Localized molecular orbitals, semiempirical

Stewart, J. J. P. 1996. Applications of Localized Molecular-Orbitals to the Solution of Semiempirical Self-Consistent-Fielf Equations. Int. J. Q. Chem. 58,133. 

Fukui et al. studied the bond interchange in the course of ammonia addition to formaldehyde by means of a localized molecular orbital method, based on the analysis of the semiempirical INDO molecular orbitals of the isolated molecules and of the reacting system [127], Here, the N... C = 0 angle was fixed at 107°, since preliminary calculations gave results in fairly good agreement with the experimental reaction path, i.e. the Biirgi-Dunitz trajectory. 

J. J. P. Stewart Application of localized molecular orbitals to the solution of semiempirical self-consistent field equations, Int. J. Quantum Chem. 58, 133-146 (1996). 

Local density functional (LDF) quantum mechanical calculations for materials science. deMon for density functional calculations. Turbomole for Hartree-Fock and MP2 ab initio calculations. ZINDO for extended Fliickel, PPP, CNDO, and INDO semiempirical molecular orbital calculations and prediction of electronic spectra. Plane Wave for band structures of semiconductors. ESOCS for electronic structure of solids. Silicon Graphics and IBM workstation versions. 

We do not include in this review semiempirical quantum chemical methods that do not initially solve the Fock equations for a set of molecular orbitals. This is a subject unto itself. Such methods create orbitals by a fixed ansatz, such as localized orbitals formed from hybrid atomic orbitals, avoid matrix multiplication and diagonalization, and can be developed up to third... 

Tel. 612-683-3688, fax 612-683-3099, e-mail mcole cray.com DGauss for density functional theory calculations with non-local, SCF corrections, and geometry optimization. CADPAC 5.0 for ab initio calculations. MND091 for semiempirical molecular orbital calculations. A package with a graphics front-end for structure input and visualizations of electron density, electrostatic potentials, and molecular orbitals. Silicon Graphics and Macintosh (under X-Windows) networked to a Cray. 

This work cast valuable light on these systems, as UV-vis spectroscopic analysis clearly identified a charge-transfer band centered at = 319 nm for 4b, for example, and excitation at this wavelength led to emission at Xeni = 480nm (Figure 15.3). Semiempirical (MNDO) calculations established that the highest occupied molecular orbital (HOMO) was primarily localized on the boron cage cluster, while the lowest occupied molecular orbital (LUMO) was mostly concentrated... 

The first step in using Lewis structures is to convert the schematic form of the structure into molecular orbitals. These molecular orbitals, initially localized on one or two atoms, form the basis for a new method that appears to hold great promise for making the semiempirical calculation of very large systems practical. 

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