Semi-empirical quantum calculations

Labarre JF (1978) Conformational Analysis in Inorganic Chemistry Semi-Empirical Quantum Calculation vs. Experiment. 35 1-35 Lammers M, Follmann H (1983) The Ribonucleotide Reductases A Unique Group of Metalloenzymes Essential for Cell Proliferation. 54 27-91 Le Brun NE, Thomson AJ, Moore GR (1997) Metal Centres of Bacterioferritins of Non-Heam-Iron-Containing Cyrochromes 6557. 88 103-138... 

Labarre, J. F. Conformational Analysis in Inorganic Chemistry Semi-Empirical Quantum Calculation vs. Experiment. Vol. 35, pp. 1-35. 

J.-F. Labarre Conformational Analysis in Inorganic Chemistry Semi-Empiric Quantum Calculations vs. Experiment D. B. Cook Hie Approximate Calculation of Molecular Electronic Structures as a Theory ofValence... 

This question has been addressed [49] by performing the same semi-empirical quantum calculations applied to DPP and DPC to the model molecule shown in Fig. 57 and denoted large carbonate . 

Keywords carbon nanotubes, defects and vacancies, geometry and electronic structures, semi-empirical quantum calculations. 

The structures were fully optimized by semi-empirical quantum calculation with VAMP program of Material Studio package (Accelrys Co.). PM3 Hamiltonian was used in the calculations. 

In this chapter, we present new results based on semi-empirical quantum calculations (PM3) that include solvation and charging effects simultaneously on the same model SFA.71 These calculations were carried out in HyperChem 5.0 (Hypercube, Inc.). Solvation was carried out with two approaches. In the first approach, the neutral, gas-phase SFA model was simulated, then this molecule was deprotonated at each of four carboxylic acid sites. Finally, a solvation sphere of H20 molecules was used to surround the anionic SFA and the structure obtained via molecular dynamics simulations and energy minimizations as an isolated nanodroplet. This approach has the advantage of allowing maximum flexibility of the model SFA. Larger model systems may require long simulation runs to sample all available conformations, but isolation of the SFA and water allows each component to move more freely. 

Combined QM/MM methods Currently in most QM/MM implementations, the quantum calculations are carried out at the semi-empirical level, such as AMI or MNDO. Semi-empirical quantum calculations have often serious limitations. More accurate calculations, using ab initio and DFT schemes will become feasible in the near future. In combined methods, the QM/MM coupling needs to be investigated further, as well as the treatment of cutting covalent bonds in the studies of large molecules. 

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