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Ernest R. Davidson

Other affiliations: Lawrence Livermore National Laboratory, Indiana University, IBM  ...read more
Bio: Ernest R. Davidson is an academic researcher from University of Washington. The author has contributed to research in topics: Configuration interaction & Ab initio. The author has an hindex of 78, co-authored 480 publications receiving 30616 citations. Previous affiliations of Ernest R. Davidson include Lawrence Livermore National Laboratory & Indiana University.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the restrictions placed on the ground state potential energy of a diatomic molecule by the inequality d2(R2E)/dR2<0 are discussed, which leads to rather weak smoothness conditions on E(R).
Abstract: The restrictions placed on the ground‐state potential energy of a diatomic molecule by the inequality d2(R2E)/dR2<0 are discussed. This leads to rather weak smoothness conditions on E(R).

17 citations

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TL;DR: In this article, a correction to quasi-degenerate variational perturbation theory is proposed that is similar to the average coupled pair functional method, which is shown to give improved results when applied to small model systems.
Abstract: A correction to quasi-degenerate variational perturbation theory is proposed that is similar to the average coupled pair functional method. The correction is shown to lack solid theoretical justification when applied to importance-selected multireference calculations and to systems with irreducible interpair contributions to the correlation energy. The method is shown to give improved results when applied to small model systems.

17 citations

Journal ArticleDOI
TL;DR: In this paper, the intrapair and interpair electron correlation energies of the radical NaCl2 were reported and the total interpair correlation energy dominated, and the 6-311+G* basis set recovered only 32% of the total estimated correlation energy and 44% of this amount came from the core electrons.
Abstract: This article reports the intrapair and interpair electron correlation energies of the radical NaCl2. The total interpair correlation energy dominates. Hence, the interpair electron correlation energy must be considered in building models for correcting computed correlation energies. The 6-311+G* basis set recovers only 32% of the total estimated correlation energy and 44% of this amount came from the core electrons. © 1995 John Wiley & Sons, Inc.

17 citations

Journal ArticleDOI
TL;DR: In this article, the (e,2e) cross-section for transitions to the n − 2 final state of He+ and the 2 − 2sσg, final states of H2 have been measured relative to the cross-sections for the respective ground state ions, using a highly sensitive momentum dispersive multichannel electron momentum spectrometer.
Abstract: The (e,2e) cross-section for transitions to the n = 2 final state of He+ and the 2sσg, final state of have been measured, relative to the cross-section for the transitions to the respective ground state ions, using a highly sensitive momentum dispersive multichannel electron momentum spectrometer. The experimental results for He are compared with plane wave impulse approximation (PWIA) cross-section calculations carried out using two previously published GI wavefunctions and also with two cross-section calculations based on explicitly correlated wavefunctions with energy errors of less than 10 nHartree. The H2 results are compared with calculations by J.W. Liu and V.H. Smith Jr. (Phys. Rev. A, 31, 3003 (1985); erratum: Phys. Rev. A, 39, 3703 (1989)). For both He and H2, significant differences are observed between the measured relative cross-sections and those calculated using the PWIA. While the measurements for He differ from previous work, the results for H2 are consistent with some earlier measurements.

17 citations

Journal ArticleDOI
TL;DR: In this paper, a qualitative analysis suggests that two different electron counts, 20 and 22, are possible for the butterfly structures of these systems, and detailed ab initio computations substantiate this analysis and show that the 20-electron butterfly structure becomes increasingly favored over the tetrahedral one when the 2 atoms have increasing electronegativity difference.
Abstract: Ab initio and extended Hueckel calculations have been used to discuss the bonding scheme in X{sub 2}Y{sub 2} neutral and ionic main group clusters. A qualitative analysis suggests that two different electron counts, 20 and 22, are possible for the butterfly structures of these systems. This results from two orbital crossings in the correlation diagram for the tetrahedral (T{sub d}) {yields} butterfly (C{sub 2{nu}}) {yields} square-planar (D{sub 2h}) transformation. Detailed ab initio computations substantiate this analysis and show that the 20-electron butterfly structure becomes increasingly favored over the tetrahedral one in X{sub 2}Y{sub 2} clusters when the 2 atoms have increasing electronegativity difference. These results are in agreement with the known structures for the Pb{sub 2}Sb{sub 2}{sup 2{minus}} and Sb{sub 2}Bi{sub 2}{sup 2{minus}} clusters (tetrahedral-like) and the Tl{sub 2}Te{sub 2}{sup 2{minus}} one (butterfly-like).

16 citations


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Journal ArticleDOI
TL;DR: A detailed description and comparison of algorithms for performing ab-initio quantum-mechanical calculations using pseudopotentials and a plane-wave basis set is presented in this article. But this is not a comparison of our algorithm with the one presented in this paper.

47,666 citations

Journal ArticleDOI
TL;DR: In this paper, a detailed study of correlation effects in the oxygen atom was conducted, and it was shown that primitive basis sets of primitive Gaussian functions effectively and efficiently describe correlation effects.
Abstract: In the past, basis sets for use in correlated molecular calculations have largely been taken from single configuration calculations. Recently, Almlof, Taylor, and co‐workers have found that basis sets of natural orbitals derived from correlated atomic calculations (ANOs) provide an excellent description of molecular correlation effects. We report here a careful study of correlation effects in the oxygen atom, establishing that compact sets of primitive Gaussian functions effectively and efficiently describe correlation effects i f the exponents of the functions are optimized in atomic correlated calculations, although the primitive (s p) functions for describing correlation effects can be taken from atomic Hartree–Fock calculations i f the appropriate primitive set is used. Test calculations on oxygen‐containing molecules indicate that these primitive basis sets describe molecular correlation effects as well as the ANO sets of Almlof and Taylor. Guided by the calculations on oxygen, basis sets for use in correlated atomic and molecular calculations were developed for all of the first row atoms from boron through neon and for hydrogen. As in the oxygen atom calculations, it was found that the incremental energy lowerings due to the addition of correlating functions fall into distinct groups. This leads to the concept of c o r r e l a t i o n c o n s i s t e n t b a s i s s e t s, i.e., sets which include all functions in a given group as well as all functions in any higher groups. Correlation consistent sets are given for all of the atoms considered. The most accurate sets determined in this way, [5s4p3d2f1g], consistently yield 99% of the correlation energy obtained with the corresponding ANO sets, even though the latter contains 50% more primitive functions and twice as many primitive polarization functions. It is estimated that this set yields 94%–97% of the total (HF+1+2) correlation energy for the atoms neon through boron.

26,705 citations

Journal ArticleDOI
TL;DR: The M06-2X meta-exchange correlation function is proposed in this paper, which is parametrized including both transition metals and nonmetals, and is a high-non-locality functional with double the amount of nonlocal exchange.
Abstract: We present two new hybrid meta exchange- correlation functionals, called M06 and M06-2X. The M06 functional is parametrized including both transition metals and nonmetals, whereas the M06-2X functional is a high-nonlocality functional with double the amount of nonlocal exchange (2X), and it is parametrized only for nonmetals.The functionals, along with the previously published M06-L local functional and the M06-HF full-Hartree–Fock functionals, constitute the M06 suite of complementary functionals. We assess these four functionals by comparing their performance to that of 12 other functionals and Hartree–Fock theory for 403 energetic data in 29 diverse databases, including ten databases for thermochemistry, four databases for kinetics, eight databases for noncovalent interactions, three databases for transition metal bonding, one database for metal atom excitation energies, and three databases for molecular excitation energies. We also illustrate the performance of these 17 methods for three databases containing 40 bond lengths and for databases containing 38 vibrational frequencies and 15 vibrational zero point energies. We recommend the M06-2X functional for applications involving main-group thermochemistry, kinetics, noncovalent interactions, and electronic excitation energies to valence and Rydberg states. We recommend the M06 functional for application in organometallic and inorganometallic chemistry and for noncovalent interactions.

22,326 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: A description of the ab initio quantum chemistry package GAMESS, which can be treated with wave functions ranging from the simplest closed‐shell case up to a general MCSCF case, permitting calculations at the necessary level of sophistication.
Abstract: A description of the ab initio quantum chemistry package GAMESS is presented. Chemical systems containing atoms through radon can be treated with wave functions ranging from the simplest closed-shell case up to a general MCSCF case, permitting calculations at the necessary level of sophistication. Emphasis is given to novel features of the program. The parallelization strategy used in the RHF, ROHF, UHF, and GVB sections of the program is described, and detailed speecup results are given. Parallel calculations can be run on ordinary workstations as well as dedicated parallel machines. © John Wiley & Sons, Inc.

18,546 citations