magnetic-field-induced linear birefringence, the so-called Cotton-Mouton effect. A density-matrix-based scheme for analytical calculations of frequency-dependent molecular properties for self-consistent field models has recently been developed, which is also valid with frequency- and field-dependent basis sets. Applying this scheme to Hartree-Fock wave functions and using London atomic orbitals in order to obtain gauge-origin-independent results, we have calculated the hypermagnetizability anisotropy. Our results show that the use of London orbitals leads to somewhat better basis-set convergence for the hypermagnetizability compared to conventional basis sets and that London orbitals are mandatory in order to obtain reliable magnetizability anisotropies.
Cheng, Lan; Xiao, Yunlong; Liu, Wenjian
2009-12-28
It is recognized only recently that the incorporation of the magnetic balance condition is absolutely essential for four-component relativistic theories of magnetic properties. Another important issue to be handled is the so-called gauge problem in calculations of, e.g., molecular magnetic shielding tensors with finite bases. It is shown here that the magnetic balance can be adapted to distributed gauge origins, leading to, e.g., magnetically balanced gauge-including atomic orbitals (MB-GIAOs) in which each magnetically balanced atomic orbital has its own local gauge origin placed on its center. Such a MB-GIAO scheme can be combined with any level of theory for electron correlation. The first implementation is done here at the coupled-perturbed Dirac-Kohn-Sham level. The calculated molecular magnetic shielding tensors are not only independent of the choice of gauge origin but also converge rapidly to the basis set limit. Close inspections reveal that (zeroth order) negative energy states are only important for the expansion of first order electronic core orbitals. Their contributions to the paramagnetism are therefore transferable from atoms to molecule and are essentially canceled out for chemical shifts. This allows for simplifications of the coupled-perturbed equations.
Exact equations of motion for natural orbitals of strongly driven two-electron systems
Rapp, J; Bauer, D
2014-01-01
Natural orbital theory is a computationally useful approach to the few and many-body quantum problem. While natural orbitals are known and applied since many years in electronic structure applications, their potential for time-dependent problems is being investigated only since recently. Correlated two-particle systems are of particular importance because the structure of the two-body reduced density matrix expanded in natural orbitals is known exactly in this case. However, in the time-dependent case the natural orbitals carry time-dependent phases that allow for certain time-dependent gauge transformations of the first kind. Different phase conventions will, in general, lead to different equations of motion for the natural orbitals. A particular phase choice allows us to derive the exact equations of motion for the natural orbitals of any (laser-) driven two-electron system explicitly, i.e., without any dependence on quantities that, in practice, require further approximations. For illustration, we solve th...
Spin-orbit coupled two-electron Fermi gases of ytterbium atoms
Song, Bo; Zhang, Shanchao; Zou, Yueyang; Haciyev, Elnur; Huang, Wei; Liu, Xiong-Jun; Jo, Gyu-Boong
2016-01-01
We demonstrate the spin-orbit coupling (SOC) in a two-electron Fermi gas of $^{173}$Yb atoms by coupling two hyperfine ground states via the two-photon Raman transition. Due to the SU($N$) symmetry of the $^1$S$_0$ ground-state manifold which is insensitive to external magnetic field, an optical AC Stark effect is applied to split the ground spin states and separate an effective spin-1/2 subspace out from other hyperfine levels for the realization of SOC. With a momentum-dependent spin-orbit gap being suddenly opened by switching on the Raman transition, the dephasing of spin dynamics is observed, as a consequence of the momentum-dependent Rabi oscillations. Moreover, the momentum asymmetry of the spin-orbit coupled Fermi gas is also examined after projection onto the bare spin state and the corresponding momentum distribution is measured for different two-photon detuning. The realization of SOC for Yb fermions may open a new avenue to the study of novel spin-orbit physics with alkaline-earth-like atoms.
Explicitly correlated atomic orbital basis second order Møller-Plesset theory.
Hollman, David S; Wilke, Jeremiah J; Schaefer, Henry F
2013-02-14
The scope of problems treatable by ab initio wavefunction methods has expanded greatly through the application of local approximations. In particular, atomic orbital (AO) based wavefunction methods have emerged as powerful techniques for exploiting sparsity and have been applied to biomolecules as large as 1707 atoms [S. A. Maurer, D. S. Lambrecht, D. Flaig, and C. Ochsenfeld, J. Chem. Phys. 136, 144107 (2012)]. Correlated wavefunction methods, however, converge notoriously slowly to the basis set limit and, excepting the use of large basis sets, will suffer from a severe basis set incompleteness error (BSIE). The use of larger basis sets is prohibitively expensive for AO basis methods since, for example, second-order Møller-Plesset perturbation theory (MP2) scales linearly with the number of atoms, but still scales as O(N(5)) in the number of functions per atom. Explicitly correlated F12 methods have been shown to drastically reduce BSIE for even modestly sized basis sets. In this work, we therefore explore an atomic orbital based formulation of explicitly correlated MP2-F12 theory. We present working equations for the new method, which produce results identical to the widely used molecular orbital (MO) version of MP2-F12 without resorting to a delocalized MO basis. We conclude with a discussion of several possible approaches to a priori screening of contraction terms in our method and the prospects for a linear scaling implementation of AO-MP2-F12. The discussion includes concrete examples involving noble gas dimers and linear alkane chains.
Dynamics of Finite Energy Airy Beams Carrying Orbital Angular Momentum in Multilevel Atomic Vapors
Wu, Zhenkun; Wang, Shun; Hu, Weifei; Gu, Yuzong
2016-10-01
We numerically investigate the dynamics of inward circular finite-energy Airy beams carrying different orbital angular momentum (OAM) numbers in a close-Λ three-level atomic vapor with the electromagnetically induced transparency (EIT) window. We report that due to the EIT induced by the microwave field, the transverse intensity distribution properties of Airy beam can be feasibly manipulated and modulated through adjusting OAM numbers l and the frequency detuning, as well as the propagation distance, in the multi-level atomic systems. What's more, the rotation of the beam also can be observed with different positions in atomic ensembles. The investigation may provide a useful tool for studying particle manipulation, signal processing and propagation in graded-index (GRIN) fibers.
Goos-Hänchen shifts in spin-orbit-coupled cold atoms
Zhou, Lu; Qin, Jie-Li; Lan, Zhihao; Dong, Guangjiong; Zhang, Weiping
2015-03-01
We consider a matter wave packet of cold atom gas impinging upon a step potential created by an optical light field. In the presence of spin-orbit coupling, the atomic eigenstates contain two types of evanescent states, one of which is an ordinary evanescent state with a pure imaginary wave vector while the other possesses a complex wave vector and is recognized as an oscillating evanescent state. We show that the presence and interplay of these two types of evanescent states can give rise to two different mechanisms for total internal reflection, and thus lead to an unusual Goos-Hänchen (GH) effect. As a result, not only large positive but also large negative GH shifts can be observed in the reflected atomic beam. The dependence of the GH shift on the incident angle, energy, and height of the step potential is studied numerically.
Institute of Scientific and Technical Information of China (English)
WANG De-Hua; LIN Sheng-Lu
2004-01-01
@@ We show how to extract the closed orbits from the quantum spectra data. According to the closed orbit theory,each closed orbit produces a sharp peak in the recurrence spectra of a non-hydrogenic atom in parallel electric and magnetic fields. For a given initial state, closed-orbit theory gives the dependence of this recurrence amplitude on the initial angle of an orbit. By comparing the recurrence amplitude for different initial states, we can determine the initial angles of the closed classical orbits from the quantum recurrence spectra. Therefore, by integrating the Hamiltonian motion equations, we can obtain the closed orbits directly. This method can also be used to extract the closed orbits from the experimental data.
Energy Technology Data Exchange (ETDEWEB)
Lin, Lin; Chen, Mohan; Yang, Chao; He, Lixin
2012-02-10
We describe how to apply the recently developed pole expansion plus selected inversion (PEpSI) technique to Kohn-Sham density function theory (DFT) electronic structure calculations that are based on atomic orbital discretization. We give analytic expressions for evaluating charge density, total energy, Helmholtz free energy and atomic forces without using the eigenvalues and eigenvectors of the Kohn-Sham Hamiltonian. We also show how to update the chemical potential without using Kohn-Sham eigenvalues. The advantage of using PEpSI is that it has a much lower computational complexity than that associated with the matrix diagonalization procedure. We demonstrate the performance gain by comparing the timing of PEpSI with that of diagonalization on insulating and metallic nanotubes. For these quasi-1D systems, the complexity of PEpSI is linear with respect to the number of atoms. This linear scaling can be observed in our computational experiments when the number of atoms in a nanotube is larger than a few hundreds. Both the wall clock time and the memory requirement of PEpSI is modest. This makes it even possible to perform Kohn-Sham DFT calculations for 10,000-atom nanotubes on a single processor. We also show that the use of PEpSI does not lead to loss of accuracy required in a practical DFT calculation.
Atomic Oxygen Interactions With Silicone Contamination on Spacecraft in Low Earth Orbit Studied
Banks, Bruce A.
2001-01-01
Silicones have been widely used on spacecraft as potting compounds, adhesives, seals, gaskets, hydrophobic surfaces, and atomic oxygen protective coatings. Contamination of optical and thermal control surfaces on spacecraft in low Earth orbit (LEO) has been an ever-present problem as a result of the interaction of atomic oxygen with volatile species from silicones and hydrocarbons onboard spacecraft. These interactions can deposit a contaminant that is a risk to spacecraft performance because it can form an optically absorbing film on the surfaces of Sun sensors, star trackers, or optical components or can increase the solar absorptance of thermal control surfaces. The transmittance, absorptance, and reflectance of such contaminant films seem to vary widely from very transparent SiOx films to much more absorbing SiOx-based films that contain hydrocarbons. At the NASA Glenn Research Center, silicone contamination that was oxidized by atomic oxygen has been examined from LEO spacecraft (including the Long Duration Exposure Facility and the Mir space station solar arrays) and from ground laboratory LEO simulations. The findings resulted in the development of predictive models that may help explain the underlying issues and effects. Atomic oxygen interactions with silicone volatiles and mixtures of silicone and hydrocarbon volatiles produce glassy SiOx-based contaminant coatings. The addition of hydrocarbon volatiles in the presence of silicone volatiles appears to cause much more absorbing (and consequently less transmitting) contaminant films than when no hydrocarbon volatiles are present. On the basis of the LDEF and Mir results, conditions of high atomic oxygen flux relative to low contaminant flux appear to result in more transparent contaminant films than do conditions of low atomic oxygen flux with high contaminant flux. Modeling predictions indicate that the deposition of contaminant films early in a LEO flight should depend much more on atomic oxygen flux than
Orbitals from local RDMFT: Are they Kohn-Sham or Natural Orbitals?
Theophilou, Iris; Gidopoulos, Nikitas I; Rubio, Angel; Helbig, Nicole
2015-01-01
Recently, an approximation was introduced in reduced density matrix functional theory (RDMFT), called local-RDMFT, where functionals of the one-body reduced density matrix (1-RDM) are minimized under the additional condition that the optimal orbitals satisfy a single electron Schr\\"odinger equation with a local potential. In the present work, we assess the impact of this additional condition on the optimal orbitals. In particular we compare orbitals obtained by local-RDMFT with those obtained with the full minimization (without the extra condition) by comparing them with the exact NOs and orbitals from a density functional calculation using the local density approximation (LDA). We find that the orbitals from local-RMDFT are very close to LDA orbitals, contrary to those of the full minimization that resemble the exact NOs. Since local RDMFT preserves the good quality of the description of strong static correlation, this finding opens the way to a mixed density/density matrix scheme, where Kohn-Sham orbitals o...
Orbitals from local RDMFT: Are they Kohn-Sham or natural orbitals?
Energy Technology Data Exchange (ETDEWEB)
Theophilou, Iris; Helbig, Nicole [Peter-Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich (Germany); Lathiotakis, Nektarios N. [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Vass. Constantinou 48, GR-11635 Athens (Greece); Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Saale) (Germany); Gidopoulos, Nikitas I. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Rubio, Angel [Max Planck Institute for the Structure and Dynamics of Matter and Center for Free-Electron Laser Science, Luruper Chaussee 149, 22761 Hamburg (Germany); Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Dpto. Física de Materiales, Universidad del País Vasco, CFM CSIC-UPV/EHU-MPC and DIPC, Av. Tolosa 72, E-20018 San Sebastián (Spain)
2015-08-07
Recently, an approximate theoretical framework was introduced, called local reduced density matrix functional theory (local-RDMFT), where functionals of the one-body reduced density matrix (1-RDM) are minimized under the additional condition that the optimal orbitals satisfy a single electron Schrödinger equation with a local potential. In the present work, we focus on the character of these optimal orbitals. In particular, we compare orbitals obtained by local-RDMFT with those obtained with the full minimization (without the extra condition) by contrasting them against the exact NOs and orbitals from a density functional calculation using the local density approximation (LDA). We find that the orbitals from local-RMDFT are very close to LDA orbitals, contrary to those of the full minimization that resemble the exact NOs. Since local RDMFT preserves the good quality of the description of strong static correlation, this finding opens the way to a mixed density/density matrix scheme, where Kohn-Sham orbitals obtain fractional occupations from a minimization of the occupation numbers using 1-RDM functionals. This will allow for a description of strong correlation at a cost only minimally higher than a density functional calculation.
Natural orbit approximations in single power-law potentials
Struck, Curtis
2014-01-01
In a previous paper, I demonstrated the accuracy of simple, precessing, power ellipse (p-ellipse) approximations to orbits of low-to-moderate eccentricity in power-law potentials. Here I explore several extensions of these approximations to improve accuracy, especially for nearly radial orbits. 1) It is found that moderately improved orbital fits can be achieved with higher order perturbation expansions (in eccentricity), with the addition of `harmonic' terms to the solution. 2) Alternately, a matching of the extreme radial excursions of an orbit can be imposed, and a more accurate estimate of the eccentricity parameter is obtained. However, the error in the precession frequency is usually increased. 3) A correction function of small magnitude corrects the frequency problem. With this correction, even first order approximations yield excellent fits at quite high eccentricity over a range of potential indices that includes flat and falling rotation curve cases. 4) Adding a first harmonic term to fit the breadt...
Matzkin, A.; Dando, P. A.; Monteiro, T. S.
2003-02-01
In a previous work [Phys. Rev. A 66, 013410 (2002)], we noted a partial disagreement between quantum R matrix and semiclassical calculations of photoabsorption spectra of molecules in a magnetic field. We show that this disagreement is due to a nonvanishing contribution of processes, which are forbidden according to the usual semiclassical formalism. Formulas to include these processes are obtained by using a refined stationary phase approximation. The resulting higher order in ħ contributions also account for previously unexplained “recurrences without closed orbits.” Quantum and semiclassical photoabsorption spectra for Rydberg atoms and molecules in a magnetic field are calculated and compared to assess the validity of the first-order forbidden orbit contributions.
Matzkin, A; Monteiro, T S
2003-01-01
In a previous work [Phys. Rev. A \\textbf{66}, 0134XX (2002)] we noted a partial disagreement between quantum R-matrix and semiclassical calculations of photoabsorption spectra of molecules in a magnetic field. We show this disagreement is due to a non-vanishing contribution of processes which are forbidden according to the usual semiclassical formalism. Formulas to include these processes are obtained by using a refined stationary phase approximation. The resulting higher order in $\\hbar$ contributions also account for previously unexplained ``recurrences without closed-orbits''. Quantum and semiclassical photoabsorption spectra for Rydberg atoms and molecules in a magnetic field are calculated and compared to assess the validity of the first-order forbidden orbit contributions.
Zitterbewegung with spin-orbit coupled ultracold atoms in a fluctuating optical lattice
Argonov, V. Yu; Makarov, D. V.
2016-09-01
The dynamics of non-interacting ultracold atoms with artificial spin-orbit coupling is considered. Spin-orbit coupling is created using two moving optical lattices with orthogonal polarizations. Our main goal is to study influence of lattice noise on Rabi oscillations. Special attention is paid to the phenomenon of the Zitterbewegung being trembling motion caused by Rabi transitions between states with different velocities. Phase and amplitude fluctuations of lattices are modelled by means of the two-dimensional stochastic Ornstein-Uhlenbeck process, also known as harmonic noise. In the the noiseless case the problem is solved analytically in terms of the momentum representation. It is shown that lattice noise significantly extends duration of the Zitterbewegung as compared to the noiseless case. This effect originates from noise-induced decoherence of Rabi oscillations.
Linear scaling coupled cluster and perturbation theories in the atomic orbital basis
Scuseria, Gustavo E.; Ayala, Philippe Y.
1999-11-01
We present a reformulation of the coupled cluster equations in the atomic orbital (AO) basis that leads to a linear scaling algorithm for large molecules. Neglecting excitation amplitudes in a screening process designed to achieve a target energy accuracy, we obtain an AO coupled cluster method which is competitive in terms of number of amplitudes with the traditional molecular orbital (MO) solution, even for small molecules. For large molecules, the decay properties of integrals and excitation amplitudes becomes evident and our AO method yields a linear scaling algorithm with respect to molecular size. We present benchmark calculations to demonstrate that our AO reformulation of the many-body electron correlation problem defeats the "exponential scaling wall" that has characterized high-level MO quantum chemistry calculations for many years.
Atomic Gaussian type orbitals and their Fourier transforms via the Rayleigh expansion
Yükçü, Niyazi
2016-03-01
Gaussian type orbitals (GTOs), which are one of the types of exponential type orbitals (ETOs), are used usually as basis functions in the multi-center atomic and molecular integrals to better understand physical and chemical properties of matter. In the Fourier transform method (FTM), basis functions have not simplicity to make mathematical operations, but their Fourier transforms are easier to use. In this work, with the help of FTM, Rayleigh expansion and some properties of unnormalized GTOs, we present new mathematical results for the Fourier transform of GTOs in terms of Laguerre polynomials, hypergeometric and Whittaker functions. Physical and analytical properties of GTOs are discussed and some numerical results have been given in a table. Finally, we compare our mathematical results with the other known literature results by using a computer program and details of evaluation are presented.
Hübener, Hannes; Giustino, Feliciano
2014-02-01
We present the implementation of linear-response time-dependent density functional theory based on the self-consistent Sternheimer equation and employing a basis set of numerical pseudo-atomic orbitals. We demonstrate this method by presenting test calculations on systems of increasing size ranging from benzene to chlorophyll a, and by comparing our results with those obtained within Casida's formalism and with previous calculations. We provide a detailed assessment of the accuracy of this method, both in relation to the use of local orbitals for describing electronic excitations and to the handling of the frequency response using Padé approximants. We establish a simple criterion for estimating a priori the accuracy of the basis set in the calculation of optical spectra. We show that the computational cost of this method scales quadratically with the system size.
Natural orbit approximations in single power-law potentials
Struck, Curtis
2015-01-01
In a previous paper, I demonstrated the accuracy of simple, precessing, power ellipse (p-ellipse) approximations to orbits of low-to-moderate eccentricity in power-law potentials. Here, I explore several extensions of these approximations to improve accuracy, especially for nearly radial orbits. (1) It is found that moderately improved orbital fits can be achieved with higher order perturbation expansions (in eccentricity), with the addition of `harmonic' terms to the solution. (2) Alternately, a matching of the extreme radial excursions of an orbit can be imposed, and a more accurate estimate of the eccentricity parameter is obtained. However, the error in the precession frequency is usually increased. (3) A correction function of small magnitude corrects the frequency problem. With this correction, even first-order approximations yield excellent fits at quite high eccentricity over a range of potential indices that includes flat and falling rotation-curve cases. (4) Adding a first harmonic term to fit the breadth of the orbital loops, and determining the fundamental and harmonic coefficients by matching to three orbital positions further improves the fit. With a couple of additional small corrections, one obtains excellent fits to orbits with radial ranges of more than a thousand for some potentials. These simple corrections to the basic p-ellipse are basically in the form of several successive approximations, and can provide high accuracy. They suggest new results including that the apsidal precession rate scales approximately as log(1 - e) at very high eccentricities e. New insights are also provided on the occurrence of periodic orbits in various potentials, especially at high eccentricity.
Graph of atomic orbitals and the molecular structure-descriptors based on it
Directory of Open Access Journals (Sweden)
ANDREY A. TOROPOV
2005-04-01
Full Text Available The graph of atomic orbitals (GAO is a novel type of molecular graph, recently proposed by one of the authors. Various molecular structure-descriptors computed for GAO are compared with their analogs computed for ordinary molecular graphs. The quality of these structure-descriptors was tested for correlation with the normal boiling points of alkanes and cycloalkanes. In all the studied cases, the results based on GAO are similar to, and usually slightly better than, those obtained by means of ordinary molecular graps.
Off-axis retrieval of orbital angular momentum of light stored in cold atoms
de Oliveira, R A; Barbosa, P S; Martins, W S; Barreiro, S; Felinto, D; Bloch, D; Tabosa, J W R
2014-01-01
We report on the storage of orbital angu- lar momentum (OAM) of light of a Laguerre-Gaussian mode in an ensemble of cold cesium atoms and its re- trieval along an axis different from the incident light beam. We employed a time-delayed four-wave mixing configuration to demonstrate that at small angle (2o), after storage, the retrieved beam carries the same OAM as the one encoded in the input beam. A calculation based on mode decomposition of the retrieved beam over the Laguerre-Gaussian basis is in agreement with the experimental observations done at small angle values. However, the calculation shows that the OAM retrieving would get lost at larger angles, reducing the fidelity of such storing-retrieving process. In addition, we have also observed that by applying an external magnetic field to the atomic ensemble the retrieved OAM presents Larmor oscillations, demonstrating the possibility of its manipulation and off-axis retrieval.
Lin, Lin; Yang, Chao; He, Lixin
2012-01-01
We describe how to apply the recently developed pole expansion plus selected inversion (PEpSI) technique to Kohn-Sham density function theory (DFT) electronic structure calculations that are based on atomic orbital discretization. We give analytic expressions for evaluating charge density, total energy, Helmholtz free energy and atomic forces without using the eigenvalues and eigenvectors of the Kohn-Sham Hamiltonian. We also show how to update the chemical potential without using Kohn-Sham eigenvalues. The advantage of using PEpSI is that it has a much lower computational complexity than that associated with the matrix diagonalization procedure. We demonstrate the performance gain by comparing the timing of PEpSI with that of diagonalization on insulating and metallic nanotubes. For these quasi-1D systems, the complexity of PEpSI is linear with respect to the number of atoms. This linear scaling can be observed in our computational experiments when the number of atoms in a nanotube is larger than a few hundr...
Energy Technology Data Exchange (ETDEWEB)
Koide, M. [Department of Science and Technology, Meisei University, Tokyo 191-8656 (Japan)]. E-mail: mkoide@galaxy.ocn.ne.jp; Koike, F. [School of Medicine, Kitasato University, Kanagawa 228-8555 (Japan); Azuma, Y. [PhotonFactory, IMSS, KEK, Ibaraki 305-0801 (Japan); Nagata, T. [Department of Science and Technology, Meisei University, Tokyo 191-8656 (Japan)
2005-06-15
We study the origin of dual window-type 3s->4p photoexcitation resonances of potassium atoms that have been observed previously [M. Koide et al., J. Phys. Soc. Jpn. 71 (2002) 1676] by means of photoion spectroscopy. We also consider the sub-valence shell photoexcitations of other alkali metal atoms. In potassium 3p photoionizations, the photoion energy levels may be labeled by their total angular momenta, and they are well separated due to the spin-orbit couplings in 3p subshells. The system of a photoion and a photoelectron is therefore a superposition of different total spin states if expressed in terms of the LS-coupling scheme. The ionization continuum may couple with several intermediate discrete states with different total spin quantum numbers, giving a possibility to observe split resonance structures in the spectra of 3s->np photoexcitations and in other alkali-atom photoexcitations. We discuss the dual window-type resonances in potassium, rubidium, and cesium atoms.
Guseinov, I I
2010-01-01
The new combined formulas have been established for the complex and real rotation-angular functions arising in the evaluation of two-center overlap integrals over arbitrary atomic orbitals in molecular coordinate system. These formulas can be useful in the study of different quantum mechanical problems in both the theory and practice of calculations dealing with atoms, molecules, nuclei and solids when the integer and noninteger n complex and real atomic orbitals basis sets are emploed. This work presented the development of our previous paper (I.I. Guseinov, Phys. Rev. A, 32 (1985) 1864).
Institute of Scientific and Technical Information of China (English)
YUN Su-Jun; WANG Fu-He; ZHOU Yun-Song; DU Meng-Li
2007-01-01
We study the oscillations in the spontaneous emission rate of an atom near a dielectric slab. The emission rate is calculated as a function of system size using quantum electrodynamics. It exhibits multi-periodic oscillations.Four frequencies of the oscillations are extracted by Fourier transforms. They agree with actions of photon closed-orbits going away and returning to the atom. These oscillations are explained as manifestations of quantum interference effects between the emitted photon wave near the atom and the returning photon waves travelling along various closed-orbits.
Tunneling wave packets of atoms from intense elliptically polarized fields in natural geometry
Han, Meng; Li, Min; Liu, Ming-Ming; Liu, Yunquan
2017-02-01
We study strong-field tunneling of atoms in intense elliptically polarized laser fields in natural tunneling geometry. We obtain the temporal- and spatial-dependent tunneling ionization rates, the transverse and longitudinal momentum distributions, and the position distributions of the tunnel exit in parabolic coordinates. The tunneling electron wave packets at the tunnel exit are three dimensionally characterized for both momentum and spatial distributions. The conjunction between the tunneling point and the classical propagation of the widely used semiclassical model are naturally connected. We further calculate the ellipticity-dependent photoelectron momentum distributions on the detector, which are validated by comparison with the exact results through numerically solving the time-dependent Schrödinger equation. The theory clarifies crucial questions about strong-field tunneling ionization, which has important implications for the attoclock with elliptical or circular fields, photoelectron holography, molecular orbital imaging, etc.
Asymmetry of the natural line profile for the hydrogen atom.
Labzowsky, L N; Solovyev, D A; Plunien, G; Soff, G
2001-10-01
The asymmetry of the natural line profile for transitions in hydrogenlike atoms is evaluated within a QED framework. For the Lyman- alpha 1s-2p absorption transition in neutral hydrogen this asymmetry results in an additional energy shift of 2.929 856 Hz. For the 2s(1/2)-2p(3/2) transition it amounts to -1.512 674 Hz. As a new feature this correction turns out to be process dependent. The quoted numbers refer to the Compton-scattering process.
Xu, Guochang
2008-01-01
This is the first book of the satellite era which describes orbit theory with analytical solutions of the second order with respect to all possible disturbances. Based on such theory, the algorithms of orbits determination are completely revolutionized.
Atomic Oxygen Erosion Yield Prediction for Spacecraft Polymers in Low Earth Orbit
Banks, Bruce A.; Backus, Jane A.; Manno, Michael V.; Waters, Deborah L.; Cameron, Kevin C.; deGroh, Kim K.
2009-01-01
The ability to predict the atomic oxygen erosion yield of polymers based on their chemistry and physical properties has been only partially successful because of a lack of reliable low Earth orbit (LEO) erosion yield data. Unfortunately, many of the early experiments did not utilize dehydrated mass loss measurements for erosion yield determination, and the resulting mass loss due to atomic oxygen exposure may have been compromised because samples were often not in consistent states of dehydration during the pre-flight and post-flight mass measurements. This is a particular problem for short duration mission exposures or low erosion yield materials. However, as a result of the retrieval of the Polymer Erosion and Contamination Experiment (PEACE) flown as part of the Materials International Space Station Experiment 2 (MISSE 2), the erosion yields of 38 polymers and pyrolytic graphite were accurately measured. The experiment was exposed to the LEO environment for 3.95 years from August 16, 2001 to July 30, 2005 and was successfully retrieved during a space walk on July 30, 2005 during Discovery s STS-114 Return to Flight mission. The 40 different materials tested (including Kapton H fluence witness samples) were selected specifically to represent a variety of polymers used in space as well as a wide variety of polymer chemical structures. The MISSE 2 PEACE Polymers experiment used carefully dehydrated mass measurements, as well as accurate density measurements to obtain accurate erosion yield data for high-fluence (8.43 1021 atoms/sq cm). The resulting data was used to develop an erosion yield predictive tool with a correlation coefficient of 0.895 and uncertainty of +/-6.3 10(exp -25)cu cm/atom. The predictive tool utilizes the chemical structures and physical properties of polymers to predict in-space atomic oxygen erosion yields. A predictive tool concept (September 2009 version) is presented which represents an improvement over an earlier (December 2008) version.
Atomic Oxygen Erosion Yield Predictive Tool for Spacecraft Polymers in Low Earth Orbit
Bank, Bruce A.; de Groh, Kim K.; Backus, Jane A.
2008-01-01
A predictive tool was developed to estimate the low Earth orbit (LEO) atomic oxygen erosion yield of polymers based on the results of the Polymer Erosion and Contamination Experiment (PEACE) Polymers experiment flown as part of the Materials International Space Station Experiment 2 (MISSE 2). The MISSE 2 PEACE experiment accurately measured the erosion yield of a wide variety of polymers and pyrolytic graphite. The 40 different materials tested were selected specifically to represent a variety of polymers used in space as well as a wide variety of polymer chemical structures. The resulting erosion yield data was used to develop a predictive tool which utilizes chemical structure and physical properties of polymers that can be measured in ground laboratory testing to predict the in-space atomic oxygen erosion yield of a polymer. The properties include chemical structure, bonding information, density and ash content. The resulting predictive tool has a correlation coefficient of 0.914 when compared with actual MISSE 2 space data for 38 polymers and pyrolytic graphite. The intent of the predictive tool is to be able to make estimates of atomic oxygen erosion yields for new polymers without requiring expensive and time consumptive in-space testing.
Bzowski, M
2008-01-01
Contect: With the forthcoming launch of a NASA SMEX mission IBEX devoted to imaging of heliospheric interface by in-situ detection of Energetic Neutral Atoms (ENA) an important issue becomes recognizing of transport of these atoms from the termination shock of the solar wind to Earth orbit. Aims: Investigate modifications of energy and of survival probability of the H ENA detectable by IBEX (0.01 -- 6 keV) between the termination shock and Earth orbit taking into account the influence of the variable and anisotropic solar wind and solar EUV radiation. Methods: Energy change of the atoms is calculated by numerical simulations of orbits of the H ENA atoms from ~100 AU from the Sun down to Earth orbit, taking into account solar gravity and Lyman-$\\alpha$ radiation pressure, which is variable in time and depends on radial velocity of the atom. To calculate survival probabilities of the atoms against onization, a detailed 3D and time-dependent model of H ENA ionization based on observations of the solar wind and E...
Directory of Open Access Journals (Sweden)
Eduardo A. Castro
2004-12-01
Full Text Available We report the results of a calculation of the normal boiling points of a representative set of 200 organic molecules through the application of QSPR theory. For this purpose we have used a particular set of flexible molecular descriptors, the so called Correlation Weighting of Atomic Orbitals with Extended Connectivity of Zero- and First-Order Graphs of Atomic Orbitals. Although in general the results show suitable behavior to predict this physical chemistry property, the existence of some deviant behaviors points to a need to complement this index with some other sort of molecular descriptors. Some possible extensions of this study are discussed.
Quickening nature's pulse: atomic agriculture at the International Atomic Energy Agency.
Hamblin, Jacob Darwin
2015-01-01
Mutation breeders in the 1960s seemed poised to use atomic energy to speed up mutation rates in plants in order to develop new crop varieties, for the benefit of all people. Although skepticism had slowed this work in the United States, the International Atomic Energy Agency (IAEA) nurtured the scientific field, its community of experts, and an imagined version of the future that put humans in control of their destiny. The IAEA acted as a center of dissemination and support for experts and ideas even when they had fallen from favor elsewhere. Through the lens of the IAEA, plant breeding bore the appearance of a socially progressive, ultra-modern science destined to alleviate population pressures. Administrators at the IAEA also were desperate for success stories, hoping to highlight mutation plant breeding as a potential solution to the world's ills. The community of mutation plant breeders gained a lifeline from the consistent clarion call from the Vienna-based agency to use atomic energy to understand the natural world and quicken its pulse with radioisotopes.
Institute of Scientific and Technical Information of China (English)
Wang De-Hua
2007-01-01
Using the closed orbit theory,we study the classical motion and calculate the photoabsorption spectra of Rydberg hydrogen atom between two parallel metallic surfaces.The results show that the metallic surfaces have a significant effect on the photoabsorption process.When the distances between the hydrogen atom and the two metallic surfaces are close to a critical value dc,the number of the closed orbits is the greatest.When the distance larger or smaller than dc,the number of the closed orbits decreases and the absorption spectra are shown to exhibit a damping oscillation.This work is an interesting new application of closed-orbit theory and is of potential experimental interest.
Brics, M; Bauer, D
2016-01-01
Recently introduced time-dependent renormalized-natural-orbital theory (TDRNOT) is based on the equations of motion for the so-called natural orbitals, i.e., the eigenfunctions of the one-body reduced density matrix. Exact TDRNOT can be formulated for any time-dependent two-electron system in either spin configuration. In this paper, the method is tested against high-order harmonic generation (HHG) and Fano profiles in absorption spectra with the help of a numerically exactly solvable one-dimensional model He atom, starting from the spin-singlet ground state. Such benchmarks are challenging because Fano profiles originate from transitions involving autoionizing states, and HHG is a strong-field phenomenon well beyond linear response. TDRNOT with just one natural orbital per spin in the helium spin-singlet case is equivalent to time-dependent Hartree-Fock or time-dependent density functional theory (TDDFT) in exact exchange-only approximation. It is not unexpected that TDDFT fails in reproducing Fano profiles ...
Embedded-cluster calculations in a numeric atomic orbital density-functional theory framework.
Berger, Daniel; Logsdail, Andrew J; Oberhofer, Harald; Farrow, Matthew R; Catlow, C Richard A; Sherwood, Paul; Sokol, Alexey A; Blum, Volker; Reuter, Karsten
2014-07-14
We integrate the all-electron electronic structure code FHI-aims into the general ChemShell package for solid-state embedding quantum and molecular mechanical (QM/MM) calculations. A major undertaking in this integration is the implementation of pseudopotential functionality into FHI-aims to describe cations at the QM/MM boundary through effective core potentials and therewith prevent spurious overpolarization of the electronic density. Based on numeric atomic orbital basis sets, FHI-aims offers particularly efficient access to exact exchange and second order perturbation theory, rendering the established QM/MM setup an ideal tool for hybrid and double-hybrid level density functional theory calculations of solid systems. We illustrate this capability by calculating the reduction potential of Fe in the Fe-substituted ZSM-5 zeolitic framework and the reaction energy profile for (photo-)catalytic water oxidation at TiO2(110).
Embedded-cluster calculations in a numeric atomic orbital density-functional theory framework
Berger, Daniel; Logsdail, Andrew J.; Oberhofer, Harald; Farrow, Matthew R.; Catlow, C. Richard A.; Sherwood, Paul; Sokol, Alexey A.; Blum, Volker; Reuter, Karsten
2014-07-01
We integrate the all-electron electronic structure code FHI-aims into the general ChemShell package for solid-state embedding quantum and molecular mechanical (QM/MM) calculations. A major undertaking in this integration is the implementation of pseudopotential functionality into FHI-aims to describe cations at the QM/MM boundary through effective core potentials and therewith prevent spurious overpolarization of the electronic density. Based on numeric atomic orbital basis sets, FHI-aims offers particularly efficient access to exact exchange and second order perturbation theory, rendering the established QM/MM setup an ideal tool for hybrid and double-hybrid level density functional theory calculations of solid systems. We illustrate this capability by calculating the reduction potential of Fe in the Fe-substituted ZSM-5 zeolitic framework and the reaction energy profile for (photo-)catalytic water oxidation at TiO2(110).
Bzowski, M.
2008-01-01
Context: With the forthcoming launch of a NASA SMEX mission IBEX devoted to imaging of heliospheric interface by in-situ detection of Energetic Neutral Atoms (ENA) an important issue becomes recognizing of transport of these atoms from the termination shock of the solar wind to Earth orbit. Aims: Investigate modifications of energy and of survival probability of the H ENA detectable by IBEX (0.01 -- 6 keV) between the termination shock and Earth orbit taking into account the influence of the ...
Energy Technology Data Exchange (ETDEWEB)
Smeyers, Y.G.; Delgado-Barrio, G.
1976-05-01
The half-projected Hartree--Fock function for singlet states (HPHF) is analyzed in terms of natural electronic configurations. For this purpose the HPHF spinless density matrix and its natural orbitals are first deduced. It is found that the HPHF function does not contain any contribution from odd-times excited configurations. It is seen in addition, in the case of the singlet ground states, this function is approximately equivalent to two closed-shell configurations, although the nature of the excited one depends on the nuclear geometry. An example is given in the case of the LiH ground state. Finally, the application of this model for studying systems of more than two atoms is criticized.
Weyl spin-orbit-coupling-induced interactions in uniform and trapped atomic quantum fluids
Gupta, Reena; Singh, G. S.; Bosse, Jürgen
2013-11-01
We establish through analytical and numerical studies of thermodynamic quantities for noninteracting atomic gases that the isotropic three-dimensional spin-orbit coupling, the Weyl coupling, induces interaction which counters “effective” attraction (repulsion) of the exchange symmetry present in zero-coupling Bose (Fermi) gas. The exact analytical expressions for the grand potential and hence for several thermodynamic quantities have been obtained for this purpose in both uniform and trapped cases. It is enunciated that many interesting features of spin-orbit-coupled systems revealed theoretically can be understood in terms of coupling-induced modifications in statistical interparticle potential. The temperature dependence of the chemical potential, specific heat, and isothermal compressibility for a uniform Bose gas is found to have signature of the incipient Bose-Einstein condensation in the very weak coupling regime although the system does not really go in the Bose-condensed phase. The transition temperature in the harmonically trapped case decreases with an increase of coupling strength consistent with the weakening of the statistical attractive interaction. Anomalous behavior of some thermodynamic quantities, partly akin to that in dimensions less than two, appears for uniform fermions as soon as the Fermi level goes down the Dirac point on increasing the coupling strength. It is suggested that the fluctuation-dissipation theorem can be utilized to verify anomalous behaviors from studies of long-wavelength fluctuations in bunching and antibunching effects.
Corsetti, Fabiano
2014-01-01
The implementation of the orbital minimization method (OMM) for solving the self-consistent Kohn-Sham (KS) problem for electronic structure calculations in a basis of non-orthogonal numerical atomic orbitals of finite-range is reported. We explore the possibilities for using the OMM as an exact cubic-scaling solver for the KS problem, and compare its performance with that of explicit diagonalization in realistic systems. We analyze the efficiency of the method depending on the choice of line search algorithm and on two free parameters, the scale of the kinetic energy preconditioning and the eigenspectrum shift. The results of several timing tests are then discussed, showing that the OMM can achieve a noticeable speedup with respect to diagonalization even for minimal basis sets for which the number of occupied eigenstates represents a significant fraction of the total basis size (>15%). We investigate the hard and soft parallel scaling of the method on multiple cores, finding a performance equal to or better ...
Werner, Hans-Joachim
2016-11-01
The accuracy of multipole approximations for distant pair energies in local second-order Møller-Plesset perturbation theory (LMP2) as introduced by Hetzer et al. [Chem. Phys. Lett. 290, 143 (1998)] is investigated for three chemical reactions involving molecules with up to 92 atoms. Various iterative and non-iterative approaches are compared, using different energy thresholds for distant pair selection. It is demonstrated that the simple non-iterative dipole-dipole approximation, which has been used in several recent pair natural orbitals (PNO)-LMP2 and PNO-LCCSD (local coupled-cluster with singles and doubles) methods, may underestimate the distant pair energies by up to 50% and can lead to significant errors in relative energies, unless very tight thresholds are used. The accuracy can be much improved by including higher multipole orders and by optimizing the distant pair amplitudes iteratively along with all other amplitudes. A new approach is presented in which very small special PNO domains for distant pairs are used in the iterative approach. This reduces the number of distant pair amplitudes by 3 orders of magnitude and keeps the additional computational effort for the iterative optimization of distant pair amplitudes minimal.
Grimme, Stefan; Brandenburg, Jan Gerit; Bannwarth, Christoph; Hansen, Andreas
2015-08-01
A density functional theory (DFT) based composite electronic structure approach is proposed to efficiently compute structures and interaction energies in large chemical systems. It is based on the well-known and numerically robust Perdew-Burke-Ernzerhoff (PBE) generalized-gradient-approximation in a modified global hybrid functional with a relatively large amount of non-local Fock-exchange. The orbitals are expanded in Ahlrichs-type valence-double zeta atomic orbital (AO) Gaussian basis sets, which are available for many elements. In order to correct for the basis set superposition error (BSSE) and to account for the important long-range London dispersion effects, our well-established atom-pairwise potentials are used. In the design of the new method, particular attention has been paid to an accurate description of structural parameters in various covalent and non-covalent bonding situations as well as in periodic systems. Together with the recently proposed three-fold corrected (3c) Hartree-Fock method, the new composite scheme (termed PBEh-3c) represents the next member in a hierarchy of "low-cost" electronic structure approaches. They are mainly free of BSSE and account for most interactions in a physically sound and asymptotically correct manner. PBEh-3c yields good results for thermochemical properties in the huge GMTKN30 energy database. Furthermore, the method shows excellent performance for non-covalent interaction energies in small and large complexes. For evaluating its performance on equilibrium structures, a new compilation of standard test sets is suggested. These consist of small (light) molecules, partially flexible, medium-sized organic molecules, molecules comprising heavy main group elements, larger systems with long bonds, 3d-transition metal systems, non-covalently bound complexes (S22 and S66×8 sets), and peptide conformations. For these sets, overall deviations from accurate reference data are smaller than for various other tested DFT methods
Grimme, Stefan; Brandenburg, Jan Gerit; Bannwarth, Christoph; Hansen, Andreas
2015-08-07
A density functional theory (DFT) based composite electronic structure approach is proposed to efficiently compute structures and interaction energies in large chemical systems. It is based on the well-known and numerically robust Perdew-Burke-Ernzerhoff (PBE) generalized-gradient-approximation in a modified global hybrid functional with a relatively large amount of non-local Fock-exchange. The orbitals are expanded in Ahlrichs-type valence-double zeta atomic orbital (AO) Gaussian basis sets, which are available for many elements. In order to correct for the basis set superposition error (BSSE) and to account for the important long-range London dispersion effects, our well-established atom-pairwise potentials are used. In the design of the new method, particular attention has been paid to an accurate description of structural parameters in various covalent and non-covalent bonding situations as well as in periodic systems. Together with the recently proposed three-fold corrected (3c) Hartree-Fock method, the new composite scheme (termed PBEh-3c) represents the next member in a hierarchy of "low-cost" electronic structure approaches. They are mainly free of BSSE and account for most interactions in a physically sound and asymptotically correct manner. PBEh-3c yields good results for thermochemical properties in the huge GMTKN30 energy database. Furthermore, the method shows excellent performance for non-covalent interaction energies in small and large complexes. For evaluating its performance on equilibrium structures, a new compilation of standard test sets is suggested. These consist of small (light) molecules, partially flexible, medium-sized organic molecules, molecules comprising heavy main group elements, larger systems with long bonds, 3d-transition metal systems, non-covalently bound complexes (S22 and S66×8 sets), and peptide conformations. For these sets, overall deviations from accurate reference data are smaller than for various other tested DFT methods
Energy Technology Data Exchange (ETDEWEB)
Grimme, Stefan, E-mail: grimme@thch.uni-bonn.de; Brandenburg, Jan Gerit; Bannwarth, Christoph; Hansen, Andreas [Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms Universität Bonn, Beringstraße 4, 53115 Bonn (Germany)
2015-08-07
A density functional theory (DFT) based composite electronic structure approach is proposed to efficiently compute structures and interaction energies in large chemical systems. It is based on the well-known and numerically robust Perdew-Burke-Ernzerhoff (PBE) generalized-gradient-approximation in a modified global hybrid functional with a relatively large amount of non-local Fock-exchange. The orbitals are expanded in Ahlrichs-type valence-double zeta atomic orbital (AO) Gaussian basis sets, which are available for many elements. In order to correct for the basis set superposition error (BSSE) and to account for the important long-range London dispersion effects, our well-established atom-pairwise potentials are used. In the design of the new method, particular attention has been paid to an accurate description of structural parameters in various covalent and non-covalent bonding situations as well as in periodic systems. Together with the recently proposed three-fold corrected (3c) Hartree-Fock method, the new composite scheme (termed PBEh-3c) represents the next member in a hierarchy of “low-cost” electronic structure approaches. They are mainly free of BSSE and account for most interactions in a physically sound and asymptotically correct manner. PBEh-3c yields good results for thermochemical properties in the huge GMTKN30 energy database. Furthermore, the method shows excellent performance for non-covalent interaction energies in small and large complexes. For evaluating its performance on equilibrium structures, a new compilation of standard test sets is suggested. These consist of small (light) molecules, partially flexible, medium-sized organic molecules, molecules comprising heavy main group elements, larger systems with long bonds, 3d-transition metal systems, non-covalently bound complexes (S22 and S66×8 sets), and peptide conformations. For these sets, overall deviations from accurate reference data are smaller than for various other tested DFT
Rhile, Ian J.
2014-01-01
Atomic orbitals are a theme throughout the undergraduate chemistry curriculum, and visualizing them has been a theme in this journal. Contour plots as isosurfaces or contour lines in a plane are the most familiar representations of the hydrogen wave functions. In these representations, a surface of a fixed value of the wave function ? is plotted…
Tew, David P; Helmich, Benjamin; Hättig, Christof
2011-08-21
We explore using a pair natural orbital analysis of approximate first-order pair functions as means to truncate the space of both virtual and complementary auxiliary orbitals in the context of explicitly correlated F12 methods using localised occupied orbitals. We demonstrate that this offers an attractive procedure and that only 10-40 virtual orbitals per significant pair are required to obtain second-order valence correlation energies to within 1-2% of the basis set limit. Moreover, for this level of virtual truncation, only 10-40 complementary auxiliary orbitals per pair are required for an accurate resolution of the identity in the computation of the three- and four-electron integrals that arise in explicitly correlated methods.
Huang, Yongxian; Tian, Xiubo; Yang, Shiqin; Chu, Paul K
2007-10-01
A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach (2.289-2.984) x 10(16) at.cm(2) s at an oxygen pressure of 1.5 Pa and rf power of 400 W. The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.
Song, Chenchen; Martínez, Todd J.
2016-05-01
We present a tensor hypercontracted (THC) scaled opposite spin second order Møller-Plesset perturbation theory (SOS-MP2) method. By using THC, we reduce the formal scaling of SOS-MP2 with respect to molecular size from quartic to cubic. We achieve further efficiency by exploiting sparsity in the atomic orbitals and using graphical processing units (GPUs) to accelerate integral construction and matrix multiplication. The practical scaling of GPU-accelerated atomic orbital-based THC-SOS-MP2 calculations is found to be N2.6 for reference data sets of water clusters and alanine polypeptides containing up to 1600 basis functions. The errors in correlation energy with respect to density-fitting-SOS-MP2 are less than 0.5 kcal/mol for all systems tested (up to 162 atoms).
Liquid Water through Density-Functional Molecular Dynamics: Plane-Wave vs Atomic-Orbital Basis Sets
Miceli, Giacomo; Pasquarello, Alfredo
2016-01-01
We determine and compare structural, dynamical, and electronic properties of liquid water at near ambient conditions through density-functional molecular dynamics simulations, when using either plane-wave or atomic-orbital basis sets. In both frameworks, the electronic structure and the atomic forces are self-consistently determined within the same theoretical scheme based on a nonlocal density functional accounting for van der Waals interactions. The overall properties of liquid water achieved within the two frameworks are in excellent agreement with each other. Thus, our study supports that implementations with plane-wave or atomic-orbital basis sets yield equivalent results and can be used indiscriminately in study of liquid water or aqueous solutions.
Institute of Scientific and Technical Information of China (English)
WANG De-Hua
2010-01-01
@@ In a paper published by us,[1] we studied how to extract the closed orbit of the non-hydrogenic atom in parallel electric and magnetic fields. However, there was another paper published in 1996 by Courtney,[2] which studied the initial conditions of closed classical orbits from quantum spectra of hydrogen atom in magnetic field.
Mikajlo, E A; Ford, M J
2003-01-01
This paper presents an experimental measurement of the electronic structure of Na sub 2 O in the solid phase using electron momentum spectroscopy and compares the results with ab initio calculations performed within the linear combination of atomic orbitals (LCAO) approximation. While Hartree-Fock (HF) can reproduce elastic properties we find it overestimates splitting of the oxygen valence bands by around 30% and the width of the O 2p band by a factor of 2. Our experimental values are 15.85 +- 0.2 and 0.6 +- 0.2 eV for these two quantities, respectively. Density functional methods are significantly better, with the hybrid functional PBE0 predicting the oxygen bandgap to within the experimental error. PBE0 also gives the best estimate of the Na core level energies. In contrast, HF performs best for the splitting between the oxygen and sodium bands. Our experimental values of 32.85 +- 0.2 and 27.45 +- 0.2 eV for the Na 2p-Na 2s and O 2p-Na 2p splittings agree well with previous measurements. Distribution of el...
Multiple Majorana zero modes in atomic Fermi double wires with spin-orbit coupling
Wang, Liang-Liang; Gong, Ming; Liu, W.-M.
2017-08-01
Majorana zero modes, quasiparticles with non-Abelian statistics, have gained increasing interest for their fundamental role as building blocks in topological quantum computation. Previous studies have mainly focused on two well-separated Majorana zero modes, which could form two degenerate states serving as one nonlocal qubit for fault-tolerant quantum memory. However, creating and manipulating multiple Majorana zero modes, which could encode more qubits, remain an ongoing research topic. Here we report that multiple Majorana zero modes can exist in atomic Fermi double wires with spin-orbit coupling and perpendicular Zeeman field. This system belongs to the topological BDI class, thus all the topological superfluids are classified by integer numbers. Especially, diverse topological superfluids can be formed in a trap, where the zero energy modes can be found at the interfaces between different topological superfluids. The structure of these zero energy modes in the trap can be engineered by the trapping potential as well as other system parameters. This system would be a significant step towards utilization of Majorana zero modes in quantum computation.
Time-dependent renormalized-natural-orbital theory applied to laser-driven H$_2^+$
Hanusch, A; Brics, M; Bauer, D
2016-01-01
Recently introduced time-dependent renormalized-natural orbital theory (TDRNOT) is extended towards a multi-component approach in order to describe H$_2^+$ beyond the Born-Oppenheimer approximation. Two kinds of natural orbitals, describing the electronic and the nuclear degrees of freedom are introduced, and the exact equations of motion for them are derived. The theory is benchmarked by comparing numerically exact results of the time-dependent Schr\\"odinger equation for a H$_2^+$ model system with the corresponding TDRNOT predictions. Ground state properties, linear response spectra, fragmentation, and high-order harmonic generation are investigated.
Menezes, Filipe; Kats, Daniel; Werner, Hans-Joachim
2016-09-01
We present a CASPT2 method which exploits local approximations to achieve linear scaling of the computational effort with the molecular size, provided the active space is small and local. The inactive orbitals are localized, and the virtual space for each electron pair is spanned by a domain of pair-natural orbitals (PNOs). The configuration space is internally contracted, and the PNOs are defined for uniquely defined orthogonal pairs. Distant pair energies are obtained by multipole approximations, so that the number of configurations that are explicitly treated in the CASPT2 scales linearly with molecular size (assuming a constant active space). The PNOs are generated using approximate amplitudes obtained in a pair-specific semi-canonical basis of projected atomic orbitals (PAOs). The evaluation and transformation of the two-electron integrals use the same parallel local density fitting techniques as recently described for linear-scaling PNO-LMP2 (local second-order Møller-Plesset perturbation theory). The implementation of the amplitude equations, which are solved iteratively, employs the local integrated tensor framework. The efficiency and accuracy of the method are tested for excitation energies and correlation energies. It is demonstrated that the errors introduced by the local approximations are very small. They can be well controlled by few parameters for the distant pair approximation, initial PAO domains, and the PNO domains.
Agapito, Luis; Calzolari, Arrigo; Ferretti, Andrea; Nardelli, Marco
2013-03-01
Metal-organic frameworks (MOF) are a new class of artificial crystalline materials. Because of their flexibility for synthesis and instrinsic ultrahigh surface area and porosity, MOFs show superior performance in gas storage, catalysis, and sensing applications. We use an efficient projection of plane-wave wavefunctions onto atomic orbitals for studying the electronic properties of these intriguing materials. The present scheme harnesses the robust periodic algorithms and systematic convergence of the plane-wave method for an atomistic electronic (Landauer conductance) and chemical (charge transfer, bond and atomic charge) analysis that provides guidelines for the design of MOF electronic materials.
Datta, Dipayan; Kossmann, Simone; Neese, Frank
2016-09-01
The domain-based local pair-natural orbital coupled-cluster (DLPNO-CC) theory has recently emerged as an efficient and powerful quantum-chemical method for the calculation of energies of molecules comprised of several hundred atoms. It has been demonstrated that the DLPNO-CC approach attains the accuracy of a standard canonical coupled-cluster calculation to about 99.9% of the basis set correlation energy while realizing linear scaling of the computational cost with respect to system size. This is achieved by combining (a) localized occupied orbitals, (b) large virtual orbital correlation domains spanned by the projected atomic orbitals (PAOs), and (c) compaction of the virtual space through a truncated pair natural orbital (PNO) basis. In this paper, we report on the implementation of an analytic scheme for the calculation of the first derivatives of the DLPNO-CC energy for basis set independent perturbations within the singles and doubles approximation (DLPNO-CCSD) for closed-shell molecules. Perturbation-independent one-particle density matrices have been implemented in order to account for the response of the CC wave function to the external perturbation. Orbital-relaxation effects due to external perturbation are not taken into account in the current implementation. We investigate in detail the dependence of the computed first-order electrical properties (e.g., dipole moment) on the three major truncation parameters used in a DLPNO-CC calculation, namely, the natural orbital occupation number cutoff used for the construction of the PNOs, the weak electron-pair cutoff, and the domain size cutoff. No additional truncation parameter has been introduced for property calculation. We present benchmark calculations on dipole moments for a set of 10 molecules consisting of 20-40 atoms. We demonstrate that 98%-99% accuracy relative to the canonical CCSD results can be consistently achieved in these calculations. However, this comes with the price of tightening the
Natural orbitals representation and Fermi sea depletion in finite nuclei and nuclear matter
Psonis, V P; Massen, S E
2013-01-01
The natural orbitals and natural occupation numbers of various N = Z, sp and sd shell nuclei are calculated by applying a correlated one-body density matrix. The correlated density matrix has been evaluated by considering central correlations of Jastrow type and an approximation named factor cluster expansion. The correlation effects on the natural orbitals, natural occupation numbers and the Fermi sea depletion are discussed and analysed. In addition, an approximate expression for the correlated one-body density matrix of the nuclear matter has been used for the evaluation of the relative momentum distribution and the Fermi sea depletion. We found that the value of the Fermi sea depletion is higher in closed shell nuclei compared to open shell ones and it is lower compared to the case of nuclear matter. This statement could be confirmed by relevant experimental studies.
HYBRID ORBITALS OF CARBON ATOMS IN THE D6hC36 MOLECULE UNDER THE ROTATING ELLIPSOID MODEL
Institute of Scientific and Technical Information of China (English)
Tong Guo-ping
2000-01-01
The hybrid orbitals of carbon atoms in the D6h C36 molecule arestudied using two rotating ellipsoid models. The model 1 is 1.66R for theshort semi-axis and 2.34R for the long semi-axis, and the model 2 is 1.78R and 2.26R respectively, where R is the C-C bond length. By comparison,we think the model 2 to be more proper in revealing the electronic properties of the D6h C36 molecule. The component of s orbitals in the states hybridized for each of the atoms is much larger than C60, in which the sorbit component is 0.0380 and the porbit is 0.9620. The most component is 0.2098and the least is 0.0482 for model 1; the most is 0.1764 and the least is0.0656 for model 2.
Coe, J P; 10.1063/1.4767436
2013-01-01
Approximate natural orbitals are investigated as a way to improve a Monte Carlo configuration interaction (MCCI) calculation. We introduce a way to approximate the natural orbitals in MCCI and test these and approximate natural orbitals from MP2 and QCISD in MCCI calculations of single-point energies. The efficiency and accuracy of approximate natural orbitals in MCCI potential curve calculations for the double hydrogen dissociation of water, the dissociation of carbon monoxide and the dissociation of the nitrogen molecule are then considered in comparison with standard MCCI when using full configuration interaction as a benchmark. We also use the method to produce a potential curve for water in an aug-cc-pVTZ basis. A new way to quantify the accuracy of a potential curve is put forward that takes into account all of the points and that the curve can be shifted by a constant. We adapt a second-order perturbation scheme to work with MCCI (MCCIPT2) and improve the efficiency of the removal of duplicate states i...
Xiong, Xiao-Gen; Yanai, Takeshi
2017-07-11
The Projector Augmented Wave (PAW) method developed by Blöchl is well recognized as an efficient, accurate pseudopotential approach in solid-state density functional theory (DFT) calculations with the plane-wave basis. Here we present an approach to incorporate the PAW method into the Gauss-type function (GTF) based DFT implementation, which is widely used for molecular quantum chemistry calculations. The nodal and high-exponent GTF components of valence molecular orbitals (MOs) are removed or pseudized by the ultrasoft PAW treatment, while there is elaborate transparency to construct an accurate and well-controlled pseudopotential from all-electron atomic description and to reconstruct an all-electron form of valence MOs from the pseudo MOs. The smoothness of the pseudo MOs should benefit the efficiency of GTF-based DFT calculations in terms of elimination of high-exponent primitive GTFs and reduction of grid points in the numerical quadrature. The processes of the PAW method are divided into basis-independent and -dependent parts. The former is carried out using the previously developed PAW libraries libpaw and atompaw. The present scheme is implemented by incorporating libpaw into the conventional GTF-based DFT solver. The details of the formulations and implementations of GTF-related PAW procedures are presented. The test calculations are shown for illustrating the performance. With the near-complete GTF basis at the cc-pVQZ level, the total energies obtained using our PAW method with suited frozen core treatments converge to those with the conventional all-electron GTF-based method with a rather small absolute error.
Isaev, L.; Schachenmayer, J.; Rey, A. M.
2016-09-01
We show that an interplay between quantum effects, strong on-site ferromagnetic exchange interaction, and antiferromagnetic correlations in Kondo lattices can give rise to an exotic spin-orbit coupled metallic state in regimes where classical treatments predict a trivial insulating behavior. This phenomenon can be simulated with ultracold alkaline-earth fermionic atoms subject to a laser-induced magnetic field by observing dynamics of spin-charge excitations in quench experiments.
Isaev, L; Schachenmayer, J; Rey, A M
2016-09-23
We show that an interplay between quantum effects, strong on-site ferromagnetic exchange interaction, and antiferromagnetic correlations in Kondo lattices can give rise to an exotic spin-orbit coupled metallic state in regimes where classical treatments predict a trivial insulating behavior. This phenomenon can be simulated with ultracold alkaline-earth fermionic atoms subject to a laser-induced magnetic field by observing dynamics of spin-charge excitations in quench experiments.
Energy Technology Data Exchange (ETDEWEB)
Lindfors-Vrejoiu, Ionela; Engelmayer, Johannes; Loosdrecht, Paul H.M. van [II. Physikalisches Institut, Koeln Univ. (Germany); Jin, Lei; Jia, Chun-Lin [Peter Gruenberg Institut (PGI-5) and Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C), Forschungszentrum Juelich GmbH (Germany); Himcinschi, Cameliu [Institut fuer Theoretische Physik, TU Bergakademie Freiberg (Germany); Hensling, Felix; Waser, Rainer; Dittmann, Regina [Peter Gruenberg Institut (PGI-7), Forschungszentrum Juelich GmbH (Germany)
2017-03-15
Orbital ordering has been less investigated in epitaxial thin films, due to the difficulty to evidence directly the occurrence of this phenomenon in thin film samples. Atomic resolution electron microscopy enabled us to observe the structural details of the ultrathin LaVO{sub 3} films. The transition to orbital ordering of epitaxial layers as thin as ∼4 nm was probed by temperature-dependent Raman scattering spectroscopy of multilayer samples. From the occurrence and temperature dependence of the 700 cm{sup -1} Raman active mode it can be inferred that the structural phase transition associated with orbital ordering takes place in ultrathin LaVO{sub 3} films at about 130 K. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Church, Jonathan; Pezeshki, Soroosh; Davis, Christal; Lin, Hai
2013-12-19
ClC transport proteins show a distinct "broken-helix" architecture, in which certain α-helices are oriented with their N-terminal ends pointed toward the binding sites where the chloride ions are held extensively by the backbone amide nitrogen atoms from the helices. To understand the effectiveness of such binding structures, we carried out natural bond orbital analysis and energy decomposition analysis employing truncated active-site model systems for the bound chloride ions along the translocation pore of the EcClC proteins. Our results indicated that the chloride ions are stabilized in such a binding environment by electrostatic, polarization, and charge-transfer interactions with the backbone and a few side chains. Up to ~25% of the formal charges of the chloride ions were found smeared out to the surroundings primarily via charge transfer from the chloride's lone pair n(Cl) orbitals to the protein's antibonding σ*(N-H) or σ*(O-H) orbitals; those σ* orbitals are localized at the polar N-H and O-H bonds in the chloride's first solvation shells formed by the backbone amide groups and the side chains of residues Ser107, Arg147, Glu148, and Tyr445. Polarizations by the chloride ions were dominated by the redistribution of charge densities among the π orbitals and lone pair orbitals of the protein atoms, in particular the atoms of the backbone peptide links and of the side chains of Arg147, Glu148, and Tyr445. The substantial amounts of electron density involved in charge transfer and in polarization were consistent with the large energetic contributions by the two processes revealed by the energy decomposition analysis. The significant polarization and charge-transfer effects may have impacts on the mechanisms and dynamics of the chloride transport by the ClC proteins.
Statistical Nature of Atomic Disorder in Irradiated Crystals
Boulle, A.; Debelle, A.
2016-06-01
Atomic disorder in irradiated materials is investigated by means of x-ray diffraction, using cubic SiC single crystals as a model material. It is shown that, besides the determination of depth-resolved strain and damage profiles, x-ray diffraction can be efficiently used to determine the probability density function (PDF) of the atomic displacements within the crystal. This task is achieved by analyzing the diffraction-order dependence of the damage profiles. We thereby demonstrate that atomic displacements undergo Lévy flights, with a displacement PDF exhibiting heavy tails [with a tail index in the γ =0.73 - 0.37 range, i.e., far from the commonly assumed Gaussian case (γ =2 )]. It is further demonstrated that these heavy tails are crucial to account for the amorphization kinetics in SiC. From the retrieved displacement PDFs we introduce a dimensionless parameter fDXRD to quantify the disordering. fDXRD is found to be consistent with both independent measurements using ion channeling and with molecular dynamics calculations.
The atomic weight and isotopic composition of boron and their variation in nature
Energy Technology Data Exchange (ETDEWEB)
Holden, N.E.
1993-08-01
The boron isotopic composition and atomic weight value and their variation in nature are reviewed. Questions are raised about the previously recommended value and the uncertainty for the atomic weight. The problem of what constitutes an acceptable range for normal material and what should then be considered geologically exceptional is discussed. Recent measurements make some previous decisions in need of re-evaluation.
The Orbital Nature of 81 Ellipsoidal Red Giant Binaries in the Large Magellanic Cloud
Nie, J. D.; Wood, P. R.; Nicholls, C. P.
2017-02-01
In this paper, we collect a sample of 81 ellipsoidal red giant binaries in the Large Magellanic Cloud (LMC), and we study their orbital natures individually and statistically. The sample contains 59 systems with circular orbits and 22 systems with eccentric orbits. We derive orbital solutions using the 2010 version of the Wilson–Devinney code. The sample is selection-bias corrected, and the orbital parameter distributions are compared to model predictions for the LMC and to observations in the solar vicinity. The masses of the red giant primaries are found to range from about 0.6 to 9 {M}ȯ with a peak at around 1.5 {M}ȯ , in agreement with studies of the star formation history of the LMC, which find a burst of star formation beginning around 4 Gyr ago. The observed distribution of mass ratios q={m}2/{m}1 is more consistent with the flat q distribution derived for the solar vicinity by Raghavan et al. than it is with the solar vicinity q distribution derived by Duquennoy & Mayor. There is no evidence for an excess number of systems with equal mass components. We find that about 20% of the ellipsoidal binaries have eccentric orbits, twice the fraction estimated by Soszynski et al. Our eccentricity evolution test shows that the existence of eccentric ellipsoidal red giant binaries on the upper parts of the red giant branch (RGB) can only be explained if tidal circularization rates are ∼1/100 the rates given by the usual theory of tidal dissipation in convective stars.
Spin-orbit and rotational couplings in radiative association of C(3P) and N(4S) atoms.
Antipov, Sergey V; Gustafsson, Magnus; Nyman, Gunnar
2011-11-14
The role of spin-orbit and rotational couplings in radiative association of C((3)P) and N((4)S) atoms is investigated. Couplings among doublet electronic states of the CN radical are considered, giving rise to a 6-state model of the process. The solution of the dynamical problem is based on the L(2) method, where a complex absorbing potential is added to the Hamiltonian operator in order to treat continuum and bound levels in the same manner. Comparison of the energy-dependent rate coefficients calculated with and without spin-orbit and rotational couplings shows that the couplings have a strong effect on the resonance structure and low-energy baseline of the rate coefficient.
Phillips, Patrick J.; Rui, Xue; Georgescu, Alexandru B.; Disa, Ankit S.; Longo, Paolo; Okunishi, Eiji; Walker, Fred; Ahn, Charles H.; Ismail-Beigi, Sohrab; Klie, Robert F.
2017-05-01
Epitaxial strain, layer confinement, and inversion symmetry breaking have emerged as powerful new approaches to control the electronic and atomic-scale structural properties of complex metal oxides. Trivalent rare-earth (RE) nickelate R E NiO3 heterostructures have been shown to be exemplars since the orbital occupancy, degeneracy, and, consequently, electronic/magnetic properties can be altered as a function of epitaxial strain, layer thickness, and superlattice structure. One recent example is the tricomponent LaTiO3-LaNiO3-LaAlO3 superlattice which exhibits charge transfer and orbital polarization as the result of its interfacial dipole electric field. A crucial step towards control of these parameters for future electronic and magnetic device applications is to develop an understanding of both the magnitude and range of the octahedral network's response towards interfacial strain and electric fields. An approach that provides atomic-scale resolution and sensitivity towards the local octahedral distortions and orbital occupancy is therefore required. Here, we employ atomic-resolution imaging coupled with electron spectroscopies and first-principles theory to examine the role of interfacial charge transfer and symmetry breaking in a tricomponent nickelate superlattice system. We find that nearly complete charge transfer occurs between the LaTiO3 and LaNiO3 layers, resulting in a mixed Ni2 +/Ni3 + valence state. We further demonstrate that this charge transfer is highly localized with a range of about 1 unit cell within the LaNiO3 layers. We also show how Wannier-function-based electron counting provides a simple physical picture of the electron distribution that connects directly with formal valence charges. The results presented here provide important feedback to synthesis efforts aimed at stabilizing new electronic phases that are not accessible by conventional bulk or epitaxial film approaches.
Ji, Wen-Xin; Xu, Wei; Schwarz, W H Eugen; Wang, Shu-Guang
2015-03-15
Lanthanide trihalide molecules LnX3 (X = F, Cl, Br, I) were quantum chemically investigated, in particular detail for Ln = Lu (lutetium). We applied density functional theory (DFT) at the nonrelativistic and scalar and SO-coupled relativistic levels, and also the ab initio coupled cluster approach. The chemically active electron shells of the lanthanide atoms comprise the 5d and 6s (and 6p) valence atomic orbitals (AO) and also the filled inner 4f semivalence and outer 5p semicore shells. Four different frozen-core approximations for Lu were compared: the (1s(2) -4d(10) ) [Pd] medium core, the [Pd+5s(2) 5p(6) = Xe] and [Pd+4f(14) ] large cores, and the [Pd+4f(14) +5s(2) 5p(6) ] very large core. The errors of LuX bonding are more serious on freezing the 5p(6) shell than the 4f(14) shell, more serious upon core-freezing than on the effective-core-potential approximation. The LnX distances correlate linearly with the AO radii of the ionic outer shells, Ln(3+) -5p(6) and X(-) -np(6) , characteristic for dominantly ionic Ln(3+) -X(-) binding. The heavier halogen atoms also bind covalently with the Ln-5d shell. Scalar relativistic effects contract and destabilize the LuX bonds, spin orbit coupling hardly affects the geometries but the bond energies, owing to SO effects in the free atoms. The relativistic changes of bond energy BE, bond length Re , bond force k, and bond stretching frequency vs do not follow the simple rules of Badger and Gordy (Re ∼BE∼k∼vs ). The so-called degeneracy-driven covalence, meaning strong mixing of accidentally near-degenerate, nearly nonoverlapping AOs without BE contribution is critically discussed. © 2015 Wiley Periodicals, Inc.
Photon-Induced Spin-Orbit Coupling in Ultracold Atoms inside Optical Cavity
Directory of Open Access Journals (Sweden)
Lin Dong
2015-05-01
Full Text Available We consider an atom inside a ring cavity, where a plane-wave cavity field together with an external coherent laser beam induces a two-photon Raman transition between two hyperfine ground states of the atom. This cavity-assisted Raman transition induces effective coupling between atom’s internal degrees of freedom and its center-of-mass motion. In the meantime, atomic dynamics exerts a back-action to cavity photons. We investigate the properties of this system by adopting a mean-field and a full quantum approach, and show that the interplay between the atomic dynamics and the cavity field gives rise to intriguing nonlinear phenomena.
Liu, Chao-Fei; JuzeliÅ«nas, Gediminas; Liu, W. M.
2017-02-01
Atomic-molecular Bose-Einstein condensates (BECs) offer brand new opportunities to revolutionize quantum gases and probe the variation of fundamental constants with unprecedented sensitivity. The recent realization of spin-orbit coupling (SOC) in BECs provides a new platform for exploring completely new phenomena unrealizable elsewhere. In this study, we find a way of creating a Rashba-Dresselhaus SOC in atomic-molecular BECs by combining the spin-dependent photoassociation and Raman coupling, which can control the formation and distribution of a different type of topological excitation—carbon-dioxide-like skyrmion. This skyrmion is formed by two half-skyrmions of molecular BECs coupling with one skyrmion of atomic BECs, where the two half-skyrmions locate at both sides of one skyrmion. Carbon-dioxide-like skyrmion can be detected by measuring the vortices structures using the time-of-flight absorption imaging technique in real experiments. Furthermore, we find that SOC can effectively change the occurrence of the Chern number in k space, which causes the creation of topological spin textures from some separated carbon-dioxide-like monomers each with topological charge -2 to a polymer chain of the skyrmions. This work helps in creating dual SOC atomic-molecular BECs and opens avenues to manipulate topological excitations.
Bast, Radovan; Thorvaldsen, Andreas J.; Ringholm, Magnus; Ruud, Kenneth
2009-02-01
We present the first analytic calculations of the second hyperpolarizability in a relativistic framework. The calculations are made possible by our recent developments of a response theory built on a quasienergy formalism, in which the basis set may be both time and perturbation dependent. The approach is formulated for an arbitrary self-consistent field state in the atomic orbital basis. The implementation consists of a stand-alone code that only requires the unperturbed density in the atomic orbital basis as input, as well as a linear response solver by which we can determine the perturbed density matrices to different orders, at each new order solving equations that have the same structure as the linear response equation. Using these features of our formalism, we extend in this paper our approach to the relativistic domain, utilizing both two- and four-component relativistic wave functions. We apply the formalism to the calculation of the electronic and pure vibrational contributions to the second hyperpolarizability tensor for the hydrogen halides. Our results demonstrate that relativistic effects can be substantial for frequency-dependent second hyperpolarizabilities. Due to changes in the pole structure when going to the relativistic domain, the relativistic corrections to the hyperpolarizabilities are not transferable between different optical processes, except for very low frequencies.
Energy Technology Data Exchange (ETDEWEB)
Bast, Radovan; Thorvaldsen, Andreas J.; Ringholm, Magnus [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromso, N-9037 Tromso (Norway); Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromso, N-9037 Tromso (Norway)], E-mail: kenneth.ruud@chem.uit.no
2009-02-17
We present the first analytic calculations of the second hyperpolarizability in a relativistic framework. The calculations are made possible by our recent developments of a response theory built on a quasienergy formalism, in which the basis set may be both time and perturbation dependent. The approach is formulated for an arbitrary self-consistent field state in the atomic orbital basis. The implementation consists of a stand-alone code that only requires the unperturbed density in the atomic orbital basis as input, as well as a linear response solver by which we can determine the perturbed density matrices to different orders, at each new order solving equations that have the same structure as the linear response equation. Using these features of our formalism, we extend in this paper our approach to the relativistic domain, utilizing both two- and four-component relativistic wave functions. We apply the formalism to the calculation of the electronic and pure vibrational contributions to the second hyperpolarizability tensor for the hydrogen halides. Our results demonstrate that relativistic effects can be substantial for frequency-dependent second hyperpolarizabilities. Due to changes in the pole structure when going to the relativistic domain, the relativistic corrections to the hyperpolarizabilities are not transferable between different optical processes, except for very low frequencies.
Skachkov, Dmitry; Krykunov, Mykhaylo; Kadantsev, Eugene; Ziegler, Tom
2010-05-11
We present here a method that can calculate NMR shielding tensors from first principles for systems with translational invariance. Our approach is based on Kohn-Sham density functional theory and gauge-including atomic orbitals. Our scheme determines the shielding tensor as the second derivative of the total electronic energy with respect to an external magnetic field and a nuclear magnetic moment. The induced current density due to a periodic perturbation from nuclear magnetic moments is obtained through numerical differentiation, whereas the influence of the responding perturbation in terms of the external magnetic field is evaluated analytically. The method is implemented into the periodic program BAND. It employs a Bloch basis set made up of Slater-type or numeric atomic orbitals and represents the Kohn-Sham potential fully without the use of effective core potentials. Results from calculations of NMR shielding constants based on the present approach are presented for isolated molecules as well as systems with one-, two- and three-dimensional periodicity. The reported values are compared to experiment and results from calculations on cluster models.
Helmich-Paris, Benjamin; Repisky, Michal; Visscher, Lucas
2016-07-07
We present a formulation of Laplace-transformed atomic orbital-based second-order Møller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy contributions, which show the same long-range decay with the inter-electronic/atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the proper distance behavior is introduced to the quaternion Schwarz-type estimates as for non-relativistic MP2.
Helmich-Paris, Benjamin; Visscher, Lucas
2016-01-01
We present a formulation of Laplace-transformed atomic orbital-based second-order M{\\o}ller-Plesset perturbation theory (MP2) energies for two-component Hamiltonians in the Kramers-restricted formalism. This low-order scaling technique can be used to enable correlated relativistic calculations for large molecular systems. We show that the working equations to compute the relativistic MP2 energy differ by merely a change of algebra (quaternion instead of real) from their non-relativistic counterparts. With a proof-of-principle implementation we study the effect of the nuclear charge on the magnitude of half-transformed integrals and show that for light elements spin-free and spin-orbit MP2 energies are almost identical. Furthermore, we investigate the effect of separation of charge distributions on the Coulomb and exchange energy con- tributions, which show the same long-range decay with the inter-electronic / atomic distance as for non-relativistic MP2. A linearly scaling implementation is possible if the pro...
Büschleb, Martin; Dorich, Stéphane; Hanessian, Stephen; Tao, Daniel; Schenthal, Kyle B; Overman, Larry E
2016-03-18
Strategies for the total synthesis of complex natural products that contain two or more contiguous stereogenic quaternary carbon atoms in their intricate structures are reviewed with 12 representative examples. Emphasis has been put on methods to create quaternary carbon stereocenters, including syntheses of the same natural product by different groups, thereby showcasing the diversity of thought and individual creativity. A compendium of selected natural products containing two or more contiguous stereogenic quaternary carbon atoms and key reactions in their total or partial syntheses is provided in the Supporting Information.
Ragot, Sébastien
2008-04-01
The ground-state Hartree-Fock (HF) wavefunction of Hooke's atom is not known in closed form, contrary to the exact solution. The single HF orbital involved has thus far been studied using expansion techniques only, leading to slightly disparate energies. Therefore, the present letter aims at proposing alternative definitions of the HF wavefunction. First, the HF limit is ascertained using a simple expansion, which makes it possible to formulate explicit expressions of HF properties. The resulting energy, 2.038 438 871 8 Eh, is found stable at the tenth digit. Second and more instructive, an analysis of the Hartree equation makes it possible to infer a remarkably simple and accurate HF orbital, i.e., φHF(r)=nHFe-αr2√r2+β2, leading to an energy exceeding by 5.76×10-7 Eh only the above HF limit. This orbital makes it possible to obtain (near) Hartree-Fock properties in closed form, which in turn enables handy comparisons with exact quantities.
Photoionization of neutral atoms by X waves carrying orbital angular momentum
Müller, Robert A.; Seipt, Daniel; Beerwerth, Randolf; Ornigotti, Marco; Szameit, Alexander; Fritzsche, Stephan; Surzhykov, Andrey
2016-10-01
In contrast to plane waves, twisted or vortex beams have a complex spatial structure. Both their intensity and energy flow vary within the wave front. Beyond that, polychromatic vortex beams, such as X waves, have a spatially dependent energy distribution. We propose a method to measure this (local) energy spectrum. The method is based on the measurement of the energy distribution of photoelectrons from alkali-metal atoms. On the basis of our fully relativistic calculations, we argue that even ensembles of atoms can be used to probe the local energy spectrum of short twisted pulses.
The Bond Order of C2 from a Strictly N-Representable Natural Orbital Energy Functional Perspective.
Piris, Mario; Lopez, Xabier; Ugalde, Jesus M
2016-03-14
The bond order of the ground electronic state of the carbon dimer has been analyzed in the light of natural orbital functional theory calculations carried out with an approximate, albeit strictly N-representable, energy functional. Three distinct solutions have been found from the Euler equations of the minimization of the energy functional with respect to the natural orbitals and their occupation numbers, which expand upon increasing values of the internuclear coordinate. In the close vicinity of the minimum energy region, two of the solutions compete around a discontinuity point. The former, corresponding to the absolute minimum energy, features two valence natural orbitals of each of the following symmetries, σ, σ*, π and π*, and has three bonding interactions and one antibonding interaction, which is very suggestive of a bond order large than two but smaller than three. The latter, features one σ-σ* linked pair of natural orbitals and three degenerate pseudo-bonding like orbitals, paired each with one triply degenerate pseudo-antibonding orbital, which points to a bond order larger than three. When correlation effects, other than Hartree-Fock for example, between the paired natural orbitals are accounted for, this second solution vanishes yielding a smooth continuous dissociation curve. Comparison of the vibrational energies and electron ionization energies, calculated on this curve, with their corresponding experimental marks, lend further support to a bond order for C2 intermediate between acetylene and ethylene.
H{sub 4}: A challenging system for natural orbital functional approximations
Energy Technology Data Exchange (ETDEWEB)
Ramos-Cordoba, Eloy, E-mail: eloy.raco@gmail.com, E-mail: ematito@gmail.com; Lopez, Xabier [Faculty of Chemistry, University of the Basque Country UPV/EHU, and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Euskadi (Spain); Piris, Mario; Matito, Eduard, E-mail: eloy.raco@gmail.com, E-mail: ematito@gmail.com [Faculty of Chemistry, University of the Basque Country UPV/EHU, and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Euskadi (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao (Spain)
2015-10-28
The correct description of nondynamic correlation by electronic structure methods not belonging to the multireference family is a challenging issue. The transition of D{sub 2h} to D{sub 4h} symmetry in H{sub 4} molecule is among the most simple archetypal examples to illustrate the consequences of missing nondynamic correlation effects. The resurgence of interest in density matrix functional methods has brought several new methods including the family of Piris Natural Orbital Functionals (PNOF). In this work, we compare PNOF5 and PNOF6, which include nondynamic electron correlation effects to some extent, with other standard ab initio methods in the H{sub 4} D{sub 4h}/D{sub 2h} potential energy surface (PES). Thus far, the wrongful behavior of single-reference methods at the D{sub 2h}–D{sub 4h} transition of H{sub 4} has been attributed to wrong account of nondynamic correlation effects, whereas in geminal-based approaches, it has been assigned to a wrong coupling of spins and the localized nature of the orbitals. We will show that actually interpair nondynamic correlation is the key to a cusp-free qualitatively correct description of H{sub 4} PES. By introducing interpair nondynamic correlation, PNOF6 is shown to avoid cusps and provide the correct smooth PES features at distances close to the equilibrium, total and local spin properties along with the correct electron delocalization, as reflected by natural orbitals and multicenter delocalization indices.
Institute of Scientific and Technical Information of China (English)
刘洪毓
2007-01-01
Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what
Neese, Frank; Wennmohs, Frank; Hansen, Andreas
2009-03-01
Coupled-electron pair approximations (CEPAs) and coupled-pair functionals (CPFs) have been popular in the 1970s and 1980s and have yielded excellent results for small molecules. Recently, interest in CEPA and CPF methods has been renewed. It has been shown that these methods lead to competitive thermochemical, kinetic, and structural predictions. They greatly surpass second order Møller-Plesset and popular density functional theory based approaches in accuracy and are intermediate in quality between CCSD and CCSD(T) in extended benchmark studies. In this work an efficient production level implementation of the closed shell CEPA and CPF methods is reported that can be applied to medium sized molecules in the range of 50-100 atoms and up to about 2000 basis functions. The internal space is spanned by localized internal orbitals. The external space is greatly compressed through the method of pair natural orbitals (PNOs) that was also introduced by the pioneers of the CEPA approaches. Our implementation also makes extended use of density fitting (or resolution of the identity) techniques in order to speed up the laborious integral transformations. The method is called local pair natural orbital CEPA (LPNO-CEPA) (LPNO-CPF). The implementation is centered around the concepts of electron pairs and matrix operations. Altogether three cutoff parameters are introduced that control the size of the significant pair list, the average number of PNOs per electron pair, and the number of contributing basis functions per PNO. With the conservatively chosen default values of these thresholds, the method recovers about 99.8% of the canonical correlation energy. This translates to absolute deviations from the canonical result of only a few kcal mol-1. Extended numerical test calculations demonstrate that LPNO-CEPA (LPNO-CPF) has essentially the same accuracy as parent CEPA (CPF) methods for thermochemistry, kinetics, weak interactions, and potential energy surfaces but is up to 500
Institute of Scientific and Technical Information of China (English)
Xiong Zhuang; Bacalis N C
2006-01-01
An analytic configuration interaction method based on variationally optimized internally orthogonalized modified Laguerre orbitals is presented. We have developed the corresponding computer code. For application, we study the ls2s 1S isoelectronic sequence from helium to neon, and compare with other methods. By taking into account the Eckart upper-bound theorem, we obtained more accurate and more intuitively understandable results than Hartree-Fock and multi-configuration Hartree-Fock reported results.
Energy Technology Data Exchange (ETDEWEB)
Yip, Frank L; McCurdy, C. William; Rescigno, Thomas N
2010-04-19
A general approach for ab initio calculations of electronic continuum processes is described in which the many-electron wave function is expanded using a combination of orbitals at short range and the finite-element discrete variable representation(FEM-DVR) at larger distances. The orbital portion of the basis allows the efficient construction of many-electron configurations in which some of the electrons are bound, but because the orbitals are constructed from an underlying FEM-DVR grid, the calculation of two-electron integrals retains the efficiency of the primitive FEM-DVR approach. As an example, double photoionization of beryllium is treated in a calculation in which the 1s{sup 2} core is frozen. This approach extends the use of exterior complex scaling (ECS) successfully applied to helium and H{sub 2} to calculations with two active electrons on more complicated targets. Integrated, energy-differential and triply-differential cross sections are exhibited, and the results agree well with other theoretical investigations.
Directory of Open Access Journals (Sweden)
Mansoureh Pishehabadi
2016-10-01
Full Text Available In this study, physio-chemical properties of effective compounds of fennel plant were investigated through using computational chemistry. To do this, trans-anethole, estragole, 3'- hydroxyanethole and 4- methoxycinnamyl alcohol compounds that the most active ingredient combinations make up the fennel plant have been carried out at three different levels of HF, BLYP and B3LYP theories using 6-31G*, 6-311G*, 6-311G**, 6-311+G and 6-311++G basis sets. Additionally, ab initio calculation in the gas phase have been studied and physio-chemical parameters including Gibbs free energy, thermal energy, enthalpy, entropy, and thermal capacity in constant volume (CV of these compounds have been computed as well as Gibbs free energy in polar solvents such as ethanol and methanol and water. Based on these obtained data the structural stabilities of these flavorful compounds have been discussed. However, in these herbal effective compounds presented here the natural bond orbital (NBO analysis has been performed which seemed quite informative to show some important atomic and structural features. The result lead to the issue that all those compounds in polar solvents, particularly alcoholic solvents solved and the compounds can be used sufficiently to extract the active ingredients of herb fennel.
Institute of Scientific and Technical Information of China (English)
Humei Wang; Wei Yang; Junfeng Li
2005-01-01
Using the reference orbital element approach, the precise governing equations for the relative motion of formation flight are formulated. A number of ideal formations with respect to an elliptic orbit can be designed based on the relative motion analysis from the equations. The features of the oscillating reference orbital elements are studied by using the perturbation theory. The changes in the relative orbit under perturbation are divided into three categories, termed scale enlargement, drift and distortion respectively. By properly choosing the initial mean orbital elements for the leader and follower satellites, the deviations from originally regular formation orbit caused by the perturbation can be suppressed. Thereby the natural formation is set up. It behaves either like non-disturbed or need little control to maintain.The presented reference orbital element approach highlights the kinematics properties of the relative motion and is convenient to incorporate the results of perturbation analysis on orbital elements. This method of formation design has advantages over other methods in seeking natural formation and in initializing formation.
The Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field.
Xiong, Hui; Mignolet, Benoit; Fang, Li; Osipov, Timur; Wolf, Thomas J A; Sistrunk, Emily; Gühr, Markus; Remacle, Francoise; Berrah, Nora
2017-12-01
The interaction of gas phase endohedral fullerene Ho3N@C80 with intense (0.1-5 × 10(14) W/cm(2)), short (30 fs), 800 nm laser pulses was investigated. The power law dependence of Ho3N@C80(q+), q = 1-2, was found to be different from that of C60. Time-dependent density functional theory computations revealed different light-induced ionization mechanisms. Unlike in C60, in doped fullerenes, the breaking of the cage spherical symmetry makes super atomic molecular orbital (SAMO) states optically active. Theoretical calculations suggest that the fast ionization of the SAMO states in Ho3N@C80 is responsible for the n = 3 power law for singly charged parent molecules at intensities lower than 1.2 × 10(14) W/cm(2).
Lehtola, Susi; Jónsson, Elvar Ö; Jónsson, Hannes
2016-09-13
The spurious interaction of an electron with itself-self-interaction error-is one of the biggest problems in modern density-functional theory. Some of its most glaring effects, such as qualitatively incorrect charge separation upon dissociation, can be removed by an approximate self-interaction correction due to Perdew and Zunger (PZ) (Perdew, J.; Zunger, A. Phys. Rev. B 1981, 23, 5048). However, the correction introduces an explicit dependence on the occupied orbital densities, which makes proper minimization of the functional difficult. Previous work (Vydrov et al., J. Chem. Phys. 2006, 124, 094108) has suggested that the application of the PZ correction results in worse atomization energies than those obtained with the uncorrected parent functional. But, it has only recently been found that the correct minimization of the PZ energy functional requires complex-valued orbitals, which have not been used in previous work on atomization energies. Here, we study the effect of the proper use of complex-valued orbitals on the atomization energies of molecules in the W4-11 data set (Karton, A.; Daon, S.; Martin, J. M. Chem. Phys. Lett. 2001, 510, 165). We find that the correction has a tendency to weaken the binding of molecules. The correction using complex-valued orbitals is invariably found to yield better atomization energies than the correction with real-valued orbitals. The correction applied to the PBEsol exchange-correlation functional results in a functional that is more accurate than the (uncorrected) PBE functional.
Institute of Scientific and Technical Information of China (English)
Shubao Wang; Xueyou Xu; Hongyun Li; Zhengmao Jia; Shenglu Lin
2008-01-01
The formulas of the quantum electrodynamics have been applied to calculate the spontaneous emission rate of excited atom in dielectric microcavity.The results exhibit damping oscillating Patterns which depend sensitively on the scaling parameter and geometrical structure.Compared with the case that the emitting atom is immersed in dielectric,the spontaneous emission rate is depressed obviously and the center or the mean value of the oscillations is intimately related to the real refractive index of the local position where the atom is.In order to explain this phenomenon,we utilize the closed-orbit theory to deal with the classical trajectories of the emitted photon.and extract the corresponding frequencies of the oscillations by Fourier transform.It is found that the oscillations can be represented in terms of the closed-orbits of the photon motion constrained in dielectric microcavity,thus providing another perspective on the spontaneous emission of atom sandwiched by dielectric slabs.
The role of radial nodes of atomic orbitals for chemical bonding and the periodic table.
Kaupp, Martin
2007-01-15
The role of radial nodes, or of their absence, in valence orbitals for chemical bonding and periodic trends is discussed from a unified viewpoint. In particular, we emphasize the special role of the absence of a radial node whenever a shell with angular quantum number l is occupied for the first time (lack of "primogenic repulsion"), as with the 1s, 2p, 3d, and 4f shells. Although the consequences of the very compact 2p shell (e.g. good isovalent hybridization, multiple bonding, high electronegativity, lone-pair repulsion, octet rule) are relatively well known, it seems that some of the aspects of the very compact 3d shell in transition-metal chemistry are less well appreciated, e.g., the often weakened and stretched bonds at equilibrium structure, the frequently colored complexes, and the importance of nondynamical electron-correlation effects in bonding. Copyright (c) 2006 Wiley Periodicals, Inc.
Even-odd spatial nonequivalence for atomic quantum gases with isotropic spin-orbit couplings
Singh, G. S.; Gupta, Reena
2014-05-01
A general expression for the density of states (DOS) of power-law trapped d-dimensional ideal quantum gases with isotropic spin-orbit couplings (SOCs) is derived and is found to bifurcate into even- dand odd- d classes. The expressions for the grand potential and hence for several thermodynamic quantities are then shown to be amenable to exact analytical forms provided d is an odd integer. Also, a condition γ transition temperature and the condensate fraction in a 3D Bose gas under combined presence of the harmonic trapping and the Weyl coupling shows that the condensation is favored by the former but disfavored by the latter. This countering behavior is discussed to be in conformity with the exchange-symmetry-induced statistical interactions resulting from these two entities as enunciated recently [Phys. Rev. A 88, 053607 (2013)].
The Use of an Air-Natural Gas Flame in Atomic Absorption.
Melucci, Robert C.
1983-01-01
Points out that excellent results are obtained using an air-natural gas flame in atomic absorption experiments rather than using an air-acetylene flame. Good results are obtained for alkali metals, copper, cadmium, and zinc but not for the alkaline earths since they form refractory oxides. (Author/JN)
Enhancing Laos Students' Understanding of Nature of Science in Physics Learning about Atom for Peace
Sengdala, Phoxay; Yuenyong, Chokchai
2014-01-01
This paper aimed to study of Grade 12 students' understanding of nature of science in learning about atom for peace through science technology and society (STS) approach. Participants were 51 Grade 12 who study in Thongphong high school Vientiane Capital City Lao PDR, 1st semester of 2012 academic year. This research regarded interpretive…
Vardimon, R.; Matt, M.; Nielaba, P.; Cuevas, J. C.; Tal, O.
2016-02-01
With the goal of elucidating the nature of spin-dependent electronic transport in ferromagnetic atomic contacts, we present here a combined experimental and theoretical study of the conductance and shot noise of metallic atomic contacts made of the 3 d ferromagnetic materials Fe, Co, and Ni. For comparison, we also present the corresponding results for the noble metal Cu. Conductance and shot noise measurements, performed using a low-temperature break-junction setup, show that in these ferromagnetic nanowires, (i) there is no conductance quantization of any kind, (ii) transport is dominated by several partially open conduction channels, even in the case of single-atom contacts, and (iii) the Fano factor of large contacts saturates to values that clearly differ from those of monovalent (nonmagnetic) metals. We rationalize these observations with the help of a theoretical approach that combines molecular dynamics simulations to describe the junction formation with nonequilibrium Green's function techniques to compute the transport properties within the Landauer-Büttiker framework. Our theoretical approach successfully reproduces all the basic experimental results and it shows that all the observations can be traced back to the fact that the d bands of the minority-spin electrons play a fundamental role in the transport through ferromagnetic atomic-size contacts. These d bands give rise to partially open conduction channels for any contact size, which in turn lead naturally to the different observations described above. Thus, the transport picture for these nanoscale ferromagnetic wires that emerges from the ensemble of our results is clearly at variance with the well established conduction mechanism that governs the transport in macroscopic ferromagnetic wires, where the d bands are responsible for the magnetism but do not take part in the charge flow. These insights provide a fundamental framework for ferromagnetic-based spintronics at the nanoscale.
Energy Technology Data Exchange (ETDEWEB)
Riplinger, Christoph; Pinski, Peter; Becker, Ute; Neese, Frank, E-mail: frank.neese@cec.mpg.de, E-mail: evaleev@vt.edu [Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr (Germany); Valeev, Edward F., E-mail: frank.neese@cec.mpg.de, E-mail: evaleev@vt.edu [Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061 (United States)
2016-01-14
Domain based local pair natural orbital coupled cluster theory with single-, double-, and perturbative triple excitations (DLPNO-CCSD(T)) is a highly efficient local correlation method. It is known to be accurate and robust and can be used in a black box fashion in order to obtain coupled cluster quality total energies for large molecules with several hundred atoms. While previous implementations showed near linear scaling up to a few hundred atoms, several nonlinear scaling steps limited the applicability of the method for very large systems. In this work, these limitations are overcome and a linear scaling DLPNO-CCSD(T) method for closed shell systems is reported. The new implementation is based on the concept of sparse maps that was introduced in Part I of this series [P. Pinski, C. Riplinger, E. F. Valeev, and F. Neese, J. Chem. Phys. 143, 034108 (2015)]. Using the sparse map infrastructure, all essential computational steps (integral transformation and storage, initial guess, pair natural orbital construction, amplitude iterations, triples correction) are achieved in a linear scaling fashion. In addition, a number of additional algorithmic improvements are reported that lead to significant speedups of the method. The new, linear-scaling DLPNO-CCSD(T) implementation typically is 7 times faster than the previous implementation and consumes 4 times less disk space for large three-dimensional systems. For linear systems, the performance gains and memory savings are substantially larger. Calculations with more than 20 000 basis functions and 1000 atoms are reported in this work. In all cases, the time required for the coupled cluster step is comparable to or lower than for the preceding Hartree-Fock calculation, even if this is carried out with the efficient resolution-of-the-identity and chain-of-spheres approximations. The new implementation even reduces the error in absolute correlation energies by about a factor of two, compared to the already accurate
Devarajan, Deepa; Gustafson, Samantha J.; Bickelhaupt, F. Matthias; Ess, Daniel H.
2015-01-01
Undergraduate organic chemistry textbooks and Internet websites use a variety of approaches for presenting and explaining the impact of halogen atom size on trends in bond strengths and/or acidity of hydrogen halides. In particular, several textbooks and Internet websites explain these trends by invoking decreasing orbital overlap between the…
A pair natural orbital implementation of the coupled cluster model CC2 for excitation energies.
Helmich, Benjamin; Hättig, Christof
2013-08-28
We demonstrate how to extend the pair natural orbital (PNO) methodology for excited states, presented in a previous work for the perturbative doubles correction to configuration interaction singles (CIS(D)), to iterative coupled cluster methods such as the approximate singles and doubles model CC2. The original O(N(5)) scaling of the PNO construction is reduced by using orbital-specific virtuals (OSVs) as an intermediate step without spoiling the initial accuracy of the PNO method. Furthermore, a slower error convergence for charge-transfer states is analyzed and resolved by a numerical Laplace transformation during the PNO construction, so that an equally accurate treatment of local and charge-transfer excitations is achieved. With state-specific truncated PNO expansions, the eigenvalue problem is solved by combining the Davidson algorithm with deflation to project out roots that have already been determined and an automated refresh with a generation of new PNOs to achieve self-consistency of the PNO space. For a large test set, we found that truncation errors for PNO-CC2 excitation energies are only slightly larger than for PNO-CIS(D). The computational efficiency of PNO-CC2 is demonstrated for a large organic dye, where a reduction of the doubles space by a factor of more than 1000 is obtained compared to the canonical calculation. A compression of the doubles space by a factor 30 is achieved by a unified OSV space only. Moreover, calculations with the still preliminary PNO-CC2 implementation on a series of glycine oligomers revealed an early break even point with a canonical RI-CC2 implementation between 100 and 300 basis functions.
A pair natural orbital implementation of the coupled cluster model CC2 for excitation energies
Helmich, Benjamin; Hättig, Christof
2013-08-01
We demonstrate how to extend the pair natural orbital (PNO) methodology for excited states, presented in a previous work for the perturbative doubles correction to configuration interaction singles (CIS(D)), to iterative coupled cluster methods such as the approximate singles and doubles model CC2. The original O(N^5) scaling of the PNO construction is reduced by using orbital-specific virtuals (OSVs) as an intermediate step without spoiling the initial accuracy of the PNO method. Furthermore, a slower error convergence for charge-transfer states is analyzed and resolved by a numerical Laplace transformation during the PNO construction, so that an equally accurate treatment of local and charge-transfer excitations is achieved. With state-specific truncated PNO expansions, the eigenvalue problem is solved by combining the Davidson algorithm with deflation to project out roots that have already been determined and an automated refresh with a generation of new PNOs to achieve self-consistency of the PNO space. For a large test set, we found that truncation errors for PNO-CC2 excitation energies are only slightly larger than for PNO-CIS(D). The computational efficiency of PNO-CC2 is demonstrated for a large organic dye, where a reduction of the doubles space by a factor of more than 1000 is obtained compared to the canonical calculation. A compression of the doubles space by a factor 30 is achieved by a unified OSV space only. Moreover, calculations with the still preliminary PNO-CC2 implementation on a series of glycine oligomers revealed an early break even point with a canonical RI-CC2 implementation between 100 and 300 basis functions.
Goings, Joshua J; Li, Xiaosong
2016-06-21
One of the challenges of interpreting electronic circular dichroism (ECD) band spectra is that different states may have different rotatory strength signs, determined by their absolute configuration. If the states are closely spaced and opposite in sign, observed transitions may be washed out by nearby states, unlike absorption spectra where transitions are always positive additive. To accurately compute ECD bands, it is necessary to compute a large number of excited states, which may be prohibitively costly if one uses the linear-response time-dependent density functional theory (TDDFT) framework. Here we implement a real-time, atomic-orbital based TDDFT method for computing the entire ECD spectrum simultaneously. The method is advantageous for large systems with a high density of states. In contrast to previous implementations based on real-space grids, the method is variational, independent of nuclear orientation, and does not rely on pseudopotential approximations, making it suitable for computation of chiroptical properties well into the X-ray regime.
Duo, Shuwang; Song, Mimi; Liu, Tingzhi; Hu, Changyuan; Li, Meishuan
2013-02-01
A novel polyimide (PI) hybrid nanocomposite containing polyhedral oligomeric silsesquioxane (POSS) had been prepared by copolymerization of trisilanolphenyl-POSS, 4,4'-oxydianiline (ODA), and pyromellitic dianhydride (PMDA). The AO resistance of these PI/POSS hybrid films was tested in the ground-based AO simulation facility. Exposed and unexposed surfaces were characterized by SEM and X-ray photoelectron spectroscopy. SEM images showed that the surface of the 20 wt% PI/POSS became much less rough than that of the pristine polyimide. Mass measurements of the samples showed that the erosion yield of the PI/POSS (20 wt.%) hybrid film was 1.2 x 10(-25) cm3/atom, and reduced to 4% of the polyimide film. The XPS data indicated that the carbon content of the near-surface region was decreased from 60.1 to 13.2 at% after AO exposure. The oxygen and silicon concentrations in the near-surface region increased to 1.96 after AO exposure. The nanometer-sized structure of POSS, with its large surface area, had led AO-irradiated samples to form a SiO2 passivation layer, which protected the underlying polymer from further AO attack. The incorporation of POSS into the polyimide could dramatically improve the AO resistance of polyimide films in low earth orbit environment.
Nature of sodium atoms/(Na(+), e(-)) contact pairs in liquid tetrahydrofuran.
Glover, William J; Larsen, Ross E; Schwartz, Benjamin J
2010-09-09
With no internal vibrational or rotational degrees of freedom, atomic solutes serve as the simplest possible probe of a condensed-phase environment's influence on solute electronic structure. Of the various atomic species that can be formed in solution, the quasi-one-electron alkali atoms in ether solvents have been the most widely studied experimentally, primarily due to the convenient location of their absorption spectra at visible wavelengths. The nature of solvated alkali atoms, however, remains controversial: the consensus view is that solvated alkali atoms exist as (Na(+), e(-)) tight-contact pairs (TCPs), species in which the alkali valence electron is significantly displaced from the alkali nucleus and confined primarily by the first solvent shell. Thus, to shed light on the nature of alkali atoms in solution and to further our understanding of condensed-phase effects on solutes' electronic structure, we have performed mixed quantum/classical molecular dynamics simulations of sodium atoms in liquid tetrahydrofuran (Na(0)/THF). Our interest in this particular system stems from recent pump-probe experiments in our group, which found that the rate at which this species is solvated depends on how it was created ( Science 2008 , 321 , 1817 ); in other words, the solvation dynamics of this system do not obey linear response. Our simulations reproduce the experimental spectroscopy of this system and clearly indicate that neutral Na atoms exist as (Na(+), e(-)) TCPs in solution. We find that the driving force for the displacement of sodium's valence electron is the formation of a tight solvation shell around the partially exposed Na(+). On average, four THF oxygens coordinate the cation end of the TCP; however, we also observe fluctuations to other solvent coordination numbers. Furthermore, we find that species with different solvent coordination numbers have unique absorption spectra and that interconversion between species with different solvent coordination
Indian Academy of Sciences (India)
M K Subramanian; P M Anbarasan; S Manimegalai
2010-05-01
Quantum mechanical calculations of energies, geometries and vibrational wave numbers of 7-amino-4-trifluoromethyl coumarin (7A4TFMC) were carried out using Hartree–Fock (HF) and density functional theory (DFT) using hybrid functional BLYP and B3LYP with 6-31G(d,p) as basis set. The optimized geometrical parameters obtained by HF and DFT calculations are in good agreement with the experimental X-ray data. The best method to reproduce the experimental wave numbers is B3LYP method with the 6-31G(d,p) basis set. The difference between the observed and scaled wave number values of most of the fundamentals is very small. A detailed interpretation of the infrared spectra of 7A4TFMC was also reported. The entropy of the title compound was also performed at HF using the hybrid functional BLYP and B3LYP with 6-31 G(d,p) as basis set levels of theory. Natural bond orbital (NBO) analysis of the title molecule is also carried out. The theoretical spectrogram for FTIR spectra of the title molecule has been constructed.
Maschio, Lorenzo; Kirtman, Bernard; Rérat, Michel; Orlando, Roberto; Dovesi, Roberto
2013-10-28
We present a fully analytical formulation for calculating Raman intensities of crystalline periodic systems using a local basis set. Numerical differentiation with respect to atomic coordinates and with respect to wavevectors is entirely avoided as is the determination of crystal orbital coefficient derivatives with respect to nuclear displacements. Instead, our method utilizes the orbital energy-weighted density matrix and is based on the self-consistent solution of first- and second-order Coupled Perturbed Hartree-Fock/Kohn-Sham equations for the electronic response to external electric fields at the equilibrium geometry. This method has also been implemented in the Crystal program, which uses a Gaussian type basis set.
Prabavathi, N; Senthil Nayaki, N; Venkatram Reddy, B
2015-02-05
Vibrational spectral analysis of the molecules 3,6-dichloro-4-methylpyridazine (DMP) and 3,6-dichloropyridazine-4-carboxylic acid (DPC) was carried out using FT-IR and FT-Raman spectroscopic techniques. The molecular structure and vibrational spectra of DMP and DPC were obtained by the density functional theory (DFT) method, using B3LYP functional, with 6-311++G(d,p) basis set. A detailed interpretation of the Infrared and Raman spectra of the two molecules were reported based on potential energy distribution (PED). The theoretically predicted FTIR and FT-Raman spectra of the titled molecules have been simulated and were compared with the experimental spectra. Determination of electric dipole moment (μ) and hyperpolarizability β0 helps to study the non-linear optical (NLO) behavior of DMP and DPC. Stability of the molecules arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. (13)C and (1)H NMR spectra were recorded and (13)C and (1)H NMR chemical shifts of the molecules were calculated using the gauge independent atomic orbital (GIAO) method. UV-visible spectrum of the compounds was also recorded in the region 200-1100 nm and electronic properties, HOMO (Highest Occupied Molecular Orbitals) and LUMO (Lowest Unoccupied Molecular Orbitals) energies were measured by time-dependent TD-DFT approach. Charge density distribution and site of chemical reactivity of the molecule have been studied by mapping electron density isosurface with molecular electrostatic potential (MESP). Copyright © 2014 Elsevier B.V. All rights reserved.
Xavier, S.; Periandy, S.; Carthigayan, K.; Sebastian, S.
2016-12-01
Vibrational spectral analysis of Diphenyl Carbonate (DPC) is carried out by using FT-IR and FT-Raman spectroscopic techniques. It is found that all vibrational modes are in the expected region. Gaussian computational calculations were performed using B3LYP method with 6-311++G (d, p) basis set. The computed geometric parameters are in good agreement with XRD data. The observation shows that the structure of the carbonate group is unsymmetrical by ∼5° due to the attachment of the two phenyl rings. The stability of the molecule arising from hyperconjugative interaction and charge delocalization are analyzed by Natural Bond Orbital (NBO) study and the results show the lone pair transition has higher stabilization energy compared to all other. The 1H and 13C NMR chemical shifts are calculated using the Gauge-Including Atomic Orbital (GIAO) method with B3LYP/6-311++G (d, p) method. The chemical shifts computed theoretically go very closer to the experimental results. A study on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies and Molecular electrostatic potential (MEP) exhibit the high reactivity nature of the molecule. The non-linear optical property of the DPC molecule predicted theoretically found to be good candidate for NLO material. TG/DTA analysis was made and decomposition of the molecule with respect to the temperature was studied. DPC having the anthelmintic activity is docked in the Hemoglobin of Fasciola hepatica protein. The DPC has been screened to antimicrobial activity and found to exhibit antibacterial effects.
Pavošević, Fabijan; Pinski, Peter; Riplinger, Christoph; Neese, Frank; Valeev, Edward F.
2016-04-01
We present a formulation of the explicitly correlated second-order Møller-Plesset (MP2-F12) energy in which all nontrivial post-mean-field steps are formulated with linear computational complexity in system size. The two key ideas are the use of pair-natural orbitals for compact representation of wave function amplitudes and the use of domain approximation to impose the block sparsity. This development utilizes the concepts for sparse representation of tensors described in the context of the domain based local pair-natural orbital-MP2 (DLPNO-MP2) method by us recently [Pinski et al., J. Chem. Phys. 143, 034108 (2015)]. Novel developments reported here include the use of domains not only for the projected atomic orbitals, but also for the complementary auxiliary basis set (CABS) used to approximate the three- and four-electron integrals of the F12 theory, and a simplification of the standard B intermediate of the F12 theory that avoids computation of four-index two-electron integrals that involve two CABS indices. For quasi-1-dimensional systems (n-alkanes), the O (" separators="N ) DLPNO-MP2-F12 method becomes less expensive than the conventional O (" separators="N5 ) MP2-F12 for n between 10 and 15, for double- and triple-zeta basis sets; for the largest alkane, C200H402, in def2-TZVP basis, the observed computational complexity is N˜1.6, largely due to the cubic cost of computing the mean-field operators. The method reproduces the canonical MP2-F12 energy with high precision: 99.9% of the canonical correlation energy is recovered with the default truncation parameters. Although its cost is significantly higher than that of DLPNO-MP2 method, the cost increase is compensated by the great reduction of the basis set error due to explicit correlation.
DEFF Research Database (Denmark)
Kjærgaard, Thomas; Jørgensen, Poul; Thorvaldsen, Andreas;
2009-01-01
-orbital density-matrix based formulation of response theory and use London atomic orbitals to parametrize the magnetic field dependence. It yields a computational procedure which is both gauge-origin independent and suitable for linear-scaling at the level of time-dependent Hartree-Fock and density functional......A Lagrangian approach has been used to derive gauge-origin independent expressions for two properties that rationalize magneto-optical activity, namely the Verdet constant V(ω) of the Faraday effect and the B term of magnetic circular dichroism. The approach is expressed in terms of an atomic...... theory. The formulation includes a modified preconditioned conjugated gradient algorithm, which projects out the excited state component from the solution to the linear response equation. This is required when solving one of the response equations for the determination of the B term and divergence...
Atomic force microscopy characterization of the surface wettability of natural fibres
Pietak, Alexis; Korte, Sandra; Tan, Emelyn; Downard, Alison; Staiger, Mark P.
2007-01-01
Natural fibres represent a readily available source of ecologically friendly and inexpensive reinforcement in composites with degradable thermoplastics, however chemical treatments of fibres are required to prepare feasible composites. It is desirable to characterize the surface wettability of fibres after chemical treatment as the polarity of cellulose-based fibres influences compatibility with a polymer matrix. Assessment of the surface wettability of natural fibres using conventional methods presents a challenge as the surfaces are morphologically and chemically heterogeneous, rough, and can be strongly wicking. In this work it is shown that under atmospheric conditions the adhesion force between an atomic force microscopy (AFM) tip and the fibre surface can estimate the water contact angle and surface wettability of the fibre. AFM adhesion force measurements are suitable for the more difficult surfaces of natural fibres and in addition allow for correlations between microstructural features and surface wettability characteristics.
Epov, Vladimir N
2011-08-07
A novel approach is suggested to investigate the mechanisms of chemical complexation reactions based on the results of Fujii with co-workers; they have experimentally observed that several metals and metalloids demonstrate mass-independent isotope fractionation during the reactions with the DC18C6 crown ether using solvent-solvent extraction. In this manuscript, the isotope fractionation caused by the magnetic isotope effect is used to understand the mechanisms of chemical exchange reactions. Due to the rule that reactions are allowed for certain electron spin states, and forbidden for others, magnetic isotopes show chemical anomalies during these reactions. Mass-independent fractionation is suggested to take place due to the hyperfine interaction of the nuclear spin with the electron spin of the intermediate product. Moreover, the sign of the mass-independent fractionation is found to be dependent on the element and its species, which is also explained by the magnetic isotope effect. For example, highly negative mass-independent isotope fractionation of magnetic isotopes was observed for reactions of DC18C6 with SnCl(2) species and with several Ru(III) chloro-species, and highly positive for reactions of this ether with TeCl(6)(2-), and with several Cd(II) and Pd(II) species. The atomic radius of an element is also a critical parameter for the reaction with crown ether, particularly the element ions with [Kr]4d(n)5s(m) electron shell fits the best with the DC18C6 crown ring. It is demonstrated that the magnetic isotope effect in combination with the theory of orbital hybridization can help to understand the mechanism of complexation reactions. The suggested approach is also applied to explain previously published mass-independent fractionation of Hg isotopes in other types of chemical exchange reactions.
Sub-natural $N$-type Resonance in Cesium Atomic Vapor: splitting in magnetic fields
Slavov, D; Sarkisyan, D; Mirzoyan, R; Krasteva, A; Wilson-Gordon, A D; Cartaleva, S
2013-01-01
The sub-natural-width $N$-type resonance in {\\Lambda}-system, on the $D_2$ line of Cs atoms is studied for the first time in the presence of a buffer gas (neon) and the radiations of two continuous narrow band diode lasers. $L$ = 1 cm long cell is used to investigate $N$-type process. The $N$-type resonance in a magnetic field for $^{133}$Cs atoms is shown to split into seven or eight components, depending on the magnetic field and laser radiation directions. The results obtained indicate that levels $F_g$ = 3, 4 are initial and final in the N resonance formation. The experimental results with magnetic field agree well with the theoretical curves.
Application of atomic force microscopy to the study of natural and model soil particles.
Cheng, S; Bryant, R; Doerr, S H; Rhodri Williams, P; Wright, C J
2008-09-01
The structure and surface chemistry of soil particles has extensive impact on many bulk scale properties and processes of soil systems and consequently the environments that they support. There are a number of physiochemical mechanisms that operate at the nanoscale which affect the soil's capability to maintain native vegetation and crops; this includes soil hydrophobicity and the soil's capacity to hold water and nutrients. The present study used atomic force microscopy in a novel approach to provide unique insight into the nanoscale properties of natural soil particles that control the physiochemical interaction of material within the soil column. There have been few atomic force microscopy studies of soil, perhaps a reflection of the heterogeneous nature of the system. The present study adopted an imaging and force measurement research strategy that accounted for the heterogeneity and used model systems to aid interpretation. The surface roughness of natural soil particles increased with depth in the soil column a consequence of the attachment of organic material within the crevices of the soil particles. The roughness root mean square calculated from ten 25 microm(2) images for five different soil particles from a Netherlands soil was 53.0 nm, 68.0 nm, 92.2 nm and 106.4 nm for the respective soil depths of 0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm. A novel analysis method of atomic force microscopy phase images based on phase angle distribution across a surface was used to interpret the nanoscale distribution of organic material attached to natural and model soil particles. Phase angle distributions obtained from phase images of model surfaces were found to be bimodal, indicating multiple layers of material, which changed with the concentration of adsorbed humic acid. Phase angle distributions obtained from phase images of natural soil particles indicated a trend of decreasing surface coverage with increasing depth in the soil column. This was consistent with
On the natures of the spin and orbital parts of optical angular momentum
Barnett, Stephen M.; Allen, L.; Cameron, Robert P.; Gilson, Claire R.; Padgett, Miles J.; Speirits, Fiona C.; Yao, Alison M.
2016-06-01
The modern field of optical angular momentum began with the realisation by Allen et al in 1992 that, in addition to the spin associated with polarisation, light beams with helical phase fronts carry orbital angular momentum. There has been much confusion and debate, however, surrounding the intricacies of the field and, in particular, the separation of the angular momentum into its spin and orbital parts. Here we take the opportunity to state the current position as we understand it, which we present as six perspectives: (i) we start with a reprise of the 1992 paper in which it was pointed out that the Laguerre-Gaussian modes, familiar from laser physics, carry orbital angular momentum. (ii) The total angular momentum may be separated into spin and orbital parts, but neither alone is a true angular momentum. (iii) The spin and orbital parts, although not themselves true angular momenta, are distinct and physically meaningful, as has been demonstrated clearly in a range of experiments. (iv) The orbital part of the angular momentum in the direction of propagation of a beam is not simply the azimuthal component of the linear momentum. (v) The component of spin in the direction of propagation is not the helicity, although these are related quantities. (vi) Finally, the spin and orbital parts of the angular momentum correspond to distinct symmetries of the free electromagnetic field and hence are separately conserved quantities.
Saitow, Masaaki; Becker, Ute; Riplinger, Christoph; Valeev, Edward F; Neese, Frank
2017-04-28
The Coupled-Cluster expansion, truncated after single and double excitations (CCSD), provides accurate and reliable molecular electronic wave functions and energies for many molecular systems around their equilibrium geometries. However, the high computational cost, which is well-known to scale as O(N(6)) with system size N, has limited its practical application to small systems consisting of not more than approximately 20-30 atoms. To overcome these limitations, low-order scaling approximations to CCSD have been intensively investigated over the past few years. In our previous work, we have shown that by combining the pair natural orbital (PNO) approach and the concept of orbital domains it is possible to achieve fully linear scaling CC implementations (DLPNO-CCSD and DLPNO-CCSD(T)) that recover around 99.9% of the total correlation energy [C. Riplinger et al., J. Chem. Phys. 144, 024109 (2016)]. The production level implementations of the DLPNO-CCSD and DLPNO-CCSD(T) methods were shown to be applicable to realistic systems composed of a few hundred atoms in a routine, black-box fashion on relatively modest hardware. In 2011, a reduced-scaling CCSD approach for high-spin open-shell unrestricted Hartree-Fock reference wave functions was proposed (UHF-LPNO-CCSD) [A. Hansen et al., J. Chem. Phys. 135, 214102 (2011)]. After a few years of experience with this method, a few shortcomings of UHF-LPNO-CCSD were noticed that required a redesign of the method, which is the subject of this paper. To this end, we employ the high-spin open-shell variant of the N-electron valence perturbation theory formalism to define the initial guess wave function, and consequently also the open-shell PNOs. The new PNO ansatz properly converges to the closed-shell limit since all truncations and approximations have been made in strict analogy to the closed-shell case. Furthermore, given the fact that the formalism uses a single set of orbitals, only a single PNO integral transformation is
Ching, Wai-Yim; Rulis, Paul
2009-03-11
Over the last eight years, a large number of x-ray absorption near edge structure (XANES) and/or electron energy loss near edge structure (ELNES) spectroscopic calculations for complex oxides and nitrides have been performed using the supercell-OLCAO (orthogonalized linear combination of atomic orbitals) method, obtaining results in very good agreement with experiments. The method takes into account the core-hole effect and includes the dipole matrix elements calculated from ab initio wavefunctions. In this paper, we describe the method in considerable detail, emphasizing the special advantages of this method for large complex systems. Selected results are reviewed and several hitherto unpublished results are also presented. These include the Y K edge of Y ions segregated to the core of a Σ31 grain boundary in alumina, O K edges of water molecules, C K edges in different types of single walled carbon nanotubes, and the Co K edge in the cyanocobalamin (vitamin B(12)) molecule. On the basis of these results, it is argued that the interpretation of specific features of the calculated XANES/ELNES edges is not simple for complex material systems because of the delocalized nature of the conduction band states. The long-standing notion of the 'fingerprinting' technique for spectral interpretation of experimental data is not tenable. A better approach is to fully characterize the structure under study, using either crystalline data or accurate ab initio modeling. Comparison between calculated XANES/ELNES spectra and available measurements enables us to ascertain the validity of the modeled structure. For complex crystals or structures, it is necessary to use the weighted sum of the spectra from structurally nonequivalent sites for comparison with the measured data. Future application of the supercell-OLCAO method to complex biomolecular systems is also discussed.
Energy Technology Data Exchange (ETDEWEB)
Ching, W.-Y.; Rulis, Paul [Department of Physics, University of Missouri-Kansas City, Kansas City, MO 64110 (United States)
2009-03-11
Over the last eight years, a large number of x-ray absorption near edge structure (XANES) and/or electron energy loss near edge structure (ELNES) spectroscopic calculations for complex oxides and nitrides have been performed using the supercell-OLCAO (orthogonalized linear combination of atomic orbitals) method, obtaining results in very good agreement with experiments. The method takes into account the core-hole effect and includes the dipole matrix elements calculated from ab initio wavefunctions. In this paper, we describe the method in considerable detail, emphasizing the special advantages of this method for large complex systems. Selected results are reviewed and several hitherto unpublished results are also presented. These include the Y K edge of Y ions segregated to the core of a {sigma}31 grain boundary in alumina, O K edges of water molecules, C K edges in different types of single walled carbon nanotubes, and the Co K edge in the cyanocobalamin (vitamin B{sub 12}) molecule. On the basis of these results, it is argued that the interpretation of specific features of the calculated XANES/ELNES edges is not simple for complex material systems because of the delocalized nature of the conduction band states. The long-standing notion of the 'fingerprinting' technique for spectral interpretation of experimental data is not tenable. A better approach is to fully characterize the structure under study, using either crystalline data or accurate ab initio modeling. Comparison between calculated XANES/ELNES spectra and available measurements enables us to ascertain the validity of the modeled structure. For complex crystals or structures, it is necessary to use the weighted sum of the spectra from structurally nonequivalent sites for comparison with the measured data. Future application of the supercell-OLCAO method to complex biomolecular systems is also discussed.
Ching, Wai-Yim; Rulis, Paul
2009-03-01
Over the last eight years, a large number of x-ray absorption near edge structure (XANES) and/or electron energy loss near edge structure (ELNES) spectroscopic calculations for complex oxides and nitrides have been performed using the supercell-OLCAO (orthogonalized linear combination of atomic orbitals) method, obtaining results in very good agreement with experiments. The method takes into account the core-hole effect and includes the dipole matrix elements calculated from ab initio wavefunctions. In this paper, we describe the method in considerable detail, emphasizing the special advantages of this method for large complex systems. Selected results are reviewed and several hitherto unpublished results are also presented. These include the Y K edge of Y ions segregated to the core of a Σ31 grain boundary in alumina, O K edges of water molecules, C K edges in different types of single walled carbon nanotubes, and the Co K edge in the cyanocobalamin (vitamin B12) molecule. On the basis of these results, it is argued that the interpretation of specific features of the calculated XANES/ELNES edges is not simple for complex material systems because of the delocalized nature of the conduction band states. The long-standing notion of the 'fingerprinting' technique for spectral interpretation of experimental data is not tenable. A better approach is to fully characterize the structure under study, using either crystalline data or accurate ab initio modeling. Comparison between calculated XANES/ELNES spectra and available measurements enables us to ascertain the validity of the modeled structure. For complex crystals or structures, it is necessary to use the weighted sum of the spectra from structurally nonequivalent sites for comparison with the measured data. Future application of the supercell-OLCAO method to complex biomolecular systems is also discussed.
Energy Technology Data Exchange (ETDEWEB)
Yevgeny A. Golubev; Olga V. Kovaleva; Nikolay P. Yushkin [Institute of Geology of RAS, Syktyvkar (Russian Federation)
2008-01-15
The supermolecular structures of natural bitumens of the thermal consequent row asphaltites lower kerites (albertites), higher kerites (impsonites), anthraxolites from the Timan-Pechora petroleum province and Karelian shungite rocks, Russia, were studied in details. The experimental technique used was atomic force microscopy (AFM), following fracture preparation. The element distribution of the sample surfaces was analyzed by an X-ray microanalyser 'Link ISIS', combined with a scanning electron microscope (SEM). In this work, we characterized the supermolecular evolution of natural solid bitumens in the carbonization sequence by quantitative parameters. We showed that supermolecular structure can be important in defining to which classification group solid bitumens belong. 29 refs., 7 figs., 2 tabs.
Bistoni, Giovanni
2017-06-12
The validity of the main approximations used in canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) in standard chemical applications is discussed. In particular, we investigate the dependence of the results on the number of electrons included in the correlation treatment in frozen-core (FC) calculations and on the main threshold governing the accuracy of DLPNO all-electron (AE) calculations. Initially, scalar relativistic orbital energies for the ground state of the atoms from Li to Rn in the periodic table are calculated. An energy criterion is applied for determining the orbitals that can be excluded from the correlation treatment in FC coupled cluster calculations without significant loss of accuracy. The heterolytic dissociation energy (HDE) of a series of metal compounds (LiF, NaF, AlF3, CaF2, CuF, GaF3, YF3, AgF, InF3, HfF4 and AuF) is calculated at the canonical CCSD(T) level, and the dependence of the results on the number of correlated electrons is investigated. Although for many of the studied reactions sub-valence correlation effects contribute significantly to the HDE, the use of an energy criterion permits a conservative definition of the size of the core, allowing FC calculations to be performed in a black-box fashion while retaining chemical accuracy. A comparison of the CCSD and the DLPNO-CCSD methods in describing the core-core, core-valence and valence-valence components of the correlation energy is given. It is found that more conservative thresholds must be used for electron pairs containing at least one core electron in order to achieve high accuracy in AE DLPNO-CCSD calculations relative to FC calculations. With the new settings, the DLPNO-CCSD method reproduces canonical CCSD results in both AE and FC calculations with the same accuracy.
Chlorophylls - natural solar cells
Jantschi, Lorentz; Balan, Mugur C; Sestras, Radu E
2011-01-01
A molecular modeling study was conducted on a series of six natural occurring chlorophylls. Quantum chemistry calculated orbital energies were used to estimate frequency of transitions between occupied molecular orbital and unoccupied molecular orbital energy levels of chlorophyll molecules in vivo conditions in standard (ASTMG173) environmental conditions. Obtained results are in good agreement with energies necessary to fix the Magnesium atom by chlorophyll molecules and with occurrence of chlorophylls in living vegetal organisms.
自旋-轨道耦合下冷原子的双反射∗%Double reflection of spin-orbit-coupled cold atoms
Institute of Scientific and Technical Information of China (English)
黄珍; 曾文; 古艺; 刘利; 周鲁; 张卫平
2016-01-01
随着中性冷原子气体的人造自旋-轨道耦合的实验实现，近年来人们开始关注与之相关的可能应用，其中包括自旋-轨道耦合下原子反射镜的研究。本文在前人研究的基础上，考虑一束自旋-轨道耦合的冷原子气体入射到有限高势垒的情形，通过将部分反射和全反射情况进行对比，发现了与之前研究不同的性质。我们发现，在全反射条件下，反射原子的极化率随入射角变化较大，而随自旋-轨道耦合强度和原子入射能量的变化较小。但在发生部分反射的情况下，反射原子的极化率不仅随入射角变化较大，随自旋-轨道耦合强度和原子的入射能量变化也十分明显。我们仔细研究了自旋-轨道耦合原子气体的反射性质并讨论了其可能的应用。%Artificial spin-orbit coupling in neutral cold atom have been experimentally implemented in alkali-metal atoms. Nowadays people begin to explore its possible applications. One of the most interesting applications is the atomic mirror, which is a key element in atom optics. And spin-orbit coupling provides the atomic beam with the possibility that the atomic spin can flip during its propagation, thus can be used to prepare the quantum-state-selective atomic mirror. In 2008, Juzeliūnas, et al. [Juzeliūnas G, et al. 2008 Phys. Rev. Lett. 100 200405] studied a spin-orbit-coupled matter wave packet of cold atom gas impinging on an infinite step potential created by the optical light field. Results showed that there is not only ordinary specular reflection, but also non-specular one. The reflected atoms split into two beams and double reflection takes place. Based on the previous study, here we consider a matter wave packet of spin-orbit-coupled cold atom gas impinging on a finite step potential created by the optical light field. Due to the effect of the spin-orbit coupling, in addition to the propagating state, the eigenstates of cold atoms
Hättig, Christof; Tew, David P; Helmich, Benjamin
2012-05-28
We present an algorithm for computing explicitly correlated second- and third-order Møller-Plesset energies near the basis set limit for large molecules with a cost that scales formally as N(4) with system size N. This is achieved through a hybrid approach where locality is exploited first through orbital specific virtuals (OSVs) and subsequently through pair natural orbitals (PNOs) and integrals are approximated using density fitting. Our method combines the low orbital transformation costs of the OSVs with the compactness of the PNO representation of the doubles amplitude vector. The N(4) scaling does not rely upon the a priori definition of domains, enforced truncation of pair lists, or even screening and the energies converge smoothly to the canonical values with decreasing occupation number thresholds, used in the selection of the PNO basis. For MP2.5 intermolecular interaction energies, we find that 99% of benchmark basis set limit correlation energy contributions are recovered using an aug-cc-pVTZ basis and that on average only 50 PNOs are required to correlate the significant orbital pairs.
Hättig, Christof; Tew, David P.; Helmich, Benjamin
2012-05-01
We present an algorithm for computing explicitly correlated second- and third-order Møller-Plesset energies near the basis set limit for large molecules with a cost that scales formally as N^4 with system size N. This is achieved through a hybrid approach where locality is exploited first through orbital specific virtuals (OSVs) and subsequently through pair natural orbitals (PNOs) and integrals are approximated using density fitting. Our method combines the low orbital transformation costs of the OSVs with the compactness of the PNO representation of the doubles amplitude vector. The N^4 scaling does not rely upon the a priori definition of domains, enforced truncation of pair lists, or even screening and the energies converge smoothly to the canonical values with decreasing occupation number thresholds, used in the selection of the PNO basis. For MP2.5 intermolecular interaction energies, we find that 99% of benchmark basis set limit correlation energy contributions are recovered using an aug-cc-pVTZ basis and that on average only 50 PNOs are required to correlate the significant orbital pairs.
Loibl, Stefan; Schütz, Martin
2012-08-28
An efficient method for the calculation of nuclear magnetic resonance (NMR) shielding tensors is presented, which treats electron correlation at the level of second-order Mo̸ller-Plesset perturbation theory. It uses spatially localized functions to span occupied and virtual molecular orbital spaces, respectively, which are expanded in a basis of gauge including atomic orbitals (GIAOs or London atomic orbitals). Doubly excited determinants are restricted to local subsets of the virtual space and pair energies with an interorbital distance beyond a certain threshold are omitted. Furthermore, density fitting is employed to factorize the electron repulsion integrals. Ordinary Gaussians are employed as fitting functions. It is shown that the errors in the resulting NMR shielding constant, introduced (i) by the local approximation and (ii) by density fitting, are very small or even negligible. The capabilities of the new program are demonstrated by calculations on some extended molecular systems, such as the cyclobutane pyrimidine dimer photolesion with adjacent nucleobases in the native intrahelical DNA double strand (ATTA sequence). Systems of that size were not accessible to correlated ab initio calculations of NMR spectra before. The presented method thus opens the door to new and interesting applications in this area.
元素轨道电负性与原子轨道能级%The Element Orbital Electronegativity and Atomic Orbital Energy Levels
Institute of Scientific and Technical Information of China (English)
李国英
2001-01-01
A new orbital electronegativity scale has been offered. The new scale with clear physical meaning is more reasonable than other scale. Its method of calculation is much simpler.% 根据价轨道的能量，建立了一种新的元素轨道电负性标度，新标度的物理意义明确，方法简单，数值合理，数据完整。并且给出了一些分子(或基团)的轨道电负性值。
Fu, Mingkai; Ma, Haitao; Cao, Jianwei; Bian, Wensheng
2017-04-07
Owing to the exciting potential applications of ultracold atoms and molecules in many fields, developing new cooling schemes has attracted great interests in recent years. Here, we investigate laser cooling of CaBr molecules and design a photonic scheme for the production of ultracold Br atoms using the highly accurate ab initio and dynamical methods. We find that the AΠ1/22(ν(')=0)→X(2)Σ1/2(+)(ν=0) transition for CaBr features a large vibrational branching ratio, a significant photon-scattering rate, and no intermediate electronic-state interference, indicating that the ultracold CaBr could be produced through a three-laser cooling scheme. Moreover, an efficient four-pulse excitation scheme from the ground rovibrational level of the cooled CaBr molecules is proposed to yield ultracold Br atoms, in which a few spin-orbit excited states are utilized as the intermediate states. The importance of the spin-orbit coupling is underscored in this work.
Holmstrom, M; Barabash, S; Brinkfeldt, K; Moore, T E; Simpson, D
2007-01-01
The low energy neutral atom imagers on Mars Express and IMAGE have revealed that the neutral atom populations in interplanetary space come from a variety of sources and challenge our current understanding of heliospheric physics. For example, both in cruise phase and at Mars, the neutral particle instrument NPD on Mars Express observed "unexplained neutral beams" unrelated to Mars which appear to be either of heliospheric or solar wind origin. Likewise, the NPI instrument on Mars Express has revealed streams of neutral atoms with different properties than those observed by NPD. Independently, IMAGE/LENA has reported neutral atom observations that may be interpreted as a "secondary stream" having different characteristics and flowing from a higher ecliptic longitude than the nominal upstream direction. Both sets of observations do not appear to fit in easily with the neutral atom environment from 1.0-1.57 AU as it is currently understood. In this paper we examine some highly suggestive similarities in the IMAG...
Atomic switch networks—nanoarchitectonic design of a complex system for natural computing
Demis, E. C.; Aguilera, R.; Sillin, H. O.; Scharnhorst, K.; Sandouk, E. J.; Aono, M.; Stieg, A. Z.; Gimzewski, J. K.
2015-05-01
Self-organized complex systems are ubiquitous in nature, and the structural complexity of these natural systems can be used as a model to design new classes of functional nanotechnology based on highly interconnected networks of interacting units. Conventional fabrication methods for electronic computing devices are subject to known scaling limits, confining the diversity of possible architectures. This work explores methods of fabricating a self-organized complex device known as an atomic switch network and discusses its potential utility in computing. Through a merger of top-down and bottom-up techniques guided by mathematical and nanoarchitectonic design principles, we have produced functional devices comprising nanoscale elements whose intrinsic nonlinear dynamics and memorization capabilities produce robust patterns of distributed activity and a capacity for nonlinear transformation of input signals when configured in the appropriate network architecture. Their operational characteristics represent a unique potential for hardware implementation of natural computation, specifically in the area of reservoir computing—a burgeoning field that investigates the computational aptitude of complex biologically inspired systems.
Mignolet, B.; Remacle, F.
2016-12-01
Fullerenes have a dense manifold of excited states composed of valence excited states and Rydberg states. Among Rydberg states, one distinguishes Super Atom Molecular Orbitals (SAMO), excited states in which an electron is promoted to a diffuse nanometer size molecular orbital with a hydrogenic-like character. Unlike typical Rydberg states, the electronic density of the SAMO states is mainly localized inside and in the close vicinity of the fullerene cage. In this proceeding, we propose a time-saving way to compute the electronic structure of the SAMO and Rydberg states of fullerenes at the TDDFT level by limiting the number of excitations allowed to build the excited states. We investigate the effect of limiting the number of excitations in C60 and compare it to the experimental binding energies. We also investigate the effect of the functional and basis set on the binding energies of the SAMO states.
NANOMECHANICAL MAPPING OF CARBON BLACK REINFORCED NATURAL RUBBER BY ATOMIC FORCE MICROSCOPY
Institute of Scientific and Technical Information of China (English)
Toshio Nishi; Hideyuki Nukaga; So Fujinami; Ken Nakajima
2007-01-01
Atomic force microscopy (AFM) has the advantage of obtaining mechanical properties as well as topographic information at the same time. By analyzing force-distance curves measured over two-dimensional area using Hertzian contact mechanics, Young's modulus mapping was obtained with nanometer-scale resolution. Furthermore, the sample deformation by the force exerted was also estimated from the force-distance curve analyses. We could thus reconstruct a real topographic image by incorporating apparent topographic image with deformation image. We applied this method to carbon black reinforced natural rubber to obtain Young's modulus distribution image together with reconstructed real topographic image.Then we were able to recognize three regions; rubber matrix, carbon black (or bound rubber) and intermediate regions.Though the existence of these regions had been investigated by pulsed nuclear magnetic resonance, this paper would be the first to report on the quantitative evaluation of the interfacial region in real space.
The atomic weight and isotopic composition of nitrogen and their variation in nature
Energy Technology Data Exchange (ETDEWEB)
Holden, N.E.
1987-01-01
Two stable isotopes of nitrogen exist in nature, /sup 14/N and /sup 15/N. The less abundant isotope, /sup 15/N, was discovered in 1929 by Naude, who studied the band spectra of nitric oxide, NO. However, the main source of a standard for this element is the air in the atmosphere, which is made up of approximately 78% N/sub 2/. Reviewed in this paper is the measurements of the isotopic composition in air and its variation around the world. Also investigated is the variation of the isotopic composition in the various compounds or sources of nitrogen compared to the value in air. Data on the atomic weight and non-terrestrial data for nitrogen is also reviewed.
Orbit-Attitude Changes of Objects in Near Earth Space Induced by Natural Charging
2017-05-02
COVERED (From - To) 21-05-2015 – 21-02-2017 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Orbit- Attitude Changes of Objects in Near Earth Space Induced...charging plasma conditions lead to significant secular perturbations in the investigated cases. 15. SUBJECT TERMS State-of-the Art; Attitude ...non-equilibrium scenario, charging takes place according to the differential equation, ∑ j I j = C dφdt . The time scale for charging of a spherical
Téllez S., Claudio A.; Costa, Anilton C.; Mondragón, M. A.; Ferreira, Glaucio B.; Versiane, O.; Rangel, J. L.; Lima, G. Müller; Martin, A. A.
2016-12-01
Theoretical and experimental bands have been assigned for the Fourier Transform Infrared and Raman spectra of the bis(diethyldithiocarbamate)Mn(II) complex, [Mn(DDTC)2]. The calculations have been based on the DFT/B3LYP method, second derivative spectra and band deconvolution analysis. The UV-vis experimental spectra were measured in acetonitrile solution, and the calculated electronic spectrum was obtained using the TD/B3LYP method with 6-311G(d, p) basis set for all atoms. Charge transfer bands and those d-d spin forbidden were assigned in the UV-vis spectrum. The natural bond orbital analysis was carried out using the DFT/B3LYP method and the Mn(II) hybridization leading to the planar geometry of the framework was discussed. Surface enhanced Raman scattering (SERS) was also performed. Mulliken charges of the normal modes were obtained and related to the SERS enhanced bands.
Krishtal, Alisa; Van Alsenoy, Christian
2010-01-01
Holas and March (Phys. Rev. A51, 2040 (1995)) wrote the gradient of the one-body potential V(r) in terms of low-order derivatives of the idempotent Dirac density matrix built from a single Slater determinant of Kohn-Sham orbitals. Here, this is first combined with the study of Dawson and March (J. Chem. Phys. 81, 5850 (1984)) to express the single-particle kinetic energy density of the Be atom ground-state in terms of both the electron density n(r) and potential V(r). While this is the more compact formulation, we then, by removing V(r), demonstrate that the ratio t(r)/n(r) depends, though non-locally, only on the single variable n'(r)/n(r), no high-order gradients entering for the spherical Be atom.
Guo, Yang; Sivalingam, Kantharuban; Valeev, Edward F.; Neese, Frank
2016-03-01
Multi-reference (MR) electronic structure methods, such as MR configuration interaction or MR perturbation theory, can provide reliable energies and properties for many molecular phenomena like bond breaking, excited states, transition states or magnetic properties of transition metal complexes and clusters. However, owing to their inherent complexity, most MR methods are still too computationally expensive for large systems. Therefore the development of more computationally attractive MR approaches is necessary to enable routine application for large-scale chemical systems. Among the state-of-the-art MR methods, second-order N-electron valence state perturbation theory (NEVPT2) is an efficient, size-consistent, and intruder-state-free method. However, there are still two important bottlenecks in practical applications of NEVPT2 to large systems: (a) the high computational cost of NEVPT2 for large molecules, even with moderate active spaces and (b) the prohibitive cost for treating large active spaces. In this work, we address problem (a) by developing a linear scaling "partially contracted" NEVPT2 method. This development uses the idea of domain-based local pair natural orbitals (DLPNOs) to form a highly efficient algorithm. As shown previously in the framework of single-reference methods, the DLPNO concept leads to an enormous reduction in computational effort while at the same time providing high accuracy (approaching 99.9% of the correlation energy), robustness, and black-box character. In the DLPNO approach, the virtual space is spanned by pair natural orbitals that are expanded in terms of projected atomic orbitals in large orbital domains, while the inactive space is spanned by localized orbitals. The active orbitals are left untouched. Our implementation features a highly efficient "electron pair prescreening" that skips the negligible inactive pairs. The surviving pairs are treated using the partially contracted NEVPT2 formalism. A detailed comparison
Determination of iron in natural and mineral waters by flame atomic absorption spectrometry
Directory of Open Access Journals (Sweden)
ROLANDAS KAZLAUSKAS
2004-05-01
Full Text Available Simple methods for the determination of Fe in natural and mineral waters by flame atomic absorption spectrometry (AAS are suggested. The results of the investigation of selectivity of the proposed AAS method proved that this procedure is not affected by high concentrations of other metals. The calibration graph for iron was linear at levels near the detection limit up to at least 0.10 mg ml-1. For the determination of microamounts of iron in mineral waters, an extraction AAS technique was developed. Iron was retained as Fe-8-oxyquinoline complex and extracted into chloroform. The optimal conditions for the extraction of the iron complex were determined. The AAS method was applied to the determination of Fe in mineral waters and natural waters from different areas of Lithuania. The accuracy of the developed method was sufficient and evaluated in comparison with a photometric method. The obtained results demonstrated that the procedure could be successfully applied for the analysis of water samples with satisfactory accuracy.
Orbital solutions of eight close sdB binaries and constraints on the nature of the unseen companions
Geier, S; Heber, U; Kupfer, T; Maxted, P F L; Barlow, B N; Vuckovic, M; Tillich, A; Mueller, S; Edelmann, H; Classen, L; McLeod, A F
2014-01-01
The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims at finding hot subdwarf stars (sdBs) with massive compact companions such as white dwarfs, neutron stars, or stellar-mass black holes. In a supplementary programme we obtained time-resolved spectroscopy of known hot subdwarf binary candidates. Here we present orbital solutions of eight close sdB binaries with orbital periods ranging from 0.1 to 10 days, which allow us to derive lower limits on the masses of their companions. Additionally, a dedicated photometric follow-up campaign was conducted to obtain light curves of the reflection-effect binary HS 2043+0615. We are able to constrain the most likely nature of the companions in all cases but one, making use of information derived from photometry and spectroscopy. Four sdBs have white dwarf companions, while another three are orbited by low-mass main sequence stars of spectral type M.
Atoms, Nature, and Man; Man-made Radioactivity in the Environment
Energy Technology Data Exchange (ETDEWEB)
Hines, Neal O.
1966-01-01
This booklet describes the environmental investigations that have been conducted with the aid of the atom since the first atomic detonation near Alamogordo, New Mexico, in 1945. The earth's mysteries, however, are not easily unlocked, and investigations of our environment with atomic tools have only begun. The story thus is one of beginnings but of beginnings that point the way, it is hoped, to a new understanding of the world in the atomic future.
Lazar, Petr; Zbořil, Radek; Pumera, Martin; Otyepka, Michal
2014-07-21
Boron and nitrogen doped graphenes are highly promising materials for electrochemical applications, such as energy storage, generation and sensing. The doped graphenes can be prepared by a broad variety of chemical approaches. The substitution of a carbon atom should induce n-type behavior in the case of nitrogen and p-type behavior in the case of boron-doped graphene; however, the real situation is more complex. The electrochemical experiments show that boron-doped graphene prepared by hydroboration reaction exhibits similar properties as the nitrogen doped graphene; according to theory, the electrochemical behavior of B and N doped graphenes should be opposite. Here we analyze the electronic structure of N/B-doped graphene (at ∼5% coverage) by theoretical calculations. We consider graphene doped by both substitution and addition reactions. The density of states (DOS) plots show that graphene doped by substitution of the carbon atom by N/B behaves as expected, i.e., as an n/p-doped material. N-doped graphene also has a lower value of the workfunction (3.10 eV) with respect to that of the pristine graphene (4.31 eV), whereas the workfunction of B-doped graphene is increased to the value of 5.57 eV. On the other hand, the workfunctions of graphene doped by addition of -NH2 (4.77 eV) and -BH2 (4.54 eV) groups are both slightly increased and therefore the chemical nature of the dopant is less distinguishable. This shows that mode of doping depends significantly on the synthesis method used, as it leads to different types of behaviour, and, in turn, different electronic and electrochemical properties of doped graphene, as observed in electrocatalytic experiments. This study has a tremendous impact on the design of doped graphene systems from the point of view of synthetic chemistry.
Physics of higher orbital bands in optical lattices: a review
Li, Xiaopeng; Liu, W. Vincent
2015-01-01
Orbital degree of freedom plays a fundamental role in understanding the unconventional properties in solid state materials. Experimental progress in quantum atomic gases has demonstrated that high orbitals in optical lattices can be used to construct quantum emulators of exotic models beyond natural crystals, where novel many-body states such as complex Bose-Einstein condensation and topological semimetals emerge. A brief introduction of orbital degree of freedom in optical lattices is given ...
Aringazin, A. K.
2002-01-01
In this paper we overview some results on the hydrogen atom in external static uniform magnetic fields. We focus on the case of very strong magnetic field, B>>B_0=2.3x10^9 Gauss, use various approximate models and, particularly, in the adiabatic approximation have calculated exactly the integral defining the effective potential. This potential appears to be finite at z=0. Our consideration of the problem of highly magnetized atoms and molecules is motivated by the recently developed MagneGas ...
Institute of Scientific and Technical Information of China (English)
CHEN LaiWen; WANG JingHua; LEE Chun-Hian
2009-01-01
When hyperthermal atomic oxygen collides with a silicon surface, an ultrathin oxidation regime characterized by fractional atomic-oxygen anions having low diffusive and reactive barriers, along with their enhanced diffusion due to both the electric field and image potential, will form on the surface. In accordance with these properties, an attempt was made in the present study to modify the AlmeidaGoncalves-Baumvol (AGB) model by setting the diffusivity and reaction rate constant to be diffusion-length dependence. According to the modified model, numerical parametric studies for oxidation thin growth were performed. The dependencies of the diffusion coefficient, the reaction rate constant,the attenuation length, and the adjustable parameter upon the translational kinetic energy, flux, temperature, and tangential flux of atomic oxygen were analyzed briefly via the fitting of the experimental data given by Tagawa et al. The numerical results confirmed the rationality of the modified diffusion-reaction model. The model together with the computer code developed in this study would be a useful tool for thickness evaluation of the protective film against the oxidation of atomic oxygen toward spacecraft surface materials in LEO environment.
Institute of Scientific and Technical Information of China (English)
LEE; Chun-Hian
2009-01-01
When hyperthermal atomic oxygen collides with a silicon surface, an ultrathin oxidation regime characterized by fractional atomic-oxygen anions having low diffusive and reactive barriers, along with their enhanced diffusion due to both the electric field and image potential, will form on the surface. In ac- cordance with these properties, an attempt was made in the present study to modify the Almeida- Goncalves-Baumvol (AGB) model by setting the diffusivity and reaction rate constant to be diffu- sion-length dependence. According to the modified model, numerical parametric studies for oxidation thin growth were performed. The dependencies of the diffusion coefficient, the reaction rate constant, the attenuation length, and the adjustable parameter upon the translational kinetic energy, flux, tem- perature, and tangential flux of atomic oxygen were analyzed briefly via the fitting of the experimental data given by Tagawa et al. The numerical results confirmed the rationality of the modified diffu- sion-reaction model. The model together with the computer code developed in this study would be a useful tool for thickness evaluation of the protective film against the oxidation of atomic oxygen toward spacecraft surface materials in LEO environment.
Tsuzuki, Seiji; Hayamizu, Kikuko; Seki, Shiro; Ohno, Yasutaka; Kobayashi, Yo; Miyashiro, Hajime
2008-08-14
Interactions of the lithium bis(trifluoromethylsulfonyl)amide (LiTFSA) complex with N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium (DEME), 1-ethyl-3-methylimidazolium (EMIM) cations, neutral diethylether (DEE), and the DEMETFSA complex were studied by ab initio molecular orbital calculations. An interaction energy potential calculated for the DEME cation with the LiTFSA complex has a minimum when the Li atom has contact with the oxygen atom of DEME cation, while potentials for the EMIM cation with the LiTFSA complex are always repulsive. The MP2/6-311G**//HF/6-311G** level interaction energy calculated for the DEME cation with the LiTFSA complex was -18.4 kcal/mol. The interaction energy for the neutral DEE with the LiTFSA complex was larger (-21.1 kcal/mol). The interaction energy for the DEMETFSA complex with LiTFSA complex is greater (-23.2 kcal/mol). The electrostatic and induction interactions are the major source of the attraction in the two systems. The substantial attraction between the DEME cation and the LiTFSA complex suggests that the interaction between the Li cation and the oxygen atom of DEME cation plays important roles in determining the mobility of the Li cation in DEME-based room temperature ionic liquids.
Energy Technology Data Exchange (ETDEWEB)
Sanfilippo, Andrea; Ren, Xinguo; Tkatchenko, Alexandre; Blum, Volker; Reuter, Karsten; Scheffler, Matthias [Fritz-Haber-Institut, Berlin (Germany); Rinke, Patrick [Fritz-Haber-Institut, Berlin (Germany); University of California, Santa Barbara, CA (United States)
2008-07-01
Well known deficiencies of present-day exchange-correlation functionals in density-functional theory (DFT) comprise the spurious self-interaction, the absence of non-local correlation (van der Waals, image interactions), and the absence of the derivative discontinuity with respect to changes in the electron number. We present a unified framework to overcome these deficiencies by many-body perturbation theory in the bare (Hartree-Fock,MP2) and the screened Coulomb interaction (Hedin's GW approximation). Using numeric atomic-centered orbitals as basis sets, the efficiency of our formulation relies on the representation of intermediate quantities like the polarizability, and bare and screened Coulomb potentials by a second, auxiliary set of atom-centered basis functions. For an extended set of finite systems spanning individual atoms, small molecules (water dimer, methane, silane, benzene), metal clusters (Na{sub n}), and biomolecules (alanine) we demonstrate that our implementation in the new DFT code FHI-aims is significantly more efficient than existing formulations based on traditional plane wave or Gaussian basis sets.
Marinov, A; Kolb, D; Pape, A; Kashiv, Y; Brandt, R; Gentry, R V; Miller, H W
2008-01-01
Evidence for the existence of a superheavy nucleus with atomic mass number A=292 and abundance (1-10)x10^(-12) relative to 232Th has been found in a study of natural Th using inductively coupled plasma-sector field mass spectrometry. The measured mass matches the predictions [1,2] for the mass of an isotope with atomic number Z=122 or a nearby element. Its estimated half-life of t1/2 >= 10^8 y suggests that a long-lived isomeric state exists in this isotope. The possibility that it might belong to a new class of long-lived high spin super- and hyperdeformed isomeric states is discussed.[3-6
Energy Technology Data Exchange (ETDEWEB)
Hernando, Antonio; Crespo, Patricia [Instituto de Magnetismo Aplicado, UCM-CSIC-ADIF, Las Rozas. P.O. Box 155, 28230 Madrid (Spain); Dept. Fisica de Materiales, Universidad Complutense, Madrid (Spain); Garcia, Miguel Angel [Instituto de Ceramica y Vidrio, CSIC, C/ Kelsen, 5, Madrid 28049 (Spain); Coey, Michael [Trinity College Dublin, Dublin (Ireland); Ayuela, Andres; Echenique, Pedro Miguel [Centro de Fisica de Materiales, CFM-MPC CSIC-UPV/EHU, Donostia International Physics Center (DIPC), 20018 San Sebastian (Spain); Departamento de Fisica de Materiales, Fac. de Quimicas, Universidad del Pais Vasco UPV-EHU, 20018 San Sebastian (Spain)
2011-10-15
In this article we review the exotic magnetism of nanoparticles (NPs) formed by substances that are not magnetic in bulk as described with generality in Section 1. In particular, the intrinsic character of the magnetism observed on capped Au and ZnO NPs is analysed. X-ray magnetic circular dichroism (XMCD) analysis has shown that the magnetic moments are intrinsic and lie in the Au and Zn atoms, respectively, as analysed in Section 2, where the general theoretical ideas are also revisited. Since impurity atoms bonded to the surface act as donor or acceptor of electrons that occupy the surface states, the anomalous magnetic response is analysed in terms of the surface band in Section 3. Finally, Section 4 summarizes our last theoretical proposal. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Hancox, Cindy I; Doret, S Charles; Hummon, Matthew T; Krems, Roman V; Doyle, John M
2005-01-14
The Zeeman relaxation rate in cold collisions of Ti(3d(2)4s(2) 3F2) with He is measured. We find that collisional transfer of angular momentum is dramatically suppressed due to the presence of the filled 4s(2) shell. The degree of electronic interaction anisotropy, which is responsible for Zeeman relaxation, is estimated to be about 200 times smaller in the Ti-He complex than in He complexes with typical non-S-state atoms.
Hansen, Andreas; Liakos, Dimitrios G.; Neese, Frank
2011-12-01
A production level implementation of the high-spin open-shell (spin unrestricted) single reference coupled pair, quadratic configuration interaction and coupled cluster methods with up to doubly excited determinants in the framework of the local pair natural orbital (LPNO) concept is reported. This work is an extension of the closed-shell LPNO methods developed earlier [F. Neese, F. Wennmohs, and A. Hansen, J. Chem. Phys. 130, 114108 (2009), 10.1063/1.3086717; F. Neese, A. Hansen, and D. G. Liakos, J. Chem. Phys. 131, 064103 (2009), 10.1063/1.3173827]. The internal space is spanned by localized orbitals, while the external space for each electron pair is represented by a truncated PNO expansion. The laborious integral transformation associated with the large number of PNOs becomes feasible through the extensive use of density fitting (resolution of the identity (RI)) techniques. Technical complications arising for the open-shell case and the use of quasi-restricted orbitals for the construction of the reference determinant are discussed in detail. As in the closed-shell case, only three cutoff parameters control the average number of PNOs per electron pair, the size of the significant pair list, and the number of contributing auxiliary basis functions per PNO. The chosen threshold default values ensure robustness and the results of the parent canonical methods are reproduced to high accuracy. Comprehensive numerical tests on absolute and relative energies as well as timings consistently show that the outstanding performance of the LPNO methods carries over to the open-shell case with minor modifications. Finally, hyperfine couplings calculated with the variational LPNO-CEPA/1 method, for which a well-defined expectation value type density exists, indicate the great potential of the LPNO approach for the efficient calculation of molecular properties.
Hansen, D Flemming; Westler, William M; Kunze, Micha B A; Markley, John L; Weinhold, Frank; Led, Jens J
2012-03-14
A natural bond orbital (NBO) analysis of unpaired electron spin density in metalloproteins is presented, which allows a fast and robust calculation of paramagnetic NMR parameters. Approximately 90% of the unpaired electron spin density occupies metal-ligand NBOs, allowing the majority of the density to be modeled by only a few NBOs that reflect the chemical bonding environment. We show that the paramagnetic relaxation rate of protons can be calculated accurately using only the metal-ligand NBOs and that these rates are in good agreement with corresponding rates measured experimentally. This holds, in particular, for protons of ligand residues where the point-dipole approximation breaks down. To describe the paramagnetic relaxation of heavy nuclei, also the electron spin density in the local orbitals must be taken into account. Geometric distance restraints for (15)N can be derived from the paramagnetic relaxation enhancement and the Fermi contact shift when local NBOs are included in the analysis. Thus, the NBO approach allows us to include experimental paramagnetic NMR parameters of (15)N nuclei as restraints in a structure optimization protocol. We performed a molecular dynamics simulation and structure determination of oxidized rubredoxin using the experimentally obtained paramagnetic NMR parameters of (15)N. The corresponding structures obtained are in good agreement with the crystal structure of rubredoxin. Thus, the NBO approach allows an accurate description of the geometric structure and the dynamics of metalloproteins, when NMR parameters are available of nuclei in the immediate vicinity of the metal-site.
Maurer, Marina; Ochsenfeld, Christian
2013-05-07
An atomic-orbital (AO) based formulation for calculating nuclear magnetic resonance chemical shieldings at the second-order Møller-Plesset perturbation theory level is introduced, which provides a basis for reducing the scaling of the computational effort with the molecular size from the fifth power to linear and for a specific nucleus to sublinear. The latter sublinear scaling in the rate-determining steps becomes possible by avoiding global perturbations with respect to the magnetic field and by solving for quantities that involve the local nuclear magnetic spin perturbation instead. For avoiding the calculation of the second-order perturbed density matrix, we extend our AO-based reformulation of the Z-vector method within a density matrix-based scheme. Our pilot implementation illustrates the fast convergence with respect to the required number of Laplace points and the asymptotic scaling behavior in the rate-determining steps.
Kumar, Chandan; Kjærgaard, Thomas; Helgaker, Trygve; Fliegl, Heike
2016-12-21
An atomic orbital density matrix based response formulation of the nuclei-selected approach of Beer, Kussmann, and Ochsenfeld [J. Chem. Phys. 134, 074102 (2011)] to calculate nuclear magnetic resonance (NMR) shielding tensors has been developed and implemented into LSDalton allowing for a simultaneous solution of the response equations, which significantly improves the performance. The response formulation to calculate nuclei-selected NMR shielding tensors can be used together with the density-fitting approximation that allows efficient calculation of Coulomb integrals. It is shown that using density-fitting does not lead to a significant loss in accuracy for both the nuclei-selected and the conventional ways to calculate NMR shielding constants and should thus be used for applications with LSDalton.
Sure, Rebecca; Brandenburg, Jan Gerit; Grimme, Stefan
2016-04-01
In quantum chemical computations the combination of Hartree-Fock or a density functional theory (DFT) approximation with relatively small atomic orbital basis sets of double-zeta quality is still widely used, for example, in the popular B3LYP/6-31G* approach. In this Review, we critically analyze the two main sources of error in such computations, that is, the basis set superposition error on the one hand and the missing London dispersion interactions on the other. We review various strategies to correct those errors and present exemplary calculations on mainly noncovalently bound systems of widely varying size. Energies and geometries of small dimers, large supramolecular complexes, and molecular crystals are covered. We conclude that it is not justified to rely on fortunate error compensation, as the main inconsistencies can be cured by modern correction schemes which clearly outperform the plain mean-field methods.
Gervais, B; Zanuttini, D; Douady, J
2016-05-21
We analyze the role of the spin-orbit (SO) coupling in the dissociative dynamics of excited alkali atoms at the surface of small rare gas clusters. The electronic structure of the whole system is deduced from a one-electron model based on core polarization pseudo-potentials. It allows us to obtain in the same footing the energy, forces, and non-adiabatic couplings used to simulate the dynamics by means of a surface hopping method. The fine structure state population is analyzed by considering the relative magnitude of the SO coupling ξ, with respect to the spin-free potential energy. We identify three regimes of ξ-values leading to different evolution of adiabatic state population after excitation of the system in the uppermost state of the lowest np (2)P shell. For sufficiently small ξ, the final population of the J=12 atomic states, P12, grows up linearly from P12=13 at ξ = 0 after a diabatic dynamics. For large values of ξ, we observe a rather adiabatic dynamics with P12 decreasing as ξ increases. For intermediate values of ξ, the coupling is extremely efficient and a complete transfer of population is observed for the set of parameters associated to NaAr3 and NaAr4 clusters.
Gregory, J. C.; Raiker, G. N.; Bijvoet, J. A.; Nerren, P. D.; Sutherland, W. T.; Mogro-Camperso, A.; Turner, L. G.; Kwok, Hoi; Raistrick, I. D.; Cross, J. B.
1995-01-01
In 1992, UAH (University of Alabama in Huntsville) conducted a unique experiment on STS-46 in which YBa2Cu3O7 (commonly known as '1-2-3' superconductor) high-T(c) superconducting thin film samples prepared at three different laboratories were exposed to 5 eV atomic oxygen in low Earth orbit on the ambient and 320 C hot plate during the first flight of the CONCAP-2 (Complex Autonomous Payload) experiment carrier. The resistance of the thin films was measured in flight during the atomic oxygen exposure and heating cycle. Superconducting properties were measured in the laboratory before and after the flight by the individual experimenters. Films with good superconducting properties, and which were exposed to the oxygen flux, survived the flight including those heated to 320 C (600 K) with properties essentially unchanged, while other samples which were heated but not exposed to oxygen were degraded. The properties of other flight controls held at ambient temperature appear unchanged and indistinguishable from those of ground controls, whether exposed to oxygen or not.
Stability Analysis of the In-Orbit Satellite Atomic Clocks%GPS在轨卫星原子钟的稳定性分析
Institute of Scientific and Technical Information of China (English)
李长会; 闫国锋
2012-01-01
导航卫星星载原子钟的相位或频率数据,作为导航系统应用研究的基础,将直接影响导航系统时间尺度建立以及定位的精度和准确性.本文针对由IGS官网提供的四种GPS卫星钟的钟差数据,采用修正阿伦方差进行了稳定性分析,得到了一些有益的结论.%As the application research basis of navigation system, the phase or frequency data of in - orbit satellite atomic clocks directly affect the precision and accuracy of navigation system. This paper analyzes the stability of four types of data of GPS satellite a-tomic clocks which is provided by the official website of IGS using Allan variance method and reaches some beneficial conclusions.
Brics, M
2013-01-01
Favorably scaling numerical time-dependent many-electron techniques such as time-dependent density functional theory (TDDFT) with adiabatic exchange-correlation potentials typically fail in capturing highly correlated electron dynamics. We propose a method based on natural orbitals, i.e., the eigenfunctions of the one-body reduced density matrix, that is almost as inexpensive numerically as adiabatic TDDFT, but which is capable of describing correlated phenomena such as doubly excited states, autoionization, Fano profiles in the photoelectron spectra, and strong-field ionization in general. Equations of motion (EOM) for natural orbitals and their occupation numbers have been derived earlier. We show that by using renormalized natural orbitals (RNO) both can be combined into one equation governed by a hermitian effective Hamiltonian. We specialize on the two-electron spin-singlet system, known as being a "worst case" testing ground for TDDFT, and employ the widely used, numerically exactly solvable, one-dimens...
Rodriguez-Serrano, Angela; Rai-Constapel, Vidisha; Daza, Martha C; Doerr, Markus; Marian, Christel M
2015-05-07
The effect of substituting the intra-cyclic sulphur of thionine by oxygen (oxonine) and selenium (selenine) on the intersystem crossing (ISC) efficiency has been studied using high level quantum mechanical methods. The ISC rate constants are considerably increased when going from O towards Se while the fluorescence rate constants remain unchanged. For the three dyes, all accessible ISC channels are driven by vibronic spin-orbit coupling (SOC) between ππ* states. The interplay between the ground and low-lying excited states has been investigated in order to determine the dominant relaxation pathways. In oxonine the relaxation to the ground state after photoexcitation in water proceeds essentially via fluorescence from the S1(πHπL*) bright state (kF = 2.10 × 10(8) s(-1)), in agreement with the high experimental fluorescence quantum yield. In aqueous solution of thionine, the ISC rate constant (kISC ∼ 1 × 10(9) s(-1)) is one order of magnitude higher than fluorescence (kF = 1.66 × 10(8) s(-1)) which is consistent with its high triplet quantum yield observed in water (ϕT = 0.53). Due to a stronger vibronic SOC in selenine, the ISC rate is very high (kISC ∼ 10(10) s(-1)) and much faster than fluorescence (kF = 1.59 × 10(8) s(-1)). This suggests selenine-based dyes as very efficient triplet photosensitizers.
The Holographic Nature of Bohr Atomic Model%波尔原子模型及其全息性
Institute of Scientific and Technical Information of China (English)
赵丽特; 王喜建; 周党培
2016-01-01
This paper shows the holographic nature of the micro world and the macro world in physics by comparing the Bohr atomic model and the movement of the planets in the solar system.%文章通过波尔原子模型和太阳系中行星运动的对比，展现物理学中微观世界和宏观世界的全息性。
Sheng, X W; Mentel, Ł M; Gritsenko, O V; Baerends, E J
2013-04-28
This paper gives a natural orbital (NO) based analysis of the van der Waals interaction in (singlet) H2 at long distance. The van der Waals interaction, even if not leading to a distinct van der Waals well, affects the shape of the interaction potential in the van der Waals distance range of 5-9 bohrs and can be clearly distinguished from chemical bonding effects. In the NO basis the van der Waals interaction can be quantitatively covered with, apart from the ground state configurations (1σ(g))(2) and (1σ(u))(2), just the 4 configurations (2σ(g))(2) and (2σ(u))(2), and (1π(u))(2) and (1π(g))(2). The physics of the dispersion interaction requires and explains the peculiar relatively large positive CI coefficients of the doubly excited electron configurations (2σ(u))(2) and (1π(g))(2) (the occupancy amplitudes of the 2σ(u) and 1π(gx, y) NOs) in the distance range 5-9 bohrs, which have been observed before by Cioslowski and Pernal [Chem. Phys. Lett. 430, 188 (2006)]. We show that such positive occupancy amplitudes do not necessarily lead to the existence of zero occupation numbers at some H-H distances.
The nature of words in human protolanguages: it's not a holophrastic-atomic meanings dichotomy.
Dowman, Mike
2008-01-01
There is an ongoing debate as to whether the words in early presyntactic forms of human language had simple atomic meanings like modern words, or whether they were holophrastic. Simulations were conducted using an iterated learning model in which the agents were able to associate words with meanings, but in which they were not able to use syntactic rules to combine words into phrases or sentences. In some of these simulations words emerged that had neither holophrastic nor atomic meanings, demonstrating the possibility of protolanguages intermediate between these two extremes. Further simulations show how increases in cognitive or articulatory capacity would have produced changes in the type of words that was dominant in protolanguages. It is likely that at some point in time humans spoke a protolanguage in which most words had neither holophrastic nor atomic meanings.
Physics of higher orbital bands in optical lattices: a review
Li, Xiaopeng; Liu, W. Vincent
2016-11-01
The orbital degree of freedom plays a fundamental role in understanding the unconventional properties in solid state materials. Experimental progress in quantum atomic gases has demonstrated that high orbitals in optical lattices can be used to construct quantum emulators of exotic models beyond natural crystals, where novel many-body states such as complex Bose-Einstein condensates and topological semimetals emerge. A brief introduction of orbital degrees of freedom in optical lattices is given and a summary of exotic orbital models and resulting many-body phases is provided. Experimental consequences of the novel phases are also discussed.
Atoms in static fields Chaos or Diffraction?
Dando, P A
1998-01-01
A brief review of the manifestations of classical chaos observed in atomic systems is presented. Particular attention is paid to the analysis of atomic spectra by periodic orbit-type theories. For diamagnetic non-hydrogenic Rydberg atoms, the dynamical explanation for observed spectral features has been disputed. By building on our previous work on the photoabsorption spectrum, we show how, by the addition of diffractive terms, the spectral fluctuations in the energy level spectrum of general Rydberg atoms can be obtained with remarkable precision from the Gutzwiller trace formula. This provides further evidence that non-hydrogenic systems are most naturally described in terms of diffraction rather than classical chaos.
Tuzzolino, A. J.; Simpson, J. A.; Mckibben, R. B.; Voss, H. D.; Gursky, H.
1993-01-01
The characteristics of a space dust instrument which would be ideally suited to carry out near-Earth dust measurements on a possible Long Duraction Exposure Facility reflight mission (LDEF 2) is discussed. As a model for the trajectory portion of the instrument proposed for LDEF 2, the characteristics of a SPAce DUSt instrument (SPADUS) currently under development for flight on the USA ARGOS mission to measure the flux, mass, velocity, and trajectory of near-Earth dust is summarized. Since natural (cosmic) dust and man-made dust particles (orbital debris) have different velocity and trajectory distributions, they are distinguished by means of the SPADUS velocity/trajectory information. The SPADUS measurements will cover the dust mass range approximately 5 x 10(exp -12) g (2 microns diameter) to approximately 1 x 10(exp -5) g (200 microns diameter), with an expected mean error in particle trajectory of approximately 7 deg (isotropic flux). Arrays of capture cell devices positioned behind the trajectory instrumentation would provide for Earth-based chemical and isotopic analysis of captured dust. The SPADUS measurement principles, characteristics, its role in the ARGOS mission, and its application to an LDEF 2 mission are summarized.
Schmitz, Gunnar; Hättig, Christof
2016-12-01
We present an implementation of pair natural orbital coupled cluster singles and doubles with perturbative triples, PNO-CCSD(T), which avoids the quasi-canonical triples approximation (T0) where couplings due to off-diagonal Fock matrix elements are neglected. A numerical Laplace transformation of the canonical expression for the perturbative (T) triples correction is used to avoid an I/O and storage bottleneck for the triples amplitudes. Results for a test set of reaction energies show that only very few Laplace grid points are needed to obtain converged energy differences and that PNO-CCSD(T) is a more robust approximation than PNO-CCSD(T0) with a reduced mean absolute deviation from canonical CCSD(T) results. We combine the PNO-based (T) triples correction with the explicitly correlated PNO-CCSD(F12*) method and investigate the use of specialized F12-PNOs in the conventional triples correction. We find that no significant additional errors are introduced and that PNO-CCSD(F12*)(T) can be applied in a black box manner.
Doser, Bernd; Lambrecht, Daniel S; Kussmann, Jörg; Ochsenfeld, Christian
2009-02-14
A Laplace-transformed second-order Moller-Plesset perturbation theory (MP2) method is presented, which allows to achieve linear scaling of the computational effort with molecular size for electronically local structures. Also for systems with a delocalized electronic structure, a cubic or even quadratic scaling behavior is achieved. Numerically significant contributions to the atomic orbital (AO)-MP2 energy are preselected using the so-called multipole-based integral estimates (MBIE) introduced earlier by us [J. Chem. Phys. 123, 184102 (2005)]. Since MBIE provides rigorous upper bounds, numerical accuracy is fully controlled and the exact MP2 result is attained. While the choice of thresholds for a specific accuracy is only weakly dependent upon the molecular system, our AO-MP2 scheme offers the possibility for incremental thresholding: for only little additional computational expense, the numerical accuracy can be systematically converged. We illustrate this dependence upon numerical thresholds for the calculation of intermolecular interaction energies for the S22 test set. The efficiency and accuracy of our AO-MP2 method is demonstrated for linear alkanes, stacked DNA base pairs, and carbon nanotubes: e.g., for DNA systems the crossover toward conventional MP2 schemes occurs between one and two base pairs. In this way, it is for the first time possible to compute wave function-based correlation energies for systems containing more than 1000 atoms with 10 000 basis functions as illustrated for a 16 base pair DNA system on a single-core computer, where no empirical restrictions are introduced and numerical accuracy is fully preserved.
Strohmayer, T E
2002-01-01
RX J1914.4+2456 is a candidate double-degenerate binary (AM CVn) with a putative 569 s orbital period. If this identification is correct, then it has one of the shortest binary orbital periods known, and gravitational radiation should drive the orbital evolution and mass transfer if the binary is semi-detached. Here we report the results of a coherent timing study of the archival ROSAT data for RX J1914.4+2456. We performed a phase coherent timing analysis using all five ROSAT observations spanning a 4 year period. We demonstrate that all the data can be phase connected, and we show that the 1.756 mHz orbital frequency is increasing at a rate of 1.5 e-17 Hz/s, consistent with the expected loss of angular momentum from the binary system via gravitational radiation. In addition to providing evidence for the emission of gravitational waves, our measurement of the orbital decay constrains models for the X-ray emission and the nature of the secondary. If stable mass accretion drives the X-ray flux, then orbital de...
Institute of Scientific and Technical Information of China (English)
金锐; 高翔; 曾德灵; 顾春; 岳现房; 李家明
2016-01-01
Ionized atoms widely exist in plasmas, and studies of properties of ionized atoms are the foundations of frontier science researches such as astrophysics and controlled nuclear fusions. For example, the information about the ground configurations of atoms is required for accurately calculating the physical quantities such as energy levels and dynamical processes. The configurations for different ionized atoms can be obtained with the photo-electron energy spectrum exper-iment, however it is very time-consuming to obtain so many data of all ions. Therefore the more economical theoretical study will be of great importance. As is well known, the configurations of neutral atoms can be determined according to Mendeleev order while those of highly ionized atoms are hydrogen-like due to the strong Coulombic potential of their nuclei. Then with the variations of ionization degree and atomic number along the periodic table, there would appear the interesting competitions between electronic orbitals. Although some theoretical results exist for ions 3 6 Z 6 118, 3 6 N e 6 105 (where Z is the atomic number and N e is the electron number), there are many errors in the results for highly ionized atoms. Therefore, the ground configurations of ionized atoms and their orbital competitions still deserve to be systematically studied. Based on the independent electron approximation, we calculate the energy levels of all possible competition con-figurations of all the neutral and ionized atoms in the extended periodic tables (2 6 Z 6 119) by Dirac-Slater method. Then the ground configurations are determined by calculating the chosen lowest total energy. The advantages of Dirac-Slater method are as follows. 1) It has been shown that the Dirac-Slater calculation is accurate enough for studying the ground properties of atoms, such as the 1st threshold, and that higher accuracy will be obtained for highly ionized atoms, because the electron correlation becomes less important. 2
Liu, Xiaofeng; Li, Qingzhong; Li, Ran; Li, Wenzuo; Cheng, Jianbo
2011-12-15
Ab initio calculations have been performed for the complexes of benzene with HArF, HKrF, and HXeF. The computed results indicate that the complexes of benzene-HArF exist in different conformations and among them those with π-hydrogen bonds are the more stable than those with C-H···F hydrogen bonds. Interestingly, the Ar-H stretching frequency is redshifted in the more stable isomer and blueshifted in the less stable form. The Ng (Ng=Ar, Kr, and Xe) atomic number dependence of the Ng-H···π and C-H···F hydrogen bonds has been explored. The result indicates that the strength of Ng-H···π and C-H···F hydrogen bonds is weakened with the increase of Ng atomic number. Natural bond orbital analysis has been performed to understand the interaction nature, frequency shift of H-Ng stretch, and dependence of Ng-H···π and C-H···F hydrogen bonds on the Ng atomic number.
Yong, Chin W
2016-08-22
DL_F Notation is an easy-to-understand, standardized atom typesetting expression for molecular simulations for a range of organic force field (FF) schemes such as OPLSAA, PCFF, and CVFF. It is implemented within DL_FIELD, a software program that facilitates the setting up of molecular FF models for DL_POLY molecular dynamics simulation software. By making use of the Notation, a single core conversion module (the DL_F conversion Engine) implemented within DL_FIELD can be used to analyze a molecular structure and determine the types of atoms for a given FF scheme. Users only need to provide the molecular input structure in a simple xyz format and DL_FIELD can produce the necessary force field file for DL_POLY automatically. In commensurate with the development concept of DL_FIELD, which placed emphasis on robustness and user friendliness, the Engine provides a single-step solution to setup complex FF models. This allows users to switch from one of the above-mentioned FF seamlessly to another while at the same time provides a consistent atom typing that is expressed in a natural chemical sense.
Orbital excitation blockade and algorithmic cooling in quantum gases.
Bakr, Waseem S; Preiss, Philipp M; Tai, M Eric; Ma, Ruichao; Simon, Jonathan; Greiner, Markus
2011-12-21
Interaction blockade occurs when strong interactions in a confined, few-body system prevent a particle from occupying an otherwise accessible quantum state. Blockade phenomena reveal the underlying granular nature of quantum systems and allow for the detection and manipulation of the constituent particles, be they electrons, spins, atoms or photons. Applications include single-electron transistors based on electronic Coulomb blockade and quantum logic gates in Rydberg atoms. Here we report a form of interaction blockade that occurs when transferring ultracold atoms between orbitals in an optical lattice. We call this orbital excitation blockade (OEB). In this system, atoms at the same lattice site undergo coherent collisions described by a contact interaction whose strength depends strongly on the orbital wavefunctions of the atoms. We induce coherent orbital excitations by modulating the lattice depth, and observe staircase-like excitation behaviour as we cross the interaction-split resonances by tuning the modulation frequency. As an application of OEB, we demonstrate algorithmic cooling of quantum gases: a sequence of reversible OEB-based quantum operations isolates the entropy in one part of the system and then an irreversible step removes the entropy from the gas. This technique may make it possible to cool quantum gases to have the ultralow entropies required for quantum simulation of strongly correlated electron systems. In addition, the close analogy between OEB and dipole blockade in Rydberg atoms provides a plan for the implementation of two-quantum-bit gates in a quantum computing architecture with natural scalability.
Attoclock reveals natural coordinates of the laser-induced tunnelling current flow in atoms
DEFF Research Database (Denmark)
Pfeiffer, Adrian N.; Cirelli, Claudio; Smolarski, Mathias;
2012-01-01
the attoclock technique4 to obtain experimental information about the electron tunnelling geometry (the natural coordinates of the tunnelling current flow) and exit point. We confirm vanishing tunnelling delay time, show the importance of the inclusion of Stark shifts5, 6 and report on multi-electron effects...
Effect of the nature of the substrate on the surface chemistry of atomic layer deposition precursors
Yao, Yunxi; Coyle, Jason P.; Barry, Seán T.; Zaera, Francisco
2017-02-01
The thermal chemistry of Cu(I)-sec-butyl-2-iminopyrrolidinate, a promising copper amidinate complex for atomic layer deposition (ALD) applications, was explored comparatively on several surfaces by using a combination of surface-sensitive techniques, specifically temperature-programmed desorption and x-ray photoelectron spectroscopy (XPS). The substrates explored include single crystals of transition metals (Ni(110) and Cu(110)), thin oxide films (NiO/Ni(110) and SiO2/Ta), and oxygen-treated metals (O/Cu(110)). Decomposition of the pyrrolidinate ligand leads to the desorption of several gas-phase products, including CH3CN, HCN and butene from the metals and CO and CO2 from the oxygen-containing surfaces. In all cases dehydrogenation of the organic moieties is accompanied by hydrogen removal from the surface, in the form of H2 on metals and mainly as water from the metal oxides, but the threshold for this chemistry varies wildly, from 270 K on Ni(110) to 430 K on O/Cu(110), 470 K on Cu(110), 500 K on NiO/Ni(110), and 570 K on SiO2/Ta. Copper reduction is also observed in both the Cu 2p3/2 XPS and the Cu L3 VV Auger (AES) spectra, reaching completion by 300 K on Ni(110) but occurring only between 500 and 600 K on Cu(110). On NiO/Ni(110), both Cu(I) and Cu(0) coexist between 200 and 500 K, and on SiO2/Ta a change happens between 500 and 600 K but the reduction is limited, with the copper atoms retaining a significant ionic character. Additional experiments to test adsorption at higher temperatures led to the identification of temperature windows for the self-limiting precursor uptake required for ALD between approximately 300 and 450 K on both Ni(110) and NiO/Ni(110); the range on SiO2 had been previously determined to be wider, reaching an upper limit at about 500 K. Finally, deposition of copper metal films via ALD cycles with O2 as the co-reactant was successfully accomplished on the Ni(110) substrate.
Moore, Brian G.
2000-06-01
The plotting program Gnuplot is freely available, general purpose, easy to use, and available on a variety of platforms. Complex three-dimensional surfaces, including the familiar angular parts of the hydrogen atom orbitals, are easily represented using Gnuplot. Contour plots allow viewing the radial and angular variation of the probability density in an orbital. Examples are given of how Gnuplot is used in an undergraduate physical chemistry class to view familiar atomic orbitals in new ways or to generate views of orbital functions that the student may have not seen before. Gnuplot may also be easily integrated into the environment of a Web page; an example of this is discussed (and is available at http://onsager.bd.psu.edu/~moore/orbitals_gnuplot). The plotting commands are entered with a form and a CGI script is used to run Gnuplot and display the result back to the browser.
Minenkov, Yury; Bistoni, Giovanni; Riplinger, Christoph; Auer, Alexander A; Neese, Frank; Cavallo, Luigi
2017-04-05
In this work, we tested canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) for a set of 32 ligand exchange and association/dissociation reaction enthalpies involving ionic complexes of Li, Be, Na, Mg, Ca, Sr, Ba and Pb(ii). Two strategies were investigated: in the former, only valence electrons were included in the correlation treatment, giving rise to the computationally very efficient FC (frozen core) approach; in the latter, all non-ECP electrons were included in the correlation treatment, giving rise to the AE (all electron) approach. Apart from reactions involving Li and Be, the FC approach resulted in non-homogeneous performance. The FC approach leads to very small errors (core (sub-valence) orbitals of metals and the valence orbitals of oxygen and halogens in the molecular orbitals treated as core, and due to neglecting core-core and core-valence correlation effects. These large errors are reduced to a few kcal mol(-1) if the AE approach is used or the sub-valence orbitals of metals are included in the correlation treatment. On the technical side, the CCSD(T) and DLPNO-CCSD(T) results differ by a fraction of kcal mol(-1), indicating the latter method as the perfect choice when the CPU efficiency is essential. For completely black-box applications, as requested in catalysis or thermochemical calculations, we recommend the DLPNO-CCSD(T) method with all electrons that are not covered by effective core potentials included in the correlation treatment and correlation-consistent polarized core valence basis sets of cc-pwCVQZ(-PP) quality.
Minenkov, Yury
2017-03-07
In this work, we tested canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) for a set of 32 ligand exchange and association/dissociation reaction enthalpies involving ionic complexes of Li, Be, Na, Mg, Ca, Sr, Ba and Pb(ii). Two strategies were investigated: in the former, only valence electrons were included in the correlation treatment, giving rise to the computationally very efficient FC (frozen core) approach; in the latter, all non-ECP electrons were included in the correlation treatment, giving rise to the AE (all electron) approach. Apart from reactions involving Li and Be, the FC approach resulted in non-homogeneous performance. The FC approach leads to very small errors (<2 kcal mol-1) for some reactions of Na, Mg, Ca, Sr, Ba and Pb, while for a few reactions of Ca and Ba deviations up to 40 kcal mol-1 have been obtained. Large errors are both due to artificial mixing of the core (sub-valence) orbitals of metals and the valence orbitals of oxygen and halogens in the molecular orbitals treated as core, and due to neglecting core-core and core-valence correlation effects. These large errors are reduced to a few kcal mol-1 if the AE approach is used or the sub-valence orbitals of metals are included in the correlation treatment. On the technical side, the CCSD(T) and DLPNO-CCSD(T) results differ by a fraction of kcal mol-1, indicating the latter method as the perfect choice when the CPU efficiency is essential. For completely black-box applications, as requested in catalysis or thermochemical calculations, we recommend the DLPNO-CCSD(T) method with all electrons that are not covered by effective core potentials included in the correlation treatment and correlation-consistent polarized core valence basis sets of cc-pwCVQZ(-PP) quality.
Zotos, Euaggelos E
2015-01-01
We numerically investigate the case of the planar circular restricted three-body problem where the more massive primary is an oblate spheroid. A thorough numerical analysis takes place in the configuration $(x,y)$ and the $(x,E)$ space in which we classify initial conditions of orbits into three categories: (i) bounded, (ii) escaping and (iii) collisional. Our results reveal that the oblateness coefficient has a huge impact on the character of orbits. Interpreting the collisional motion as leaking in the phase space we related our results to both chaotic scattering and the theory of leaking Hamiltonian systems. We successfully located the escape as well as the collisional basins and we managed to correlate them with the corresponding escape and collision times. We hope our contribution to be useful for a further understanding of the escape and collision properties of motion in this interesting version of the restricted three-body problem.
Zotos, Euaggelos E
2015-01-01
The case of the planar circular photogravitational restricted three-body problem where the more massive primary is an emitter of radiation is numerically investigated. A thorough numerical analysis takes place in the configuration $(x,y)$ and the $(x,C)$ space in which we classify initial conditions of orbits into three main categories: (i) bounded, (ii) escaping and (iii) collisional. Our results reveal that the radiation pressure factor has a huge impact on the character of orbits. Interpreting the collisional motion as leaking in the phase space we related our results to both chaotic scattering and the theory of leaking Hamiltonian systems. We successfully located the escape as well as the collisional basins and we managed to correlate them with the corresponding escape and collision times. We hope our contribution to be useful for a further understanding of the escape and collision properties of motion in this interesting version of the restricted three-body problem.
梯状光晶格中自旋轨道耦合的排斥费米气体%Spin-orbit coupled Fermi atoms loaded in an optical ladder lattice
Institute of Scientific and Technical Information of China (English)
郭飞翔; 周晓凡; 赵华
2015-01-01
采用密度矩阵重整化群 ( density-matrix-renormalization-group, DMRG) 方法, 研究梯状光晶格中排斥相互作用费米气体的基态属性. 研究表明, Zeeman场能够激发系统的相分离 (完全极化相和部分极化相), 而自旋轨道耦合效应能抑制相分离, 使整个晶格处于部分极化相, 在不同的强弱排斥相互作用系统中, 极化率会随自旋轨道耦合改变表现出不同的变化规律.%The density-matrix-renormalization-group ( DMRG ) method is used to numerically calculate the ground state of repulsively interacting Fermi atoms loaded in optical ladder lattices. It is found that the system exhibits the spatial separation of a fully spin-polarized phase from the partially polarized phase for the suitable intensity of Zeeman field without the effect of spin-orbit coupled atoms. The spin-orbit coupling drives the fully spin-polarized phase to the partially spin-polarized phase in the whole system. The spin polarizations of weak and strong repulsively interac-ting systems vary differently with spin-orbit interaction strength.
Li, Shunfang; Zhao, Xingju; Shi, Jinlei; Jia, Yu; Guo, Zhengxiao; Cho, Jun-Hyung; Gao, Yanfei; Zhang, Zhenyu
2016-09-28
Exploration of the catalytic activity of low-dimensional transition metal (TM) or noble metal catalysts is a vital subject of modern materials science because of their instrumental role in numerous industrial applications. Recent experimental advances have demonstrated the utilization of single atoms on different substrates as effective catalysts, which exhibit amazing catalytic properties such as more efficient catalytic performance and higher selectivity in chemical reactions as compared to their nanostructured counterparts; however, the underlying microscopic mechanisms operative in these single atom catalysts still remain elusive. Based on first-principles calculations, herein, we present a comparative study of the key kinetic rate processes involved in CO oxidation using a monomer or dimer of two representative TMs (Pd and Ni) on defective TiO2(110) substrates (TMn@TiO2(110), n = 1, 2) to elucidate the underlying mechanism of single-atom catalysis. We reveal that the O2 activation rates of the single atom TM catalysts deposited on TiO2(110) are governed cooperatively by the classic spin-selection rule and the well-known frontier orbital theory (or generalized d-band picture) that emphasizes the energy gap between the frontier orbitals of the TM catalysts and O2 molecule. We further illuminate that the subsequent CO oxidation reactions proceed via the Langmuir-Hinshelwood mechanism with contrasting reaction barriers for the Pd monomer and dimer catalysts. These findings not only provide an explanation for existing observations of distinctly different catalytic activities of Pd@TiO2(110) and Pd2@TiO2(110) [Kaden et al., Science, 2009, 326, 826-829] but also shed new insights into future utilization and optimization of single-atom catalysis.
Energy Technology Data Exchange (ETDEWEB)
Hagarová, Ingrid, E-mail: hagarova@fns.uniba.sk; Bujdoš, Marek; Matúš, Peter; Kubová, Jana
2013-10-01
In this work, a relatively simple and sensitive method for separation/preconcentration of trace lead from natural waters prior to its determination by electrothermal atomic absorption spectrometry has been proposed. The method is based on the extraction of Pb–dithizone chelate with coacervates made up of lauric acid in the presence of potassium ions and methanol. Several important factors affecting extraction efficiency such as pH, concentration of lauric acid and dithizone, ionic strength, incubation and centrifugation time were investigated and optimized. After separation of aqueous bulk solution from surfactant-rich phase, the final extract was redissolved by using 500 μl of methanol acidified with 0.2 mol l{sup −1} HNO{sub 3}. Under the optimized conditions (using initial sample volume of 10 ml), enrichment factor of 17.0, detection limit of 0.12 μg l{sup −1}, quantification limit of 0.38 μg l{sup −1}, relative standard deviation of 4.2% (for 2 μg l{sup −1} of Pb; n = 26), linearity of the calibration graph in the range of 0.5–4.0 μg l{sup −1} (with correlation coefficient better than 0.995) were achieved. The method was validated by the analysis of certified reference material (TMDA-61). Extraction recoveries for the CRM, spiked model solutions and spiked natural water samples were in the range of 91–96%. Finally, the method was applied to the separation/preconcentration and determination of trace lead in natural waters. - Highlights: • The potential of coacervates for the extraction of metal ions is examined. • No difficulties in coupling of ETAAS with the proposed CAE are observed. • Achieved preconcentration factor results in enhanced sensitivity. • Analytical performance is confirmed by the reliable determination of trace Pb. • The proposed CAE is ecofriendly and efficient.
Hagarová, Ingrid; Bujdoš, Marek; Matúš, Peter; Kubová, Jana
2013-10-01
In this work, a relatively simple and sensitive method for separation/preconcentration of trace lead from natural waters prior to its determination by electrothermal atomic absorption spectrometry has been proposed. The method is based on the extraction of Pb-dithizone chelate with coacervates made up of lauric acid in the presence of potassium ions and methanol. Several important factors affecting extraction efficiency such as pH, concentration of lauric acid and dithizone, ionic strength, incubation and centrifugation time were investigated and optimized. After separation of aqueous bulk solution from surfactant-rich phase, the final extract was redissolved by using 500 μl of methanol acidified with 0.2 mol l- 1 HNO3. Under the optimized conditions (using initial sample volume of 10 ml), enrichment factor of 17.0, detection limit of 0.12 μg l- 1, quantification limit of 0.38 μg l- 1, relative standard deviation of 4.2% (for 2 μg l- 1 of Pb; n = 26), linearity of the calibration graph in the range of 0.5-4.0 μg l- 1 (with correlation coefficient better than 0.995) were achieved. The method was validated by the analysis of certified reference material (TMDA-61). Extraction recoveries for the CRM, spiked model solutions and spiked natural water samples were in the range of 91-96%. Finally, the method was applied to the separation/preconcentration and determination of trace lead in natural waters.
Gritsenko, O. V.
2017-09-01
We demonstrate a crucial role of fractional occupation numbers (FONs) of natural orbitals (NOs) in the description of double excitations in time-dependent NO functional theory (TDNOFT). An analytical dependence of the double excitation energy ωα on the ratio of the FONs is derived in a model from the matrix diagonalization problem. In the large ratio Heitler-London limit the derived formula reproduces the correct asymptotics of ωα of the ionic state of double excitation character. In the small ratio Møller-Plesset, MP limit the reverse relation of static MP perturbation theory emerges in the dynamical response theory to provide ωα .
Caledonia, G. E.; Krech, R. H.
1985-01-01
A technique for the generation, in the laboratory, of thermally 'cold', high flux of energetic oxygen atoms is presented. The flux of nearly mono-energetic oxygen atoms is obtained after a laser-induced breakdown of oxygen molecules followed by a rapid expansion of the recombining plasma. The experimental apparatus, the optical and spectral measurements, the O-atom source characterization, and the material degradation studies are discussed. Average oxygen atom velocities of about 5 to 13 km/s are measured with an estimated flux of 10 to the 18th per pulse, over pulse durations of several microseconds. The flow of the O2 gas for about 200 microseconds before applying the laser pulse is found to give best results. It is also found that the energetic O-atom irradiation of sample targets such as Al, Fe, and polyethylene, induces mass removal. In addition, spectral scans of the radiation reveals the existence of two main spectral subsets.
Yi, Di; Liu, Jian; Hsu, Shang-Lin; Zhang, Lipeng; Choi, Yongseong; Kim, Jong-Woo; Chen, Zuhuang; Clarkson, James D; Serrao, Claudy R; Arenholz, Elke; Ryan, Philip J; Xu, Haixuan; Birgeneau, Robert J; Ramesh, Ramamoorthy
2016-06-07
Magnetic anisotropy (MA) is one of the most important material properties for modern spintronic devices. Conventional manipulation of the intrinsic MA, i.e., magnetocrystalline anisotropy (MCA), typically depends upon crystal symmetry. Extrinsic control over the MA is usually achieved by introducing shape anisotropy or exchange bias from another magnetically ordered material. Here we demonstrate a pathway to manipulate MA of 3d transition-metal oxides (TMOs) by digitally inserting nonmagnetic 5d TMOs with pronounced spin-orbit coupling (SOC). High-quality superlattices comprising ferromagnetic La2/3Sr1/3MnO3 (LSMO) and paramagnetic SrIrO3 (SIO) are synthesized with the precise control of thickness at the atomic scale. Magnetic easy-axis reorientation is observed by controlling the dimensionality of SIO, mediated through the emergence of a novel spin-orbit state within the nominally paramagnetic SIO.
Institute of Scientific and Technical Information of China (English)
刘晓辉; 陈默涵; 李鹏飞; 沈瑜; 任新国; 郭光灿; 何力新
2015-01-01
随着超级计算机硬件和数值算法迅速发展,使得目前利用密度泛函理论研究上千个原子体系的电子能带和结构等性质变得可行. 数值原子轨道基组由于其基组较小和局域等特性, 可以很好地与电子结构计算中的线性标度算法等的新算法结合, 用来研究较大尺寸的物理体系. 本文详细介绍了一款中国科学技术大学量子信息重点实验室自主开发的基于数值原子轨道基组的第一性原理计算软件 Atomic-orbital Based Ab-initio Computation at UStc. 大量的测试结果表明: 该软件具有很好的准确性和较高的并行效率, 可以用于包含1000个原子左右的系统的电子结构和原子结构的研究以及分子动力学模拟计算.%With the rapid development of supercomputers and the advances of numerical algorithms, nowadays it is possible to study the electronic, structural and dynamical properties of complicated physical systems containing thousands of atoms using density functional theory (DFT). The numerical atomic orbitals are ideal basis sets for large-scale DFT calculations in terms of their small base size and localized characteristic, and can be mostly easily combined with linear scaling methods. Here we introduce a first-principles simulation package "Atomic-orbital Based Ab-initio Computation at UStc (ABACUS)", developed at the Key Laboratory of Quantum Information, University of Science and Technology of China. This package provides a useful tool to study the electronic, structural and molecular dynamic properties of systems containing up to 1000 atoms. In this paper, we introduce briefly the main algorithms used in the package, including construction of the atomic orbital bases, construction of the Kohn-Sham Hamiltonian in the atomic basis sets, and some details of solving Kohn-Sham equations, including charge mixing, charge extrapolation, smearing etc. We then give some examples calculated using ABACUS: 1) the energy orders
Energy Technology Data Exchange (ETDEWEB)
Michelotti, L.
1995-01-01
The past fifteen years have witnessed a remarkable development of methods for analyzing single particle orbit dynamics in accelerators. Unlike their more classic counterparts, which act upon differential equations, these methods proceed by manipulating Poincare maps directly. This attribute makes them well matched for studying accelerators whose physics is most naturally modelled in terms of maps, an observation that has been championed most vigorously by Forest. In the following sections the author sketchs a little background, explains some of the physics underlying these techniques, and discusses the best computing strategy for implementing them in conjunction with modeling accelerators.
Energy Technology Data Exchange (ETDEWEB)
Opher, M.; Prested, C. [Astronomy Department, Boston University, 725 Commonwealth Avenue, Boston, MA (United States); McComas, D. J. [Southwest Research Institute, San Antonio, TX 78238 (United States); Schwadron, N. A. [Department of Physics and Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Drake, J. F., E-mail: mopher@bu.edu [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742 (United States)
2013-10-20
We are able to show by comparing modeled energetic neutral atoms (ENAs) spectra to those measured by Interstellar Boundary Explorer (IBEX) that the models along the Voyager 1 (V1) trajectory that best agree with the low energy IBEX data include extra heating due to ram and magnetic energy in the quasi-stagnation region or a kappa ion distribution (with κ = 2.0) in the outer heliosheath. The model explored is the multi-ion, multi-fluid (MI-MF) which treats the pick-up ions and the thermal ion fluids with separate Maxwellian distributions. These effects are included ad hoc in the modeled ENA since they are not present in the model. These results indicate that the low energy spectra of ENAs as measured by IBEX is sensitive to the physical nature of the heliosheath and to effects not traditionally present in current global models. Therefore, by comparing the low energy ENA spectra to models, we can potentially probe the heliosheath in locations beyond those probed by V1 and Voyager 2 (V2)
Institute of Scientific and Technical Information of China (English)
GUO Jin; MA Jun; SHI Xuehua
2007-01-01
To understand the water purification mechanism of potassium permanganate as a coagulation-aid during the preoxidation process,the microtopography of its reductive products,the newly formed hydrous manganese dioxide and the aged hydrous manganese dioxide,was investigated.The morphology of natural organic matter(NOM)adsorbed by the newly formed hydrous manganese dioxide was also compared with that of NOM alone.By using the tapping mode atomic force microscopy(AFM),the observation results show that the newly formed hydrous manganese dioxide possess a perforated sheet(with a thickness of 0-1.75 nm)as well as some spherical particle structures compared with the hydrous manganese dioxide with 2 h aging time,which demonstrated that the newly formed hydrous manganese dioxide had a large surface area and adsorption capacity.When 1 mmol/L newly formed hydrous manganese dioxide was added,the microtopography of NOM molecules shifted from a loosely dispersed pancake shape(with adsorption height of 5-8.5 nm)to a densely dispersed and uniform spherical structure.These results provide a valid proof that it is the perfect adsorption capability of the newly formed hydrous manganese dioxide that might result in the coagulation aid effect of potassium permanganate preoxidation.
Nanda, Kaushik D; Krylov, Anna I
2017-07-20
Observables such as two-photon absorption cross sections cannot be computed from the wave functions of initial and final states alone because of their nonlinear nature. Rather, they depend on the entire manifold of the excited states, which follows from the familiar sum-over-states expressions of second- and higher-order properties. Consequently, the interpretation of the computed nonlinear optical properties in terms of molecular orbitals is not straightforward and usually relies on approximate few-states models. Here, we show that the two-photon absorption (2PA) transitions can be visualized using response one-particle transition density matrices, which are defined as transition density matrices between the zero-order and first-order perturbed states. We also extend the concept of natural transition orbitals to 2PA transitions. We illustrate the utility of this new tool, which provides a rigorous black box alternative to traditional qualitative few-states analysis, by considering 2PA transitions in ethylene, trans-stilbene, and para-nitroaniline.
Derman, Aysegül; Kayacan, Kadriye
2017-01-01
A non-experimental descriptive and correlational design was used to examine the "notion of the nature of scientific model, atom achievement and correlation between the two" held by a total sample of 76 prospective science teachers. "Students' Understanding of Models in Science" scale was utilized to evaluate the views of the…
... hemolytic streptococci may also cause orbital cellulitis. Orbital cellulitis infections in children may get worse very quickly and ... in the space around the eye. An orbital cellulitis infection can get worse very quickly. A person with ...
Random phase approximation with second-order screened exchange for current-carrying atomic states
Zhu, Wuming; Zhang, Liang; Trickey, S. B.
2016-12-01
The direct random phase approximation (RPA) and RPA with second-order screened exchange (SOSEX) have been implemented with complex orbitals as a basis for treating open-shell atoms. Both RPA and RPA+SOSEX are natural implicit current density functionals because the paramagnetic current density implicitly is included through the use of complex orbitals. We confirm that inclusion of the SOSEX correction improves the total energy accuracy substantially compared to RPA, especially for smaller-Z atoms. Computational complexity makes post self-consistent-field (post-SCF) evaluation of RPA-type expressions commonplace, so orbital basis origins and properties become important. Sizable differences are found in correlation energies, total atomic energies, and ionization energies for RPA-type functionals evaluated in the post-SCF fashion with orbital sets obtained from different schemes. Reference orbitals from Kohn-Sham calculations with semi-local functionals are more suitable for RPA+SOSEX to generate accurate total energies, but reference orbitals from exact exchange (non-local) yield essentially energetically degenerate open-shell atom ground states. RPA+SOSEX correlation combined with exact exchange calculated from a hybrid reference orbital set (half the exchange calculated from exact-exchange orbitals, the other half of the exchange from orbitals optimized for the Perdew-Burke-Ernzerhof (PBE) exchange functional) gives the best overall performance. Numerical results show that the RPA-like functional with SOSEX correction can be used as a practical implicit current density functional when current effects should be included.
Kaltenbach, Robin; Diehl, Dörte; Schaumann, Gabriele E.
2017-04-01
Organic coatings are considered as main cause of soil water repellency (SWR). This phenomenon plays a crucial role in the rhizosphere, at the interface of plant water uptake and soil hydraulics. Still, there is little knowledge about the nanoscale properties of natural soil compounds such as root-mucilage and its mechanistic effect on wettability. In this study, dried films of natural root-mucilage from Sorghum (Sorghum sp., MOENCH) on glass substrates were studied in order to explore experimental and evaluation methods that allow to link between macroscopic wettability and nano-/microscopic surface properties in this model soil system. SWR was assessed by optical contact angle (CA) measurements. The nanostructure of topography and adhesion forces of the mucilage surfaces was revealed by atomic force microscopy (AFM) measurements in ambient air, using PeakForce Quantitative Nanomechanical Mapping (PFQNM). Undiluted mucilage formed hydrophobic films on the substrate with CA > 90° and rather homogeneous nanostructure. Contact angles showed reduced water repellency of surfaces, when concentration of mucilage was decreased by dilution. AFM height and adhesion images displayed incomplete mucilage surface coverage for diluted samples. Hole-like structures in the film frequently exhibited increased adhesion forces. Spatial analysis of the AFM data via variograms enabled a numerical description of such 'adhesion holes'. The use of geostatistical approaches in AFM studies of the complex surface structure of soil compounds was considered meaningful in view of the need of comprehensive analysis of large AFM image data sets that exceed the capability of comparative visual inspection. Furthermore, force curves measured with the AFM showed increased break-free distances and pull-off forces inside the observed 'adhesion holes', indicating enhanced capillary forces due to adsorbed water films at hydrophilic domains for ambient RH (40 ± 2 %). This offers the possibility of
Sebastian, S.; Sylvestre, S.; Jayarajan, D.; Amalanathan, M.; Oudayakumar, K.; Gnanapoongothai, T.; Jayavarthanan, T.
2013-01-01
In this work, we report harmonic vibrational frequencies, molecular structure, NBO and HOMO, LUMO analysis of Umbelliferone also known as 7-hydroxycoumarin (7HC). The optimized geometric bond lengths and bond angles obtained by computation (monomer and dimmer) shows good agreement with experimental XRD data. Harmonic frequencies of 7HC were determined and analyzed by DFT utilizing 6-311+G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of Normal Coordinate Analysis (NCA) following the Scaled Quantum Mechanical Force Field Methodology (SQMFF). The change in electron density (ED) in the σ* and π* antibonding orbitals and stabilization energies E(2) have been calculated by Natural Bond Orbital (NBO) analysis to give clear evidence of stabilization originating in the hyperconjugation of hydrogen-bonded interaction. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) complements with the experimental findings. The simulated spectra satisfactorily coincides with the experimental spectra. Microbial activity of studied compounds was tested against Staphylococcus aureus, Streptococcus pyogenes, Bacillus subtilis, Escherichia coli, Psuedomonas aeruginosa, Klebsiella pneumoniae, Proteus mirabilis, Shigella flexneri, Salmonella typhi and Enterococcus faecalis.
Zhao, Zongyan; Cao, Yuechan; Yi, Juan; He, Xijia; Ma, Chenshuo; Qiu, Jianbei
2012-04-23
As a promising solar-energy material, the electronic structure and optical properties of Beta phase indium sulfide (β-In(2)S(3)) are still not thoroughly understood. This paper devotes to solve these issues using density functional theory calculations. β-In(2)S(3) is found to be an indirect band gap semiconductor. The roles of its atoms at different lattice positions are not exactly identical because of the unique crystal structure. Additonally, a significant phenomenon of optical anisotropy was observed near the absorption edge. Owing to the low coordination numbers of the In3 and S2 atoms, the corresponding In3-5s states and S2-3p states are crucial for the composition of the band-edge electronic structure, leading to special optical properties and excellent optoelectronic performances.
Controlling interactions between highly magnetic atoms with Feshbach resonances.
Kotochigova, Svetlana
2014-09-01
This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.
Controlling interactions between highly-magnetic atoms with Feshbach resonances
Kotochigova, Svetlana
2014-01-01
This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic $^7$S$_3$ chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on Dysprosium and Erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.
Chaudhuri, Supriya K.; Mukherjee, Prasanta K.; Fricke, Burkhard
2017-03-01
The effect of Debye and quantum plasma environment on the structural properties such as spin orbit splitting, relativistic mass correction and Darwin term for a few iso-electronic members of hydrogen viz. C5 +, O7 +, Ne9 +, Mg11 +, Si13 +, S15 +, Ar17 +, Ca19 + and Ti21 + has been analysed systematically for the first time for a range of coupling strengths of the plasma. The Debye plasma environment has been treated under a standard screened Coulomb potential (SCP) while the quantum plasma has been treated under an exponential cosine screened Coulomb potential (ECSCP). Estimation of the spin orbit splitting under SCP and ECSCP plasma is restricted to the lowest two dipole allowed states while for the other two properties, the ground state as well as the first two excited states have been chosen. Calculations have been extended to nuclear charges for which appreciable relativistic corrections are noted. In all cases calculations have been extended up to such screening parameters for which the respective excitation energies tend towards their stability limit determined by the ionisation potential at that screening parameter. Interesting behavior of the respective properties with respect to the plasma coupling strength has been noted.
Directory of Open Access Journals (Sweden)
Graves N.
2013-01-01
Full Text Available A model is proposed for the hydrogen atom in which the electron is an objectively real particle orbiting at very near to light speed. The model is based on the postulate that certain velocity terms associated with orbiting bodies can be considered as being af- fected by relativity. This leads to a model for the atom in which the stable electron orbits are associated with orbital velocities where Gamma is n /α , leading to the idea that it is Gamma that is quantized and not angular momentum as in the Bohr and other models. The model provides a mechanism which leads to quantization of energy levels within the atom and also provides a simple mechanical explanation for the Fine Struc- ture Constant. The mechanism is closely associated with the Sampling theorem and the related phenomenon of aliasing developed in the mid-20th century by engineers at Bell labs.
Absorption and Recurrence Spectra of Sodium Rydberg Atom in a Strong External Magnetic Field
Institute of Scientific and Technical Information of China (English)
WANG De-Hua; LIN Sheng-Lu
2004-01-01
Using core-scattered closed-orbit theory, we calculate the photoabsorption and the scaled recurrence spectra of sodium Rydberg atom in strong magnetic field below ionization threshold. The non-Coulombic nature of the ionic core have been modified by a model potential, which includes an attractive Coulomb potential and a short-ranged core potential. A family of core-scattered nonhydrogenic closed orbits have also been discovered. The Fourier transformed spectra of sodium atom have allowed direct comparison between peaks in such plot and the scaled action values of closed orbits. The new peaks in the recurrence spectra of sodium atom have been considered as effects caused by the core scattering of returning waves at the ionic core. The results are compared with those of hydrogen case, which show that the core-scattered effects play an important role in alkali-metal atoms.
Absorption and Recurrence Spectra of Sodium Rydberg Atom in a Strong External Magnetic Field
Institute of Scientific and Technical Information of China (English)
WANGDe-Hua; LINSheng-Lu
2004-01-01
Using core-scattered closed-orbit theory, we calculate the photoabsorption and the scaled recurrence spectra of sodium Rydberg atom in strong magnetic fied below ionization threshoM. The non-Coulombic nature of the ionic core have been modified by a model potential, which includes an attractive Coulomb potential and a short-ranged core potential. A family of core-scattered nonhydrogenic closed orbits have also been discovered. The Fourier transformed spectra of sodium atom have allowed direct comparison between peaks in such plot and the scaled action values of closed orbits. The new peaks in the recurrence spectra of sodium atom have been considered as effects caused by the core scattering of returning waves at the ionic core. The results are compared with those of hydrogen case, which show that the core-scattered effects play an important role in alkali-metal atoms.
van Holten, Theo
2017-01-01
The present book takes the discovery that quantum-like behaviour is not solely reserved to atomic particles one step further. If electrons are modelled as vibrating droplets instead of the usually assumed point objects, and if the classical laws of nature are applied, then exactly the same behaviour as in quantum theory is found, quantitatively correct! The world of atoms is strange and quantum mechanics, the theory of this world, is almost magic. Or is it? Tiny droplets of oil bouncing round on a fluid surface can also mimic the world of quantum mechanics. For the layman - for whom the main part of this book is written - this is good news. If the everyday laws of nature can conspire to show up quantum-like phenomena, there is hope to form mental pictures how the atomic world works. The book is almost formula-free, and explains everything by using many sketches and diagrams. The mathematical derivations underlying the main text are kept separate in a -peer reviewed - appendix. The author, a retired professor ...
Kirker, Ian; Kaltsoyannis, Nikolas
2011-01-07
The title compounds are studied with scalar relativistic, gradient-corrected (PBE) and hybrid (PBE0) density functional theory. The metal-Cp centroid distances shorten from ThCp(3) to NpCp(3), but lengthen again from PuCp(3) to CmCp(3). Examination of the valence molecular orbital structures reveals that the highest-lying Cp π(2,3)-based orbitals transform as 1e + 2e + 1a(1) + 1a(2). Above these levels come the predominantly metal-based 5f orbitals, which stabilise across the actinide series such that in CmCp(3) the 5f manifold is at more negative energy than the Cp π(2,3)-based levels. Mulliken population analysis shows metal d orbital participation in the e symmetry Cp π(2,3)-based orbitals. Metal 5f character is found in the 1a(1) and 1a(2) levels, and this contribution increases significantly from ThCp(3) to AmCp(3). This is in agreement with the metal spin densities, which are enhanced above their formal value in NpCp(3), PuCp(3) and especially AmCp(3) with both PBE and PBE0. However, atoms-in-molecules analysis of the electron densities indicates that the An-Cp bonding is very ionic, increasingly so as the actinide becomes heavier. It is concluded that the large metal orbital contributions to the Cp π(2,3)-based levels, and enhanced metal spin densities toward the middle of the actinide series arise from a coincidental energy match of metal and ligand orbitals, and do not reflect genuinely increased covalency (in the sense of appreciable overlap between metal and ligand levels and a build up of electron density in the region between the actinide and carbon nuclei).
Loibl, Stefan; Schütz, Martin
2014-07-14
In this paper, we present theory and implementation of an efficient program for calculating magnetizabilities and rotational g tensors of closed-shell molecules at the level of local second-order Møller-Plesset perturbation theory (MP2) using London orbitals. Density fitting is employed to factorize the electron repulsion integrals with ordinary Gaussians as fitting functions. The presented program for the calculation of magnetizabilities and rotational g tensors is based on a previous implementation of NMR shielding tensors reported by S. Loibl and M. Schütz [J. Chem. Phys. 137, 084107 (2012)]. Extensive test calculations show (i) that the errors introduced by density fitting are negligible, and (ii) that the errors of the local approximation are still rather small, although larger than for nuclear magnetic resonance (NMR) shielding tensors. Electron correlation effects for magnetizabilities are tiny for most of the molecules considered here. MP2 appears to overestimate the correlation contribution of magnetizabilities such that it does not constitute an improvement over Hartree-Fock (when comparing to higher-order methods like CCSD(T)). For rotational g tensors the situation is different and MP2 provides a significant improvement in accuracy over Hartree-Fock. The computational performance of the new program was tested for two extended systems, the larger comprising about 2200 basis functions. It turns out that a magnetizability (or rotational g tensor) calculation takes about 1.5 times longer than a corresponding NMR shielding tensor calculation.
Bistoni, Giovanni; Auer, Alexander A; Neese, Frank
2017-01-18
The interaction of Lewis acids and bases in both classical Lewis adducts and frustrated Lewis pairs (FLPs) is investigated to elucidate the role that London dispersion plays in different situations. The analysis comprises 14 different adducts between tris(pentafluorophenyl)borane and a series of phosphines, carbenes, and amines with various substituents, differing in both steric and electronic properties. The domain-based local pair natural orbital coupled-cluster (DLPNO-CCSD(T)) method is used in conjunction with the recently introduced local energy decomposition (LED) analysis to obtain state-of-the-art dissociation energies and, at the same time, a clear-cut definition of the London dispersion component of the interaction, with the ultimate goal of aiding in the development of designing principles for acid/base pairs with well-defined bonding features and reactivity. In agreement with previous DFT investigations, it is found that the London dispersion dominates the interaction energy in FLPs, and is also remarkably strong in Lewis adducts. In these latter systems, its magnitude can be easily modulated by modifying the polarizability of the substituents on the basic center, which is consistent with the recently introduced concept of dispersion energy donors. By counteracting the destabilizing energy contribution associated with the deformation of the monomers, the London dispersion drives the stability of many Lewis adducts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Téllez Soto, C A; Costa, A C; Ramos, J M; Vieira, L S; Rost, N C V; Versiane, O; Rangel, J L; Mondragón, M A; Raniero, L; Martin, A A
2013-12-01
Surface-enhanced Raman scattering (SERS) was used to study the interactions of the normal modes of the diethyldithiocarbamate copper (II) complex, [Cu(DDTC)2] on nano-structured mixture silver-gold surfaces and on silver surfaces. The electronic spectrum of this complex was measured and the charge transfer bands were assigned through the TD-PBE1PBE procedure. Natural bond orbital (NBO) were also carried out to study the Cu(II) hybridation leading to the square planar geometry of the framework of the [Cu(DDTC)2] complex, and to study which are the donor NBO and the acceptor NBO in meaningful charge transfer through the Second Order Perturbation Theory Analysis of the Fox Matrix in NBO basis. To see the electronic dispersion, the Mulliken electronic charges (MAC) were calculated for each normal mode and correlated with the SERS effect. Full assignment of the SERS spectra was also supported by carefully analysis of the distorted geometries generated by the normal modes.
Ronca, Enrico; Angeli, Celestino; Belpassi, Leonardo; De Angelis, Filippo; Tarantelli, Francesco; Pastore, Mariachiara
2014-09-09
Making use of the recently developed excited state charge displacement analysis [E. Ronca et al., J. Chem. Phys. 140, 054110 (2014)], suited to quantitatively characterize the charge fluxes coming along an electronic excitation, we investigate the role of the density relaxation effects in the overall description of electronically excited states of different nature, namely, valence, ionic, and charge transfer (CT), considering a large set of prototypical small and medium-sized molecular systems. By comparing the response densities provided by time-dependent density functional theory (TDDFT) and the corresponding relaxed densities obtained by applying the Z-vector postlinear-response approach [N. C. Handy and H. F. Schaefer, J. Chem. Phys. 81, 5031 (1984)] with those obtained by highly correlated state-of-the-art wave function calculations, we show that the inclusion of the relaxation effects is imperative to get an accurate description of the considered excited states. We also examine what happens at the quality of the response function when an increasing amount of Hartree-Fock (HF) exchange is included in the functional, showing that the usually improved excitation energies in the case of CT states are not always the consequence of an improved description of their overall properties. Remarkably, we find that the relaxation of the response densities is always able to reproduce, independently of the extent of HF exchange in the functional, the benchmark wave function densities. Finally, we propose a novel and computationally convenient strategy, based on the use of the natural orbitals derived from the relaxed TDDFT density to build zero-order wave function for multireference perturbation theory calculations. For a significant set of different excited states, the proposed approach provided accurate excitation energies, comparable to those obtained by computationally demanding ab initio calculations.
Energy Technology Data Exchange (ETDEWEB)
Sato, Soshi, E-mail: sato.soshi@cies.tohoku.ac.jp; Honjo, Hiroaki; Niwa, Masaaki [Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan); JST-ACCEL, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan); Ikeda, Shoji [Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan); JST-ACCEL, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Ohno, Hideo [Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); WPI-Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Endoh, Tetsuo [Center for Innovative Integrated Electronic Systems, Tohoku University, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan); JST-ACCEL, 468-1 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan); Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Graduate School of Engineering, Tohoku University, 6-6 Aza-aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan)
2015-04-06
We have investigated the redox reaction on the surface of Ta/CoFeB/MgO/CoFeB magnetic tunnel junction stack samples after annealing at 300, 350, and 400 °C for 1 h using angle-resolved X-ray photoelectron spectroscopy for precise analysis of the chemical bonding states. At a capping tantalum layer thickness of 1 nm, both the capping tantalum layer and the surface of the underneath CoFeB layer in the as-deposited stack sample were naturally oxidized. By comparison of the Co 2p and Fe 2p spectra among the as-deposited and annealed samples, reduction of the naturally oxidized cobalt and iron atoms occurred on the surface of the CoFeB layer. The reduction reaction was more significant at higher annealing temperature. Oxidized cobalt and iron were reduced by boron atoms that diffused toward the surface of the top CoFeB layer. A single CoFeB layer was prepared on SiO{sub 2}, and a confirmatory evidence of the redox reaction with boron diffusion was obtained by angle-resolved X-ray photoelectron spectroscopy analysis of the naturally oxidized surface of the CoFeB single layer after annealing. The redox reaction is theoretically reasonable based on the Ellingham diagram.
Gritsenko, Oleg; Baerends, Evert Jan
2006-02-07
A treatment of van der Waals (vdW) interaction by density-matrix functional theory requires a description of this interaction in terms of natural orbitals (NOs) and their occupation numbers. From an analysis of the configuration-interaction (CI) wave function of the 3Sigmau + state of H2 and the exact NO expansion of the two-electron triplet wave function, we demonstrate that the construction of such a functional is straightforward in this case. A quantitative description of the vdW interaction is already obtained with, in addition to the standard part arising from the Hartree-Fock determinant /1sigmag(r1)1sigmau(r2)/, only two additional terms in the two-electron density, one from the first "excited" determinant /2sigmag(r1)2sigmau(r2)/ and one from the state of 3Sigmau + symmetry belonging to the (1pig)1(1piu)1 configuration. The potential-energy curve of the 3Sigmau + state calculated around the vdW minimum with the exact density-matrix functional employing only these eight NOs and NO occupations is in excellent agreement with the full CI one and reproduces well the benchmark potential curve of Kolos and Wolniewicz [J. Chem. Phys. 43, 2429 (1965)]. The corresponding terms in the two-electron density rho2(r1,r2), containing specific products of NOs combined with prefactors that depend on the occupation numbers, can be shown to produce exchange-correlation holes that correspond precisely to the well-known intuitive picture of the dispersion interaction as an instantaneous dipole-induced dipole (higher multipole) effect. Indeed, (induced) higher multipoles account for almost 50% of the total vdW bond energy. These results serve as a basis for both a density-matrix functional theory of van der Waals bonding and for the construction of orbital-dependent functionals in density-functional theory that could be used for this type of bonding.
Origin of the Spin-Orbit Interaction
Spavieri, Gianfranco
2015-01-01
We consider a semi-classical model to describe the origin of the spin-orbit interaction in a simple system such as the hydrogen atom. The interaction energy U is calculated in the rest-frame of the nucleus, around which an electron, having linear velocity v and magnetic dipole-moment mu, travels in a circular orbit. The interaction energy U is due to the coupling of the induced electric dipole p=(v/c)x mu with the electric field En of the nucleus. Assuming the radius of the electron's orbit remains constant during a spin-flip transition, our model predicts that the energy of the system changes by Delta_E = U/2, the factor 1/2 emerging naturally as a consequence of equilibrium and the change of the kinetic energy of the electron. The correct 1/2 factor for the spin-orbit coupling energy is thus derived without the need to invoke the well-known Thomas precession in the rest-frame of the electron.
A novel technique to achieve atomic macro-coherence as a tool to determine the nature of neutrinos
Boyero García, R.; Carpentier, A. V.; Gómez-Cadenas, J. J.; Peralta Conde, A.
2016-10-01
The photon spectrum in macro-coherent atomic deexcitation via radiative emission of neutrino pairs has been proposed as a sensitive probe of the neutrino mass spectrum, capable of competing with conventional neutrino experiments. In this paper, we revisit this intriguing possibility, presenting an alternative method for inducing large coherence in a target based on adiabatic techniques. More concretely, we propose the use of a modified version of coherent population return (CPR), namely two-photon CPR, that turns out to be extremely robust with respect to the experimental parameters and capable of inducing a coherence close to 100 % in the target.
Designing high-performance layered thermoelectric materials through orbital engineering
Zhang, Jiawei; Song, Lirong; Madsen, Georg K. H.; Fischer, Karl F. F.; Zhang, Wenqing; Shi, Xun; Iversen, Bo B.
2016-03-01
Thermoelectric technology, which possesses potential application in recycling industrial waste heat as energy, calls for novel high-performance materials. The systematic exploration of novel thermoelectric materials with excellent electronic transport properties is severely hindered by limited insight into the underlying bonding orbitals of atomic structures. Here we propose a simple yet successful strategy to discover and design high-performance layered thermoelectric materials through minimizing the crystal field splitting energy of orbitals to realize high orbital degeneracy. The approach naturally leads to design maps for optimizing the thermoelectric power factor through forming solid solutions and biaxial strain. Using this approach, we predict a series of potential thermoelectric candidates from layered CaAl2Si2-type Zintl compounds. Several of them contain nontoxic, low-cost and earth-abundant elements. Moreover, the approach can be extended to several other non-cubic materials, thereby substantially accelerating the screening and design of new thermoelectric materials.
Designing high-performance layered thermoelectric materials through orbital engineering.
Zhang, Jiawei; Song, Lirong; Madsen, Georg K H; Fischer, Karl F F; Zhang, Wenqing; Shi, Xun; Iversen, Bo B
2016-01-01
Thermoelectric technology, which possesses potential application in recycling industrial waste heat as energy, calls for novel high-performance materials. The systematic exploration of novel thermoelectric materials with excellent electronic transport properties is severely hindered by limited insight into the underlying bonding orbitals of atomic structures. Here we propose a simple yet successful strategy to discover and design high-performance layered thermoelectric materials through minimizing the crystal field splitting energy of orbitals to realize high orbital degeneracy. The approach naturally leads to design maps for optimizing the thermoelectric power factor through forming solid solutions and biaxial strain. Using this approach, we predict a series of potential thermoelectric candidates from layered CaAl2Si2-type Zintl compounds. Several of them contain nontoxic, low-cost and earth-abundant elements. Moreover, the approach can be extended to several other non-cubic materials, thereby substantially accelerating the screening and design of new thermoelectric materials.
Energy Technology Data Exchange (ETDEWEB)
Rodriguez-Bautista, Mariano; Díaz-García, Cecilia; Navarrete-López, Alejandra M.; Vargas, Rubicelia; Garza, Jorge, E-mail: jgo@xanum.uam.mx [Departamento de Química, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, Iztapalapa C. P. 09340, México D. F., México (Mexico)
2015-07-21
In this report, we use a new basis set for Hartree-Fock calculations related to many-electron atoms confined by soft walls. One- and two-electron integrals were programmed in a code based in parallel programming techniques. The results obtained with this proposal for hydrogen and helium atoms were contrasted with other proposals to study just one and two electron confined atoms, where we have reproduced or improved the results previously reported. Usually, an atom enclosed by hard walls has been used as a model to study confinement effects on orbital energies, the main conclusion reached by this model is that orbital energies always go up when the confinement radius is reduced. However, such an observation is not necessarily valid for atoms confined by penetrable walls. The main reason behind this result is that for atoms with large polarizability, like beryllium or potassium, external orbitals are delocalized when the confinement is imposed and consequently, the internal orbitals behave as if they were in an ionized atom. Naturally, the shell structure of these atoms is modified drastically when they are confined. The delocalization was an argument proposed for atoms confined by hard walls, but it was never verified. In this work, the confinement imposed by soft walls allows to analyze the delocalization concept in many-electron atoms.
Rodriguez-Bautista, Mariano; Díaz-García, Cecilia; Navarrete-López, Alejandra M; Vargas, Rubicelia; Garza, Jorge
2015-07-21
In this report, we use a new basis set for Hartree-Fock calculations related to many-electron atoms confined by soft walls. One- and two-electron integrals were programmed in a code based in parallel programming techniques. The results obtained with this proposal for hydrogen and helium atoms were contrasted with other proposals to study just one and two electron confined atoms, where we have reproduced or improved the results previously reported. Usually, an atom enclosed by hard walls has been used as a model to study confinement effects on orbital energies, the main conclusion reached by this model is that orbital energies always go up when the confinement radius is reduced. However, such an observation is not necessarily valid for atoms confined by penetrable walls. The main reason behind this result is that for atoms with large polarizability, like beryllium or potassium, external orbitals are delocalized when the confinement is imposed and consequently, the internal orbitals behave as if they were in an ionized atom. Naturally, the shell structure of these atoms is modified drastically when they are confined. The delocalization was an argument proposed for atoms confined by hard walls, but it was never verified. In this work, the confinement imposed by soft walls allows to analyze the delocalization concept in many-electron atoms.
Rodriguez-Bautista, Mariano; Díaz-García, Cecilia; Navarrete-López, Alejandra M.; Vargas, Rubicelia; Garza, Jorge
2015-07-01
In this report, we use a new basis set for Hartree-Fock calculations related to many-electron atoms confined by soft walls. One- and two-electron integrals were programmed in a code based in parallel programming techniques. The results obtained with this proposal for hydrogen and helium atoms were contrasted with other proposals to study just one and two electron confined atoms, where we have reproduced or improved the results previously reported. Usually, an atom enclosed by hard walls has been used as a model to study confinement effects on orbital energies, the main conclusion reached by this model is that orbital energies always go up when the confinement radius is reduced. However, such an observation is not necessarily valid for atoms confined by penetrable walls. The main reason behind this result is that for atoms with large polarizability, like beryllium or potassium, external orbitals are delocalized when the confinement is imposed and consequently, the internal orbitals behave as if they were in an ionized atom. Naturally, the shell structure of these atoms is modified drastically when they are confined. The delocalization was an argument proposed for atoms confined by hard walls, but it was never verified. In this work, the confinement imposed by soft walls allows to analyze the delocalization concept in many-electron atoms.
Institute of Scientific and Technical Information of China (English)
王俊; 高先龙
2015-01-01
It was investigated the properties of spin-orbit coupled atomic fermi gases under a Zeeman field. By solving the Bogoliubove-de Gennes equation self-consistently, it was found that the system supported the topol-ogical superfluid state and the Fulde-Ferrell-Larkin-Ovchinnikov superfluid state respectively when the system under the different strength of Zeeman field and filling factors. When the system turned into topological super-fluid state, a pair of zero-energy Majorana fermions were found.%研究了具有自旋轨道耦合的冷原子费米气在外磁场作用下的物理性质。通过自洽求解Bogoliubove-de Gennes方程，发现了在不同磁场强度和粒子填充数下，体系分别存在拓扑超流态和 Fulde-Ferrell-Larkin-Ovchinnikov超流态。当体系处于拓扑超流态时，存在零能Majorana费米子。
Hamaya, S.; Maeda, H.; Funaki, M.; Fukui, H.
2008-12-01
The relativistic calculation of nuclear magnetic shielding tensors in hydrogen halides is performed using the second-order regular approximation to the normalized elimination of the small component (SORA-NESC) method with the inclusion of the perturbation terms from the metric operator. This computational scheme is denoted as SORA-Met. The SORA-Met calculation yields anisotropies, Δσ =σ∥-σ⊥, for the halogen nuclei in hydrogen halides that are too small. In the NESC theory, the small component of the spinor is combined to the large component via the operator σ⃗ṡπ⃗U/2c, in which π⃗=p⃗+A⃗, U is a nonunitary transformation operator, and c ≅137.036 a.u. is the velocity of light. The operator U depends on the vector potential A⃗ (i.e., the magnetic perturbations in the system) with the leading order c-2 and the magnetic perturbation terms of U contribute to the Hamiltonian and metric operators of the system in the leading order c-4. It is shown that the small Δσ for halogen nuclei found in our previous studies is related to the neglect of the U(0,1) perturbation operator of U, which is independent of the external magnetic field and of the first order with respect to the nuclear magnetic dipole moment. Introduction of gauge-including atomic orbitals and a finite-size nuclear model is also discussed.
Hydrogenoid orbitals revisited: From Slater orbitals to Coulomb Sturmians
Indian Academy of Sciences (India)
Danilo Calderini; Simonetta Cavalli; Cecilia Coletti; Gaia Grossi; Vincenzo Qquilanti
2012-01-01
The simple connection between the Slater orbitals, venerable in quantum chemistry, and the Coulomb Sturmian orbitals, more recently employed in atomic and molecular physics, is pointed out explicitly in view of the renewed interest in both as basis sets in applied quantum mechanics. Research in Slater orbitals mainly concerns multicentre, many-body integrals, whereas that on Sturmians exploits their orthonormality and completeness with no need of continuum states. An account of recent progress is outlined, also with reference to relationships between the two basis sets, and with the momentum space and hyperspherical harmonics representations.
Blackstone, Christopher C.; Sanov, Andrei
2016-06-01
Using the generalized model for photodetachment of electrons from mixed-character molecular orbitals, we gain insight into the nature of the HOMO of HO2- by treating it as a coherent superpostion of one p- and one d-type atomic orbital. Fitting the pd model function to the ab initio calculated HOMO of HO2- yields a fractional d-character, γp, of 0.979. The modeled curve of the anisotropy parameter, β, as a function of electron kinetic energy for a pd-type mixed character orbital is matched to the experimental data.
... Goodlick TA, Kay MD, Glaser JS, Tse DT, Chang WJ. Orbital disease and neuro-ophthalmology. In: Tasman ... 423. Review Date 8/20/2016 Updated by: Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La ...
稀土原子与离子的自然辐射寿命测量%Natural radiative lifetime measurements of rare-earth atoms and ions
Institute of Scientific and Technical Information of China (English)
蒋红玫; 杨博思; 李贺龙; 徐淮良
2013-01-01
Advances in the techniques available for natural radiative lifetime measurement of excited states of free atoms and ions are presented.The disadvantages and advantages of several often-used methods for radia-tive lifetime measurements of free atoms and ions of rare-earth elements are reviewed by taking La Ⅰ and PrⅡas examples.Then, the techniques of the laser ablation to produce free atoms and ions are introduced by taking SmⅡas an example, and the time-resolved laser induced fluorescence (LIF) spectroscopy for the radi-ative lifetime measurements is discussed in detail .The limitation of this method of LIF combined with laser ab-lation is summarized and a possibly useful solution is suggested , which may be helpful to further improve the precision of radiative lifetime measurements.%概述了当前自由原子和离子的激发态自然辐射寿命测量技术的进展。以LaⅠ和Pr Ⅱ为例，系统介绍了几种稀土元素自由原子和离子激发态寿命测量技术并分析了它们的优缺点；以Sm Ⅱ为例，详细介绍了激光烧蚀产生自由原子（离子）技术及结合激光诱导荧光时间分辨光谱技术进行激发态寿命测量的优缺点。最后，探讨了改进上述技术局限性的解决思路，以期进一步提高辐射寿命测量的精确度。
Synthetic Spin-Orbit Coupling in an Optical Lattice Clock
Wall, Michael L.; Koller, Andrew P.; Li, Shuming; Zhang, Xibo; Cooper, Nigel R.; Ye, Jun; Rey, Ana Maria
2016-01-01
We propose the use of optical lattice clocks operated with fermionic alkaline-earth atoms to study spin-orbit coupling (SOC) in interacting many-body systems. The SOC emerges naturally during the clock interrogation, when atoms are allowed to tunnel and accumulate a phase set by the ratio of the "magic" lattice wavelength to the clock transition wavelength. We demonstrate how standard protocols such as Rabi and Ramsey spectroscopy that take advantage of the sub-Hertz resolution of state-of-the-art clock lasers can perform momentum-resolved band tomography and determine SOC-induced s -wave collisions in nuclear-spin-polarized fermions. With the use of a second counterpropagating clock beam, we propose a method for engineering controlled atomic transport and study how it is modified by p - and s -wave interactions. The proposed spectroscopic probes provide clean and well-resolved signatures at current clock operating temperatures.
DEFF Research Database (Denmark)
Yazdanfard, Younes; Heegard, Steffen; Fledelius, Hans C.
2001-01-01
Ophthalmology, penetrating orbital injury, orbital foreign body, ultrasound, computed tomography (CT), histology......Ophthalmology, penetrating orbital injury, orbital foreign body, ultrasound, computed tomography (CT), histology...
Liu, Yao-Min; Zhang, Feng-Ping; Jiao, Bao-Yu; Rao, Jin-Yu; Leng, Geng
2017-04-14
An automated, home-constructed, and low cost dispersive liquid-liquid microextraction (DLLME) device that directly coupled to a high performance liquid chromatography (HPLC) - cold vapour atomic fluorescence spectroscopy (CVAFS) system was designed and developed for the determination of trace concentrations of methylmercury (MeHg(+)), ethylmercury (EtHg(+)) and inorganic mercury (Hg(2+)) in natural waters. With a simple, miniaturized and efficient automated DLLME system, nanogram amounts of these mercury species were extracted from natural water samples and injected into a hyphenated HPLC-CVAFS for quantification. The complete analytical procedure, including chelation, extraction, phase separation, collection and injection of the extracts, as well as HPLC-CVAFS quantification, was automated. Key parameters, such as the type and volume of the chelation, extraction and dispersive solvent, aspiration speed, sample pH, salt effect and matrix effect, were thoroughly investigated. Under the optimum conditions, linear range was 10-1200ngL(-1) for EtHg(+) and 5-450ngL(-1) for MeHg(+) and Hg(2+). Limits of detection were 3.0ngL(-1) for EtHg(+) and 1.5ngL(-1) for MeHg(+) and Hg(2+). Reproducibility and recoveries were assessed by spiking three natural water samples with different Hg concentrations, giving recoveries from 88.4-96.1%, and relative standard deviations <5.1%.
A new kinematical definition of orbital eccentricity
Directory of Open Access Journals (Sweden)
Ninković S.
2009-01-01
Full Text Available A new concept of orbital eccentricity is given. The dimensionless quantities proposed in the present paper to serve as orbital eccentricities have a kinematical nature. The purpose is to use them in describing the motion for the case of three-dimensional orbits. A comparison done for nearly planar orbits shows that the values of the eccentricities proposed here do not differ significantly from those corresponding to the eccentricities of geometric nature usually applied.
Tsogas, George Z; Giokas, Dimosthenis L; Vlessidis, Athanasios G
2009-04-30
In this study three major types of preconcentration methods based upon different principles (cation exchange, physical absorption and hydrophobic extraction) were evaluated and optimized for the extraction and determination of three highly toxic heavy metals namely Cd, Pb and Sn by graphite furnace and hybrid generation atomic absorption spectrometry in real samples. The optimum analytical conditions were examined and the analytical features of each method were revealed and compared. Detection limits as low as 0.003-0.025 microg L(-1) for Cd(2+), 0.05-0.10 microg L(-1) for Pb(2+) and 0.1-0.25 microg L(-1) for Sn(4+) depending on the extraction method were obtained with RSD values between 3.08% and 6.11%. A preliminary assessment of the pollution status of three important natural ecosystems in Epirus region (NW Greece) was performed and some early conclusions were drawn and discussed.
Directory of Open Access Journals (Sweden)
Elías Gómez Macías
2006-01-01
Full Text Available Partiendo de óxido de magnesio comercial se preparó una suspensión acuosa, la cual se secó y calcinó para conferirle estabilidad térmica. El material, tanto fresco como usado, se caracterizó mediante DRX, área superficial BET y SEM-EPMA. El catalizador mostró una matriz de MgO tipo periclasa con CaO en la superficie. Las pruebas de actividad catalítica se efectuaron en lecho fijo empacado con partículas obtenidas mediante prensado, trituración y clasificación del material. El flujo de reactivos consistió en mezclas gas natural-aire por debajo del límite inferior de inflamabilidad. Para diferentes flujos y temperaturas de entrada de la mezcla reactiva, se midieron las concentraciones de CH4, CO2 y CO en los gases de combustión con un analizador de gases tipo infrarrojo no dispersivo (NDIR. Para alcanzar conversión total de metano se requirió aumentar la temperatura de entrada al lecho a medida que se incrementó el flujo de gases reaccionantes. Los resultados obtenidos permiten desarrollar un sistema de combustión catalítica de bajo costo con un material térmicamente estable, que promueva la alta eficiencia en la combustión de gas natural y elimine los problemas de estabilidad, seguridad y de impacto ambiental negativo inherentes a los procesos de combustión térmica convencional.
Trapping of Single Atoms with Single Photons in Cavity QED
Doherty, A C; Hood, C J; Kimble, H J
2000-01-01
Two recent experiments have reported the trapping of individual atoms inside optical resonators by the mechanical forces associated with single photons [Hood et al., Science 287, 1447 (2000) and Pinkse et al., Nature 404, 365 (2000)]. Here we analyze the trapping dynamics in these settings, focusing on two points of interest. Firstly, we investigate the extent to which light-induced forces in these experiments are distinct from their free-space counterparts. Secondly, we explore the quantitative features of the resulting atomic motion and how these dynamics are mapped onto variations of the intracavity field. Not surprisingly, qualitatively distinct atomic dynamics arise as the coupling and dissipative rates are varied. For the experiment of Hood et al., we show that atomic motion is largely conservative and is predominantly in radial orbits transverse to the cavity axis. A comparison with the free-space theory demonstrates that the fluctuations of the dipole force are suppressed by an order of magnitude. Thi...
A Quantum Model of Atoms (the Energy Levels of Atoms).
Rafie, Francois
2001-01-01
Discusses the model for all atoms which was developed on the same basis as Bohr's model for the hydrogen atom. Calculates the radii and the energies of the orbits. Demonstrates how the model obeys the de Broglie's hypothesis that the moving electron exhibits both wave and particle properties. (Author/ASK)
Kim, Yang-Soo; Kim, Hee-Jin; Jeon, Young-A; Kang, Yong-Mook
2009-02-12
The electronic structures of LiTiS(2) and LiTiO(2) (having alpha-NaFeO(2) structure) have been investigated using discrete variational Xalpha molecular orbital methods. The alpha-NaFeO(2) structure is the equilibrium structure for LiCoO(2), which is widely used as a commercial cathode material for lithium secondary batteries. This study especially focused on the charge state of Li ions and the magnitude of covalency around Li ions. When the average voltage of lithium intercalation was calculated using pseudopotential methods, the average intercalation voltage of LiTiO(2) (2.076 V) was higher than that of LiTiS(2) (1.958 V). This can be explained by the differences in Mulliken charge of lithium and the bond overlap population between the intercalated Li ions and anion in LiTiO(2) as well as LiTiS(2). The Mulliken charge, which is the ionicity of Li atom, was approximately 0.12 in LiTiS(2), and the bond overlap population (BOP) indicating the covalency between Ti and S was about 0.339. When compared with the BOP (0.6) of C-H, which is one of the most famous example of covalent bonding, the intercalated Li ions in LiTiS(2) tend to form a quite strong covalent bond with the host material. In contrast, the Mulliken charge of lithium was about 0.79, which means that Li is fully ionized and the BOP, the covalency between Ti and O, was 0.181 in LiTiO(2). Because of the high ionicity of Li and the weak covalency between Ti and the nearest anion, LiTiO(2) has a higher intercalation voltage than LiTiS(2).
Periodic orbits for three and four co-orbital bodies
Verrier, P. E.; McInnes, C. R.
2014-08-01
We investigate the natural families of periodic orbits associated with the equilibrium configurations of the planar-restricted 1 + n-body problem for the case 2 ≤ n ≤ 4 equal-mass satellites. Such periodic orbits can be used to model both trojan exoplanetary systems and parking orbits for captured asteroids within the Solar system. For n = 2, there are two families of periodic orbits associated with the equilibria of the system: the well-known horseshoe and tadpole orbits. For n = 3, there are three families that emanate from the equilibrium configurations of the satellites, while for n = 4, there are six such families as well as numerous additional connecting families. The families of periodic orbits are all of the horseshoe or tadpole type, and several have regions of neutral linear stability.
Periodic orbits for 3 and 4 co-orbital bodies
Verrier, Patricia
2014-01-01
We investigate the natural families of periodic orbits associated with the equilibrium configurations of the the planar restricted $1+n$ body problem for the case $2\\leq n \\leq 4$ equal mass satellites. Such periodic orbits can be used to model both trojan exoplanetary systems and parking orbits for captured asteroids within the solar system. For $n=2$ there are two families of periodic orbits associated with the equilibria of the system: the well known horseshoe and tadpole orbits. For $n=3$ there are three families that emanate from the equilibrium configurations of the satellites, while for $n=4$ there are six such families as well as numerous additional connecting families. The families of periodic orbits are all of the horseshoe or tadpole type, and several have regions of neutral linear stability.
Tsekov, R
2014-01-01
The finite size effect of electron and nucleus is accounted for in the model of atom. Due to their hard sphere repulsion the energy of the 1s orbital decreases and the corrections amount up to 8 % in Uranium. Several models for boundary conditions on the atomic nucleus surface are discussed as well.
Optical angular momentum and atoms.
Franke-Arnold, Sonja
2017-02-28
Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Author(s).
Diffractive molecular-orbital tomography
Zhai, Chunyang; Zhu, Xiaosong; Lan, Pengfei; Wang, Feng; He, Lixin; Shi, Wenjing; Li, Yang; Li, Min; Zhang, Qingbin; Lu, Peixiang
2017-03-01
High-order-harmonic generation in the interaction of femtosecond lasers with atoms and molecules opens the path to molecular-orbital tomography and to probe the electronic dynamics with attosecond-Ångström resolutions. Molecular-orbital tomography requires both the amplitude and phase of the high-order harmonics. Yet the measurement of phases requires sophisticated techniques and represents formidable challenges at present. Here we report a scheme, called diffractive molecular-orbital tomography, to retrieve the molecular orbital solely from the amplitude of high-order harmonics without measuring any phase information. We have applied this method to image the molecular orbitals of N2, CO2, and C2H2 . The retrieved orbital is further improved by taking account the correction of Coulomb potential. The diffractive molecular-orbital tomography scheme, removing the roadblock of phase measurement, significantly simplifies the molecular-orbital tomography procedure and paves an efficient and robust way to the imaging of more complex molecules.
Institute of Scientific and Technical Information of China (English)
黄艳菊; 倪良; 王蕾; 朱翀
2011-01-01
A metal-organic complex [Ni(Pht)(Medpq)(H2O)3]n (1) (Pht=phthalic acid, Medpq=2-methyldipyrido[3,2-f:2',3'-h]quinoxaline) has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG, single-crystal X-ray diffraction and theoretical calculations. In the crystal structure, the nickel atom is hexa-coordinated with two nitrogen atoms from Medpq ligand, one oxygen atom from Pht ligand and three oxygen atoms from three different coordination water molecules, assuming a slightly distorted octahedral geometry. Furthermore, it exhibits a zero-dimensional structure with Pht-Ni-Medpq as building units. Natural bond orbital (NBO) analysis was performed by using the NBO method built in Gaussian03 Program. The calculation results show there is the obvious covalent interaction between the coordinated atoms and Ni(Ⅱ) ion.%采用水热法合成了一种新型金属配合物[Ni(Pht)(Medpq)(H2O)3]n(1)(Pht=phthalic acid,Medpq=2-methyldipyrido[3,2-f:2',3'-h]quinoxaline),并对其进行了元素分析、红外光谱、热重表征、X射线单晶衍射测定和理论计算.在晶体中,Ni(Ⅱ)与来自于Medpq分子上的2个氮原子,邻苯二甲酸上的1个氧原子及来自于3个不同的配位水分子上的3个氧原子配位,形成畸变的八面体构型.整个晶体由Pht-Ni-Medpq单元组成零维结构.应用Guassian03W程序,在HF/LANL2DZ水平上对标题化合物的自然键轨道(NBO)进行了分析,结果表明Ni(Ⅱ)与配位原子间的价键类型都属于共价键范畴.
Sánchez-Márquez, Jesús
2016-11-01
A new methodology to obtain reactivity indices has been defined. This is based on reactivity functions such as the Fukui function or the dual descriptor and makes it possible to project the information of reactivity functions over molecular orbitals instead of the atoms of the molecule (atomic reactivity indices). The methodology focuses on the molecule's natural bond orbitals (bond reactivity indices) because these orbitals (with physical meaning) have the advantage of being very localized, allowing the reaction site of an electrophile or nucleophile to be determined within a very precise molecular region. This methodology gives a reactivity index for every Natural Bond Orbital (NBO), and we have verified that they have equivalent information to the reactivity functions. A representative set of molecules has been used to test the new definitions. Also, the bond reactivity index has been related with the atomic reactivity one, and complementary information has been obtained from the comparison. Finally, a new atomic reactivity index has been defined and compared with previous definitions.
Orbital compression syndrome presenting as orbital cellulitis in a child with sickle cell anemia.
Douvoyiannis, Miltiadis; Fakioglu, Esra; Litman, Nathan
2010-04-01
Orbital bone infarction with subsequent orbital compression syndrome presenting as orbital cellulitis is reported in a child with sickle cell anemia. She deteriorated despite the use of antibiotics and improved after the surgical drainage of the collection. Radiographic findings, absence of sinusitis, hemorrhagic nature of the collection, and negative cultures all were consistent with orbital compression syndrome secondary to a vasoocclusive crisis. This condition needs to be differentiated from the more common orbital cellulitis secondary to sinusitis.
Murphy, Andrew; Haestad, Jace; Morgan, Thomas
2015-09-01
We report characteristics of closed classical orbits in an electric field in phase space produced in photoabsorption. Rydberg states of atomic and molecular hydrogen and helium are considered. The core potential used for the hydrogen molecule is an effective one electron one center core potential evaluated at the internuclear equilibrium distance. Poincare surfaces of section in phase space are generated by integrating the equations of motion in semiparabolic coordinates u = (r + z) 1 / 2 and v = (r - z) 1 / 2, and plotting the location in phase space (pv versus v) whenever u = 0, with the electric field in the z direction. Combination orbits produced by Rydberg electron core scattering are studied and the evolution in phase space of these combination orbits due to scattering from one closed orbit into another is investigated. Connections are made to measured laser photoabsorption experiments that excite Rydberg states (20 recurrence spectra. The phase space structures responsible for the spectra are identified.
Bondarescu, Ruxandra; Jetzer, Philippe; Angélil, Raymond; Saha, Prasenjit; Lundgren, Andrew
2015-01-01
The successful miniaturisation of extremely accurate atomic clocks and atom interferometers invites prospects for satellite missions to perform precision experiments. We discuss the effects predicted by general relativity and alternative theories of gravity that can be detected by a clock, which orbits the Earth. Our experiment relies on the precise tracking of the spacecraft using its observed tick-rate. The spacecraft's reconstructed four-dimensional trajectory will reveal the nature of gravitational perturbations in Earth's gravitational field, potentially differentiating between different theories of gravity. This mission can measure multiple relativistic effects all during the course of a single experiment, and constrain the Parametrized Post-Newtonian Parameters around the Earth. A satellite carrying a clock of fractional timing inaccuracy of $\\Delta f/f \\sim 10^{-16}$ in an elliptic orbit around the Earth would constrain the PPN parameters $|\\beta -1|, |\\gamma-1| \\lesssim 10^{-6}$. We also briefly revi...
Recolliding orbits in an intense laser field
Kamor, Adam; Chandre, Cristel; UZer, Turgay
2013-01-01
We show that a family of key periodic orbits drive the recollision process in a strong circulary polarized laser field. These orbits, coined recolliding periodic orbits, exist for a wide range of parameters and their relative influence changes as the laser and atomic parameters are varied. We find the necessary conditions for recollision-driven nonsequential double ionization to occur. The outlined mechanism is universal in that it applies equally well beyond atoms: The internal structure of the target species plays a minor role in the recollision process.
Geometric orbit datum and orbit covers
Institute of Scientific and Technical Information of China (English)
梁科; 侯自新
2001-01-01
Vogan conjectured that the parabolic induction of orbit data is independent of the choice of the parabolic subgroup. In this paper we first give the parabolic induction of orbit covers, whose relationship with geometric orbit datum is also induced. Hence we show a geometric interpretation of orbit data and finally prove the conjugation for geometric orbit datum using geometric method.
Leopold, Kerstin; Foulkes, Michael; Worsfold, Paul J
2009-05-01
A novel solid-phase preconcentration method is reported, using in-house gold-coated silica adsorbent packed in a microcolumn, for the determination of dissolved mercury in natural waters by atomic fluorescence spectrometry (AFS). The adsorbent was prepared by chemical reduction of a Au(III) solution with hydroxylamine in the presence of suspended silica particles. The resulting Au nanoparticles on the silica surface were highly efficient for adsorbing different mercury species from acidified waters without additional reagents. The acidified aqueous samples were passed over the microcolumn, either incorporated in a fully automated flow injection (FI) system directly coupled to the AFS or as part of a portable FI system for in situ preconcentration. After rinsing and drying of the column, Hg(0) was released by heating and directed to the AFS cell for quantification. The method offers significant advantages because no reagents are needed for species conversion, preconcentration, sample storage, or desorption and therefore the risk of contamination is minimized and blank values are lowered. This results in a low detection limit of 180 pg L(-1) using a sample volume of only 7 mL and good reproducibility, with relative standard deviations 90% in spiked river waters (spiked [Hg] = 0, 1, 5, 10 ng L(-1)), and the experimental value for the certified reference material ORMS-4 (elevated mercury in river water) was 22.3 +/- 2.6 ng Hg L(-1) which was in good agreement with the certified value of 22.0 +/- 1.6 ng Hg L(-1) (recovery = 101%). The method was successfully applied to seven different natural waters and wastewaters ([Hg] 0.5-4.6 ng L(-1)) from south west England.
Directory of Open Access Journals (Sweden)
Abdollahi Atousa
2014-07-01
Full Text Available A novel dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO for simultaneous separation/preconcentration of ultra trace amounts of mercury was used. A method based on amalgamation was used for collection of gaseous mercury on gold coated sand (Gold trap. The concentration of mercury was determined by cold vapor atomic absorption spectrometry (CV-AAS. The DLLME-SFO behavior of mercury by using dithizone as complexing agent was systematically investigated. The factors influencing, the complex formation and extraction of DLLME-SFO method such as type and volume of extraction and disperser solvents, pH, concentration of salt, centrifuging time and concentration of the chelating agent were optimized. The method was successfully applied to the determination of mercury in drinking and natural water and satisfactory relative recoveries (95–105% were achieved. The proposed procedure was based on very low consumption of organic solvents. The other benefits of the system were sensitive, simple, friendly to the environment, rejection of matrix constituent, low cost, the time consuming and high enrichment factor.
Bhunia, Snehasis; Singh, Ajeet; Ojha, Animesh K
2017-03-01
Complexes of the dipeptide phenylalanine-phenylalanine (Phe-Phe) with divalent metal cations (Cu(2+), Zn(2+), Ca(2+) and Ba(2+)) were studied at the B3LYP and MP2 levels of theory with the basis sets 6-311++G(d,p) and 6-31 + G(d) in the gas phase. The relative energies of these complexes indicated that cation-π bidentate/tridentate conformations are more favourable than other conformations with uncoordinated rings. These findings were confirmed by the calculated values of thermodynamic parameters such as the Gibbs free energy. Natural bond orbital (NBO) analysis was carried out to explore the metal-ligand coordination in Phe-Phe-Cu(2+)/Zn(2+) complexes. Possible orbital transitions, types of orbitals and their occupancies were determined for a range of Phe-Phe-Cu(2+)/Zn(2+) complexes. The charge transfer involved in various orbital transitions was explored by considering the second-order perturbation energy. NBO analysis revealed that the change transfer is stronger when the metal cation uses both the 4s + 4p subshells rather than just its 4p subshell. We also performed molecular dynamics (MD) simulations to check the stability and consistency of the most favourable binding motifs of Cu(2+), Zn(2+), Ca(2+) and Ba(2+) with Phe-Phe over time. The structures of the Phe-Phe-Cu(2+)/Zn(2+)/Ca(2+)/Ba(2+) complexes obtained using MD simulation were found to be in good agreement with those obtained in the DFT-based calculations. Graphical Abstract Conformational search on encapsulation of divalent metal cations (Ca(2+), Zn(2+), Ca(2+), Ba(2+)) by the Phe-Phe dipeptide.
Molecular integrals for exponential-type orbitals using hyperspherical harmonics
DEFF Research Database (Denmark)
Avery, James Emil; Avery, John Scales
2015-01-01
Exponential-type orbitals are better suited to calculations of molecular electronic structure than are Gaussians, since ETO's can accurately represent the behavior of molecular orbitals near to atomic nuclei, as well as their long-distance exponential decay. Orbitals based on Gaussians fail in bo...
Calleja, Eduardo Manuel
The superconducting cuprates represent one of the most intriguing condensed matter systems due to their potential to impact future technologies. As such they have garnered a substantial amount of theoretical and experimental interest over the last 27 years. In spite of this fact, many questions remain unanswered such as the nature of the superconducting pairing mechanism and the origin of the structure of their phase diagram. Spectroscopic Imagining Scanning Tunneling Microscopy (SI-STM) has proven to be an extremely useful probe for studying these materials due to the fact that SI-STM allows for the simultaneous measurement of the real space electronic states with atomic precision and the nature of the momentum K-space states. In this thesis the design and construction of a 5K SI-STM designed for looking at cleavable surfaces, such as the superconducting cuprates, is presented. The k-space nature of the electronic states on Bi2212, as measured by SI-STM, seems to indicate that there is a portion of the Fermi surface which does not super conduct. However, evidence from other probes is mixed. In this thesis, a framework which explains how these "Fermi Arcs" can arise from experimental effects is presented. Followed by an experiment on Bi2212 that shows how one could mistakenly see this "Fermi Arc" signal by adjusting simple experimental dials. In addition, in this thesis we present a comprehensive study of Bi2212 samples where Fe has been substituted for Cu in the CuO plane. This study reveals a highly localized bound state, with the density of states showing a large asymmetry favoring the hole side. The density of states can be interpreted within a co-tunneling picture which is only valid if the impurity is coupled to the conduction electrons resulting in a local Kondo-like effect. This is the first time a Kondo-like impurity is observed in a d-wave superconductor. Comparisons to experiments where Kondo impurities are observed in s-wave superconductors are
Measuring Scars of Periodic Orbits
Kaplan, L
1999-01-01
The phenomenon of periodic orbit scarring of eigenstates of classically chaotic systems is attracting increasing attention. Scarring is one of the most important ``corrections'' to the ideal random eigenstates suggested by random matrix theory. This paper discusses measures of scars and in so doing also tries to clarify the concepts and effects of eigenfunction scarring. We propose a new, universal scar measure which takes into account an entire periodic orbit and the linearized dynamics in its vicinity. This measure is tuned to pick out those structures which are induced in quantum eigenstates by unstable periodic orbits and their manifolds. It gives enhanced scarring strength as measured by eigenstate overlaps and inverse participation ratios, especially for longer orbits. We also discuss off-resonance scars which appear naturally on either side of an unstable periodic orbit.
... Eye Exams, Study Finds Additional Content Medical News Inflammation of the Orbit (Inflammatory Orbital Pseudotumor) By James ... Introduction to Eye Socket Disorders Cavernous Sinus Thrombosis Inflammation of the Orbit Orbital Cellulitis Preseptal Cellulitis Tumors ...
Arvidson, R. E.; Poulet, F.; Morris, R.V.; Bibring, J.-P.; Bell, J.F.; Squyres, S. W.; Christensen, P.R.; Bellucci, G.; Gondet, B.; Ehlmann, B.L.; Farrand, W. H.; Fergason, R.L.; Golombeck, M.; Griffes, J.L.; Grotzinger, J.; Guinness, E.A.; Herkenhoff, K. E.; Johnson, J. R.; Klingelhofer, G.; Langevin, Y.; Ming, D.; Seelos, K.; Sullivan, R.J.; Ward, J.G.; Wiseman, S.M.; Wolff, M.J.
2006-01-01
The ???5 km of traverses and observations completed by the Opportunity rover from Endurance crater to the Fruitbasket outcrop show that the Meridiani plains consist of sulfate-rich sedimentary rocks that are largely covered by poorly-sorted basaltic aeolian sands and a lag of granule-sized hematitic concretions. Orbital reflectance spectra obtained by Mars Express OMEGA over this region are dominated by pyroxene, plagioclase feldspar, crystalline hematite (i.e., concretions), and nano-phase iron oxide dust signatures, consistent with Pancam and Mini-TES observations. Mo??ssbauer Spectrometer observations indicate more olivine than observed with the other instruments, consistent with preferential optical obscuration of olivine features in mixtures with pyroxene and dust. Orbital data covering bright plains located several kilometers to the south of the landing site expose a smaller areal abundance of hematite, more dust, and a larger areal extent of outcrop compared to plains proximal to the landing site. Low-albedo, low-thermal-inertia, windswept plains located several hundred kilometers to the south of the landing site are predicted from OMEGA data to have more hematite and fine-grained olivine grains exposed as compared to the landing site. Low calcium pyroxene dominates spectral signatures from the cratered highlands to the south of Opportunity. A regional-scale model is presented for the formation of the plains explored by Opportunity, based on a rising ground water table late in the Noachian Era that trapped and altered local materials and aeolian basaltic sands. Cessation of this aqueous process led to dominance of aeolian processes and formation of the current configuration of the plains. Copyright 2006 by the American Geophysical Union.
Interaction of Hg Atom with Bare Si(111) Surface
Institute of Scientific and Technical Information of China (English)
LIU Yong-Jun; LIU Ying
2006-01-01
To evaluate the interaction between Hg atom and bare Si(111) surface, three types of silicon cluster models of Si4H7, Si7H10 and Si16H20 together with their Hg complexes were studied by using hybrid (U)B3LYP density functional theory method. Optimized geometries and energies for Hg atom on different adsorption sites indicate that: 1) the binding energies at different adsorption sites are small (ranging from ～3 to 8 kJ/mol dependent on the adsorption sites), suggesting a weak interaction between Hg atom and silicon surface; 2) the most favorable adsorption site is the on top (T) site. By analyzing their natural bonding orbitals, the possible reason of this difference is suggested.
Seyed Hassan Mostafavi
2010-01-01
Preseptal and orbital cellulitis occur more commonly in children than adults. The history and physical examination are crucial in distinguishing between preseptal and orbital cellulitis. The orbital septum delineates the anterior eyelid soft tissues from the orbital soft tissue. Infections anterior to the orbital septum are classified as preseptal cellulitis and those posterior to the orbital septum are termed orbital cellulitis. "nRecognition of orbital involvement is important not only...
Halim, Shimaa Abdel; Ibrahim, Magdy A.
2017-02-01
New derivative of heteroannulated chromone identified as 5-methyl-8H-benzo[h]chromeno[2,3-b][1,6]naphthyridine-6(5H),8-dione (5, MBCND) was easily and efficiently synthesized from DBU catalyzed condensation reaction of 2-aminochromone-3-carboxaldehyde (1) with 4-hydroxy-1-methylquinolin-2(1H)-one (2). The same product 5 was isolated from condensation reaction of aldeyde 1 with 3-(4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinolin-3-yl)-3-oxopropanoic acid (3) or ethyl 4-(4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinolin-3-yl)-2,4-dioxobutanoate (4). Structure of compound (5, MBCND) was deduced based on their elemental analyses and spectral data (IR, 1H NMR and mass spectra). Density Functional Theory (DFT) calculations at the B3LYP/6-311G (d,p) level of theory have been carried out to investigate the equilibrium geometry of the novel compound (5, MBCND). Moreover, total energy, energy of HOMO and LUMO and Mullikan atomic charges were calculated. In addition, the dipole moment, theoretical study of the electronic structure, nonlinear optical properties (NLO), and natural bonding orbital (NBO) analysis and orientation have been performed and discussed. Also the electronic absorption spectra were measured in polar (methanol) as well as non polar (dioxane) solvents and the assignment of the observed bands has been discussed by TD-DFT calculations. The correspondences between calculated and experimental transitions energies are satisfactory.
Directory of Open Access Journals (Sweden)
La Villa F.
2006-11-01
Full Text Available Cet article présente la méthode mise au point par l'Institut Français du Pétrole pour déterminer par absorption atomique sans flamme, les traces de mercure métallique contenu dans un gaz naturel. La méthode d'analyse nécessite une extraction du mercure soit sous forme d'ion mercurique en faisant passer le gaz dans une solution oxydante, soit sous forme d'amalgame avec de l'or ou de l'argent. Le premier mode opératoire s'applique aux échantillons dont la concentration en mercure est supérieure à I ttg/Nm3, le second pour des concentrations inférieures à 5 pg/Nm3. Les seuils de détection sont respectivement 10 ng (en solution et 0,3 ng (en amalgame. La répétabilité pour 100 ng de mercure (en amalgame est de ± 7% pour une probabilité de.95 %. En conclusion, dans un échantillon de gaz naturel, compte tenu du volume des prélèvements effectués, il est possible de détecter des concentrations de l'ordre du nanogramme de mercure par mètre cube de gaz. This article describes the method developed by IFP using flameless atomic absorption to determine metallic mercury traces in a natural gas. The analyst method requires a mercury extraction either in the form of mercuric ions by making the gas pass through an oxidizing solution or in the form of an amalgam with gold or silver. The former operating method applies ta samples having a mercury concentration greater than I !ag/Nm3, and the latter for concentrations smaller than 5 (-Lg/Nm3. Detection thresholds are respectively 10 ng (in solution and 0.3 ng (in amalgam. The repeatability for 100 ng of mercury (in amalgam is ± 7 % with a probability of 95%. To conclude, in a sample of natural gas, considering the volume of the samples taken, it is possible ta detect concentrations in the vicinity of one nanogrom of mercury per cubic meter of gas.
Current Trends in Atomic Spectroscopy.
Wynne, James J.
1983-01-01
Atomic spectroscopy is the study of atoms/ions through their interaction with electromagnetic radiation, in particular, interactions in which radiation is absorbed or emitted with an internal rearrangement of the atom's electrons. Discusses nature of this field, its status and future, and how it is applied to other areas of physics. (JN)
Current Trends in Atomic Spectroscopy.
Wynne, James J.
1983-01-01
Atomic spectroscopy is the study of atoms/ions through their interaction with electromagnetic radiation, in particular, interactions in which radiation is absorbed or emitted with an internal rearrangement of the atom's electrons. Discusses nature of this field, its status and future, and how it is applied to other areas of physics. (JN)
Kim, Y S
2011-01-01
In 1905, Einstein formulated his special relativity for point particles. For those particles, his Lorentz covariance and energy-momentum relation are by now firmly established. How about the hydrogen atom? It is possible to perform Lorentz boosts on the proton assuming that it is a point particle. Then what happens to the electron orbit? The orbit could go through an elliptic deformation, but it is not possible to understand this problem without quantum mechanics, where the orbit is a standing wave leading to a localized probability distribution. Is this concept consistent with Einstein's Lorentz covariance? Dirac, Wigner, and Feynman contributed important building blocks for understanding this problem. The remaining problem is to assemble those blocks to construct a Lorentz-covariant picture of quantum bound states based on standing waves. It is shown possible to assemble those building blocks using harmonic oscillators.
Gidofalvi, Gergely
2014-01-01
Molecule-optimized basis sets, based on approximate natural orbitals, are developed for accelerating the convergence of quantum calculations with strongly correlated (multi-referenced) electrons. We use a low-cost approximate solution of the anti-Hermitian contracted Schr{\\"o}dinger equation (ACSE) for the one- and two-electron reduced density matrices (RDMs) to generate an approximate set of natural orbitals for strongly correlated quantum systems. The natural-orbital basis set is truncated to generate a molecule-optimized basis set whose rank matches that of a standard correlation-consistent basis set optimized for the atoms. We show that basis-set truncation by approximate natural orbitals can be viewed as a one-electron unitary transformation of the Hamiltonian operator and suggest an extension of approximate natural-orbital truncations through two-electron unitary transformations of the Hamiltonian operator, such as those employed in the solution of the ACSE. The molecule-optimized basis set from the ACS...
Teodoro, M.; Damineli, A.; Heathcote, B.; Richardson, N. D.; Moffat, A. F. J.; St-Jean, L.; Russell, C.; Gull, T. R.; Madura, T. I.; Pollard, K. R.; Walter, F.; Coimbra, A.; Prates, R.; Fernández-Lajús, E.; Gamen, R. C.; Hickel, G.; Henrique, W.; Navarete, F.; Andrade, T.; Jablonski, F.; Luckas, P.; Locke, M.; Powles, J.; Bohlsen, T.; Chini, R.; Corcoran, M. F.; Hamaguchi, K.; Groh, J. H.; Hillier, D. J.; Weigelt, G.
2016-03-01
Eta Carinae (η Car) is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He ii λ4686 line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He ii λ4686 emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of the line equivalent width (EW), radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW variations, combined with other measurements, yield an orbital period of 2022.7 ± 0.3 days. The observed variability of the EW was reproduced by a model in which the line flux primarily arises at the apex of the wind-wind collision and scales inversely with the square of the stellar separation, if we account for the excess emission as the companion star plunges into the hot inner layers of the primary’s atmosphere, and including absorption from the disturbed primary wind between the source and the observer. This model constrains the orbital inclination to 135°-153°, and the longitude of periastron to 234°-252°. It also suggests that periastron passage occurred on {T}0=2456874.4\\quad (+/- 1.3 days). Our model also reproduced EW variations from a polar view of the primary star as determined from the observed He ii λ 4686 emission scattered off the Homunculus nebula. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program numbers 11506, 12013, 12508, 12750, and 13054. Support for program numbers 12013, 12508, and 12750 was provided by NASA
Penteado, Poliana; Egues, J. Carlos
2013-03-01
In condensed matter systems, the coupling between spatial and spin degrees of freedom through the spin-orbit (SO) interaction offers the possibility of manipulating the electron spin via its orbital motion. The proposal by Datta and Das of a `spin transistor' for example, highlights the use of the SO interaction to control the electron spin via electrical means. Recently, arrangements of crossed lasers and magnetic fields have been used to trap and cool atoms in optical lattices and also to create light-induced gauge potentials, which mimic the SO interactions in real solids. In this work, we investigate the Zitterbewegung in cold atoms by starting from the effective SO Hamiltonian derived in Ref.. Cross-dressed atoms as effective spins can provide a proper setting in which to observe this effect, as the relevant parameter range of SO strengths may be more easily attainable in this context. We find a variety of peculiar Zitterbewegung orbits in real and pseudo-spin spaces, e.g., cycloids and ellipses - all of which obtained with realistic parameters. This work is supported by FAPESP, CAPES and CNPq.
Borbolla-Pertierra, A M; Morales-Baños, D R; Martínez-Nava, L R; Garrido-Sánchez, G A; López-Hernández, C M; Velasco-Ramos, P
2017-02-01
The case is presented of a 46-year-old male with right eye proptosis and conjunctival hyperaemia, of 18 months onset. A well-defined intraconal mass was found in the computed tomography. In magnetic resonance this was hypo-intense on T1, enhanced with gadolinium and hyperintense on T2. Excisional biopsy was performed, which was reported as a well-differentiated liposarcoma in the histopathology study. Liposarcoma is a malignant adipose tissue tumour. It is very rare in the orbit, with 5 histological types, the most common being myxoid. The treatment of choice is wide surgical excision and may be accompanied with radiotherapy. As it is an infiltrative tumour, It has a high rate of recurrence. Copyright © 2016 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.
Luo, Jia; Xiang, Gang; Yu, Tian; Lan, Mu; Zhang, Xi
2016-09-01
By using first-principles calculations within the framework of density functional theory, the electronic and magnetic properties of 3d transitional metal (TM) atoms (from Sc to Zn) adsorbed monolayer GaAs nanosheets (GaAsNSs) are systematically investigated. Upon TM atom adsorption, GaAsNS, which is a nonmagnetic semiconductor, can be tuned into a magnetic semiconductor (Sc, V, and Fe adsorption), a half-metal (Mn adsorption), or a metal (Co and Cu adsorption). Our calculations show that the strong p-d hybridization between the 3d orbit of TM atoms and the 4p orbit of neighboring As atoms is responsible for the formation of chemical bonds and the origin of magnetism in the GaAsNSs with Sc, V, and Fe adsorption. However, the Mn 3d orbit with more unpaired electrons hybridizes not only with the As 4p orbit but also with the Ga 4p orbit, resulting in a stronger exchange interaction. Our results may be useful for electronic and magnetic applications of GaAsNS-based materials. Project supported by the National Natural Science Foundation of China (Grant No. 11174212).
Spin-Orbit Coupled Bose-Einstein Condensates
2016-11-03
Spin -Orbit Coupled Bose-Einstein Condensates This ARO research proposal entitled " SPIN -ORBIT COUPLED BOSE-EINSTEIN CONDENSATES" (SOBECs) explored...realized with cold atoms. A unique feature of the SOBECs is a topologically protected spin -orbital degeneracy of the ground state that results in a...Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 superfluids, spin -orbit coupling, optical lattices, topological states REPORT
Teodoro, M; Heathcote, B; Richardson, N D; Moffat, A F J; St-Jean, L; Russell, C; Gull, T R; Madura, T I; Pollard, K R; Walter, F; Coimbra, A; Prates, R; Fernández-Lajús, E; Gamen, R C; Hickel, G; Henrique, W; Navarete, F; Andrade, T; Jablonski, F; Luckas, P; Locke, M; Powles, J; Bohlsen, T; Chini, R; Corcoran, M F; Hamaguchi, K; Groh, J H; Hillier, D J; Weigelt, G
2016-01-01
{\\eta} Carinae is an extremely massive binary system in which rapid spectrum variations occur near periastron. Most notably, near periastron the He II $\\lambda 4686$ line increases rapidly in strength, drops to a minimum value, then increases briefly before fading away. To understand this behavior, we conducted an intense spectroscopic monitoring of the He II $\\lambda 4686$ emission line across the 2014.6 periastron passage using ground- and space-based telescopes. Comparison with previous data confirmed the overall repeatability of EW(He II $\\lambda 4686$), the line radial velocities, and the timing of the minimum, though the strongest peak was systematically larger in 2014 than in 2009 by 26%. The EW(He II $\\lambda 4686$) variations, combined with other measurements, yield an orbital period $2022.7\\pm0.3$ d. The observed variability of the EW(He II $\\lambda 4686$) was reproduced by a model in which the line flux primarily arises at the apex of the wind-wind collision and scales inversely with the square of ...
Murdin, P.
2000-11-01
In its most general sense, any celestial object in orbit around a similar larger object. Thus, for example, the Magellanic Clouds are satellite galaxies of our own Milky Way galaxy. Without qualification, the term is used to mean a body in orbit around a planet; an alternative term is moon. The term natural satellite distinguishes these bodies from artificial satellites—spacecraft placed in orbi...
Geology orbiter comparison study
Cutts, J. A. J.; Blasius, K. R.; Davis, D. R.; Pang, K. D.; Shreve, D. C.
1977-01-01
Instrument requirements of planetary geology orbiters were examined with the objective of determining the feasibility of applying standard instrument designs to a host of terrestrial targets. Within the basic discipline area of geochemistry, gamma-ray, X-ray fluorescence, and atomic spectroscopy remote sensing techniques were considered. Within the discipline area of geophysics, the complementary techniques of gravimetry and radar were studied. Experiments using these techniques were analyzed for comparison at the Moon, Mercury, Mars and the Galilean satellites. On the basis of these comparative assessments, the adaptability of each sensing technique was judged as a basic technique for many targets, as a single instrument applied to many targets, as a single instrument used in different mission modes, and as an instrument capability for nongeoscience objectives.
Ben-Nun, M; Mills, J D; Hinde, R J; Winstead, C L; Boatz, J A; Gallup, G A; Langhoff, P W
2009-07-02
Recent progress is reported in development of ab initio computational methods for the electronic structures of molecules employing the many-electron eigenstates of constituent atoms in spectral-product forms. The approach provides a universal atomic-product description of the electronic structure of matter as an alternative to more commonly employed valence-bond- or molecular-orbital-based representations. The Hamiltonian matrix in this representation is seen to comprise a sum over atomic energies and a pairwise sum over Coulombic interaction terms that depend only on the separations of the individual atomic pairs. Overall electron antisymmetry can be enforced by unitary transformation when appropriate, rather than as a possibly encumbering or unnecessary global constraint. The matrix representative of the antisymmetrizer in the spectral-product basis, which is equivalent to the metric matrix of the corresponding explicitly antisymmetric basis, provides the required transformation to antisymmetric or linearly independent states after Hamiltonian evaluation. Particular attention is focused in the present report on properties of the metric matrix and on the atomic-product compositions of molecular eigenstates as described in the spectral-product representations. Illustrative calculations are reported for simple but prototypically important diatomic (H(2), CH) and triatomic (H(3), CH(2)) molecules employing algorithms and computer codes devised recently for this purpose. This particular implementation of the approach combines Slater-orbital-based one- and two-electron integral evaluations, valence-bond constructions of standard tableau functions and matrices, and transformations to atomic eigenstate-product representations. The calculated metric matrices and corresponding potential energy surfaces obtained in this way elucidate a number of aspects of the spectral-product development, including the nature of closure in the representation, the general redundancy or
Rahimi, A.; Mao, S.; Kawata, D.
2014-03-01
The fossil record shows that the Earth has experienced several mass extinctions over the past 500 million years1, and it has been suggested that there is a periodicity in extinction events on timescales of tens1 and/or hundreds of millions of years. Various hypotheses have been proposed to explain the cause of the mass extinctions, including the suggestion that the Earth's ozone layer may have been destroyed by intense radiation from a nearby supernovae2- 3, exposing the Earth's surface to damaging UV radiation. Recent observations of cores taken from the ocean floor revealed atoms of a very rare isotope of iron (60Fe) believed to have arrived on Earth around 2 million years ago as fallout from a nearby supernovae4. Astronomical evidence for that past supernovae was recently found in the debris of a young cluster of massive stars5, by tracing its past orbit, putting it at the right place at the right time to explain the mild extinction event. Here we report new high-resolution (both in space and time) N-body chemodynamical simulations (carried out with our novel code GCD+6) of the evolution of a model Milky Way Galaxy, tracing the orbit of èsun-like' stars over a 500 million year period, checking the proximity to supernovae throughout the history of the orbit and comparing the times when this occurs with past mass extinctions on Earth. We additionally explain the important effects of the spiral arm pattern, radial migration of stars and Galactic chemistry on habitability.
Borsten, L; Ferrara, S; Marrani, A; Rubens, W
2012-01-01
We study both the "large" and "small" U-duality charge orbits of extremal black holes appearing in D = 5 and D = 4 Maxwell-Einstein supergravity theories with symmetric scalar manifolds. We exploit a formalism based on cubic Jordan algebras and their associated Freudenthal triple systems, in order to derive the minimal charge representatives, their stabilizers and the associated "moduli spaces". After recalling N = 8 maximal supergravity, we consider N = 2 and N = 4 theories coupled to an arbitrary number of vector multiplets, as well as N = 2 magic, STU, ST^2 and T^3 models. While the STU model may be considered as part of the general N = 2 sequence, albeit with an additional triality symmetry, the ST^2 and T^3 models demand a separate treatment, since their representative Jordan algebras are Euclidean or only admit non-zero elements of rank 3, respectively. Finally, we also consider minimally coupled N = 2, matter coupled N = 3, and "pure" N = 5 theories.
Formation around planetary displaced orbit
Institute of Scientific and Technical Information of China (English)
GONG Sheng-ping; LI Jun-feng; BAOYIN He-xi
2007-01-01
The paper investigates the relative motion around the planetary displaced orbit. Several kinds of displaced orbits for geocentric and martian cases were discussed. First, the relative motion was linearized around the displaced orbits. Then, two seminatural control laws were investigated for each kind of orbit and the stable regions were obtained for each case. One of the two control laws is the passive control law that is very attractive for engineering practice. However, the two control laws are not very suitable for the Martian mission. Another special semi-natural control law is designed based on the requirement of the Martian mission. The results show that large stable regions exist for the control law.
1996-01-01
Interviews following the 1991 co-operation Agreement between the Department of Atomic Energy (DAE) of the Government of India and the European Organization for Nuclear Research (CERN) concerning the participation in the Large Hadron Collider Project (LHC) . With Chidambaram, R, Chairman, Atomic Energy Commission and Secretary, Department of Atomic Energy, Department of Atomic Energy (DAE) of the Government of India and Professor Llewellyn-Smith, Christopher H, Director-General, CERN.
Reichel, Jakob
2010-01-01
This book provides a stimulating and multifaceted picture of a rapidly developing field. The first part reviews fundamentals of atom chip research in tutorial style, while subsequent parts focus on the topics of atom-surface interaction, coherence on atom chips, and possible future directions of atom chip research. The articles are written by leading researchers in the field in their characteristic and individual styles.
Institute of Scientific and Technical Information of China (English)
Nila; F.Moeloek
1993-01-01
Orbital anatomy, the clinical features of orbital tumors, the recent development of the diagnosis and management of orbital tumors were described. The incidence of orbital tumors in Dr. Cipto Mangunkusumo Hospital in the past years were introduced. The principle of management of orbital tumors and their prognosis were discussed.
Tang, Xiao-Dan
2017-09-01
The charge transport properties of phosphapentacene (P-PEN) derivatives were systematically explored by theoretical calculation. The dehydrogenated P-PENs have reasonable frontier molecular orbital energy levels to facilitate both electron and hole injection. The reduced reorganization energies of dehydrogenated P-PENs could be intimately connected to the bonding nature of phosphorus atoms. From the idea of homology modeling, the crystal structure of TIPSE-4P-2p is constructed and fully optimized. Fascinatingly, TIPSE-4P-2p shows the intrinsic property of ambipolar transport in both hopping and band models. Thus, introducing dehydrogenated phosphorus atoms into pentacene core could be an efficient strategy for designing ambipolar material.
Canning, A.; Galli, G.; Mauri, F.; De Vita, A.; Car, R.
1996-04-01
The implementation of an O( N) tight-binding molecular dynamics code on the Cray T3D parallel computer is discussed. The O( N) energy functional depends on non-orthogonal, localised orbitals and a chemical potential parameter which determines the number of electrons in the system. The localisation introduces a sparse nature to the orbital data and Hamiltonian matrix, greatly changing the coding on parallel machines compared to non-localised systems. The data distribution, communication routines and dynamic load-balancing scheme of the program are presented in detail together with the speed and scaling of the code on various homogeneous and inhomogeneous physical systems. Performance results will be presented for systems of 2048 to 32768 atoms on 32 to 512 processors. We discuss the relevance to quantum molecular dynamics simulations with localised orbitals, of techniques used for programming short-range classical molecular dynamics simulations on parallel machines. The absence of global communications and the localised nature of the orbitals makes these algorithms extremely scalable in terms of memory and speed on parallel systems with fast communications. The main aim of this article is to present in detail all the new concepts and programming techniques that localisation of the orbitals introduces which scientists, coming from a background in non-localised quantum molecular dynamics simulations, may be unfamiliar with.
Mondal, Bhaskar; Neese, Frank; Ye, Shengfa
2015-08-03
The development of efficient catalysts with base metals for CO2 hydrogenation has always been a major thrust of interest. A series of experimental and theoretical work has revealed that the catalytic cycle typically involves two key steps, namely, base-promoted heterolytic H2 splitting and hydride transfer to CO2, either of which can be the rate-determining step (RDS) of the entire reaction. To explore the determining factor for the nature of RDS, we present herein a comparative mechanistic investigation on CO2 hydrogenation mediated by [M(H)(η(2)-H2)(PP3(Ph))](n+) (M = Fe(II), Ru(II), and Co(III); PP3(Ph) = tris(2-(diphenylphosphino)phenyl)phosphine) type complexes. In order to construct reliable free energy profiles, we used highly correlated wave function based ab initio methods of the coupled cluster type alongside the standard density functional theory. Our calculations demonstrate that the hydricity of the metal-hydride intermediate generated by H2 splitting dictates the nature of the RDS for the Fe(II) and Co(III) systems, while the RDS for the Ru(II) catalyst appears to be ambiguous. CO2 hydrogenation catalyzed by the Fe(II) complex that possesses moderate hydricity traverses an H2-splitting RDS, whereas the RDS for the high-hydricity Co(III) species is found to be the hydride transfer. Thus, our findings suggest that hydricity can be used as a practical guide in future catalyst design. Enhancing the electron-accepting ability of low-hydricity catalysts is likely to improve their catalytic performance, while increasing the electron-donating ability of high-hydricity complexes may speed up CO2 conversion. Moreover, we also established the active roles of base NEt3 in directing the heterolytic H2 splitting and assisting product release through the formation of an acid-base complex.
Energy Technology Data Exchange (ETDEWEB)
Lu, Z.-T.; Bailey, K.; Chen, C.-Y.; Du, X.; Li, Y.-M.; O' Connor, T. P.; Young, L.
2000-05-25
A new method of ultrasensitive trace-isotope analysis has been developed based upon the technique of laser manipulation of neutral atoms. It has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. The atom counts are free of contamination from other isotopes, elements,or molecules. The method is applicable to other trace-isotopes that can be efficiently captured with a magneto-optical trap, and has a broad range of potential applications.
Energy Technology Data Exchange (ETDEWEB)
Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)
2015-01-22
The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.
Directory of Open Access Journals (Sweden)
Seyed Hassan Mostafavi
2010-05-01
Full Text Available Preseptal and orbital cellulitis occur more commonly in children than adults. The history and physical examination are crucial in distinguishing between preseptal and orbital cellulitis. The orbital septum delineates the anterior eyelid soft tissues from the orbital soft tissue. Infections anterior to the orbital septum are classified as preseptal cellulitis and those posterior to the orbital septum are termed orbital cellulitis. "nRecognition of orbital involvement is important not only because of the threatened vision loss associated with orbital cellulitis but also because of the potential for central nervous system complications including cavernous sinus thrombosis, meningitis, and death. "nOrbital imaging should be obtained in all patients suspected of having orbital cellulitis. CT is preferred to MR imaging, as the orbital tissues have high con-trast and the bone can be well visualized. Orbital CT scanning allows localization of the disease process to the preseptal area, the extraconal or intraconal fat, or the subperiosteal space. Axial CT views allow evaluation of the medial orbit and ethmoid sinuses, whereas coronal scans image the orbital roof and floor and the frontal and maxillary sinuses. If direct coronal imaging is not possible, reconstruction of thin axial cuts may help the assessment of the orbital roof and floor. Potential sources of orbital cellulitis such as sinusitis, dental infection, and facial cellulitis are often detectable on CT imaging. "nIn this presentation, the imaging considerations of the orbital infections; including imaging differentiation criteria of all types of orbital infections are reviewed.
Preseptal Cellulitis, Orbital Cellulitis, Orbital Abscess
Rana Altan Yaycıoğlu
2012-01-01
Patients with orbital infections present to our clinic usually with unilateral pain, hyperemia, and edema of the eyelids. The differentiation between preseptal and orbital cellulitis is utmost important in that the second requires hospitalization. Since in orbital cellulitis, the tissues posterior to the orbital septum are involved, signs such as conjunctival chemosis, limited eye movement, decreased vision, as well as afferent pupil defect secondary to optic nerve involvement may al...
Bilateral orbital cavernous haemangiomas.
Fries, P D; Char, D. H.
1988-01-01
Simultaneous bilateral orbital lesions are rare. The differential diagnosis includes orbital pseudotumour, metastasis, leukaemia, lymphoma, Wegener's granulomatosis, and neurofibromatosis. We report what we believe to be the first case of bilateral orbital cavernous haemangiomas.
DEFF Research Database (Denmark)
Krüger, Peter; Hofferberth, S.; Haller, E.
2005-01-01
Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...
A Simple Relativistic Bohr Atom
Terzis, Andreas F.
2008-01-01
A simple concise relativistic modification of the standard Bohr model for hydrogen-like atoms with circular orbits is presented. As the derivation requires basic knowledge of classical and relativistic mechanics, it can be taught in standard courses in modern physics and introductory quantum mechanics. In addition, it can be shown in a class that…
A Simple Relativistic Bohr Atom
Terzis, Andreas F.
2008-01-01
A simple concise relativistic modification of the standard Bohr model for hydrogen-like atoms with circular orbits is presented. As the derivation requires basic knowledge of classical and relativistic mechanics, it can be taught in standard courses in modern physics and introductory quantum mechanics. In addition, it can be shown in a class that…
Josefsson, Ida; Kunnus, Kristjan; Schreck, Simon; Foehlisch, Alexander; de Groot, Frank; Wernet, Philippe; Odelius, Michael
2012-01-01
A new ab initio approach to the calculation of X-ray spectra is demonstrated. It combines a high-level quantum chemical description of the chemical interactions and local atomic multiplet effects. We show here calculated L-edge X-ray absorption (XA) and resonant inelastic X-ray scattering spectra fo
Atom Interferometry for Fundamental Physics and Gravity Measurements in Space
Kohel, James M.
2012-01-01
Laser-cooled atoms are used as freefall test masses. The gravitational acceleration on atoms is measured by atom-wave interferometry. The fundamental concept behind atom interferometry is the quantum mechanical particle-wave duality. One can exploit the wave-like nature of atoms to construct an atom interferometer based on matter waves analogous to laser interferometers.
Atom Interferometry for Fundamental Physics and Gravity Measurements in Space
Kohel, James M.
2012-01-01
Laser-cooled atoms are used as freefall test masses. The gravitational acceleration on atoms is measured by atom-wave interferometry. The fundamental concept behind atom interferometry is the quantum mechanical particle-wave duality. One can exploit the wave-like nature of atoms to construct an atom interferometer based on matter waves analogous to laser interferometers.
Spontaneous emission of two interacting atoms near an interface
Institute of Scientific and Technical Information of China (English)
Dehua Wang
2009-01-01
The spontaneous emission rate of two interacting excited atoms near a dielectric interface is studied using the photon closed-orbit theory and the dipole image method.The total emission rate of one atom during the emission process is calculated as a function of the distance between the atom and the interface.The results suggest that the spontaneous emission rate depends not only on the atomic-interface distances,but also on the orientation of the two atomic dipoles and the initial distance between the two atoms.The oscillation in the spontaneous emission rate is caused by the interference between the outgoing electromagnetic wave emitted from one atom and other waves arriving at this atom after traveling along various classical orbits.Each peak in the Fourier transformed spontaneous emission rate corresponds with one action of photon classical orbit.
Variational electrodynamics of Atoms
De Luca, Jayme
2013-01-01
We study extrema with velocity discontinuities for the variational electromagnetic two-body problem. Along $C^2$ segments, these broken extrema satisfy the Euler-Lagrange equations of the variational principle, which are neutral differential delay equations with state-dependent deviating arguments. At points where accelerations are not defined and velocities are discontinuous, broken extrema satisfy Weierstrass-Erdmann corner conditions that energies and momenta are continuous. Here we construct periodic broken extrema near the $C^{\\infty}$ two-body circular orbits, using piecewise-defined $C^2$ solutions of the neutral differential delay equations along regular segments and a variational approximation for the boundary-layer segments. Broken periodic extrema with an integer number of corner points bifurcate from a discrete set of circular orbits, with scales defined by the Weierstrass-Erdmann corner conditions. We consider the three cases of hydrogen, muonium and positronium atoms. In each case the broken ext...
Abdollahi Atousa; Amirkavehei Mooud; Gheisari Mohammad Mehdi; Tadayon Fariba
2014-01-01
A novel dispersive liquid–liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for simultaneous separation/preconcentration of ultra trace amounts of mercury was used. A method based on amalgamation was used for collection of gaseous mercury on gold coated sand (Gold trap). The concentration of mercury was determined by cold vapor atomic absorption spectrometry (CV-AAS). The DLLME-SFO behavior of mercury by using dithizone as complexing agent was systematically ...
Poultney, S. K.
1973-01-01
In a study of particulate matter and metallic atoms in the vicinity of the mesopause, three areas have received the most effort. These areas are: the significance of cometary dust influxes to the earth's atmosphere; the relation of nightglows to atmospheric motions and aerosols; and the feasibility of using an airborne resonant scatter lidar to study polar noctilucent clouds, the sodium layer, and fireball dust.
Institute of Scientific and Technical Information of China (English)
Ji Ying SONG; Ming HOU; Li Xiang ZHANG
2006-01-01
A method for the determination of trace mercury in water samples by hydride generation atomic absorption spectrophotometry after cloud point extraction was proposed in the present work.The effects of pH, concentration of surfactant, and equilibration time on cloud point extraction were discussed. The enhancement factor of 20 and the detection limit of 0.039 μg/L were obtained for mercury with relative standard deviation of 4.8% (n = 11).
Orbital dystopia due to orbital roof defect.
Rha, Eun Young; Joo, Hong Sil; Byeon, Jun Hee
2013-01-01
We performed a retrospective review of patients who presented with delayed dystopia as a consequence of an orbital roof defect due to fractures and nontraumatic causes to search for a correlation between orbital roof defect size and surgical indications for the treatment thereof. Retrospective analyses were performed in 7 patients, all of whom presented with delayed dystopia due to orbital roof defects, between January 2001 and June 2011. The causes of orbital roof defects were displaced orbital roof fractures (5 cases), tumor (1 case), and congenital sphenoid dysplasia (1 case). All 7 patients had initially been treated conservatively and later presented with significant dystopia. The sizes of the defects were calculated on computed tomographic scans. Among the 7 patients, aspiration of cerebrospinal fluid, which caused ocular symptoms, in 1 patient with minimal displaced orbital roof and reconstruction with calvarial bone, titanium micromesh, or Medpor in 6 other patients were performed. The minimal size of the orbital roof in patients who underwent orbital roof reconstruction was 1.2 cm (defect height) x 1.0 cm (defect length), 0.94 cm(2). For all patients with orbital dystopia, displacement of the globe was corrected without any complications, regardless of whether the patient was evaluated grossly or by radiology. In this retrospective study, continuous monitoring of clinical signs and active surgical management should be considered for cases in which an orbital roof defect is detected, even if no definite symptoms are noted, to prevent delayed sequelae.
Similarity of atoms in molecules
Energy Technology Data Exchange (ETDEWEB)
Cioslowski, J.; Nanayakkara, A. (Florida State Univ., Tallahassee, FL (United States))
1993-12-01
Similarity of atoms in molecules is quantitatively assessed with a measure that employs electron densities within respective atomic basins. This atomic similarity measure does not rely on arbitrary assumptions concerning basis functions or 'atomic orbitals', is relatively inexpensive to compute, and has straightforward interpretation. Inspection of similarities between pairs of carbon, hydrogen, and fluorine atoms in the CH[sub 4], CH[sub 3]F, CH[sub 2]F[sub 2], CHF[sub 3], CF[sub 4], C[sub 2]H[sub 2], C[sub 2]H[sub 4], and C[sub 2]H[sub 6] molecules, calculated at the MP2/6-311G[sup **] level of theory, reveals that the atomic similarity is greatly reduced by a change in the number or the character of ligands (i.e. the atoms with nuclei linked through bond paths to the nucleus of the atom in question). On the other hand, atoms with formally identical (i.e. having the same nuclei and numbers of ligands) ligands resemble each other to a large degree, with the similarity indices greater than 0.95 for hydrogens and 0.99 for non-hydrogens. 19 refs., 6 tabs.
Operation of the computer model for direct atomic oxygen exposure of Earth satellites
Bourassa, R. J.; Gruenbaum, P. E.; Gillis, J. R.; Hargraves, C. R.
1995-01-01
One of the primary causes of material degradation in low Earth orbit (LEO) is exposure to atomic oxygen. When atomic oxygen molecules collide with an orbiting spacecraft, the relative velocity is 7 to 8 km/sec and the collision energy is 4 to 5 eV per atom. Under these conditions, atomic oxygen may initiate a number of chemical and physical reactions with exposed materials. These reactions contribute to material degradation, surface erosion, and contamination. Interpretation of these effects on materials and the design of space hardware to withstand on-orbit conditions requires quantitative knowledge of the atomic oxygen exposure environment. Atomic oxygen flux is a function of orbit altitude, the orientation of the orbit plan to the Sun, solar and geomagnetic activity, and the angle between exposed surfaces and the spacecraft heading. We have developed a computer model to predict the atomic oxygen exposure of spacecraft in low Earth orbit. The application of this computer model is discussed.
Burkhardt, Charles E
2006-01-01
The study of atomic physics propelled us into the quantum age in the early twentieth century and carried us into the twenty-first century with a wealth of new and, in some cases, unexplained phenomena. Topics in Atomic Physics provides a foundation for students to begin research in modern atomic physics. It can also serve as a reference because it contains material that is not easily located in other sources. A distinguishing feature is the thorough exposition of the quantum mechanical hydrogen atom using both the traditional formulation and an alternative treatment not usually found in textbooks. The alternative treatment exploits the preeminent nature of the pure Coulomb potential and places the Lenz vector operator on an equal footing with other operators corresponding to classically conserved quantities. A number of difficult to find proofs and derivations are included as is development of operator formalism that permits facile solution of the Stark effect in hydrogen. Discussion of the classical hydrogen...
Directory of Open Access Journals (Sweden)
Masato Ohnishi
2015-04-01
Full Text Available When a radial strain is applied to a carbon nanotube (CNT, the increase in local curvature induces orbital hybridization. The effect of the curvature-induced orbital hybridization on the electronic properties of CNTs, however, has not been evaluated quantitatively. In this study, the strength of orbital hybridization in CNTs under homogeneous radial strain was evaluated quantitatively. Our analyses revealed the detailed procedure of the change in electronic structure of CNTs. In addition, the dihedral angle, the angle between π-orbital axis vectors of adjacent atoms, was found to effectively predict the strength of local orbital hybridization in deformed CNTs.
Orbital Magnetism of Bloch Electrons: III. Application to Graphene
Ogata, Masao
2016-10-01
The orbital susceptibility for graphene is calculated exactly up to the first order with respect to the overlap integrals between neighboring atomic orbitals. The general and rigorous theory of orbital susceptibility developed in the preceding paper is applied to a model for graphene as a typical two-band model. It is found that there are contributions from interband, Fermi surface, and occupied states in addition to the Landau-Peierls orbital susceptibility. The relative phase between the atomic orbitals on the two sublattices related to the chirality of Dirac cones plays an important role. It is shown that there are some additional contributions to the orbital susceptibility that are not included in the previous calculations using the Peierls phase in the tight-binding model for graphene. The physical origin of this difference is clarified in terms of the corrections to the Peierls phase.
Born, Max
1989-01-01
The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.
Imboden, Matthias; Pardo, Flavio; Bolle, Cristian; Han, Han; Tareen, Ammar; Chang, Jackson; Christopher, Jason; Corman, Benjamin; Bishop, David
2013-03-01
Here we present a MEMS based method to fabricate devices with a small number of atoms. In standard semiconductor fabrication, a large amount of material is deposited, after which etching removes what is not wanted. This technique breaks down for structures that approach the single atom limit, as it is inconceivable to etch away all but one atom. What is needed is a bottom up method with single or near single atom precision. We demonstrate a MEMS device that enables nanometer position controlled deposition of gold atoms. A digitally driven plate is swept as a flux of gold atoms passes through an aperture. Appling voltages on four comb capacitors connected to the central plate by tethers enable nanometer lateral precision in the xy plane over 15x15 sq. microns. Typical MEMS structures have manufacturing resolutions on the order of a micron. Using a FIB it is possible to mill apertures as small as 10 nm in diameter. Assuming a low incident atomic flux, as well as an integrated MEMS based shutter with microsecond response time, it becomes possible to deposit single atoms. Due to their small size and low power consumption, such nano-printers can be mounted directly in a cryogenic system at ultrahigh vacuum to deposit clean quench condensed metallic structures.
Directory of Open Access Journals (Sweden)
Bondarescu Ruxandra
2015-01-01
Full Text Available The successful miniaturisation of extremely accurate atomic clocks and atom interferometers invites prospects for satellite missions to perform precision experiments. We discuss the effects predicted by general relativity and alternative theories of gravity that can be detected by a clock, which orbits the Earth. Our experiment relies on the precise tracking of the spacecraft using its observed tick-rate. The spacecraft’s reconstructed four-dimensional trajectory will reveal the nature of gravitational perturbations in Earth’s gravitational field, potentially differentiating between different theories of gravity. This mission can measure multiple relativistic effects all during the course of a single experiment, and constrain the Parametrized Post-Newtonian Parameters around the Earth. A satellite carrying a clock of fractional timing inaccuracy of Δ f / f ∼ 10−16 in an elliptic orbit around the Earth would constrain the PPN parameters |β − 1|, |γ − 1| ≲ 10−6. We also briefly review potential constraints by atom interferometers on scalar tensor theories and in particular on Chameleon and dilaton models.
Kim, C H; Alexander, P W; Smythe, L E
1976-03-01
Molybdenum is extracted as the thiocyanate complex with the quaternary long-chain aliphatic amine Aliquat 336 in chloroform, followed by evaporation of the solvent, dissolution in MIBK, and atomic-absorption spectroscopy. The method is simple, rapid and sensitive, with few interference problems for the determination of the Mo content of soils and sediments in the range 0.1-1.0 ppm with a relative standard deviation better than 5% when 1-g samples are used. Quantitative extraction from large volumes of aqueous solution has also been confirmed, allowing the determination of Mo in natural waters in the ppM range.
Controlling the Orbital Sequence in Individual Cu-Phthalocyanine Molecules
Uhlmann, C.; Swart, I.; Repp, J.
2013-01-01
We report on the controlled change of the energetic ordering of molecular orbitals. Negatively charged copper(II)phthalocyanine on NaCl/Cu(100) undergoes a Jahn–Teller distortion that lifts the degeneracy of two frontier orbitals. The energetic order of the levels can be controlled by Au and Ag atom
Orbital-Free Density Functional Theory for Molecular Structure Calculations
Institute of Scientific and Technical Information of China (English)
Huajie Chen; Aihui Zhou
2008-01-01
We give here an overview of the orbital-free density functional theory that is used for modeling atoms and molecules. We review typical approximations to the kinetic energy, exchange-correlation corrections to the kinetic and Hartree energies, and constructions of the pseudopotentials. We discuss numerical discretizations for the orbital-free methods and include several numerical results for illustrations.
Scattering of electrons from neon atoms
Dasgupta, A.; Bhatia, A. K.
1984-01-01
Scattering of electrons from neon atoms is investigated by the polarized-orbital method. The perturbed orbitals calculated with use of the Sternheimer approximation lead to the polarizability 2.803 a(0)-cube in fairly good agreement with the experimental value 2.66 a(0)-cube. Phase shifts for various partial waves are calculated in the exchange, exchange-adiabatic, and polarized-orbital approximations. They are compared with the previous results. The calculated elastic differential, total, and momentum-transfer cross sections are compared with the experimental results. The polarized-orbital approximation yields results which show general improvement over the exchange-adiabatic approximation.
Institute of Scientific and Technical Information of China (English)
陈兰芳
2016-01-01
The single-electron, two-centre atomic orbital close-coupling method is adopted to calculate elec-tron-loss cross sections of H(2s) in H(1s) + H(2s) collisions. The theoretical results are compared with experimental data. Our studies have shown that the electron-loss cross sections of H(2s) in H(1s) + H(2s) collisions calculated by the single-electron, two-centre atomic orbital close-coupling method are in reasona-ble agreement with experimental data. The ionization and de-excitation cross sections of H(2s), and the cap-ture cross sections of H(1s) in H(1s) + H(2s) collisions are also presented.%采用单电子的双中心原子轨道强耦合方法，计算了H(1s)+H(2s)碰撞体系H(2s)失去电子过程的总截面，并与前人的实验结果进行了比较。研究表明，采用双中心原子轨道强耦合方法得到的H(1s)+H(2s)体系H(2s)失去电子过程的截面与实验比较符合。同时，还给出了H(1s)+H(2s)碰撞体系H (2s)电离过程、H(1s)俘获电子过程和H(2s)退激发到H(1s)过程的理论截面。
Krause, Christine; Werner, Hans-Joachim
2012-06-07
Explicitly correlated local coupled-cluster (LCCSD-F12) methods with pair natural orbitals (PNOs), orbital specific virtual orbitals (OSVs), and projected atomic orbitals (PAOs) are compared. In all cases pair-specific virtual subspaces (domains) are used, and the convergence of the correlation energy as a function of the domain sizes is studied. Furthermore, the performance of the methods for reaction energies of 52 reactions involving 58 small and medium sized molecules is investigated. It is demonstrated that for all choices of virtual orbitals much smaller domains are needed in the explicitly correlated methods than without the explicitly correlated terms, since the latter correct a large part of the domain error, as found previously. For PNO-LCCSD-F12 with VTZ-F12 basis sets on the average only 20 PNOs per pair are needed to obtain reaction energies with a root mean square deviation of less than 1 kJ mol(-1) from complete basis set estimates. With OSVs or PAOs at least 4 times larger domains are needed for the same accuracy. A new hybrid method that combines the advantages of the OSV and PNO methods is proposed and tested. While in the current work the different local methods are only simulated using a conventional CCSD program, the implications for low-order scaling local implementations of the various methods are discussed.
Natural Orbitals from Generalized Sturmian Calculations
DEFF Research Database (Denmark)
Avery, John Scales; Avery, James Emil
2003-01-01
The generalized Sturmian method is a direct configuration interaction method for solving the Schr\\"odinger equation of a many-electron system. The configurations in the basis set are solutions to an approximate Schr\\"odinger equation with a weighted potential $\\beta_\
Discovering Chemistry With Natural Bond Orbitals
Weinhold, Frank
2012-01-01
This book explores chemical bonds, their intrinsic energies, and the corresponding dissociation energies which are relevant in reactivity problems. It offers the first book on conceptual quantum chemistry, a key area for understanding chemical principles and predicting chemical properties. It presents NBO mathematical algorithms embedded in a well-tested and widely used computer program (currently, NBO 5.9). While encouraging a "look under the hood" (Appendix A), this book mainly enables students to gain proficiency in using the NBO program to re-express complex wavefunctions in terms of intui
Adsorption of 5f-electron atoms (ThCm) on graphene surface: An all-electron ZORA-DFT study.
Du, Jiguang; Jiang, Gang
2017-12-15
All-electron calculations were performed to investigate the adsorption of 5f-electron atoms (An=ThCm) on graphene surface. The hollow site is energetically preferred for the An-graphene complexes studied. The interaction strengths between An and C decrease in the order of Th>Pa>U>Np>Pu>Cm>Am. The AnC interactions show predominately closed-shell characteristics, meanwhile ThC chemical bond formed through orbital overlaps of Th (6d) and C (2p) possesses partial covalent nature. The participation of 6d(5f)-electron into bonding orbitals are gradually weakened (enhanced) from Th to Pu because the 5f electrons are more and more diffuse. The physisorption nature of Am on graphene was observed by the weak orbital overlaps between Am (6d) and C(2p) and the half-fill 5f occupancy. The magnetic moments of An-graphene species are mainly derived from the 5f-electron due to its high delocalization. The molecular orbital (MO) and charge decomposition analysis (CDA) indicate that the 6d orbitals of An atoms play a more important role in participation of bonds relative to the 5f orbital, as well as the strong linear correlation between 6d occupancy numbers and adsorption energy highlights the significant role of 6d-electron of An in the interaction. Copyright © 2017 Elsevier Inc. All rights reserved.
A criterion for atomicity revisited
Hesselink, Wim H.
2007-01-01
Concurrent and reactive programs are specified by their behaviours in the presence of a nondeterministic environment. In a natural way, this gives a specification (ARW) of an atomic variable. Several implementations of atomic variables by lower level primitives are known. A few years ago, we formula
Kubota, T; Suzuki, K; Okutani, T
1995-07-01
A trace level of Se was collected on activated carbon (AC) as the Se(IV)-3-phenyl-5-mercapto-1,3,4-thiadiazole-2(3H)-thione (Bismuthiol II) complex. The AC was directly introduced as an AC-suspension into the graphite tube atomizer and the Se concentration was determined by atomic absorption spectroscopy (T. Okutani, T. Kubota, N. Sugiyama and Y. Turuta, Nippon Kagaku Kaishi, (1991) 375). The amount of Se in heavily contaminated samples including sediment, lake water and seawater was determined using this method. The sediments were digested with HNO(3)HClO(4)HF and the interference from AlF(3) was removed using H(3)BO(3)HClO(4). Lake water and seawater were acidified with H(2)SO(4) and digested with KMnO(4). The Se concentrations of these samples were determined by this method with satisfactory results. The above method is simple, rapid and applicable to heavily contaminated samples.
Clarifying Atomic Weights: A 2016 Four-Figure Table of Standard and Conventional Atomic Weights
Coplen, Tyler B.; Meyers, Fabienne; Holden, Norman E.
2017-01-01
To indicate that atomic weights of many elements are not constants of nature, in 2009 and 2011 the Commission on Isotopic Abundances and Atomic Weights (CIAAW) of the International Union of Pure and Applied Chemistry (IUPAC) replaced single-value standard atomic weight values with atomic weight intervals for 12 elements (hydrogen, lithium, boron,…
Hanke, J.-P.; Freimuth, F.; Nandy, A. K.; Zhang, H.; Blügel, S.; Mokrousov, Y.
2016-09-01
We address the importance of the modern theory of orbital magnetization for spintronics. Based on an all-electron first-principles approach, we demonstrate that the predictive power of the routinely employed "atom-centered" approximation is limited to materials like elemental bulk ferromagnets, while the application of the modern theory of orbital magnetization is crucial in chemically or structurally inhomogeneous systems such as magnetic thin films, and materials exhibiting nontrivial topology in reciprocal and real space, e.g., Chern insulators or noncollinear systems. We find that the modern theory is particularly crucial for describing magnetism in a class of materials that we suggest here—topological orbital ferromagnets.
Contemporary Aspects of Atomic Physics
Knott, R. G. A.
1972-01-01
The approach generally used in writing undergraduate textbooks on Atomic and Nuclear Physics presents this branch as historical in nature. Describes the concepts of astrophysics, plasma physics and spectroscopy as contemporary and intriguing for modern scientists. (PS)
Preseptal Cellulitis, Orbital Cellulitis, Orbital Abscess
Directory of Open Access Journals (Sweden)
Rana Altan Yaycıoğlu
2012-12-01
Full Text Available Patients with orbital infections present to our clinic usually with unilateral pain, hyperemia, and edema of the eyelids. The differentiation between preseptal and orbital cellulitis is utmost important in that the second requires hospitalization. Since in orbital cellulitis, the tissues posterior to the orbital septum are involved, signs such as conjunctival chemosis, limited eye movement, decreased vision, as well as afferent pupil defect secondary to optic nerve involvement may also be observed. Prompt intravenous antibiotic treatment should be started, and surgical drainage may be performed if patient shows failure to improve in 48 hours despite optimal management. Without treatment, the clinical course may progress to subperiosteal or orbital abscess, and even to cavernous sinus thrombosis. (Turk J Ophthalmol 2012; 42: Supplement 52-6
Imaging the Temporal Evolution of Molecular Orbitals during Ultrafast Dissociation
Sann, H.; Havermeier, T.; Müller, C.; Kim, H.-K.; Trinter, F.; Waitz, M.; Voigtsberger, J.; Sturm, F.; Bauer, T.; Wallauer, R.; Schneider, D.; Weller, M.; Goihl, C.; Tross, J.; Cole, K.; Wu, J.; Schöffler, M. S.; Schmidt-Böcking, H.; Jahnke, T.; Simon, M.; Dörner, R.
2016-12-01
We investigate the temporal evolution of molecular frame angular distributions of Auger electrons emitted during ultrafast dissociation of HCl following a resonant single-photon excitation. The electron emission pattern changes its shape from that of a molecular σ orbital to that of an atomic p state as the system evolves from a molecule into two separated atoms.
Directory of Open Access Journals (Sweden)
José Y. Neira
2005-03-01
Full Text Available A flow system coupled to a tungsten coil atomizer in an atomic absorption spectrometer (TCA-AAS was developed for As(III determination in waters, by extraction with sodium diethyldithiocarbamate (NaDDTC as complexing agent, and by sorption of the As(III-DDTC complex in a micro-column filled with 5 mg C18 reversed phase (10 µL dry sorbent, followed by elution with ethanol. A complete pre-concentration/elution cycle took 208 s, with 30 s sample load time (1.7 mL and 4 s elution time (71 µL. The interface and software for the synchronous control of two peristaltic pumps (RUN/ STOP, an autosampler arm, seven solenoid valves, one injection valve, the electrothermal atomizer and the spectrometer Read function were constructed. The system was characterized and validated by analytical recovery studies performed both in synthetic solutions and in natural waters. Using a 30 s pre-concentration period, the working curve was linear between 0.25 and 6.0 µg L-1 (r = 0.9976, the retention efficiency was 94±1% (6.0 µg L-1, and the pre-concentration coefficient was 28.9. The characteristic mass was 58 pg, the mean repeatability (expressed as the variation coefficient was 3.4% (n=5, the detection limit was 0.058 µg L-1 (4.1 pg in 71 µL of eluate injected into the coil, and the mean analytical recovery in natural waters was 92.6 ± 9.5 % (n=15. The procedure is simple, economic, less prone to sample loss and contamination and the useful lifetime of the micro-column was between 200-300 pre-concentration cycles.
Institute of Scientific and Technical Information of China (English)
方燕; 王蕾; 倪良; 姚加
2013-01-01
采用水热法合成了一种新型双核铅(Ⅱ)配合物[Pb2(CA)4(Medpq)2](HCA=cinnamic acid,Medpq=2-methyldipyrido[3,2-f:2,3＇-h]quinoxaline),并对其进行了元素分析、红外光谱、紫外可见光光谱、热重表征、荧光光谱、X射线单晶衍射测定和理论计算.标题配合物属于三斜晶系,空间群为Ｐ(１).在晶体中,铅与来自Medpq配体的2个氮原子和3个肉桂酸配体的5个氧原子形成七配位.应用Gaussian 03程序,对标题配合物进行了自然键轨道(NBO)分析,结果表明Pb(Ⅱ)与配位原子间的价键类型都属于共价键范畴.%A binuclear Pb(Ⅱ) complex [Pb2(CA)4(Medpq)2] (HCA=cinnamic acid,Medpq=2-methyldipyrido[3,2-f:2,3'-h]quinoxaline) has been hydrothermally synthesized and structurally characterized by elemental analysis,IR spectrum,UV-Vis spectrum,TG,fluorescent emission,single-crystal X-ray diffraction and theoretical calculations.Title compound crystallizes in triclinic,space group P(1) with a=0.854 35(17) nm,b=1.250 9(3) nm,c=1.436 6 (3) nm,α=107.45 (3)°,β=105.63 (3)°,y=97.04 (3)°.In the crystal structure,the lead atom is sevencoordinated with two nitrogen atoms from Medpq ligand and five oxygen atoms from three cinnamic acid ligands.Natural bond orbital (NBO) analysis was performed by using the NBO method built in Gaussian 03 Program.The calculation results shown an covalent interaction between the coordinated atoms and Pb(Ⅱ) ion.CCDC:859036.
Wilson, David B.
1981-01-01
Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)
Spin-Orbit Coupling and Spin Textures in Optical Superlattices
Li, Junru; Shteynas, Boris; Burchesky, Sean; Top, Furkan Cagri; Su, Edward; Lee, Jeongwon; Jamison, Alan O; Ketterle, Wolfgang
2016-01-01
We proposed and demonstrated a new approach for realizing spin orbit coupling with ultracold atoms. We use orbital levels in a double well potential as pseudospin states. Two-photon Raman transitions between left and right wells induce spin-orbit coupling. This scheme does not require near resonant light, features adjustable interactions by shaping the double well potential, and does not depend on special properties of the atoms. A pseudospinor Bose-Einstein condensate spontaneously acquires an antiferromagnetic pseudospin texture which breaks the lattice symmetry similar to a supersolid.
Natural occupation numbers in two-electron quantum rings
Energy Technology Data Exchange (ETDEWEB)
Tognetti, Vincent, E-mail: vincent.tognetti@univ-rouen.fr [Normandy Univ., COBRA UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, 1 rue Tesniére, 76821 Mont Saint Aignan, Cedex (France); Loos, Pierre-François [Research School of Chemistry, Australian National University, Canberra ACT 2601 (Australia)
2016-02-07
Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.
Natural occupation numbers in two-electron quantum rings
Tognetti, Vincent; Loos, Pierre-François
2016-02-01
Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.
Natural occupation numbers in two-electron quantum rings.
Tognetti, Vincent; Loos, Pierre-François
2016-02-07
Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.
Energy Technology Data Exchange (ETDEWEB)
Gonzales, A.P.S. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adelia, 166, 09210-170 Santo Andre (Brazil); Firmino, M.A. [Departamento de Engenharia de Materiais, Escola de Engenharia, Universidade Presbiteriana Mackenzie, Rua da Consolacao, 930, 01302-970 Sao Paulo (Brazil); Nomura, C.S. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adelia, 166, 09210-170 Santo Andre (Brazil); Rocha, F.R.P.; Oliveira, P.V. [Departamento de Quimica Fundamental, Instituto de Quimica, Universidade de Sao Paulo, Av. Prof. Lineu Prestes, 748, 05508-000 Sao Paulo (Brazil); Gaubeur, I. [Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC, Rua Santa Adelia, 166, 09210-170 Santo Andre (Brazil)], E-mail: ivanise.gaubeur@ufabc.edu.br
2009-03-23
The physical and chemical characteristics of peat were assessed through measurement of pH, percentage of organic matter, cationic exchange capacity (CEC), elemental analysis, infrared spectroscopy and quantitative analysis of metals by ICP OES. Despite the material showed to be very acid in view of the percentage of organic matter, its CEC was significant, showing potential for retention of metal ions. This characteristic was exploited by coupling a peat mini-column to a flow system based on the multicommutation approach for the in-line copper concentration prior to flame atomic absorption spectrometric determination. Cu(II) ions were adsorbed at pH 4.5 and eluted with 0.50 mol L{sup -1} HNO{sub 3}. The influence of chemical and hydrodynamic parameters, such as sample pH, buffer concentration, eluent type and concentration, sample flow-rate and preconcentration time were investigated. Under the optimized conditions, a linear response was observed between 16 and 100 {mu}g L{sup -1}, with a detection limit estimated as 3 {mu}g L{sup -1} at the 99.7% confidence level and an enrichment factor of 16. The relative standard deviation was estimated as 3.3% (n = 20). The mini-column was used for at least 100 sampling cycles without significant variation in the analytical response. Recoveries from copper spiked to lake water or groundwater as well as concentrates used in hemodialysis were in the 97.3-111% range. The results obtained for copper determination in these samples agreed with those achieved by graphite furnace atomic absorption spectrometry (GFAAS) at the 95% confidence level.
Shrestha, Kushal; Virgil, Kyle A; Jakubikova, Elena
2016-07-28
Tetrapyrrole-based pigments play a crucial role in photosynthesis as principal light absorbers in light-harvesting chemical systems. As such, accurate theoretical descriptions of the electronic absorption spectra of these pigments will aid in the proper description and understanding of the overall photophysics of photosynthesis. In this work, time-dependent density functional theory (TD-DFT) at the CAM-B3LYP/6-31G* level of theory is employed to produce the theoretical absorption spectra of several tetrapyrrole-based pigments. However, the application of TD-DFT to large systems with several hundreds of atoms can become computationally prohibitive. Therefore, in this study, TD-DFT calculations with reduced orbital spaces (ROSs) that exclude portions of occupied and virtual orbitals are pursued as a viable, computationally cost-effective alternative to conventional TD-DFT calculations. The effects of reducing orbital space size on theoretical spectra are qualitatively and quantitatively described, and both conventional and ROS results are benchmarked against experimental absorption spectra of various tetrapyrrole-based pigments. The orbital reduction approach is also applied to a large natural pigment assembly that comprises the principal light-absorbing component of the reaction center in purple bacteria. Overall, we find that TD-DFT calculations with proper and judicious orbital space reductions can adequately reproduce conventional, full orbital space, TD-DFT results of all pigments studied in this work.
National Aeronautics and Space Administration — The Lunar Orbiter Photo Gallery is an extensive collection of over 2,600 high- and moderate-resolution photographs produced by all five of the Lunar Orbiter...
DEFF Research Database (Denmark)
Riis, Troels; Jørgensen, John Leif
1999-01-01
This documents describes a test of the implementation of the ASC orbit model for the Champ satellite.......This documents describes a test of the implementation of the ASC orbit model for the Champ satellite....
Don, Henk
2011-01-01
We study the geometry of billiard orbits on rectangular billiards. A truncated billiard orbit induces a partition of the rectangle into polygons. We prove that thirteen is a sharp upper bound for the number of different areas of these polygons.
Traumatic transconjunctival orbital emphysema.
Stroh, E M; Finger, P T
1990-01-01
Orbital emphysema can be produced by trans-conjunctival migration of air from a high pressure airgun. In an industrial accident an 8 mm conjunctival laceration was produced in the superior fornix which acted as a portal of entry for air into the subconjunctival, subcutaneous, and retrobulbar spaces. Computed tomography revealed no evidence of orbital fracture and showed that traumatic orbital emphysema occurred without a broken orbital bone.
The many faces of the Bohr atom
Kragh, Helge
2013-01-01
The atomic model that Niels Bohr suggested in 1913 celebrated its greatest victories in connection with one-electron atoms. Among them were the isotopic spectral effect and what became known as Rydberg atoms, insights that were fully recognized only many years later. He considered the original ring model a first step towards an understanding of atomic structure, and during the following years he developed it into more ambitious models that, he hoped, would also describe many-electron atoms. His theory of the periodic system marked the culmination of the orbital atom within the framework of the old quantum theory. However, the theory would soon be replaced by more symbolic models that heralded the coming of the quantum-mechanical atom.
Introducing Earth's Orbital Eccentricity
Oostra, Benjamin
2015-01-01
Most students know that planetary orbits, including Earth's, are elliptical; that is Kepler's first law, and it is found in many science textbooks. But quite a few are mistaken about the details, thinking that the orbit is very eccentric, or that this effect is somehow responsible for the seasons. In fact, the Earth's orbital eccentricity is…
Is the magnetic anisotropy proportional to the orbital moment?
Energy Technology Data Exchange (ETDEWEB)
Skomski, R; Kashyap, A; Enders, A
2011-04-01
The relation between orbital moment and magnetic anisotropy is investigated by model calculations, which show that only a part of the spin-orbit coupling contributes to the anisotropy. A large part of the anisotropy energy, about 50% for iron series elements and nearly 100% for rare-earths, is stored in the nonrelativistic part of the Hamiltonian. A feature important for x-ray magnetic circular dichroism is that the orbital moment of heavy atoms rotates with the spin moment, whereas in light atoms, the orbital moment is recreated in each different direction. In the discussion, we consider three examples of current interest in different areas of magnetism, namely, spin-orbit coupling in Gd3+ and Eu2+, surface anisotropy of Nd2Fe14B, and multiferroic magnetization switching using rare-earths. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562445
Qin, Deyuan; Gao, Feng; Zhang, Zhaohui; Zhao, Liqian; Liu, Jixin; Ye, Jianping; Li, Junwei; Zheng, Fengxi
2013-10-01
A novel method, which coupled an on-line solid phase extraction (SPE) enrichment with ultraviolet vapor generation (UVG) atomic fluorescence spectrometry (AFS), was developed to improve the sensitivity of mercury determination and to remove the interference of some anion and organics to UVG of mercury. A high mercury retention efficiency and maximum exclusion of inorganic and organic matrix in water samples were achieved by using C18 SPE mini cartridge modified with sodium diethyldithiocarbamate (DDTC). Fast and efficient elution from the cartridge was found by using L-cysteine mixing solution. Furthermore, through the investigation of different UV reactor designs, the most important factor was the structure of the reactor (which corresponded roughly to the photon flux) wherein the tubing was sintered into the UV lamp to give the highest UV generation efficiency. The second factor was the materials of the tubing (which roughly corresponded to the working wavelength). Synthetic quartz, characterized by the highest transparency at 185 nm, attained the highest UVG efficiency, suggesting that the most favorable wavelength for UVG was 185 nm. Under optimum conditions, the achievable detection limit (3σ) with sample loadings of 10.0 mL was 0.03 ng L- 1 and 0.08 ng L- 1 with different manifolds, respectively. The method was successfully applied to the determination of Hg in tap water, river water and lake water samples.
Daye, Mirna; Halwani, Jalal; Hamzeh, Mariam
2013-01-01
8-Hydroxyquinoline (8-HQ) was chosen as a powerful ligand for Hg solid phase extraction. Among several chelating resins based on 8-HQ, 5-phenylazo-8-hydroxyquinoline (5Ph8HQ) is used for mercury extraction in which the adsorption dynamics were fully studied. It has been shown that Hg(II) is totally absorbed by 5Ph8HQ within the first 30 minutes of contact time with t1/2 5 minutes, following Langmuir adsorption model. At pH 4, the affinity of mercury is unchallenged by other metals except, for Cu(II), which have shown higher Kd value. With these latter characteristics, 5Ph8HQ was examined for the preconcentration of trace levels of Hg(II). The developed method showed quantitative recoveries of Hg(II) with LOD = 0.21 pg mL−1 and RSD = 3–6% using cold vapor atomic fluorescence spectroscopy (CV-AFS) with a preconcentration factor greater than 250. PMID:24459417
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Mirna Daye
2013-01-01
Full Text Available 8-Hydroxyquinoline (8-HQ was chosen as a powerful ligand for Hg solid phase extraction. Among several chelating resins based on 8-HQ, 5-phenylazo-8-hydroxyquinoline (5Ph8HQ is used for mercury extraction in which the adsorption dynamics were fully studied. It has been shown that Hg(II is totally absorbed by 5Ph8HQ within the first 30 minutes of contact time with t1/2 5 minutes, following Langmuir adsorption model. At pH 4, the affinity of mercury is unchallenged by other metals except, for Cu(II, which have shown higher Kd value. With these latter characteristics, 5Ph8HQ was examined for the preconcentration of trace levels of Hg(II. The developed method showed quantitative recoveries of Hg(II with LOD = 0.21 pg mL−1 and RSD = 3–6% using cold vapor atomic fluorescence spectroscopy (CV-AFS with a preconcentration factor greater than 250.
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Martinis, Estefania M.; Berton, Paula [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Olsina, Roberto A. [INQUISAL-CONICET, Departamento de Quimica Analitica, Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, San Luis (Argentina); Altamirano, Jorgelina C. [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Instituto de Ciencias Basicas, Universidad Nacional de Cuyo, Mendoza (Argentina); Wuilloud, Rodolfo G., E-mail: rwuilloud@lab.cricyt.edu.ar [Laboratory of Environmental Research and Services of Mendoza (LISAMEN), (CCT - CONICET - Mendoza), Av. Ruiz Leal S/N Parque General San Martin, CC. 131, M 5502 IRA Mendoza (Argentina); Instituto de Ciencias Basicas, Universidad Nacional de Cuyo, Mendoza (Argentina)
2009-08-15
A liquid-liquid extraction procedure (L-L) based on room temperature ionic liquid (RTIL) was developed for the preconcentration and determination of mercury in different water samples. The analyte was quantitatively extracted with 1-butyl-3-methylimidazolium hexafluorophosphate ([C{sub 4}mim][PF{sub 6}]) under the form of Hg-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Hg-5-Br-PADAP) complex. A volume of 500 {mu}l of 9.0 mol L{sup -1} hydrochloric acid was used to back-extract the analyte from the RTIL phase into an aqueous media prior to its analysis by flow injection-cold vapor atomic absorption spectrometry (FI-CV-AAS). A preconcentration factor of 36 was achieved upon preconcentration of 20 mL of sample. The limit of detection (LOD) obtained under the optimal conditions was 2.3 ng L{sup -1} and the relative standard deviation (RSD) for 10 replicates at 1 {mu}g L{sup -1} Hg{sup 2+} was 2.8%, calculated with peaks height. The method was successfully applied to the determination of mercury in river, sea, mineral and tap water samples and a certified reference material (CRM).
Illustrating Concepts in Physical Organic Chemistry with 3D Printed Orbitals
Robertson, Michael J.; Jorgensen, William L.
2015-01-01
Orbital theory provides a powerful tool for rationalizing and understanding many phenomena in chemistry. In most introductory chemistry courses, students are introduced to atomic and molecular orbitals in the form of two-dimensional drawings. In this work, we describe a general method for producing 3D printing files of orbital models that can be…
Conduction of molecular electronic devices: Qualitative insights through atom-atom polarizabilities
Energy Technology Data Exchange (ETDEWEB)
Stuyver, T.; Fias, S., E-mail: sfias@vub.ac.be; De Proft, F.; Geerlings, P. [ALGC, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel (Belgium); Fowler, P. W. [Department of Chemistry, University of Sheffield, Sheffield S3 7HF (United Kingdom)
2015-03-07
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
Conduction of molecular electronic devices: qualitative insights through atom-atom polarizabilities.
Stuyver, T; Fias, S; De Proft, F; Fowler, P W; Geerlings, P
2015-03-07
The atom-atom polarizability and the transmission probability at the Fermi level, as obtained through the source-and-sink-potential method for every possible configuration of contacts simultaneously, are compared for polycyclic aromatic compounds. This comparison leads to the conjecture that a positive atom-atom polarizability is a necessary condition for transmission to take place in alternant hydrocarbons without non-bonding orbitals and that the relative transmission probability for different configurations of the contacts can be predicted by analyzing the corresponding atom-atom polarizability. A theoretical link between the two considered properties is derived, leading to a mathematical explanation for the observed trends for transmission based on the atom-atom polarizability.
Automated Selection of Active Orbital Spaces
Stein, Christopher J
2016-01-01
One of the key challenges of quantum-chemical multi-configuration methods is the necessity to manually select orbitals for the active space. This selection requires both expertise and experience and can therefore impose severe limitations on the applicability of this most general class of ab initio methods. A poor choice of the active orbital space may yield even qualitatively wrong results. This is obviously a severe problem, especially for wave function methods that are designed to be systematically improvable. Here, we show how the iterative nature of the density matrix renormalization group combined with its capability to include up to about one hundred orbitals in the active space can be exploited for a systematic assessment and selection of active orbitals. These benefits allow us to implement an automated approach for active orbital space selection, which can turn multi-configuration models into black box approaches.
Schubert, Christian; Abend, Sven; Gebbe, Martina; Gersemann, Matthias; Ahlers, Holger; Müntinga, Hauke; Matthias, Jonas; Sahelgozin, Maral; Herr, Waldemar; Lämmerzahl, Claus; Ertmer, Wolfgang; Rasel, Ernst
2016-04-01
1552-1557 (QUANTUS-IV-Fallturm) and by the Deutsche Forschungsgemeinschaft in the framework of the SFB 1128 geo-Q. [1] P. Berg et al., Composite-Light-Pulse Technique for High-Precision Atom Interferometry, Phys. Rev. Lett., 114, 063002, 2015. [2] A. Peters et al., Measurement of gravitational acceleration by dropping atoms, Nature 400, 849, 1999. [3] D. Schlippert et al., Quantum Test of the Universality of Free Fall, Phys. Rev. Lett., 112, 203002, 2014. [4] A. Louchet-Chauvet et al., The influence of transverse motion within an atomic gravimeter, New J. Phys. 13, 065026, 2011. [5] Q. Bodart et al., A cold atom pyramidal gravimeter with a single laser beam, Appl. Phys. Lett. 96, 134101, 2010. [6] H. Müntinga et al., Interferometry with Bose-Einstein Condensates in Microgravity, Phys. Rev. Lett., 110, 093602, 2013. [7] T. Kovachy et al., Matter Wave Lensing to Picokelvin Temperatures, Phys. Rev. Lett. 114, 143004, 2015. [8] J. Rudolph et al., A high-flux BEC source for mobile atom interferometers, New J. Phys. 17, 065001, 2015.
Directory of Open Access Journals (Sweden)
Rahul T Chakor
2012-01-01
Full Text Available Idiopathic orbital inflammation is the third most common orbital disease, following Graves orbitopathy and lymphoproliferative diseases. We present a 11 year old girl with 15 days history of painless diplopia. There was no history of fluctuation of symptoms, drooping of eye lids or diminished vision. She had near total restricted extra-ocular movements and mild proptosis of the right eye. There was no conjunctival injection, chemosis, or bulb pain. There was no eyelid retraction or lid lag. Rest of the neurological examination was unremarkable.Erythrocyte sedimentation rate was raised with eosinophilia. Antinuclear antibodies were positive. Liver, renal and thyroid functions were normal. Antithyroid, double stranded deoxyribonucleic acid and acetylcholine receptor antibodies were negative. Repetitive nerve stimulation was negative. Magnetic resonance imaging (MRI of the orbit was typical of orbital myositis. The patient responded to oral steroids. Orbital myositis can present as painless diplopia. MRI of orbit is diagnostic in orbital myositis.
Directory of Open Access Journals (Sweden)
Jeffrey M Joseph
2011-01-01
Full Text Available Jeffrey M Joseph, Ioannis P GlavasDivision of Ophthalmic Plastic and Reconstructive Surgery, Department of Ophthalmology, School of Medicine, New York University, New York, NY, USA; Manhattan Eye, Ear, and Throat Hospital, New York, NY, USAAbstract: This review of orbital fractures has three goals: 1 to understand the clinically relevant orbital anatomy with regard to periorbital trauma and orbital fractures, 2 to explain how to assess and examine a patient after periorbital trauma, and 3 to understand the medical and surgical management of orbital fractures. The article aims to summarize the evaluation and management of commonly encountered orbital fractures from the ophthalmologic perspective and to provide an overview for all practicing ophthalmologists and ophthalmologists in training.Keywords: orbit, trauma, fracture, orbital floor, medial wall, zygomatic, zygomatic complex, zmc fracture, zygomaticomaxillary complex fractures
Theoretical Calculation of Absolute Radii of Atoms and Ions. Part 1. The Atomic Radii
Directory of Open Access Journals (Sweden)
Raka Biswas
2002-02-01
Full Text Available Abstract. A set of theoretical atomic radii corresponding to the principal maximum in the radial distribution function, 4ÃÂ€r2R2 for the outermost orbital has been calculated for the ground state of 103 elements of the periodic table using Slater orbitals. The set of theoretical radii are found to reproduce the periodic law and the Lother MeyerÃ¢Â€Â™s atomic volume curve and reproduce the expected vertical and horizontal trend of variation in atomic size in the periodic table. The d-block and f-block contractions are distinct in the calculated sizes. The computed sizes qualitatively correlate with the absolute size dependent properties like ionization potentials and electronegativity of elements. The radii are used to calculate a number of size dependent periodic physical properties of isolated atoms viz., the diamagnetic part of the atomic susceptibility, atomic polarizability and the chemical hardness. The calculated global hardness and atomic polarizability of a number of atoms are found to be close to the available experimental values and the profiles of the physical properties computed in terms of the theoretical atomic radii exhibit their inherent periodicity. A simple method of computing the absolute size of atoms has been explored and a large body of known material has been brought together to reveal how many different properties correlate with atomic size.
Loring, FH
2014-01-01
Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec
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Suvardhan, K. [Environmental Monitoring Laboratory, Department of Chemistry, S.V. University, AP (India); Rekha, D. [Environmental Monitoring Laboratory, Department of Chemistry, S.V. University, AP (India); Kumar, K. Suresh [Environmental Monitoring Laboratory, Department of Chemistry, S.V. University, AP (India); Prasad, P. Reddy [Environmental Monitoring Laboratory, Department of Chemistry, S.V. University, AP (India); Kumar, J. Dilip [Environmental Monitoring Laboratory, Department of Chemistry, S.V. University, AP (India); Jayaraj, B. [Department of Mathematics, S.V. University, Tirupati 517502, AP (India); Chiranjeevi, P. [Environmental Monitoring Laboratory, Department of Chemistry, S.V. University, AP (India)]. E-mail: chiranjeevipattium@gmail.com
2007-06-01
Cloud-point extraction was applied as a preconcentration of nickel after formation of complex with newly synthesized N-quino[8,7-b]azin-5-yl-2,3,5,6,8,9,11,12octahydrobenzo[b][1,4,7,10,13] pentaoxacyclopentadecin-15-yl-methanimine, and later determined by flame atomic absorption spectrometry (FAAS) using octyl phenoxy polyethoxy ethanol (Triton X-114) as surfactant. Nickel was complexed with N-quino[8,7-b]azin-5-yl-2,3,5,6,8,9,11,12 octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecin-15-yl-methanimine in an aqueous phase and was kept for 15 min in a thermo-stated bath at 40 deg. C. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud-point extraction were evaluated, optimized and successfully applied to the nickel determination in various water samples. Under the optimized conditions, the preconcentration system of 100 ml sample permitted an enhancement factor of 50-fold. The detailed study of various interferences made the method more selective. The detection limits obtained under optimal condition was 0.042 ng ml{sup -1}. The extraction efficiency was investigated at different nickel concentrations (20-80 ng ml{sup -1}) and good recoveries (99.05-99.93%) were obtained using present method. The proposed method has been applied successfully for the determination of nickel in various water samples and compared with reported method in terms of Student's t-test and variance ratio f-test which indicate the significance of present method over reported and spectrophotometric methods at 95% confidence 0011lev.
Suvardhan, K; Rekha, D; Kumar, K Suresh; Prasad, P Reddy; Kumar, J Dilip; Jayaraj, B; Chiranjeevi, P
2007-06-01
Cloud-point extraction was applied as a preconcentration of nickel after formation of complex with newly synthesized N-quino[8,7-b]azin-5-yl-2,3,5,6,8,9,11,12octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecin-15-yl-methanimine, and later determined by flame atomic absorption spectrometry (FAAS) using octyl phenoxy polyethoxy ethanol (Triton X-114) as surfactant. Nickel was complexed with N-quino[8,7-b]azin-5-yl-2,3,5,6,8,9,11,12octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecin-15-yl-methanimine in an aqueous phase and was kept for 15 min in a thermo-stated bath at 40 degrees C. Separation of the two phases was accomplished by centrifugation for 15 min at 4000 rpm. The chemical variables affecting the cloud-point extraction were evaluated, optimized and successfully applied to the nickel determination in various water samples. Under the optimized conditions, the preconcentration system of 100 ml sample permitted an enhancement factor of 50-fold. The detailed study of various interferences made the method more selective. The detection limits obtained under optimal condition was 0.042 ngml(-1). The extraction efficiency was investigated at different nickel concentrations (20-80 ngml(-1)) and good recoveries (99.05-99.93%) were obtained using present method. The proposed method has been applied successfully for the determination of nickel in various water samples and compared with reported method in terms of Student's t-test and variance ratio f-test which indicate the significance of present method over reported and spectrophotometric methods at 95% confidence level.
Three planets orbiting Wolf 1061
Wright, D J; Tinney, C G; Bentley, J S; Zhao, Jinglin
2015-01-01
We use archival HARPS spectra to detect three planets orbiting the M3 dwarf Wolf1061 (GJ 628). We detect a 1.36 Mearth minimum-mass planet with an orbital period P = 4.888d (Wolf1061b), a 4.25 Mearth minimum-mass planet with orbital period P = 17.867d (Wolf1061c), and a likely 5.21 Mearth minimum-mass planet with orbital period P = 67.274d (Wolf1061d). All of the planets are of sufficiently low mass that they may be rocky in nature. The 17.867d planet falls within the habitable zone for Wolf 1061 and the 67.274d planet falls just outside the outer boundary of the habitable zone. There are no signs of activity observed in the bisector spans, cross-correlation full-width-half-maxima, Calcium H & K indices, NaD indices, or H-alpha indices near the planetary periods. We use custom methods to generate a cross-correlation template tailored to the star. The resulting velocities do not suffer the strong annual variation observed in the HARPS DRS velocities. This differential technique should deliver better exploi...
THREE PLANETS ORBITING WOLF 1061
Energy Technology Data Exchange (ETDEWEB)
Wright, D. J.; Wittenmyer, R. A.; Tinney, C. G.; Bentley, J. S.; Zhao, Jinglin, E-mail: duncan.wright@unsw.edu.au [Department of Astronomy and Australian Centre for Astrobiology, School of Physics, University of New South Wales, NSW 2052 (Australia)
2016-02-01
We use archival HARPS spectra to detect three planets orbiting the M3 dwarf Wolf 1061 (GJ 628). We detect a 1.36 M{sub ⊕} minimum-mass planet with an orbital period P = 4.888 days (Wolf 1061b), a 4.25 M{sub ⊕} minimum-mass planet with orbital period P = 17.867 days (Wolf 1061c), and a likely 5.21 M{sub ⊕} minimum-mass planet with orbital period P = 67.274 days (Wolf 1061d). All of the planets are of sufficiently low mass that they may be rocky in nature. The 17.867 day planet falls within the habitable zone for Wolf 1061 and the 67.274 day planet falls just outside the outer boundary of the habitable zone. There are no signs of activity observed in the bisector spans, cross-correlation FWHMs, calcium H and K indices, NaD indices, or Hα indices near the planetary periods. We use custom methods to generate a cross-correlation template tailored to the star. The resulting velocities do not suffer the strong annual variation observed in the HARPS DRS velocities. This differential technique should deliver better exploitation of the archival HARPS data for the detection of planets at extremely low amplitudes.
Adiabatic geometric phases in hydrogenlike atoms
Sjöqvist, Erik; Yi, X. X.; Åberg, J.
2005-01-01
We examine the effect of spin-orbit coupling on geometric phases in hydrogenlike atoms exposed to a slowly varying magnetic field. The marginal geometric phases associated with the orbital angular momentum and the intrinsic spin fulfill a sum rule that explicitly relates them to the corresponding geometric phase of the whole system. The marginal geometric phases in the Zeeman and Paschen-Back limit are analyzed. We point out the existence of nodal points in the marginal phases that may be det...
Distant retrograde orbits and the asteroid hazard
Perozzi, Ettore; Ceccaroni, Marta; Valsecchi, Giovanni B.; Rossi, Alessandro
2017-08-01
Distant Retrograde Orbits (DROs) gained a novel wave of fame in space mission design because of their numerous advantages within the framework of the US plans for bringing a large asteroid sample in the vicinity of the Earth as the next target for human exploration. DROs are stable solutions of the three-body problem that can be used whenever an object, whether of natural or artificial nature, is required to remain in the neighborhood of a celestial body without being gravitationally captured by it. As such, they represent an alternative option to Halo orbits around the collinear Lagrangian points L1 and L2. Also known under other names ( e.g., quasi-satellite orbits, cis-lunar orbits, family- f orbits) these orbital configurations found interesting applications in several mission profiles, like that of a spacecraft orbiting around the small irregularly shaped satellite of Mars Phobos or the large Jovian moon Europa. In this paper a basic explanation of the DRO dynamics is presented in order to clarify some geometrical properties that characterize them. Their accessibility is then discussed from the point of view of mission analysis under different assumptions. Finally, their relevance within the framework of the present asteroid hazard protection programs is shown, stressing the significant increase in warning time they would provide in the prediction of impactors coming from the direction of the Sun.
Diffusive chaos in navigation satellites orbits
Daquin, J; Tsiganis, K
2016-01-01
The navigation satellite constellations in medium-Earth orbit exist in a background of third-body secular resonances stemming from the perturbing gravitational effects of the Moon and the Sun. The resulting chaotic motions, emanating from the overlapping of neighboring resonant harmonics, induce especially strong perturbations on the orbital eccentricity, which can be transported to large values, thereby increasing the collision risk to the constellations and possibly leading to a proliferation of space debris. We show here that this transport is of a diffusive nature and we present representative diffusion maps that are useful in obtaining a global comprehension of the dynamical structure of the navigation satellite orbits.
Nilpotent orbits in real symmetric pairs
Dietrich, Heiko; Ruggeri, Daniele; Trigiante, Mario
2016-01-01
In the classification of stationary solutions in extended supergravities with symmetric scalar manifolds, the nilpotent orbits of a real symmetric pair play an important role. In this paper we discuss two approaches to determining the nilpotent orbits of a real symmetric pair. We apply our methods to an explicit example, and thereby classify the nilpotent orbits of SL_2(R)^4 acting on the fourth tensor power of the natural 2-dimensional SL_2(R)-module. This makes it possible to classify all stationary solutions of the so-called STU-supergravity model.
Why has the bohr-sommerfeld model of the atom been ignoredby general chemistry textbooks?
Niaz, Mansoor; Cardellini, Liberato
2011-12-01
Bohr's model of the atom is considered to be important by general chemistry textbooks. A major shortcoming of this model was that it could not explain the spectra of atoms containing more than one electron. In order to increase the explanatory power of the model, Sommerfeld hypothesized the existence of elliptical orbits. This study has the following objectives: 1) Formulation of criteria based on a history and philosophy of science framework; and 2) Evaluation of university-level general chemistry textbooks based on the criteria, published in Italy and U.S.A. Presentation of a textbook was considered to be "satisfactory" if it included a description of the Bohr-Sommerfeld model along with diagrams of the elliptical orbits. Of the 28 textbooks published in Italy that were analyzed, only five were classified as "satisfactory". Of the 46 textbooks published in U.S.A., only three were classified as "satisfactory". This study has the following educational implications: a) Sommerfeld's innovation (auxiliary hypothesis) by introducing elliptical orbits, helped to restore the viability of Bohr's model; b) Bohr-Sommerfeld's model went no further than the alkali metals, which led scientists to look for other models; c) This clearly shows that scientific models are tentative in nature; d) Textbook authors and chemistry teachers do not consider the tentative nature of scientific knowledge to be important; e) Inclusion of the Bohr-Sommerfeld model in textbooks can help our students to understand how science progresses.
Bonding charge density from atomic perturbations.
Wang, Yi; Wang, William Yi; Chen, Long-Qing; Liu, Zi-Kui
2015-05-15
Charge transfer among individual atoms is the key concept in modern electronic theory of chemical bonding. In this work, we present a first-principles approach to calculating the charge transfer. Based on the effects of perturbations of an individual atom or a group of atoms on the electron charge density, we determine unambiguously the amount of electron charge associated with a particular atom or a group of atoms. We computed the topological electron loss versus gain using ethylene, graphene, MgO, and SrTiO3 as examples. Our results verify the nature of chemical bonds in these materials at the atomic level.
Nigam, Sandeep; Majumder, Chiranjib
2010-11-03
Using state-of-the-art first-principles calculations we report the interaction of M atoms (M = Cu, Ag and Au) with small Ag(n), Au(n) clusters (n = 3 and 6) and periodic Ag(111) and Au(111) surfaces. All calculations were performed using the plane wave pseudo-potential approach under the spin polarized version of the generalized gradient approximation scheme. The result shows that the equilibrium geometry of all MAg(3) and MAu(3) clusters favor a planar rhombus structure. From the charge distribution analysis of MAg(n)/MAu(n) clusters it is found that, while Cu and Ag donates electronic charge towards the host clusters, the Au atom acts as an acceptor, thus creating charge polarization in the system. The difference in orbital decomposed charges before and after the M interaction reveals that enhanced s-d hybridization is responsible for keeping the MAu(6) cluster planar, and increased p-orbital participation induces three-dimensional configurations in MAg(6) clusters. The optimization of M atom deposition on the Ag(111) and Au(111) surfaces shows that M atoms prefer to adsorb on the threefold fcc site over other well-defined sites. From the orbital decomposed charge analysis it is inferred that, although there is significant difference in the absolute magnitude of the interaction energy between M atoms and the Ag or Au substrates, the nature of chemical bonding is similar for the finite size clusters as well as in slab models.
The Relativistic Effects on the Carbon-Carbon Coupling Constants Mediated by a Heavy Atom.
Wodyński, Artur; Malkina, Olga L; Pecul, Magdalena
2016-07-21
The (2)JCC, (3)JCC, and (4)JCC spin-spin coupling constants in the systems with a heavy atom (Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Bi, and Po) in the coupling path have been calculated by means of density functional theory. The main goal was to estimate the relativistic effects on spin-spin coupling constants and to explore the factors which may influence them, including the nature of the heavy atom and carbon hybridization. The methods applied range, in order of reduced complexity, from the Dirac-Kohn-Sham (DKS) method (density functional theory with four-component Dirac-Coulomb Hamiltonian), through DFT with two- and one-component zeroth-order regular approximation (ZORA) Hamiltonians, to scalar effective core potentials (ECPs) with the nonrelativistic Hamiltonian. The use of DKS and ZORA methods leads to very similar results, and small-core ECPs of the MDF and MWB variety reproduce correctly the scalar relativistic effects. Scalar relativistic effects usually are larger than the spin-orbit coupling effects. The latter tend to influence the most the coupling constants of the sp(3)-hybridized carbon atoms and in compounds of the p-block heavy atoms. Large spin-orbit coupling contributions for the Po compounds are probably connected with the inverse of the lowest triplet excitation energy.
Overview of International Space Station orbital environments exposure flight experiments
Soares, Carlos E.; Mikatarian, Ronald R.; Schmidl, Danny; Finckenor, Miria; Neish, Michael; Imagawa, Kichiro; Dinguirard, Magdeleine; van Eesbeek, Marc; Naumov, S. F.; Krylov, A. N.; Mishina, L. V.; Gerasimov, Y. I.; Sokolova, S. P.; Kurilyonok, A. O.; Alexandrov, N. G.; Smirnova, T. N.
2004-10-01
This paper presents an overview of International Space Station (ISS) on-orbit environments exposure flight experiments. International teams are flying, or preparing to fly, externally mounted materials exposure trays and sensor packages. The samples in these trays are exposed to a combination of induced molecular contamination, ultraviolet radiation, atomic oxygen, ionizing radiation, micrometeoroids and orbital debris. Exposed materials samples are analyzed upon return. Typical analyses performed on these samples include optical property measurements, X-ray photo spectroscopy (XPS) depth profiles, scanning electron microscope (SEM) surface morphology and materials properties measurements. The objective of these studies is to characterize the long-term effects of the natural and induced environments on spacecraft materials. Ongoing flight experiments include the U.S. Materials International Space Station Experiment (MISSE) program, the Japanese Micro-Particles Capturer and Space Environment Exposure Device (SM/MPAC&SEED) experiment, the Russian SKK and Kromka experiments from RSC-Energia, and the Komplast flight experiment. Flight experiments being prepared for flight, or in development stage, include the Japanese Space Environment Data Acquisition Attached Payload (SEDA-AP), the Russian BKDO monitoring package from RSC-Energia, and the European Materials Exposure and Degradation Experiment (MEDET). Results from these ISS flight experiments will be crucial to extending the performance and life of long-duration space systems such as Space Station, Space Transportation System, and other missions for Moon and Mars exploration.
Wright, Jason T; Marcy, Geoffrey W; Han, Eunkyu; Feng, Ying; Johnson, John Asher; Howard, Andrew W; Valenti, Jeff A; Anderson, Jay; Piskunov, Nikolai
2010-01-01
We present a database of well determined orbital parameters of exoplanets. This database comprises spectroscopic orbital elements measured for 421 planets orbiting 357 stars from radial velocity and transit measurements as reported in the literature. We have also compiled fundamental transit parameters, stellar parameters, and the method used for the planets discovery. This Exoplanet Orbit Database includes all planets with robust, well measured orbital parameters reported in peer-reviewed articles. The database is available in a searchable, filterable, and sortable form on the Web at http://exoplanets.org through the Exoplanets Data Explorer Table, and the data can be plotted and explored through the Exoplanets Data Explorer Plotter. We use the Data Explorer to generate publication-ready plots giving three examples of the signatures of exoplanet migration and dynamical evolution: We illustrate the character of the apparent correlation between mass and period in exoplanet orbits, the selection different biase...
Optical nanofibres and neutral atoms
Nieddu, Thomas; Gokhroo, Vandna; Chormaic, Síle Nic
2016-05-01
Optical nanofibres are increasingly being used in cold atom experiments due to their versatility and the clear advantages they have when developing all-fibred systems for quantum technologies. They provide researchers with a method of overcoming the Rayleigh range for achieving high intensities in a focussed beam over a relatively long distance, and can act as a noninvasive tool for probing cold atoms. In this review article, we will briefly introduce the theory of mode propagation in an ultrathin optical fibre and highlight some of the more significant theoretical and experimental progresses to date, including the early work on atom probing, manipulation and trapping, the study of atom-dielectric surface interactions, and the more recent observation of nanofibre-mediated nonlinear optics phenomena in atomic media. The functionality of optical nanofibres in relation to the realisation of atom-photon hybrid quantum systems is also becoming more evident as some of the earlier technical challenges are surpassed and, recently, several schemes to implement optical memories have been proposed. We also discuss some possible directions where this research field may head, in particular, in relation to the use of optical nanofibres that can support higher-order modes with an associated orbital angular momentum.
Lunar Orbit Stability for Small Satellite Mission Design
Dono, Andres
2015-01-01
The irregular nature of the lunar gravity field will severely affect the orbit lifetime and behavior of future lunar small satellite missions. These spacecraft need stable orbits that do not require large deltaV budgets for station-keeping maneuvers. The initial classical elements of any lunar orbit are critical to address its stability and to comply with mission requirements. This publication identifies stable regions according to different initial conditions at the time of lunar orbit insertion (LOI). High fidelity numerical simulations with two different gravity models were performed. We focus in low altitude orbits where the dominant force in orbit propagation is the existence of unevenly distributed lunar mass concentrations. These orbits follow a periodic oscillation in some of the classical elements that is particularly useful for mission design. A set of orbital maintenance strategies for various mission concepts is presented.
[Orbital mycetoma: a case report].
Gueye, N N; Seck, S M; Diop, Y; Ndiaye Sow, M N; Agboton, G; Diakhaté, M; Dieng, M; Dieng, M T
2013-05-01
Mycetomas are pathological processes through which exogenous fungal or actinomycotic etiological agents produce grains. These etiological agents live in the soil and plants of endemic areas. They are introduced traumatically, primarily into the foot. The orbital location is rare. We report the case of a 17-year-old student admitted for progressive left proptosis over 2 years, following penetrating trauma by a fork in a rural setting. Examination revealed a heterogenous orbital mass with multiple fistulae, producing pus and black grains, and suggested, due to the color of the grains, a diagnosis of fungal mycetoma. MRI revealed a destructive process at the level of the lamina papracea of the ethmoid and the orbital floor. Anatomopathological examination confirmed the fungal nature of the infection, while culture in Sabouraud's medium was inconclusive. The outcome was favorable after exenteration and debridementof the ipsilateral maxillary sinus and nasal cavities, along with 4 months of ketoconazole. No recurrence has been observed for 14 months after surgery. Mycetomas are endemic to northwest Africa. Most frequently located in the foot, they are seldom seen in the orbit. The color of the grains provides a clue as to the etiology. Black-grain mycetomas are always fungal and are treated surgically--essentially like cancer--as the persistence of a single grain will cause a recurrence. The orbital location of a mycetoma is rare. In the present case report, the concept of port of entry, the clinical appearance, and the color of the grains guided the diagnosis. The histological examination of the surgical specimen confirmed the diagnosis. Copyright © 2012 Elsevier Masson SAS. All rights reserved.
Preseptal and orbital cellulitis
Emine Akçay; Gamze Dereli Can; Nurullah Çağıl
2014-01-01
Preseptal cellulitis (PC) is defined as an inflammation of the eyelid and surrounding skin, whereas orbital cellulitis (OC) is an inflammation of the posterior septum of the eyelid affecting the orbit and its contents. Periorbital tissues may become infected as a result of trauma (including insect bites) or primary bacteremia. Orbital cellulitis generally occurs as a complication of sinusitis. The most commonly isolated organisms are Staphylococcus aureus, Streptococcus pneumoniae, S. epid...
Orbital inflammation: Corticosteroids first.
Dagi Glass, Lora R; Freitag, Suzanne K
2016-01-01
Orbital inflammation is common, and may affect all ages and both genders. By combining a thorough history and physical examination, targeted ancillary laboratory testing and imaging, a presumptive diagnosis can often be made. Nearly all orbital inflammatory pathology can be empirically treated with corticosteroids, thus obviating the need for histopathologic diagnosis prior to initiation of therapy. In addition, corticosteroids may be effective in treating concurrent systemic disease. Unless orbital inflammation responds atypically or incompletely, patients can be spared biopsy.
Liakos, Dimitrios G; Neese, Frank
2015-09-08
The recently developed domain-based local pair natural orbital coupled cluster theory with single, double, and perturbative triple excitations (DLPNO-CCSD(T)) delivers results that are closely approaching those of the parent canonical coupled cluster method at a small fraction of the computational cost. A recent extended benchmark study established that, depending on the three main truncation thresholds, it is possible to approach the canonical CCSD(T) results within 1 kJ (default setting, TightPNO), 1 kcal/mol (default setting, NormalPNO), and 2-3 kcal (default setting, LoosePNO). Although thresholds for calculations with TightPNO are 2-4 times slower than those based on NormalPNO thresholds, they are still many orders of magnitude faster than canonical CCSD(T) calculations, even for small and medium sized molecules where there is little locality. The computational effort for the coupled cluster step scales nearly linearly with system size. Since, in many instances, the coupled cluster step in DLPNO-CCSD(T) is cheaper or at least not much more expensive than the preceding Hartree-Fock calculation, it is useful to compare the method against modern density functional theory (DFT), which requires an effort comparable to that of Hartree-Fock theory (at least if Hartree-Fock exchange is part of the functional definition). Double hybrid density functionals (DHDF's) even require a MP2-like step. The purpose of this article is to evaluate the cost vs accuracy ratio of DLPNO-CCSD(T) against modern DFT (including the PBE, B3LYP, M06-2X, B2PLYP, and B2GP-PLYP functionals and, where applicable, their van der Waals corrected counterparts). To eliminate any possible bias in favor of DLPNO-CCSD(T), we have chosen established benchmark sets that were specifically proposed for evaluating DFT functionals. It is demonstrated that DLPNO-CCSD(T) with any of the three default thresholds is more accurate than any of the DFT functionals. Furthermore, using the aug-cc-pVTZ basis set and
To acquire more detailed radiation drive by use of ``quasi-steady'' approximation in atomic kinetics
Ren, Guoli; Pei, Wenbing; Lan, Ke; Gu, Peijun; Li, Xin
2012-10-01
In current routine 2D simulation of hohlraum physics, we adopt the principal-quantum- number(n-level) average atom model(AAM) in NLTE plasma description. However, the detailed experimental frequency-dependant radiative drive differs from our n-level simulated drive, which reminds us the need of a more detailed atomic kinetics description. The orbital-quantum- number(nl-level) average atom model is a natural consideration, however the nl-level in-line calculation needs much more computational resource. By distinguishing the rapid bound-bound atomic processes from the relative slow bound-free atomic processes, we found a method to build up a more detailed bound electron distribution(nl-level even nlm-level) using in-line n-level calculated plasma conditions(temperature, density, and average ionization degree). We name this method ``quasi-steady approximation'' in atomic kinetics. Using this method, we re-build the nl-level bound electron distribution (Pnl), and acquire a new hohlraum radiative drive by post-processing. Comparison with the n-level post-processed hohlraum drive shows that we get an almost identical radiation flux but with more fine frequency-denpending spectrum structure which appears only in nl-level transition with same n number(n=0) .
Geometric orbit datum and orbit covers
Institute of Scientific and Technical Information of China (English)
LIANG; Ke(
2001-01-01
［1］Vogan, D. , Dixmier algebras, sheets and representation theory (in Actes du colloque en I' honneur de Jacques Dixmier),Progress in Math. 92, Boston: Birkhauser Verlag, 1990, 333－397.［2］McGovern, W., Dixmier Algebras and Orbit Method, Operator Algebras, Unitary Representations and Invariant Theory,Boston: Birkhauser, 1990, 397－416.［3］Liang, K. , Parabolic inductions of nilpotent geometric orbit datum, Chinese Science Bulletin (in Chinese) , 1996, 41 (23):2116－2118.［4］Vogan, D., Representations of Real Reductive Lie Groups, Boston-Basel-Stuttgart: Birkhauser, 1981.［5］Lustig, G., Spaltenstein, N., Induced unipotent class, J. London Math. Soc., 1997, 19. 41－52.［6］Collingwood, D. H. , McGovern, W. M. , Nilpotent Orbits in Semisimple Lie Algebras, New York: Van Nostremt Reinhold,1993.
Doughnut shape atom traps with arbitrary inclination
Energy Technology Data Exchange (ETDEWEB)
Rodriguez y Masegosa, R.; Moya C, H.; Chavez C, S. [INAOE, A.P. 51 y 216, 72000 Puebla (Mexico)
2006-07-01
Since the invention of magneto-optical trap (MOT), there have been several experimental and theoretical studies of the density distribution in these devices. To the best of our knowledge, only horizontal orbital traps have been observed, perpendicular to the coil axis. In this work we report the observation of distributions of trapped atoms in pure circular orbits without a nucleus whose orbital plane is tilted up to 90diam. with respect to the horizontal plane. We have used a stabilized time phase optical array in our experiments and conventional equipment used for MOT. (Author)
Interplay of Coulomb interaction and spin-orbit coupling
Bünemann, Jörg; Linneweber, Thorben; Löw, Ute; Anders, Frithjof B.; Gebhard, Florian
2016-07-01
We employ the Gutzwiller variational approach to investigate the interplay of Coulomb interaction and spin-orbit coupling in a three-orbital Hubbard model. Already in the paramagnetic phase we find a substantial renormalization of the spin-orbit coupling that enters the effective single-particle Hamiltonian for the quasiparticles. Only close to half band-filling and for sizable Coulomb interaction do we observe clear signatures of Hund's atomic rules for spin, orbital, and total angular momentum. For a finite local Hund's rule exchange interaction we find a ferromagnetically ordered state. The spin-orbit coupling considerably reduces the size of the ordered moment, it generates a small ordered orbital moment, and it induces a magnetic anisotropy. To investigate the magnetic anisotropy energy, we use an external magnetic field that tilts the magnetic moment away from the easy axis (1 ,1 ,1 ) .
2008-01-01
This image shows the paths of three spacecraft currently in orbit around Mars, as well as the path by which NASA's Phoenix Mars Lander will approach and land on the planet. The t-shaped crosses show where the orbiters will be when Phoenix enters the atmosphere, while the x-shaped crosses show their location at landing time. All three orbiters, NASA's Mars Reconnaissance Orbiter, NASA's Mars Odyssey and the European Space Agency's Mars Express, will be monitoring Phoenix during the final steps of its journey to the Red Planet. Phoenix will land just south of Mars's north polar ice cap.
Makarewicz, Emilia; Gordon, Agnieszka J; Mierzwicki, Krzysztof; Latajka, Zdzislaw; Berski, Slawomir
2014-06-05
Quantum chemistry methods have been applied to study the influence of the Xe atom inserted into the hydrogen-bromine bond (HBr → HXeBr), particularly on the nature of atomic interactions in the HBr···CO2 and HXeBr···CO2 complexes. Detailed analysis of the nature of chemical bonds has been carried out using topological analysis of the electron localization function, while topological analysis of electron density was used to gain insight into the nature of weak nonbonding interactions. Symmetry-adapted perturbation theory within the orbital approach was applied for greater understanding of the physical contributions to the total interaction energy.
Energy Technology Data Exchange (ETDEWEB)
Goldschmidt, B.
1990-01-01
This book is a memoir of rivalries among the Allies over the bomb, by a participant and observer. Nuclear proliferation began in the uneasy wartime collaboration of the United States, England, Canada, and Free France to produce the atom bomb. Through the changes of history, a young French chemist had a role in almost every act of this international drama. This memoir is based on Goldschmidt's own recollections, interviews with other leading figures, and 3,000 pages of newly declassified documents in Allied archives. From his own start as Marie Curie's lab assistant, Goldschmidt's career was closely intertwined with Frances complicated rise to membership in the nuclear club. As a refugee from the Nazis, he became part of the wartime nuclear energy project in Canada and found himself the only French scientist to work (although briefly) on the American atom bomb project.
Energy Technology Data Exchange (ETDEWEB)
Livingston, A.E.; Kukla, K.; Cheng, S. [Univ. of Toledo, OH (United States)] [and others
1995-08-01
In a collaboration with the Atomic Physics group at Argonne and the University of Toledo, the Atomic Physics group at the University of Notre Dame is measuring the fine structure transition energies in highly-charged lithium-like and helium-like ions using beam-foil spectroscopy. Precise measurements of 2s-2p transition energies in simple (few-electron) atomic systems provide stringent tests of several classes of current atomic- structure calculations. Analyses of measurements in helium-like Ar{sup 16+} have been completed, and the results submitted for publication. A current goal is to measure the 1s2s{sup 3}S{sub 1} - 1s2p{sup 3}P{sub 0} transition wavelength in helium-like Ni{sup 26+}. Measurements of the 1s2s{sup 2}S{sub 1/2} - 1s2p{sup 2}P{sub 1/2,3/2} transition wavelengths in lithium-like Kr{sup 33+} is planned. Wavelength and lifetime measurements in copper-like U{sup 63+} are also expected to be initiated. The group is also participating in measurements of forbidden transitions in helium-like ions. A measurement of the lifetime of the 1s2s{sup 3}S{sub 1} state in Kr{sup 34+} was published recently. In a collaboration including P. Mokler of GSI, Darmstadt, measurements have been made of the spectral distribution of the 2E1 decay continuum in helium-like Kr{sup 34+}. Initial results have been reported and further measurements are planned.
Many-body expansion of the Fock matrix in the fragment molecular orbital method
Fedorov, Dmitri G.; Kitaura, Kazuo
2017-09-01
A many-body expansion of the Fock matrix in the fragment molecular orbital method is derived up to three-body terms for restricted Hartree-Fock and density functional theory in the atomic orbital basis and compared to the expansion in the basis of fragment molecular orbitals (MOs). The physical nature of many-body corrections is revealed in terms of charge transfer terms. An improvement of the fragment MO expansion is proposed by adding exchange to the embedding. The accuracy of all developed methods is demonstrated in comparison to unfragmented results for polyalanines, a water cluster, Trp-cage (PDB: 1L2Y) and crambin (PDB: 1CRN) proteins, a zeolite cluster, a Si nano-wire, and a boron nitride ribbon. The physical nature of metallicity is discussed, and it is shown what kinds of metallic systems can be treated by fragment-based methods. The density of states is calculated for a fully closed and a partially open nano-ring of boron nitride with a diameter of 105 nm.
Atom gravimeters and gravitational redshift
Wolf, Peter; Borde, Christian J; Reynaud, Serge; Salomon, Christophe; Cohen-Tannoudji, Claude; 10.1038/nature09340
2010-01-01
In a recent paper, H. Mueller, A. Peters and S. Chu [A precision measurement of the gravitational redshift by the interference of matter waves, Nature 463, 926-929 (2010)] argued that atom interferometry experiments published a decade ago did in fact measure the gravitational redshift on the quantum clock operating at the very high Compton frequency associated with the rest mass of the Caesium atom. In the present Communication we show that this interpretation is incorrect.
Congenital orbital encephalocele, orbital dystopia, and exophthalmos.
Hwang, Kun; Kim, Han Joon
2012-07-01
We present here an exceedingly rare variant of a nonmidline basal encephalocele of the spheno-orbital type, and this was accompanied with orbital dystopia in a 56-year-old man. On examination, his left eye was located more inferolaterally than his right eye, and the patient said this had been this way since his birth. The protrusion of his left eye was aggravated when he is tired. His naked visual acuity was 0.7/0.3, and the ocular pressure was 14/12 mm Hg. The exophthalmometry was 10/14 to 16 mm. His eyeball motion was not restricted, yet diplopia was present in all directions. The distance from the midline to the medial canthus was 20/15 mm. The distance from the midline to the midpupillary line was 35/22 mm. The vertical dimension of the palpebral fissure was 12/9 mm. The height difference of the upper eyelid margin was 11 mm, and the height difference of the lower eyelid margin was 8 mm. Facial computed tomography and magnetic resonance imaging showed left sphenoid wing hypoplasia and herniation of the left anterior temporal pole and dura mater into the orbit, and this resulted into left exophthalmos and encephalomalacia in the left anterior temporal pole. To the best of our knowledge, our case is the second case of basal encephalocele and orbital dystopia.
Directory of Open Access Journals (Sweden)
Balasubramanian Thiagarajan
2014-08-01
Full Text Available This article discusses various patterns of presentations of orbital lesions. Since this article has been authored by an otolaryngologist, the entire concept has been viewed from otolaryngologist's angle. With the advent of nasal endoscope trans nasal access to orbit is becoming the order of the day. Major advantage being that external skin incision is avoided.
LUNISOLAR INVARIANT RELATIVE ORBITS
Walid Ali Rahoma
2013-01-01
The present study deal with constructing an analytical model within Hamiltonian formulation to design invariant relative orbits due to the perturbation of J2 and the lunisolar attraction. To fade the secular drift separation over the time between two neighboring orbits, two second order conditions that guarantee that drift are derived and enforced to be equal.
Reticulohistiocytoma of the Orbit
Weissman, Heather M.; Hayek, Brent R.; Grossniklaus, Hans E.
2015-01-01
Reticulohistiocytoma is a rare, benign histiocytic proliferation of the skin or soft tissue. While ocular involvement has been documented in the past, there have been no previously reported cases of reticulohistiocytoma of the orbit. In this report, the authors describe a reticulohistiocytoma of the orbit in a middle-aged woman. PMID:24807799
Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong
2016-06-01
Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm-1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.
Ludwig Boltzmann: Atomic genius
Energy Technology Data Exchange (ETDEWEB)
Cercignani, C. [Department of Mathematics, Politecnico di Milano (Italy)]. E-mail: carcer@mate.polimi.it
2006-09-15
On the centenary of the death of Ludwig Boltzmann, Carlo Cercignani examines the immense contributions of the man who pioneered our understanding of the atomic nature of matter. The man who first gave a convincing explanation of the irreversibility of the macroscopic world and the symmetry of the laws of physics was the Austrian physicist Ludwig Boltzmann, who tragically committed suicide 100 years ago this month. One of the key figures in the development of the atomic theory of matter, Boltzmann's fame will be forever linked to two fundamental contributions to science. The first was his interpretation of 'entropy' as a mathematically well-defined measure of the disorder of atoms. The second was his derivation of what is now known as the Boltzmann equation, which describes the statistical properties of a gas as made up of molecules. The equation, which described for the first time how a probability can evolve with time, allowed Boltzmann to explain why macroscopic phenomena are irreversible. The key point is that while microscopic objects like atoms can behave reversibly, we never see broken coffee cups reforming because it would involve a long series of highly improbable interactions - and not because it is forbidden by the laws of physics. (U.K.)
Quantum-Classical Connection for Hydrogen Atom-Like Systems
Syam, Debapriyo; Roy, Arup
2011-01-01
The Bohr-Sommerfeld quantum theory specifies the rules of quantization for circular and elliptical orbits for a one-electron hydrogen atom-like system. This article illustrates how a formula connecting the principal quantum number "n" and the length of the major axis of an elliptical orbit may be arrived at starting from the quantum…
Atom Trap Trace Analysis of Ca Isotopes
Energy Technology Data Exchange (ETDEWEB)
Hoekstra, S., E-mail: hoekstra@fhi-berlin.mgp.de [Fritz-Haber Institut der Max-Planck Gesellschaft (Germany); Mollema, A. K.; Morgenstern, R.; Willmann, L.; Wilschut, H. W.; Hoekstra, R. [Rijksuniversiteit Groningen, Atomic Physics, KVI (Netherlands)
2005-04-15
In our experiment we aim at the detection of the rarest, naturally occuring calcium isotope 41Ca by means of atom trap trace analysis. On basis of single-atom detection of 46Ca our present sensitivity for 41Ca is estimated to be 1 atom per hour at an abundance of 10-12. To reach a sensitivity at the level of natural abundance, which is 10-14, we need to reduce atomic beam losses. To achieve this, optical compression of the atomic beam is a promising option. We use Monte Carlo Simulations to demonstrate that optical compression of the atomic beam increases throughput of the atomic beam as well as isotope selectivity.
Energy Technology Data Exchange (ETDEWEB)
Anthemidis, Aristidis N., E-mail: anthemid@chem.auth.gr [Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University Thessaloniki, Thessaloniki 54124 (Greece); Ioannou, Kallirroy-Ioanna G. [Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University Thessaloniki, Thessaloniki 54124 (Greece)
2010-05-23
A novel on-line sequential injection (SI) dispersive liquid-liquid microextraction (DLLME) system coupled to electrothermal atomic absorption spectrometry (ETAAS) was developed for metal preconcentration in micro-scale, eliminating the laborious and time consuming procedure of phase separation with centrifugation. The potentials of the system were demonstrated for trace lead and cadmium determination in water samples. An appropriate disperser solution which contains the extraction solvent (xylene) and the chelating agent (ammonium pyrrolidine dithiocarbamate) in methanol is mixed on-line with the sample solution (aqueous phase), resulting thus, a cloudy solution, which is consisted of fine droplets of xylene, dispersed throughout the aqueous phase. Three procedures are taking place simultaneously: cloudy solution creation, analyte complex formation and extraction from aqueous phase into the fine droplets of xylene. Subsequently the droplets were retained on the hydrophobic surface of PTFE-turnings into the column. A part of 30 {mu}L of the eluent (methyl isobutyl ketone) was injected into furnace graphite for analyte atomization and quantification. The sampling frequency was 10 h{sup -1}, and the obtained enrichment factor was 80 for lead and 34 for cadmium. The detection limit was 10 ng L{sup -1} and 2 ng L{sup -1}, while the precision expressed as relative standard deviation (RSD) was 3.8% (at 0.5 {mu}g L{sup -1}) and 4.1% (at 0.03 {mu}g L{sup -1}) for lead and cadmium respectively. The proposed method was evaluated by analyzing certified reference materials and was applied to the analysis of natural waters.
Anthemidis, Aristidis N; Ioannou, Kallirroy-Ioanna G
2010-05-23
A novel on-line sequential injection (SI) dispersive liquid-liquid microextraction (DLLME) system coupled to electrothermal atomic absorption spectrometry (ETAAS) was developed for metal preconcentration in micro-scale, eliminating the laborious and time consuming procedure of phase separation with centrifugation. The potentials of the system were demonstrated for trace lead and cadmium determination in water samples. An appropriate disperser solution which contains the extraction solvent (xylene) and the chelating agent (ammonium pyrrolidine dithiocarbamate) in methanol is mixed on-line with the sample solution (aqueous phase), resulting thus, a cloudy solution, which is consisted of fine droplets of xylene, dispersed throughout the aqueous phase. Three procedures are taking place simultaneously: cloudy solution creation, analyte complex formation and extraction from aqueous phase into the fine droplets of xylene. Subsequently the droplets were retained on the hydrophobic surface of PTFE-turnings into the column. A part of 30 microL of the eluent (methyl isobutyl ketone) was injected into furnace graphite for analyte atomization and quantification. The sampling frequency was 10 h(-1), and the obtained enrichment factor was 80 for lead and 34 for cadmium. The detection limit was 10 ng L(-1) and 2 ng L(-1), while the precision expressed as relative standard deviation (RSD) was 3.8% (at 0.5 microg L(-1)) and 4.1% (at 0.03 microg L(-1)) for lead and cadmium respectively. The proposed method was evaluated by analyzing certified reference materials and was applied to the analysis of natural waters.
Atomic Oxygen Cleaning of Unpainted Plaster Sculptures
Banks, Bruce A.; Miller, Sharon K.
2017-01-01
Atomic oxygen erosion of polymers has been found to be a threat to spacecraft in low Earth orbit. As a result ground facilities have been developed to identify coatings to protect polymers such as used for solar array blankets. As a result of extensive laboratory testing, it was discovered that soot and other organic contamination on paintings could be readily removed by atomic oxygen interactions with minimal damage to the artwork. No method, other than dusting, has been found to be effective in the cleaning of unpainted plaster sculptures This presentation discusses the atomic oxygen interaction processes and how effective they are for cleaning soot damaged unpainted plaster sculptures.
Photoelectron spectroscopy of heavy atoms and molecules
Energy Technology Data Exchange (ETDEWEB)
White, M.G.
1979-07-01
The importance of relativistic interactions in the photoionization of heavy atoms and molecules has been investigated by the technique of photoelectron spectroscopy. In particular, experiments are reported which illustrate the effects of the spin-orbit interaction in the neutral ground state, final ionic states and continuum states of the photoionization target.
Atom Skimmers and Atom Lasers Utilizing Them
Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.
2005-01-01
Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.
Nori-Shargh, Davood; Mousavi, Seiedeh Negar; Kayi, Hakan
2014-05-01
Complete basis set CBS-4, hybrid-density functional theory (hybrid-DFT: B3LYP/6-311+G**) based methods and natural bond orbital (NBO) interpretations have been used to examine the contributions of the hyperconjugative, electrostatic, and steric effects on the conformational behaviors of trans-2,3-dihalo-1,4-diselenane [halo = F (1), Cl (2), Br (3)] and trans-2,5-dihalo-1,4-diselenane [halo = F (4), Cl (5), Br (6)]. Both levels of theory showed that the axial conformation stability, compared to its corresponding equatorial conformation, decreases from compounds 1 → 3 and 4 → 6. Based on the results obtained from the NBO analysis, there are significant anomeric effects for compounds 1-6. The anomeric effect associated with the electron delocalization is in favor of the axial conformation and increases from compounds 1 → 3 and 4 → 6. On the other hand, dipole moment differences between the axial and equatorial conformations [Δ(μ(eq)-μ(ax)] decrease from compounds 1 → 3. Although Δ(μ(eq)-μ(ax)) parameter decreases from compound 1 to compound 3, the dipole moment values of the axial conformations are smaller than those of their corresponding equatorial conformations. Therefore, the anomeric effect associated with the electron delocalizations (for halogen-C-Se segments) and the electrostatic model associated with the dipole-dipole interactions fail to account for the increase of the equatorial conformations stability on going from compound 1 to compound 3. Since there is no dipole moment for the axial and equatorial conformations of compounds 4-6, consequently, the conformational preferences in compounds 1-6 is in general dictated by the steric hindrance factor associated with the 1,3-syn-axial repulsions. Importantly, the CBS-4 results show that the entropy difference (∆S) between the equatorial axial conformations increases from compounds 1 → 3 and 4 → 6. This fact can be explained by the anomeric effect associated
Orbit Stabilization of Nanosat
Energy Technology Data Exchange (ETDEWEB)
JOHNSON,DAVID J.
1999-12-01
An algorithm is developed to control a pulsed {Delta}V thruster on a small satellite to allow it to fly in formation with a host satellite undergoing time dependent atmospheric drag deceleration. The algorithm uses four short thrusts per orbit to correct for differences in the average radii of the satellites due to differences in drag and one thrust to symmetrize the orbits. The radial difference between the orbits is the only input to the algorithm. The algorithm automatically stabilizes the orbits after ejection and includes provisions to allow azimuthal positional changes by modifying the drag compensation pulses. The algorithm gives radial and azimuthal deadbands of 50 cm and 3 m for a radial measurement accuracy of {+-} 5 cm and {+-} 60% period variation in the drag coefficient of the host. Approaches to further reduce the deadbands are described. The methodology of establishing a stable orbit after ejection is illustrated in an appendix. The results show the optimum ejection angle to minimize stabilization thrust is upward at 86{sup o} from the orbital velocity. At this angle the stabilization velocity that must be supplied by the thruster is half the ejection velocity. An ejection velocity of 0.02 m/sat 86{sup o} gives an azimuthal separation after ejection and orbit stabilization of 187 m. A description of liquid based gas thrusters suitable for the satellite control is included in an appendix.
HPAM: Hirshfeld partitioned atomic multipoles
Elking, Dennis M.; Perera, Lalith; Pedersen, Lee G.
2012-02-01
An implementation of the Hirshfeld (HD) and Hirshfeld-Iterated (HD-I) atomic charge density partitioning schemes is described. Atomic charges and atomic multipoles are calculated from the HD and HD-I atomic charge densities for arbitrary atomic multipole rank l on molecules of arbitrary shape and size. The HD and HD-I atomic charges/multipoles are tested by comparing molecular multipole moments and the electrostatic potential (ESP) surrounding a molecule with their reference ab initio values. In general, the HD-I atomic charges/multipoles are found to better reproduce ab initio electrostatic properties over HD atomic charges/multipoles. A systematic increase in precision for reproducing ab initio electrostatic properties is demonstrated by increasing the atomic multipole rank from l=0 (atomic charges) to l=4 (atomic hexadecapoles). Both HD and HD-I atomic multipoles up to rank l are shown to exactly reproduce ab initio molecular multipole moments of rank L for L⩽l. In addition, molecular dipole moments calculated by HD, HD-I, and ChelpG atomic charges only ( l=0) are compared with reference ab initio values. Significant errors in reproducing ab initio molecular dipole moments are found if only HD or HD-I atomic charges used. Program summaryProgram title: HPAM Catalogue identifier: AEKP_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKP_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License v2 No. of lines in distributed program, including test data, etc.: 500 809 No. of bytes in distributed program, including test data, etc.: 13 424 494 Distribution format: tar.gz Programming language: C Computer: Any Operating system: Linux RAM: Typically, a few hundred megabytes Classification: 16.13 External routines: The program requires 'formatted checkpoint' files obtained from the Gaussian 03 or Gaussian 09 quantum chemistry program. Nature of problem: An ab initio
Quark Orbital Angular Momentum
Directory of Open Access Journals (Sweden)
Burkardt Matthias
2015-01-01
Full Text Available Definitions of orbital angular momentum based on Wigner distributions are used as a framework to discuss the connection between the Ji definition of the quark orbital angular momentum and that of Jaffe and Manohar. We find that the difference between these two definitions can be interpreted as the change in the quark orbital angular momentum as it leaves the target in a DIS experiment. The mechanism responsible for that change is similar to the mechanism that causes transverse single-spin asymmetries in semi-inclusive deep-inelastic scattering.
Wijnands, Thijs; Srinivasan, B
2002-01-01
Orbit correction consists in adjusting the strengths of the corrector magnets to make the measured beam position match a predefined reference. In the LHC, this involves around 2000 sensors and more than 1000 actuators that are distributed along both rings. The orbit correction scheme should be able to compensate for very slow orbit drifts in the range of a 10-2 Hz but also for fast motions (vibrations) up to 1 Hz. In this paper we investigate correction schemes that could be used in either case. The choice of design formalisms is based on the experience we gained with the SPS and the LEP.
Teaching of Social and Philosophical Background to Atomic Theory.
Luhl, Jutta
1992-01-01
The history of atomic theory is outlined from earliest times up to the orbital model and describes a corresponding teaching method. The historical part of the paper emphasizes social and philosophical aspects in the development of atomic theory. The second part of the paper describes a method for teaching this material at the secondary level.…
A Variational Monte Carlo Approach to Atomic Structure
Davis, Stephen L.
2007-01-01
The practicality and usefulness of variational Monte Carlo calculations to atomic structure are demonstrated. It is found to succeed in quantitatively illustrating electron shielding, effective nuclear charge, l-dependence of the orbital energies, and singlet-tripetenergy splitting and ionization energy trends in atomic structure theory.
Dynamical processes in atomic and molecular physics
Ogurtsov, Gennadi
2012-01-01
Atomic and molecular physics underlie a basis for our knowledge of fundamental processes in nature and technology and in such applications as solid state physics, chemistry and biology. In recent years, atomic and molecular physics has undergone a revolutionary change due to great achievements in computing and experimental techniques. As a result, it has become possible to obtain information both on atomic and molecular characteristics and on dynamics of atomic and molecular processes. This e-book highlights the present state of investigations in the field of atomic and molecular physics. Rece
Correlation effects and orbital magnetism of Co clusters
Di Marco, L Peters I; Şaşıoğlu, E; Altun, A; Rossen, S; Friedrich, C; Blügel, S; Katsnelson, M I; Kirilyuk, A; Eriksson, O
2016-01-01
Recent experiments on isolated Co clusters have shown huge orbital magnetic moments in comparison with their bulk and surface counterparts. These clusters hence provide the unique possibility to study the evolution of the orbital magnetic moment with respect to the cluster size and how competing interactions contribute to the quenching of orbital magnetism. We investigate here different theoretical methods to calculate the spin and orbital moments of Co clusters, and assess the performances of the methods in comparison with experiments. It is shown that density functional theory in conventional local density or generalized gradient approximations, or even with a hybrid functional, severely underestimates the orbital moment. As natural extensions/corrections we considered the orbital polarization correction, the LDA+U approximation as well as the LDA+DMFT method. Our theory shows that of the considered methods, only the LDA+DMFT method provides orbital moments in agreement with experiment, thus emphasizing the...
Deciphering chemical order/disorder and material properties at the single-atom level.
Yang, Yongsoo; Chen, Chien-Chun; Scott, M C; Ophus, Colin; Xu, Rui; Pryor, Alan; Wu, Li; Sun, Fan; Theis, Wolfgang; Zhou, Jihan; Eisenbach, Markus; Kent, Paul R C; Sabirianov, Renat F; Zeng, Hao; Ercius, Peter; Miao, Jianwei
2017-02-01
Perfect crystals are rare in nature. Real materials often contain crystal defects and chemical order/disorder such as grain boundaries, dislocations, interfaces, surface reconstructions and point defects. Such disruption in periodicity strongly affects material properties and functionality. Despite rapid development of quantitative material characterization methods, correlating three-dimensional (3D) atomic arrangements of chemical order/disorder and crystal defects with material properties remains a challenge. On a parallel front, quantum mechanics calculations such as density functional theory (DFT) have progressed from the modelling of ideal bulk systems to modelling 'real' materials with dopants, dislocations, grain boundaries and interfaces; but these calculations rely heavily on average atomic models extracted from crystallography. To improve the predictive power of first-principles calculations, there is a pressing need to use atomic coordinates of real systems beyond average crystallographic measurements. Here we determine the 3D coordinates of 6,569 iron and 16,627 platinum atoms in an iron-platinum nanoparticle, and correlate chemical order/disorder and crystal defects with material properties at the single-atom level. We identify rich structural variety with unprecedented 3D detail including atomic composition, grain boundaries, anti-phase boundaries, anti-site point defects and swap defects. We show that the experimentally measured coordinates and chemical species with 22 picometre precision can be used as direct input for DFT calculations of material properties such as atomic spin and orbital magnetic moments and local magnetocrystalline anisotropy. This work combines 3D atomic structure determination of crystal defects with DFT calculations, which is expected to advance our understanding of structure-property relationships at the fundamental level.
Deciphering chemical order/disorder and material properties at the single-atom level
Yang, Yongsoo; Chen, Chien-Chun; Scott, M. C.; Ophus, Colin; Xu, Rui; Pryor, Alan; Wu, Li; Sun, Fan; Theis, Wolfgang; Zhou, Jihan; Eisenbach, Markus; Kent, Paul R. C.; Sabirianov, Renat F.; Zeng, Hao; Ercius, Peter; Miao, Jianwei
2017-02-01
Perfect crystals are rare in nature. Real materials often contain crystal defects and chemical order/disorder such as grain boundaries, dislocations, interfaces, surface reconstructions and point defects. Such disruption in periodicity strongly affects material properties and functionality. Despite rapid development of quantitative material characterization methods, correlating three-dimensional (3D) atomic arrangements of chemical order/disorder and crystal defects with material properties remains a challenge. On a parallel front, quantum mechanics calculations such as density functional theory (DFT) have progressed from the modelling of ideal bulk systems to modelling ‘real’ materials with dopants, dislocations, grain boundaries and interfaces; but these calculations rely heavily on average atomic models extracted from crystallography. To improve the predictive power of first-principles calculations, there is a pressing need to use atomic coordinates of real systems beyond average crystallographic measurements. Here we determine the 3D coordinates of 6,569 iron and 16,627 platinum atoms in an iron-platinum nanoparticle, and correlate chemical order/disorder and crystal defects with material properties at the single-atom level. We identify rich structural variety with unprecedented 3D detail including atomic composition, grain boundaries, anti-phase boundaries, anti-site point defects and swap defects. We show that the experimentally measured coordinates and chemical species with 22 picometre precision can be used as direct input for DFT calculations of material properties such as atomic spin and orbital magnetic moments and local magnetocrystalline anisotropy. This work combines 3D atomic structure determination of crystal defects with DFT calculations, which is expected to advance our understanding of structure–property relationships at the fundamental level.
Chan, Garnet Kin-Lic; Van Voorhis, Troy
2005-05-22
We describe the theory and implementation of two extensions to the density-matrix renormalization-group (DMRG) algorithm in quantum chemistry: (i) to work with an underlying nonorthogonal one-particle basis (using a biorthogonal formulation) and (ii) to use non-Hermitian and complex operators and complex wave functions, which occur naturally in biorthogonal formulations. Using these developments, we carry out ground-state calculations on ethene, butadiene, and hexatriene, in a polarized atomic-orbital basis. The description of correlation in these systems using a localized nonorthogonal basis is improved over molecular-orbital DMRG calculations, and comparable to or better than coupled-cluster calculations, although we encountered numerical problems associated with non-Hermiticity. We believe that the non-Hermitian DMRG algorithm may further become useful in conjunction with other non-Hermitian Hamiltonians, for example, similarity-transformed coupled-cluster Hamiltonians.
Schwindt, Peter [Albuquerque, NM; Johnson, Cort N [Albuquerque, NM
2012-07-03
An atomic magnetometer is disclosed which uses a pump light beam at a D1 or D2 transition of an alkali metal vapor to magnetically polarize the vapor in a heated cell, and a probe light beam at a different D2 or D1 transition to sense the magnetic field via a polarization rotation of the probe light beam. The pump and probe light beams are both directed along substantially the same optical path through an optical waveplate and through the heated cell to an optical filter which blocks the pump light beam while transmitting the probe light beam to one or more photodetectors which generate electrical signals to sense the magnetic field. The optical waveplate functions as a quarter waveplate to circularly polarize the pump light beam, and as a half waveplate to maintain the probe light beam linearly polarized.
AC Zeeman potentials for atom chip-based ultracold atoms
Fancher, Charles; Pyle, Andrew; Ziltz, Austin; Aubin, Seth
2015-05-01
We present experimental and theoretical progress on using the AC Zeeman force produced by microwave magnetic near-fields from an atom chip to manipulate and eventually trap ultracold atoms. These AC Zeeman potentials are inherently spin-dependent and can be used to apply qualitatively different potentials to different spin states simultaneously. Furthermore, AC Zeeman traps are compatible with the large DC magnetic fields necessary for accessing Feshbach resonances. Applications include spin-dependent trapped atom interferometry and experiments in 1D many-body physics. Initial experiments and results are geared towards observing the bipolar detuning-dependent nature of the AC Zeeman force at 6.8 GHz with ultracold 87Rb atoms trapped in the vicinity of an atom chip. Experimental work is also underway towards working with potassium isotopes at frequencies of 1 GHz and below. Theoretical work is focused on atom chip designs for AC Zeeman traps produced by magnetic near-fields, while also incorporating the effect of the related electric near-fields. Electromagnetic simulations of atom chip circuits are used for mapping microwave propagation in on-chip transmission line structures, accounting for the skin effect, and guiding impedance matching.
Imai, Kazue; Hayashi, Tomonori; Yamaoka, Mika; Kajimura, Junko; Yoshida, Kengo; Kusunoki, Yoichiro; Nakachi, Kei
2012-06-01
NKG2D is a primary activating receptor that triggers cell-mediated cytotoxicity in NK cells against tumor and virus-infected cells. We previously identified the NKG2D haplotypes in the natural killer gene complex region on chromosome 12p. Two major haplotype alleles, LNK1 and HNK1, were closely related to low and high natural cytotoxic activity phenotypes, respectively. Furthermore, the haplotype of HNK1/HNK1 has revealed a decreased risk of cancer compared with LNK1/LNK1. In the present study, using flow cytometry, we evaluated the functional effects of NKG2D haplotypes and five htSNPs in terms of the cell-surface expression of NKG2D protein on NK and CD8 T cells of peripheral blood among 732 atomic-bomb survivors. NKG2D expression on NK cells showed significant increases, in the order of LNK1/LNK1, LNK1/HNK1 and HNK1/HNK1 haplotypes (p for trend=0.003), or with major homozygous, heterozygous, and minor homozygous genotypes for individual htSNPs (p for trend=0.02-0.003). The same trend was observed for NKG2D expression on CD8 T cells. Our findings indicate that the NKG2D haplotypes are associated with the expression levels of NKG2D protein on NK and CD8 T cells, resulting in inter-individual variations in human cytotoxic response. Copyright © 2012 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Shereen Aiyub
2013-01-01
Full Text Available We present a case of mature congenital orbital teratoma managed with lid-sparing exenteration and dermis fat graft. This is a case report on the management of congenital orbital teratoma. A full-term baby was born in Fiji with prolapsed right globe which was surrounded by a nonpulsatile, cystic mass. Clinical and imaging features were consistent with congenital orbital teratoma. Due to limited surgical expertise, the patient was transferred to Adelaide, Australia for further management. The patient underwent a lid-sparing exenteration with frozen section control of the apical margin. A dermis fat graft from the groin was placed beneath the lid skin to provide volume. Histopathology revealed mature tissues from each of the three germ cell layers which confirmed the diagnosis of mature teratoma. We describe the successful use of demis fat graft in socket reconstruction following lid-sparing exenteration for congenital orbital teratoma.
Directory of Open Access Journals (Sweden)
Mijajlović, Ž.
2008-12-01
Full Text Available We discuss cometary orbits from the standpoint of Nonstandard (Leibnitz analysis, a relatively new branch of mathematics. In particular, we consider parabolic cometary paths. It appears that, in a sense, every parabola is an ellipse.
High Atom Number in Microsized Atom Traps
2015-12-14
Final Performance Report on ONR Grant N00014-12-1-0608 High atom number in microsized atom traps for the period 15 May 2012 through 14 September...TYPE Final Technical Report 3. DATES COVERED (From - To) 05/15/2012-09/14/2012 4. TITLE AND SUBTITLE High atom number in microsized atom traps...forces for implementing a small-footprint, large-number atom -chip instrument. Bichromatic forces rely on absorption and stimulated emission to produce
Detecting Neutral Atoms on an Atom Chip
Wilzbach, M.; Haase, A.; Schwarz, M; Heine, D.; Wicker, K.; Liu, X; Brenner, K. -H.; Groth, S.; Fernholz, Th.; Hessmo, B.; Schmiedmayer, J.
2006-01-01
Detecting single atoms (qubits) is a key requirement for implementing quantum information processing on an atom chip. The detector should ideally be integrated on the chip. Here we present and compare different methods capable of detecting neutral atoms on an atom chip. After a short introduction to fluorescence and absorption detection we discuss cavity enhanced detection of single atoms. In particular we concentrate on optical fiber based detectors such as fiber cavities and tapered fiber d...
VIBRATIONAL RAMAN OPTICAL-ACTIVITY CALCULATIONS USING LONDON ATOMIC ORBITALS
DEFF Research Database (Denmark)
Helgaker, T.; Ruud, K.; Bak, Keld L.
1994-01-01
Ab initio calculations of Raman differential intensities are presented at the self-consistent field (SCF) level of theory. The electric dipole-electric dipole, electric dipole-magnetic dipole and electric dipole-electric quadrupole polarizability tensors are calculated at the frequency of the inc...
Orbital interactions in chemistry
Albright, Thomas A; Whangbo, Myung-Hwan
2013-01-01
Explains the underlying structure that unites all disciplines in chemistry Now in its second edition, this book explores organic, organometallic, inorganic, solid state, and materials chemistry, demonstrating how common molecular orbital situations arise throughout the whole chemical spectrum. The authors explore the relationships that enable readers to grasp the theory that underlies and connects traditional fields of study within chemistry, thereby providing a conceptual framework with which to think about chemical structure and reactivity problems. Orbital Interactions
Visions of Atomic Scale Tomography
Energy Technology Data Exchange (ETDEWEB)
Kelly, T. F. [Cameca Instruments; Miller, Michael K [ORNL; Rajan, Krishna [Iowa State University; Ringer, S. P. [University of Sydney, Australia
2012-01-01
A microscope, by definition, provides structural and analytical information about objects that are too small to see with the unaided eye. From the very first microscope, efforts to improve its capabilities and push them to ever-finer length scales have been pursued. In this context, it would seem that the concept of an ultimate microscope would have received much attention by now; but has it really ever been defined? Human knowledge extends to structures on a scale much finer than atoms, so it might seem that a proton-scale microscope or a quark-scale microscope would be the ultimate. However, we argue that an atomic-scale microscope is the ultimate for the following reason: the smallest building block for either synthetic structures or natural structures is the atom. Indeed, humans and nature both engineer structures with atoms, not quarks. So far as we know, all building blocks (atoms) of a given type are identical; it is the assembly of the building blocks that makes a useful structure. Thus, would a microscope that determines the position and identity of every atom in a structure with high precision and for large volumes be the ultimate microscope? We argue, yes. In this article, we consider how it could be built, and we ponder the answer to the equally important follow-on questions: who would care if it is built, and what could be achieved with it?