LEAST SQUARES FITS OF POTENTIALS BY USING ENERGY AND GRADIENT DATA : VIBRATIONAL ANHARMONIC SPECTRA FOR H_2CO FROM DFT CALCULATIONS

摘要

We present a least-squares fitting procedure to obtain a quartic force field by using energy and gradient data arising from B3LYP/cc-pVTZ calculations on a implex-sum of Box and Behnken grid of points. We illustrate and we test for H_2CO the quartic force field and the resulting vibrational anharmonic spectra performed from 44 simplex-sum configurations and we compare our results to those obtained by using the classical 168 energy calculations.