H. Adachi

Bio: H. Adachi is an academic researcher from Northwestern University. The author has contributed to research in topics: Hartree–Fock method & Molecular orbital. The author has an hindex of 1, co-authored 1 publications receiving 417 citations. Previous affiliations of H. Adachi include Osaka University.

Calculations of molecular ionization energies using a self‐consistent‐charge Hartree–Fock–Slater method

Abstract: A numerical-variational method for performing self-consistent molecular calculations in the Hartree-Fock-Slater (HFS) model is presented Molecular wavefunctions are expanded in terms of basis sets constructed from numerical HFS solutions of selected one-center atomlike problems Binding energies and wavefunctions for the molecules are generated using a discrete variational method for a given molecular potential In the self-consistent-charge (SCC) approximation to the complete self-consistent-field (SCF) method, results of a Mulliken population analysis of the molecular eigenfunctions are used in each iteration to produce 'atomic' occupation numbers The simplest SCC potential is then obtained from overlapping spherical atomlike charge distributions Molecular ionization energies are calculated using the transition-state procedure; results are given for CO, H2O, H2S, AlCl, InCl, and the Ni5O surface complex Agreement between experimental and theoretical ionization energies for the free-molecule valence levels is generally within 1 eV The simple SCC procedure gives a reasonably good approximation to the molecular potential, as shown by comparison with experiment, and with complete SCF calculations for CO, H2O, and H2S

Fragmentation methods: a route to accurate calculations on large systems.

Abstract: Fragmentation Methods: A Route to Accurate Calculations on Large Systems Mark S. Gordon,* Dmitri G. Fedorov, Spencer R. Pruitt, and Lyudmila V. Slipchenko Department of Chemistry and Ames Laboratory, Iowa State University, Ames Iowa 50011, United States Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States

Discrete Variational Xα Cluster Calculations. I. Application to Metal Clusters

Abstract: Applications of the discrete variational (DV) Xα molecular orbital method based on the self-consistent Hartree-Fock-Slater model to metal clusters are presented. Numerical basis functions are utilized in the present calculations. Variations of orbital energies and populations with exchange scaling parameter α are investigated. It is proved that the self-consistent-charge (SCC) approximation to the SCF method gives accurate orbital energies. The numerical basis SCC-DV-Xα method is shown to be very efficient for studies of rather large metal clusters such as Ni 13 .

Density functional Gaussian‐type‐orbital approach to molecular geometries, vibrations, and reaction energies

Abstract: We present the theory, computational implementation, and applications of a density functional Gaussian‐type‐orbital approach called DGauss. For a range of typical organic and small inorganic molecules, it is found that this approach results in equilibrium geometries, vibrational frequencies, bond dissociation energies, and reaction energies that are in many cases significantly closer to experiment than those obtained with Hartree–Fock theory. On the local spin density functional level, DGauss predicts equilibrium bond lengths within about 0.02 A or better compared with experiment, bond angles, and dihedral angles to within 1–2°, and vibrational frequencies within about 3%–5%. While Hartree–Fock optimized basis sets such as the 6‐31 G** set can be used in DGauss calculations to give good geometries, the accurate prediction of reaction energies requires the use of density functional optimized Gaussian‐type basis sets. Nonlocal corrections as proposed by Becke and Perdew for the exchange and correlation ener...

Three-dimensional numerical integration for electronic structure calculations

Abstract: Two three-dimensional numerical schemes are presented for molecular integrands such as matrix alements of one-electron operators occuring in the Fock operator and expectation values of one-electron operators describing molecular properties. The schemes are based on a judicious partitioning of space so that product-Gauss integration rules can be used in each region. Convergence with the number of integration points is such that very high accuracy (8–10 digits) may be obtained with obtained with a modest number of points. The use of point group symmetry to reduce the required number of points is discussed. Examples are given for overlap, nuclear potential, and electric field gradient integrals.

A Quantum Chemical View of Density Functional Theory

Abstract: A comparison is made between traditional quantum chemical approaches to the electron correlation problem and the one taken in density functional theory (DFT). Well-known concepts of DFT, such as the exchange−correlation energy Exc = ∫ρ(r) exc(r) dr and the exchange−correlation potential vxc(r) are related to electron correlation as described in terms of density matrices and the conditional amplitude (Fermi and Coulomb holes). The Kohn−Sham one-electron or orbital model of DFT is contrasted with Hartree−Fock, and the definitions of exchange and correlation in DFT are compared with the traditional ones. The exchange−correlation energy density exc(r) is decomposed into kinetic and electron−electron potential energy components, and a practical way of calculating these from accurate wave functions is discussed, which offers a route to systematic improvement. vxc(r) is likewise decomposed, and special features (bond midpoint peak, various types of step behavior) are identified and related to electronic correlation.