Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set

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.

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

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.

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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

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。

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

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.

General atomic and molecular electronic structure system

The first spectroscopic characterization of the VO2 radical is reported along with new results for V17O and tentative assignments for the VO3 and V+2 radicals. These vanadium radicals were investigated in neon matrices at 4 K by electron spin resonance utilizing conventional high temperature vaporization and pulsed laser ablation generation methods. A detailed ESR study of VO2 showed it to be nonlinear with a 2A1 ground state; the g tensor analysis reveals the presence of an excited electronic state (2B1) approximately 1 eV above the ground state. This excited state prediction and the observed nuclear hyperfine interactions (A tensors) for 51V and 17O were compared with theoretical results obtained from various ab initio computational methods. Ab initio calculations with an extended basis set were performed at various levels of theory including UHF, ROHF, CAS‐SCF, and MR‐SDCI (multireference single and double configuration interaction). While UHF calculations of the hyperfine interaction were grossly in e...

An electron spin resonance investigation of vanadium dioxide ( 51 V 16 O 2 and 51 V 17 O 2 ) and 51 V 17 O in neon matrices with preliminary assignments for VO 3 and V +2 : Comparison with ab initio theoretical calculations

A sequence of configuration interaction (CI) wave functions, constructed so as to systematically approach the complete basis set, full CI limit, is used to argue that the only alternatives for improving the accuracy of electron affinity calculations are: (1) recovery of a sufficient fraction of the correlation energy of both anion and neutral so that the remaining error in the energy difference is acceptably small, or (2) methodological bias in favor of the more difficult to describe anion. Extended Gaussian basis sets, of the type recently employed in atomic hyperfine spin calculations are capable of recovering 95%–96% of the total O (3P) correlation energy. With much greater difficulty this basis can also recover an equivalent fraction of the O− (2 P) correlation energy. Nevertheless, the calculated electron affinity(1.31 eV) still underestimates the experimental value of 1.46 eV by 10%. Estimates based on multireference second order pertubation theory suggest that another 0.05 eV (EA=1.36 eV) is availa...

The electron affinity of oxygen: A systematic configuration interaction approach

A wavefunction similar to the Kinoshita function has been analyzed into natural orbitals. As it was for the hydrogen molecule, the first natural orbital for helium is very nearly the SCF function. The first three natural orbitals describe the atom quite well. These three terms give an energy of —2.8974 hartrees and an overlap with the exact wavefunction of 0.99979. Beyond these three terms, the natural expansion converges slowly with many terms required to even approximately fit the cusp in the correlation hole.

Natural Expansions of Exact Wavefunctions. III. The Helium-Atom Ground State

Interaction Energy of Two Ground‐State Helium Atoms at Small Internuclear Distances

Multireference ab initio methods and density functional theory with a 6-31G* basis set have been applied to study the interconversions of norbornadiene, 1,3,5-cycloheptatriene, norcaradiene, and toluene. These include the [1,5]hydrogen shift in cycloheptatriene, the [1,5]carbon shift (walk rearrangement) in norcaradiene, the ring flip of cycloheptatriene, and the formation of norcaradiene from cycloheptatriene. Our best theoretical calculations for the walk rearrangement predict that the Woodward−Hoffmann “forbidden” suprafacial-inversion transition state and the “allowed” suprafacial-retention pathway differ in energy by <1 kcal/mol. Further, both transition states are effectively biradical-like. The transition state for formation of toluene from norcaradiene proceeds via a hydrogen transfer transition state that is formed directly from the “allowed” transition state for the walk rearrangement but not from the “forbidden” transition state. Further, the transition state for the transannular hydrogen shift...

Ernest R. Davidson

Papers

An electron spin resonance investigation of vanadium dioxide ( 51 V 16 O 2 and 51 V 17 O 2 ) and 51 V 17 O in neon matrices with preliminary assignments for VO 3 and V +2 : Comparison with ab initio theoretical calculations

The electron affinity of oxygen: A systematic configuration interaction approach

Natural Expansions of Exact Wavefunctions. III. The Helium-Atom Ground State

Interaction Energy of Two Ground‐State Helium Atoms at Small Internuclear Distances

Thermal rearrangements of norcaradiene