Consistent Charge Equilibration Method Combined with Universal Force Field: Application to Amino Acid Molecules

Abstract

In the previous paper (O. Kitao and T. Ogawa, Mol. Phys., 101, 3-17 (2003).), we have proposed the consistent charge equilibration (CQEq) method. The CQEq energy term was combined with the universal force field (UFF) to develop the CQEq with UFF (CUFF). In this article, to confirm the accuracy of the CUFF, geometry optimizations by the CUFF were performed for a series of amino acid molecules. The CUFF can well reproduce the HF/6-31G ^** geometries aside from some flexible dihedral angles. The partial charges obtained by the CQEq deviate somewhat from those by the restrained electrostatic potential fit; this result suggested us a way to improve the CQEq and the CUFF.