Study of charges transferability for use in force fields

This Letter examines the topological neighborhood effects on atomic partial charges and their transferability. To determine neighborhood effects, we used Breneman and Wiberg's CHELPG charges calculated at B3LYP/6-31G* theory level and AM1 geometries for a test set of 324 molecules of insecticides, ferroelectric liquid crystals (FLC) and antiinflammatories. The Qcode atomic descriptor was applied to represent topological neighborhood. Calculated molecular dipole moments using averaged charges with various neighbor numbers indicate that partial charges have a strong dependence with the molecular topology. Five or more neighbors are demonstrated to be typically needed for accurate partial charges transferability.