Ernest R. Davidson

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.

Self-consistent effective local potentials.

Abstract: An effective local potential (ELP) is a multiplicative operator whose deviation from a given nonlocal potential has the smallest variance evaluated with a prescribed single-determinant wave function. ELPs are useful in density functional theory as alternatives to optimized effective potentials (OEPs) because they do not require special treatment in finite basis set calculations as OEPs do. We generalize the idea of variance-minimizing potentials by introducing the concept of a self-consistent ELP (SCELP), a local potential whose deviation from its nonlocal counterpart has the smallest variance in terms of its own Kohn-Sham orbitals. A semi-analytical method for computing SCELPs is presented. The OEP, ELP, and SCELP techniques are applied to the exact-exchange-only Kohn-Sham problem and are found to produce similar results for many-electron atoms.

Theory of the Proton Hyperfine Splittings of Pi‐Electron Free Radicals. I. The CH Fragment

Abstract: Using first‐order perturbation theory, a general equation is derived for the Fermi contact hyperfine splittings of any free radical. This equation is essentially the same as that obtained previously by other workers, but restrictions concerning (1) planarity of the radical, (2) sigma–pi separability, (3) choice of spin eigenfunctions, and (4) choice of orbitals used to form excited configurations have been removed. The results of calculations of the proton hyperfine splitting (aH) of the prototype pi‐electron hydrocarbon radical, the ·CH fragment, are presented. A seven‐electron wavefunction with a minimum basis set of Slater atomic orbitals is employed. The CH bonding orbital incorporates sp2 hybridization and an electronegativity parameter which is optimized by variational minimization of the ground configuration energy. Admixture of three configurations is considered; two represent the single excitation from CH bonding to antibonding orbital and the third the corresponding double excitation. The splitt...

Valence electron momentum distributions of the hydrogen halides. I. Comparison of EMS measurements and calculations using Hartree—Fock limit and configuration interaction wavefunctions for hydrogen fluoride.

Abstract: The valence orbital momentum profiles of hydrogen fluoride have been obtained using electron momentum spectroscopy at an impact energy of 1200 eV. The present results show significant differences from earlier measurements. (J. Electron Spectry. Relat. Phenom. 21 (1980) 71) for the (3σ) −1 ionization but are in good agreement for the (1π) −1 processes. The measurements are compared with calculations ranging from minimum basis set to highly saturated basis sets essentially at the Hartree-Fock limit and also with numerical Hartree-Fock calculations. The experimental momentum resolution is incorporated into the calculations using the recently developed GW-PG resolution folding method (Chem. Phys. 159 (1992) 347). The significant discrepancy remaining between SCF limit calculations and experiment indicates the importance of electron correlation and relaxation effects in describing the momentum profile corresponding to the removal of the 1π electron. These effects are investigated using multireference singles and doubles CI calculations of the full ion-neutral overlap distribution and considerable improvement in the agreement between theory and experiment is then achieved.

Nonrelativistic configuration interaction calculations for the ground state of the vanadium atom

Abstract: A new scheme for constructing L2, Lz, S2, Sz eigenfunctions within the Hartree–Fock interacting subspace has been used to generate a first‐order configuration‐interaction wavefunction for the ground 4F state of the vanadium atom in the nonrelativistic approximation. The basis set consisted of 62 Slater‐type orbitals, with l up to 5, transformed to Hartree–Fock orbitals in the ’’occupied’’ subspace and to pseudonatural orbitals in the ’’virtual’’ subspace. Approximately 70% of the correlation energy was recovered with 500 configurations (1023 terms formed from 31 496 Slater determinants). The charge density, momentum density, x‐ray scattering factor, and Compton profile were computed from both the CI and SCF wavefunctions.

Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen

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.

The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals

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.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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。

General atomic and molecular electronic structure system

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.