An approach to computing electrostatic charges for molecules

Abstract

We present an approach for deriving net atomic charges from ab initio quantum mechanical calculations using a least squares fit of the quantum mechanically calculated electrostatic potential to that of the partial charge model. Our computational approach is similar to those presented by Momany [J. Phys. Chem., 82, 592 (1978)], Smit, Derissen, and van Duijneveldt [Mol. Phys., 37, 521 (1979)], and Cox and Williams [J. Comput. Chem., 2, 304 (1981)], but differs in the approach to choosing the positions for evaluating the potential. In this article, we present applications to the molecules H 2 O, CH 3 OH, (CH 3)2 O, H 2 CO, NH 3, (CH 3 O)2 PO, deoxyribose, ribose, adenine, 9‐CH 3 adenine, thymine, 1‐CH 3 thymine, guanine, 9‐CH 3 guanine, cytosine, 1‐CH 3 cytosine, uracil, and 1‐CH 3 uracil. We also address the question of inclusion of “lone pairs,” their location and charge.