Journal ArticleDOI
Comments on a comparison of AM1 with the recently developed PM3 method
TLDR
A reparameterized version of AM1 has recently been reported and the results for several hundred molecules compared with those from AM1 itself are seen to be only marginally better than AM1, insufficient to justify the confusion caused by the release of the new treatment.Abstract:
A reparameterized version (PM3) of AM1 has recently been reported and the results for several hundred molecules compared with those from AM1 itself. The comparison implied that PM3 represents a significant improvement over the earlier treatment. The apparently poor performance of AM1 is, however, due to the inclusion of “AM1 results” for elements (A1,P,S) for which AM1 parameters were unavailable. If these are omitted, PM3 is seen to be only marginally better than AM1. Since this conclusion refers only to a specific set of stable molecules, it is not clear whether even this small improvement will apply to other species or studies of reactions. It is in any case insufficient to justify the confusion caused by the release of the new treatment.read more
Citations
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Journal ArticleDOI
Optimization of parameters for semiempirical methods. III. Extension of PM3 to Be, Mg, Zn, Ga, Ge, As, Se, Cd, In, Sn, Sb, Te, Hg, Tl, Pb, and Bi
TL;DR: In this article, the PM3 algorithm was extended to a total of 28 elements and the average ΔHf errors for the newly parameterized elements were Be: 8.6, Mg:8.4, Zn: 5.8, Tl: 6.5, Pb: 7.4 and Bi: 10.9.
Journal ArticleDOI
A priori evaluation of aqueous polarization effects through Monte Carlo QM-MM simulations
Jiali Gao,Xinfu Xia +1 more
TL;DR: The performance of the hybrid AM1-TIP3P model was further validated by consideration of bimolecular complexes with water and by computation of the free energies of solvation of organic molecules using statistical perturbation theory.
Journal ArticleDOI
AM1-SM2 and PM3-SM3 parameterized SCF solvation models for free energies in aqueous solution.
TL;DR: Two new continuum solvation models have been presented recently and offer considerably improved performance compared to AM1-SM1 for neutral molecules and essentially equivalent performance for ions.
Journal ArticleDOI
Optimization and application of lithium parameters for PM3
TL;DR: Li/PM3 gives reliable results even for large dimeric complexes, like [{4‐(CH3CR)C5H4N}Li]2, containing TMEDA or THF as coligands and reproduces the haptotropic interaction between Li+ and π‐systems.
Journal ArticleDOI
Quantitative structure-activity relationship of sesquiterpene lactones with cytotoxic activity.
Marcus Tullius Scotti,Mariane B. Fernandes,Marcelo J. P. Ferreira,Vicente de Paulo Emerenciano +3 more
TL;DR: This study investigated a set of 37 different sesquiterpene lactones, represented by 4 skeletons, with important properties for the inhibition potency discussed for the whole data set and for subsets of the different structural skeletons.
References
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Journal ArticleDOI
Development and use of quantum mechanical molecular models. 76. AM1: a new general purpose quantum mechanical molecular model
TL;DR: In this paper, a new parametric quantum mechanical molecular model, AM1 (Austin Model l), based on the NDDO approximation, is described, in which the major weaknesses of MNDO, in particular failure to reproduce hydrogen bonds, have been overcome without any increase in computing time.
Journal ArticleDOI
Optimization of parameters for semiempirical methods I. Method
TL;DR: In this paper, a new method for obtaining optimized parameters for semi-empirical methods has been developed and applied to the modified neglect of diatomic overlap (MNDO) method.
Journal ArticleDOI
Ground States of Molecules. 38. The MNDO Method. Approximations and Parameters
Michael J. S. Dewar,Walter Thiel +1 more
Journal ArticleDOI
Optimization of parameters for semiempirical methods II. Applications
TL;DR: In this paper, the average difference between the predicted heats of formation and experimental values for 657 compounds is 7.8 kcal/mol, and for 106 hypervalent compounds, 13.6 kcal/min.