Parametric method number

In progressing from CNDO to MINDO/3 to MNDO, more and more parameters were changed from depending on atomic spectra to depending on molecular data. In MNDO and AMI only the two-elearon one-center integrals were still based on atomic speara. 

In obtaining the parameters for MINDO/3, MNDO, and AMI, considerable chemical intuition had been used. In principle, a large increase in speed should result from automating the optimization process. 

for the first time, the intrinsic accuracy of a semiempirical method can be accurately determined. Hitherto, incomplete optimizations precluded any such determination. 

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Modified Negiect of Diatomic Overlap, Parametric Method Number 3 (MNDO-PM3)... 

Various parameterizations of NDDO have been proposed. Among these are modified neglect of diatomic overlap (MNDO),152 Austin Model 1 (AMI),153 and parametric method number 3 (PM3),154 all of which often perform better than those based on INDO. The parameterizations in these methods are based on atomic and molecular data. All three methods include only valence s and p functions, which are taken as Slater-type orbitals. The difference in the methods is in how the core-core repulsions are treated. These methods involve at least 12 parameters per atom, of which some are obtained from experimental data and others by fitting to experimental data. The AMI, MNDO, and PM3 methods have been focused on ground state properties such as enthalpies of formation and geometries. One of the limitations of these methods is that they can be used only with molecules that have s and p valence electrons, although MNDO has been extended to d electrons, as mentioned below. 

PM3 Modified neglect of diatomic overlap, parametric method number 3 Pro Proline... 

Modified Neglect of Diatomic Overlap Parametric Method Number 3 (MNDO-PM3) 3.10.6 The MNDO/d Method 88 89 5.5 5.6 5.4.5 Correlation Consistent Basis Sets Extrapolation Procedures Isogyric and Isodesmic Reactions 162 164 169... 

Thielwas the first to introduce a correlated version of the MNDO model, called MNDOC. The ground state parametri-zation is carried out on the level of second-order perturbation theory equivalent to a Cl with a Cl matrix containing non zero elements only in the diagonal, in the first row and in the first column. It was shown in a statistical analysis of the heats of formation that the results of MNDO and MNDOC are of similar quality, with the latter showing a slight reduction of the absolute error, but no consistent improvement over the former. In an accompanying study on reactive intermediates and transition states, MNDOC turned out to be superior to MNDO for systems that show specific correlation effects. Excited states are then treated by a perturbation Cl approach. Modifications of the parametrization of the MNDO model led eventually to the Austin model 1 (AMI) and parametric method number 3 (PM3) schemes. 

Modified Intermediate Neglect of Differential Overlap (MINDO, MINDO/3) method, 84 Modified Neglect of Diatomic Overlap (MNDO) method, 86 Modified Neglect of Diatomic Overlap, Parametric Method Number 3 (MNIX)-PM3) method, 88... 

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