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New Empirical Procedures for Improving Ab Initio Energetics



Karl K. Irikura


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.
Journal of Physical Chemistry A
No. 42


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


Irikura, K. (2002), New Empirical Procedures for Improving Ab Initio Energetics, Journal of Physical Chemistry A (Accessed April 24, 2024)
Created October 1, 2002, Updated February 17, 2017