A Polarizable High-Rank Quantum Topological Electrostatic Potential Developed Using Neural Networks: Molecular Dynamics Simulations on the Hydrogen Fluoride Dimer S. HOULDING, S. Y. LIEM, P. L. A. POPELIER School of Chemistry, University of Manchester, Faraday Building, North Campus, Manchester M60 1QD, Great Britain Received 29 March 2007; accepted 3 July 2007 Published online 17 August 2007 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/qua.21507 ABSTRACT: The HF molecule is a simple polar system that serves as a prototype for developing new potentials. Here we build on earlier work [Liem and Popelier, J Chem Phys 2003, 119, 4560] in which a high-rank multipolar potential was used to simulate liquid HF. That work was the first example of high-rank multipole moments (up to hexadecapole) being employed in conjunction with multipolar Ewald summation in a molecular dynamics simulation. This potential is now extended with polarization, which is delivered by artificial neural networks. The neural nets predict how atomic multipole moments change as the position of neighboring molecules vary. This novel approach is successfully tested on the HF dimer in vacuum. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem 107: 2817–2827, 2007 Key words: quantum chemical topology; atoms in molecules; electrostatic potential; multipole moments; molecular simulation; neural networks; polarization; charge transfer Introduction O btaining an accurate description of the poten- tial energy between interacting molecules is a vital requirement for molecular simulation. Hy- drogen fluoride has served as a popular prototype molecule to test new ideas in the design of potential energy functions. It is a simple molecule capable of forming strong hydrogen bonds, a property also exhibited by the water molecule. Existing potential functions can typically be separated into distinct components, each describing a chemically or phys- ically intuitive contribution to the overall potential Correspondence to: P. Popelier; e-mail: pla@manchester.ac.uk International Journal of Quantum Chemistry, Vol 107, 2817–2827 (2007) © 2007 Wiley Periodicals, Inc.