Acceleration of self-consistent field convergence in semiempirical molecular orbital methods

Abstract

The self-consistent field (SCF) procedure, even in semiempirical MO theory, can often be fairly tedious for large molecules. Moreover, it is often noticed that in some molecules with heteroatoms, the SCF process for the CNDO/2 and INDO MO methods is prolonged due to oscillatory behaviour. Some simple methods are presented for accelerating SCF convergence by dampening these oscillations and by reducing computational labour on each SCF iteration. Use of only the diagonal density matrix elements provides a sensitive and facile alternative method for estimating convergence. The effectiveness of these methods for saving computer time without loss of essential accuracy is also demonstrated.