Semi-empirical electronic structure method parameterization

An series of alternative, generally parameterized methods for introducing the effects of solvent into semi-empirical calculations are termed SMr, where the value of x represents the type and quality of parameterization27-76 81. These methods have potential value in studying solvation effects on the structure, electronic spectra, and reactivity of biologically... 

Although continuum solvation models do appear to reproduce the structural and spectroscopic properties of many molecules in solution, parameterization remains an issue in studies involving solvents other than water. In addition, the extension of these approaches to study proteins embedded in anisotropic environments, such as cell membranes, is clearly a difficult undertaking96. As a result, several theoretical studies have been undertaken to develop semi-empirical methods that can calculate the electronic properties of very large systems, such as proteins28,97 98. The principal problem in describing systems comprised of many basis functions is the method for solving the semi-empirical SCF equations ... 

Semi-empirical molecular orbital, MO, theory uses a combination of experimental data and quantum mechanical MO methods to model the valence electronic structure of molecules. In the MNDO (8) method each atom is parameterized using experimental data. This calculation provides molecular orbital descriptions of the valence electrons, as well as effective charges of each atom in the molecule. 

We will always need to employ methods that can account for the electronic structure of our chosen model in some sense - either (1) totally explicitly by ab initio (Hartree-Fock (HF), MpUer-Plesset perturbation theory (MPx), coupled-cluster (CC), etc.) or by density functional theory (DFT) methods with a vast range, and continuously expanding number, of different functionals (B3LYP, M06, etc.), (2) partly explicitly like in semi-empirical (SE) methods (MNDO, AMI, PMx, etc.), or (3) we can even resort to a parameterization such as in classical MD simulations (being a much less prominent method though). All these are of course standard computational methods with generality across any elements and chemistry (for classical MD only if a proper parameter set exists). There is also ab initio MD (AIMD) emerging as a tool in the field. 

AMI Combined Quantum Mechanical and Molecular Mechanical Potentials Combined Quantum Mechanics and Molecular Mechanics Approaches to Chemical and Biochemical Reactivity Divide and Conquer for Semi empirical MO Methods Hybrid Methods Hybrid Quan turn Mechanical/Molecular Mechanical (QM/MM) Meth ods Linear Scaling Methods for Electronic Structure Cal culations Mixed Quantum-Classical Methods MNDO MNDO/d Parameterization of Semiempirical MO Meth ods PM3 Quantum Mechanics/Molecular Mechanic (QM/MM) Semiempirical Methods Integrals and Scaling. 

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