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Efficient Molecular Dynamics Simulations of Multiple Radical Center Systems Based on the Fragment Molecular Orbital Method

TitleEfficient Molecular Dynamics Simulations of Multiple Radical Center Systems Based on the Fragment Molecular Orbital Method
Publication TypeJournal Article
Year of Publication2014
AuthorsNakata, H, Schmidt, M, Fedorov, DG, Kitaura, K, Nakamura, S, Gordon, MS
JournalJournal of Physical Chemistry A
Volume118
Pagination9762-9771
Date Published10
Type of ArticleArticle
ISBN Number1089-5639
Accession NumberWOS:000343334900016
Keywordsanalytic, decomposition analysis, density-functional theory, elongation method, energy, geometry optimizations, gradient, open-shell systems, perturbation-theory, potential method, quantum-mechanical calculations, wave-functions
Abstract

The fully analytic energy gradient has been developed and implemented for the restricted open-shell Hartree-Fock (ROHF) method based on the fragment molecular orbital (FMO) theory for systems that have multiple open-shell molecules. The accuracy of the analytic ROHF energy gradient is compared with the corresponding numerical gradient, illustrating the accuracy of the analytic gradient. The ROHF analytic gradient is used to perform molecular dynamics simulations of an unusual open-shell system, liquid oxygen, and mixtures of oxygen and nitrogen. These molecular dynamics simulations provide some insight about how triplet oxygen molecules interact with each other. Timings reveal that the method can calculate the energy gradient for a system containing 4000 atoms in only 6 h. Therefore, it is concluded that the FMO-ROHF method will be useful for investigating systems with multiple open shells.

DOI10.1021/jp507726m
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