Distributed multipoles from a robust basis-space implementation of the iterated stockholder atoms procedure

TL;DR

This paper introduces a robust basis-space algorithm for the iterated stockholder atoms (ISA) method, achieving rapid convergence and improved multipole moment calculations, which enhances intermolecular interaction modeling.

Contribution

A new basis-space ISA algorithm that converges faster and produces more accurate multipole moments than previous real-space methods.

Findings

Rapid convergence within 10-80 iterations regardless of system size.

Multipole moments are as good as or better than previous methods.

Improved convergence leads to better penetration energy calculations.

Abstract

The recently developed iterated stockholder atoms (ISA) approach of Lillestolen and Wheatley (Chem. Commun. {\bf 2008}, 5909 (2008)) offers a powerful method for defining atoms in a molecule. However, the real-space algorithm is known to converge very slowly, if at all. Here we present a robust, basis-space algorithm of the ISA method and demonstrate its applicability on a variety of systems. We show that this algorithm exhibits rapid convergence (taking around 10--80 iterations) with the number of iterations needed being unrelated to the system size or basis set used. Further, we show that the multipole moments calculated using this basis-space ISA method are as good as, or better than those obtained from Stone's distributed multipole analysis (J. Chem. Theory Comput. {\bf 1}, 1128 (2005) ), exhibiting better convergence properties and resulting in better behaved penetration energies. This can have significant consequences in the development of intermolecular interaction models.