Efficient model chemistries for peptides. I. Split-valence Gaussian basis sets and the heterolevel approximation in RHF and MP2 - Quantitative Biology Quantitative MethodsReportar como inadecuado




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Abstract: We present an exhaustive study of more than 250 ab initio potential energysurfaces PESs of the model dipeptide HCO-L-Ala-NH2. The model chemistriesMCs used are constructed as homo- and heterolevels involving possiblydifferent RHF and MP2 calculations for the geometry and the energy. The basissets used belong to a sample of 39 selected representants from Poplessplit-valence families, ranging from the small 3-21G to the large6-311++G2df,2pd. The reference PES to which the rest are compared is theMP2-6-311++G2df,2pd homolevel, which, as far as we are aware, is the moreaccurate PES of a dipeptide in the literature. The aim of the study presentedis twofold: On the one hand, the evaluation of the influence of polarizationand diffuse functions in the basis set, distinguishing between those placed at1st-row atoms and those placed at hydrogens, as well as the effect of differentcontraction and valence splitting schemes. On the other hand, the investigationof the heterolevel assumption, which is defined here to be that which statesthat heterolevel MCs are more efficient than homolevel MCs. The heterolevelapproximation is very commonly used in the literature, but it is seldomchecked. As far as we know, the only tests for peptides or related systems,have been performed using a small number of conformers, and this is the firsttime that this potentially very economical approximation is tested in fullPESs. In order to achieve these goals, all data sets have been compared andanalyzed in a way which captures the nearness concept in the space of MCs.



Autor: Pablo Echenique, J. L. Alonso

Fuente: https://arxiv.org/







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