title: Unrestricted Hartree-Fock based on the fragment molecular orbital method: energy and its analytic gradient.
abstract: A consideration of the surrounding environment is necessary for a meaningful analysis of the reaction activity in large molecular systems. We propose an approach to perform unrestricted Hartree-Fock (UHF) calculations within the framework of the fragment molecular orbital (FMO) method (FMO-UHF) to study large systems with unpaired electrons. Prior to an energy analysis one has to optimize geometry, which requires an accurate analytic energy gradient. We derive the FMO-UHF energy and its analytic gradient and implement them into GAMESS. The performance of FMO-UHF is evaluated for a solvated organic molecule and a solvated metal complex, as well as for the active part of a protein, in terms of energy, gradient, and geometry optimization.
authors.affiliation: Department of Biomolecular Engineering, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8501, Japan.
authors.forename: Hiroya
authors.initials: H
authors.lastname: Nakata
authors.forename: Dmitri G
authors.initials: DG
authors.lastname: Fedorov
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nagata
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yokojima
authors.forename: Koji
authors.initials: K
authors.lastname: Ogata
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kitaura
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Nakamura
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry*; D006885:Hydroxybutyrates / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010422:Pentanones / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D011789:Quantum Theory; D012995:Solubility
chemical_list: D003497:Cyclic N-Oxides; D006885:Hydroxybutyrates; D009942:Organometallic Compounds; D010422:Pentanones; D010455:Peptides; C049529:acetyl acetonate; D008345:Manganese; C003959:TEMPO