Accuracy of distributed multipoles and polarizabilities: Comparison between the LoProp and MpProp models

Localized multipole moments up to the fifth moment as well as localized dipole polarizabilities are calculated with the MpProp and the newly developed LoProp methods for a total of 20 molecules, predominantly derived from amino acids. A comparison of electrostatic potentials calculated from the multipole expansion obtained by the two methods with ab initio results shows that both methods reproduce the electrostatic interaction with an elementary charge with a mean absolute error of similar to 1.5 kJ/mol at contact distance and less than 0.1 kJ/mol at distances 2 angstrom further out when terms up to the octupole moments are included. The polarizabilities are tested with homogenous electric fields and are-found to have similar accuracy. The MpProp method gives better multipole moments unless diffuse basis sets are used, whereas LoProp gives better polarizabilities. (C) 2007 Wiley Periodicals, Inc.