title: Multipolar Ewald methods, 2: applications using a quantum mechanical force field.
abstract: A fully quantum mechanical force field (QMFF) based on a modified “divide-and-conquer” (mDC) framework is applied to a series of molecular simulation applications, using a generalized Particle Mesh Ewald method extended to multipolar charge densities. Simulation results are presented for three example applications: liquid water, p-nitrophenylphosphate reactivity in solution, and crystalline N,N-dimethylglycine. Simulations of liquid water using a parametrized mDC model are compared to TIP3P and TIP4P/Ew water models and experiment. The mDC model is shown to be superior for cluster binding energies and generally comparable for bulk properties. Examination of the dissociative pathway for dephosphorylation of p-nitrophenylphosphate shows that the mDC method evaluated with the DFTB3/3OB and DFTB3/OPhyd semiempirical models bracket the experimental barrier, whereas DFTB2 and AM1/d-PhoT QM/MM simulations exhibit deficiencies in the barriers, the latter for which is related, in part, to the anomalous underestimation of the p-nitrophenylate leaving group pKa. Simulations of crystalline N,N-dimethylglycine are performed and the overall structure and atomic fluctuations are compared with the experiment and the general AMBER force field (GAFF). The QMFF, which was not parametrized for this application, was shown to be in better agreement with crystallographic data than GAFF. Our simulations highlight some of the application areas that may benefit from using new QMFFs, and they demonstrate progress toward the development of accurate QMFFs using the recently developed mDC framework.
authors.affiliation: Center for Integrative Proteomics Research, BioMaPS Institute for Quantitative Biology and Department of Chemistry and Chemical  Biology, Rutgers University, Piscataway, New Jersey 08854-8087, United States
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Giese
authors.forename: Maria T
authors.initials: MT
authors.lastname: Panteva
authors.forename: Haoyuan
authors.initials: H
authors.lastname: Chen
authors.forename: Darrin M
authors.initials: DM
authors.lastname: York
mesh_terms: D056004:Molecular Dynamics Simulation; D009596:Nitrophenols / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000737:chemistry; D011789:Quantum Theory; D012521:Sarcosine / Q000031:analogs & derivatives / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D009596:Nitrophenols; D009943:Organophosphorus Compounds; D014867:Water; C008644:nitrophenylphosphate; C025138:dimethylglycine; D012521:Sarcosine