"Neglect of Diatomic Differential Overlap" in nonempirical quantum chemical orbital theories. I. On the justification of the neglect of diatomic differential overlap approximation

A short review of the different approaches to the justification of the Neglect of Diatomic Differential Overlap in the basis of symmetrically orthogonalized basis functions is given. Brown and Roby employed the binomial expansion for the approximation of the inverse square root of the overlap matrix. For some overlap matrices, this expansion does not converge. The always‐convergent power series given by Chandler and Grader provides a worse second‐order approximation in comparison with the second‐order binomial expansion. © 1995 John Wiley & Sons, Inc.