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.