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31st IEEE International Parallel and Distributed Processing Symposium Workshops (IPDPS)

作者： Shan, Hongzhang Williams, Samuel Johnson, Calvin McElvain, Kenneth Lawrence Berkeley Natl Lab Computat Res Div Berkeley CA 94720 USA San Diego State Univ Dept Phys San Diego CA 92182 USA Univ Calif Berkeley Dept Phys Berkeley CA 94720 USA

ISBN: (纸本)9780769561493

The configuration interaction (CI) method has been widely used to solve the non-relativistic many-body Schrodinger equation. One great challenge to implementing it efficiently on manycore architectures is its immense memory and data movement requirements. To address this issue, within each node, we exploit a hybrid MPI+OpenMP programming model in lieu of the traditional flat MPI programming model. In this paper, we develop optimizations that partition the workloads among OpenMP threads based on data locality, which is essential in ensuring applications with complex data access patterns scale well on manycore architectures. The new algorithm scales to 256 threads on the 64-core Intel Knights Landing (KNL) manycore processor and 24 threads on dual-socket Ivy Bridge (Xeon) nodes. Compared with the original implementation, the performance has been improved by up to 7x on the Knights Landing processor and 3x on the dual-socket Ivy Bridge node.

关键词： bigstick configuration-interaction method hybrid programming model Ivy bridge knights landing locality-based threading algorithm Manycore MPI multithreading OpenMP

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Relativistic Calculations of the Chemical Properties of the Superheavy Element with Z=119 and Its Homologues

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OPTICS AND SPECTROSCOPY 2021年第9期129卷 1038-1044页

作者： Tupitsyn, I. I. Malyshev, A. V. Glazov, D. A. Kaygorodov, M. Y. Kozhedub, Y. S. Savelyev, I. M. Shabaev, V. M. St Petersburg State Univ St Petersburg 199034 Russia

Relativistic calculations of the electronic structure of the superheavy element of the eighth period-eka-francium (Z = 119) and its homologues, which form the group of alkali metals, are performed in the framework of the configuration-interaction method and many-body perturbation theory using the basis of the Dirac-Fock-Sturm orbitals (DFS). The obtained values of the ionization potentials, electron affinities, and root-mean-square radii are compared with the corresponding values calculated within the nonrelativistic approximation. A comparison with the available experimental data and the results of previous theoretical calculations is given as well. The analysis of the obtained results indicates a significant influence of the relativistic effects for the francium and eka-francium atoms, which leads to a violation of the monotonic behaviour of the listed above chemical properties as a function of the alkaline-element atomic number. In addition, the quantum electrodynamics corrections to the ionization potentials are evaluated by employing the model Lamb-shift operator (QEDMOD).

关键词： superheavy elements alkali metals relativistic effects correlation effects quantum electrodynamics corrections configuration-interaction method ionization potentials electron affinities

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Black-Body Radiation Shifts and Theoretical Contributions to Atomic Clock Research

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 2010年第1期57卷 94-105页

作者： Safronova, Marianna S. Jiang, Dansha Arora, Bindiya Clark, Charles W. Kozlov, Mikhail G. Safronova, Ulyana I. Johnson, Walter R. Univ Delaware Dept Phys & Astron Newark DE 19716 USA Natl Inst Stand & Technol Div Electron & Opt Phys Gaithersburg MD 20899 USA Petersburg Nucl Phys Inst Neutron Res Div Gatchina Russia Univ Nevada Dept Phys Reno NV 89557 USA Univ Notre Dame Dept Phys Notre Dame IN 46556 USA

A review of theoretical calculations of black-body radiation (BBR) shifts in various systems of interest to atomic clock research is presented. Calculations for monovalent systems, such as Ca+, Sr+, and Rb are carried out using a relativistic all-order single-double method, where all single and double excitations of the Dirac-Fock wave function are included to all orders of perturbation theory. A recently developed method for accurate calculations of BBR shifts in divalent atoms such as Sr is discussed. This approach combines the relativistic all-order method and the configuration interaction method. The evaluation of uncertainties in theoretical values of BBR shifts is discussed in detail.

关键词： Dirac-Fock calculations atomic clocks blackbody radiation calcium configuration interactions frequency measurement perturbation theory positive ions rubidium spectral line shift strontium wave functions BBR shift Ca+ Dirac-Fock wave function Rb Sr Sr+ atomic clock research black body radiation shift configuration-interaction method divalent atoms double excitations monovalent systems relativistic all order single-double method single excitations spectral shift Atomic clocks WAVE FUNCTIONS Blackbody radiation burnt beyond repair Rubidium positive ions perturbation theory configuration interactions frequency measurement Dirac-Fock calculations

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Ab initio study of the KrH⁺ photodissociation

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JOURNAL OF CHEMICAL PHYSICS 2008年第23期128卷 234308-1-234308-7页

作者： Alekseyev, Aleksey B. Buenker, Robert J. Liebermann, Heinz-Peter Berg Univ Wuppertal Fachbereich C D-42097 Wuppertal Germany

The multireference spin-orbit configuration interaction method is employed to calculate potential energy curves for the ground and low-lying excited states of the KrH+ cation. For the first time, the spin-orbit interaction is taken into account and electric dipole moments are computed for transitions to the states responsible for the first absorption continuum (A band) of KrH+. On this basis, the partial and total absorption spectra in this energy range are obtained. It is shown that the A-band absorption is dominated by the parallel A (1)Sigma(+)<- X (1)Sigma(+) transition. In the low-energy part of the band (< 83x10(3) cm(-1)) the absorption is mainly caused by the spin-forbidden b (3)Pi(+)(0)<- X (1)Sigma(+) excitation, while perpendicular transitions to the B (1)Pi and b (3)Pi(1) states are significantly weaker. The branching ratio Gamma for the photodissociation products is calculated and it is shown to increase smoothly from 0 in the red tail of the band to 1 at E >= 90x10(3) cm(-1). The latter value corresponds to the exclusive formation of the spin-excited Kr+(P-2(1/2)) ions, which may be used to obtain laser generation on the Kr+(P-2(1/2)-P-2(3/2)) transition. (C) 2008 American Institute of Physics.

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Charge transfer and excitation in H++CH3 collisions below 10keV

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Physical Review A 2008年第1期78卷 012708-012708页

作者： Masatoshi Nagao Ken-nosuke Hida Mineo Kimura Sachchida N. Rai Heinz-Peter Liebermann Robert J. Buenker Hiroya Suno Phillip C. Stancil Department of Physics and Astronomy and the Center for Simulational Physics The University of Georgia Athens Georgia 30602 USA

Charge transfer and electronic excitation in collisions of H+ ions with CH3 from a few tens of eV up to 10keV are theoretically investigated. The adiabatic potential energy curves and corresponding wave functions are calculated by using the multireference single- and double-excitation configuration interaction method, and the scattering dynamics is studied based on the semiclassical impact parameter molecular-orbital close-coupling approach. Charge-transfer cross sections are found to be large and rather energy-dependent over the entire energy region studied. Electronic excitation is also energy-dependent with a sharp increase from below 10−17to10−16cm2. Most of the molecular products produced through charge transfer or excitation are known to be unstable and undergo fragmentation producing various hydrocarbon radical species. Hence, identification of fragmented species and their production mechanism are important for spectroscopic analysis.

关键词： configuration-interaction method CI CALCULATIONS ENERGY EXTRAPOLATION INELASTIC PROCESSES ELECTRONS REGIME STATES

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Solving the Schrodinger and Dirac equations of hydrogen molecular ion accurately by the free iterative complement interaction method

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JOURNAL OF CHEMICAL PHYSICS 2008年第12期128卷 124103-1-124103-1页

作者： Ishikawa, Atsushi Nakashima, Hiroyuki Nakatsuji, Hiroshi Quantum Chem Res Inst Nishikyo Ku Kyoto 6158245 Japan Kyoto Univ Grad Sch Engn Dept Synthet Chem & Biol Chem Nishikyo Ku Kyoto 6158510 Japan

The nonrelativistic Schrodinger equation and the relativistic four-component Dirac equation of H-2(+) were solved accurately in an analytical expansion form by the free iterative complement interaction (ICI) method combined with the variational principle. In the nonrelativistic case, we compared the free ICI wave function with the so-called "exact" wave function as two different expansions converging to the unique exact wave function and found that the free ICI method is much more efficient than the exact method. In the relativistic case, we first used the inverse Hamiltonian to guarantee Ritz-type variational principle and obtained accurate result. We also showed that the ordinary variational calculation also gives a nice convergence when the g function is appropriately chosen, since then the free ICI calculation guarantees a correct relationship between the large and small components of each adjacent order, which we call ICI balance. This is the first application of the relativistic free ICI method to molecule. We calculated both ground and excited states in good convergence, and not only the upper bound but also the lower bound of the ground-state energy. The error bound analysis has assured that the present result is highly accurate. (c) 2008 American Institute of Physics.

关键词： EXACT WAVE-FUNCTION BORN-OPPENHEIMER SEPARATION configuration-interaction method FULLY NUMERICAL-SOLUTIONS ONE-ELECTRON MOLECULES FINITE-ELEMENT-method 3-PARTICLE SYSTEMS RELATIVISTIC CALCULATIONS ENERGY H2

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Solving the electron-nuclear Schrodinger equation of helium atom and its isoelectronic ions with the free iterative-complement-interaction method

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JOURNAL OF CHEMICAL PHYSICS 2008年第15期128卷 54107-1-54107-7页

作者： Nakashima, Hiroyuki Nakatsuji, Hiroshi CREST JST Quantum Chem Res Inst Nishikyo Ku Kyoto 6158245 Japan

Our previous paper [J. Chem. Phys. 127, 224104 (2007) ] revealed that the Schrodinger equation in the fixed-nucleus approximation could be very accurately solved for helium atom and its isoelectronic ions (Z=1-10) with the free iterative-complement-interaction (ICI) method combined with the variation principle. In this report, the quantum effect of nuclear motion has further been variationally considered by the free ICI formalism for the Hamiltonian including mass-polarization operator. We obtained - 2.903 304 557 729 580 294 733 816 943 892 697 752 659 273 965 a. u. for helium atom, which is over 40 digits in accuracy, similarly to the previous result for the fixed-nucleus level. Similar accuracy was also obtained for the helium isoelectronic ions. The present results may be regarded to be the nonrelativistic limits. We have further analyzed the physics of the free ICI wave function by applying it to an imaginary atom called "eneon," [e(-) e(10+) e-](8+), in which both of the quantum effect of nuclear motion and the three-particle collisions are differently important from the helium and its isoelectronic ions. This revealed the accurate physics automatically generated by the free ICI formalism. (C) 2008 American Institute of Physics.

关键词： EXACT WAVE-FUNCTION configuration-interaction method GROUND-STATE EXPONENTIAL ANSATZ

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Role of the electric dipole moment in positron binding to the ground and excited states of the BeO molecule

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JOURNAL OF CHEMICAL PHYSICS 2007年第10期126卷 4305-1-4305-7页

作者： Buenker, Robert J. Liebermann, Heinz-Peter Pichl, Lukas Tachikawa, Masanori Kimura, Mineo Berg Univ Wuppertal Fachbereich Math & Nat Wissensch C D-42119 Wuppertal Germany Int Christian Univ Div Nat Sci Mitaka Tokyo 1818585 Japan Yokohama City Univ Grad Sch Integrated Sci Quantum Chem Div Yokohama Kanagawa 2360027 Japan Kyushu Univ Grad Sch Sci Fukuoka 8158611 Japan

Self-consistent-field and multireference single- and double-excitation configuration interaction (CI) calculations have been carried out for various electronic states of the beryllium oxide molecule and their positron-attached counterparts. Particular emphasis is placed on the correlation between the polarity of a given BeO state and the magnitude of the positron binding energy as the internuclear distance is varied. Potential curves are computed for all BeO states that correlate with the first three atomic limits for this system and good agreement is found between the experimental and calculated spectroscopic constants in all cases. The present level of CI treatment is known to underestimate the positron affinities of atoms by at least several tenths of an eV, and this fact needs to be taken into account in evaluating the results for positron binding to molecules. The lowest BeO excited states ((3,1)Pi) are not found to bind with a positron in the Franck-Condon region due to their comparatively small dipole moments caused by O to Be charge transfer relative to the X (1)Sigma(+) ground state, which in turn does have a fairly sizeable positron affinity. The situation changes significantly as dissociation proceeds, however, with both (4,2)Pi and (2)Sigma(+) positronic states lying several tenths of an eV lower than their neutral counterparts over a broad range of internuclear distance.

关键词： configuration-interaction method ALKALI HYDRIDES COMPLEXES CI SYSTEMS ATOMS

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State-specific multireference complete-active-space coupled-cluster approach versus other quantum chemical methods:: dissociation of the N₂ molecule

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MOLECULAR PHYSICS 2007年第10期105卷 1335-1357页

作者： Lyakh, Dmitry I. Ivanov, Vladimir V. Adamowicz, Ludwik Univ Arizona Dept Chem Tucson AZ 85721 USA Kharkov Natl Univ Dept Chem Kharkov Ukraine

A comprehensive comparison of different quantum-chemical methods applied to calculate the N-2 ground state potential energy curve is presented. In the comparison we highlight the multireference state-specific (MRSS) coupled- cluster (CC) approach with the complete-activespace (CAS) reference and with single and double excitations from all reference determinants in the CC operator developed in our group. The method is called CASCCSD. The energy and amplitude equations for the method and the corresponding computer code have been generated using a computerized automative procedure that in the present work was extended to produce a parallel computer code. The complete CASCCSD wave function for N-2 includes some selected eight-fold excitations in the CC operator. An analysis of the wave function estimates the importance of those excitations at large internuclear separations.

关键词： SINGLE-REFERENCE FORMALISM POTENTIAL-ENERGY SURFACES configuration-interaction method MATRIX RENORMALIZATION-GROUP ELECTRONIC-STRUCTURE methodS BODYPERTURBATION-THEORY GAUSSIAN BASIS FUNCTIONS ATOMIC BASIS SETS FIRST-ROW ATOMS EXCITED-STATES

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Low-lying quartet electronic states of nitrogen dioxide

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JOURNAL OF CHEMICAL PHYSICS 2007年第17期127卷 174303-1-174303-1页

作者： Bera, Partha P. Yamaguchi, Yukio Schaefer, Henry F., III Univ Georgia Ctr Computat Chem Athens GA 30602 USA

The environmentally active molecule nitrogen dioxide (NO2) has been systematically studied using high level theoretical methods. The electronic ground state and the low-lying quartet states of NO2 have been investigated. Single reference restricted open-shell self-consistent field (SCF), complete active space SCF (CASSCF), spin-restricted (R) and spin-unrestricted (U) configuration interaction with single and double excitations (CISD), coupled cluster with single and double excitations (CCSD), CCSD with perturbative triple excitations [CCSD(T)], and internally contracted multireference configuration interaction (ICMRCI) methods along with Dunning's correlation consistent polarized valence cc-pVXZ and augmented cc-pVXZ (where X=T,Q,5) basis sets were used in this research. At the aug-cc-pV5Z/UCCSD(T) level the classical adiabatic excitation energies (T-e values) of the three lowest-lying quartet excited states were predicted to be 83.3 kcal/mol (3.61 eV, 29 200 cm(-1)) for the (a) over tilde (4)A(2) state, 93.3 kcal/mol (4.05 eV, 32 600 cm(-1)) for the (b) over tilde B-4(2) state, and 100.8 kcal/mol (4.37 eV, 35 300 cm(-1)) for the (b) over tilde (4)A(1) state. The quantum mechanical excitation energies (T-0 values) were determined to be 81.6 kcal/mol (3.54 eV, 28 500 cm(-1)) for the (a) over tilde (4)A(2) state and 90.7 kcal/mol (3.93 eV, 31 700 cm(-1)) for the (b) over tilde B-4(2) state. The lowest quartet linear Renner-Teller (4)Pi state gives rise to the (a) over tilde (4)A(2) state with 112.8 degrees and the (b) over tilde B-4(2) state with 124.4 degrees angle(ONO) bond angles upon bending. The (b) over tilde state shows some peculiar behavior. Although CASSCF, RCISD, UCISD, RCCSD, UCCSD, and RCCSD(T) methods predicted the presence of a C-s equilibrium geometry (a double minimum (4)A(') state), SCF, UCCSD(T), and ICMRCI wave functions predicted the C-2v structure for the (b) over tilde B-4(2) state. The importance of both dynamical and nondynamical correlation

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