scispace - formally typeset
Search or ask a question
Author

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
More filters
Journal ArticleDOI
TL;DR: The traditional Roothaan-Hartree-Fock orbitals are not invariant under changes in the partitioning of the Hamiltonian into one and two body operators as mentioned in this paper.
Abstract: The traditional Roothaan‐Hartree‐Fock orbitals are not invariant under changes in the partitioning of the Hamiltonian into one and two body operators. This arbitrariness may be exploited to derive canonical orbitals adapted to specific application in spectroscopy or in correlation energy calculations.

136 citations

Journal ArticleDOI
TL;DR: In this article, a detailed study of the correlation energy of Ne has been made in order to analyze the nature of the configurationinteraction (CI) method in ab initio calculations, and both the Bethe-Goldstone method of Nesbet and the total-pair-excitation-block method (TPEB) were examined.
Abstract: A detailed study of the correlation energy of Ne has been made in order to analyze the nature of the configuration-interaction (CI) method in ab initio calculations. Both the Bethe-Goldstone method of Nesbet and the total-pair-excitation-block method (TPEB) were examined. A series of calculations was made using both "atom-centered" and "shell-centered" basis sets. The most detailed calculations gave - 0.333 a.u. (88%) for the correlation energy by the TPEB method, and - 0.396 a.u. (104%) by the sum-of-the-pairs technique. The difference between these two values is mainly the so-called pair-pair interactions, which have been considered too small to be important to other investigators. A series of perturbation calculations on the triple and quadruple excitations gives \ensuremath{\sim} 1.5% of the total correlation energy. A complete CI calculation with a very limited basis set was done on the $p$ block of Ne. The results of this calculation are in agreement with our total-atom calculation, except that now the TPEB calculation gave about 98.5%, and the sum of the pairs about 115% of the complete CI result. The effect on the pair correlation energy of a unitary transformation of the outer-shell occupied self-consistent-field orbitals was also studied. Only a small difference in the results was obtained.

134 citations

Journal ArticleDOI

130 citations

Journal ArticleDOI
TL;DR: In this article, a method for eliminating the off-diagonal lagrangian multipliers which appear in open-shell SCF theory is given, which leads to a set of coupled eigenvalue equations which can be easily solved for a new guess to the SCF orbitals.

130 citations


Cited by
More filters
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