New Empirical Procedures for Improving Ab Initio Energetics

Published

October 1, 2002

Author(s)

Karl K. Irikura

Abstract

Empirical schemes are developed for correcting the energies resulting from a moderately high-level abinitio calculation. Each method involves only a few adjustable parameters, which are determined by fitting a set of 31 high-spin atomization energies. Parameters are developed only for elements through the 2p block. The methods are based upon (1) bond lengths, (2) the electron densities at mid-bond critical points, (3)correlation energy scaline, (4) basis-set extrapolation, and (5) the number and spin of the valence electrons. A hybird method, in which correlation energy is scaled by a factor that depends upon the mid-bond electron densities, is also investigated. Each type of correction achieves a marked improvement over ab initio atomization energies; the first two are expecially effective. Additional expressions are developed to represent the expected (1ς) uncertainties for predicted atomization energies.

Citation

Journal of Physical Chemistry A

Volume

106

Issue

No. 42

Pub Type

Journals

Keywords

ab initio, atomization, bond length, electron correlation, electron density, empirical correction, quantum chemistry, thermochemistry

Citation

Irikura, K. (2002), New Empirical Procedures for Improving Ab Initio Energetics, Journal of Physical Chemistry A (Accessed April 19, 2024)