title: Projected hybrid orbitals: a general QM/MM method.
abstract: A projected hybrid orbital (PHO) method was described to model the covalent boundary in a hybrid quantum mechanical and molecular mechanical (QM/MM) system. The PHO approach can be used in ab initio wave function theory and in density functional theory with any basis set without introducing system-dependent parameters. In this method, a secondary basis set on the boundary atom is introduced to formulate a set of hybrid atomic orbtials. The primary basis set on the boundary atom used for the QM subsystem is projected onto the secondary basis to yield a representation that provides a good approximation to the electron-withdrawing power of the primary basis set to balance electronic interactions between QM and MM subsystems. The PHO method has been tested on a range of molecules and properties. Comparison with results obtained from QM calculations on the entire system shows that the present PHO method is a robust and balanced QM/MM scheme that preserves the structural and electronic properties of the QM region.
authors.affiliation: Theoretical Chemistry Institute, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University , Changchun, Jilin Province 130028, People's Republic of China.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Wang
authors.forename: Jiali
authors.initials: J
authors.lastname: Gao
mesh_terms: D004980:Ethane / Q000737:chemistry; D011522:Protons; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D011522:Protons; D004980:Ethane