BUSCADOR RECOLECTA

This corresponds to a series of approximately 40,000 quantum chemical calculations on one single system, the model dipeptide HCO-L-Ala-NH2, with 16 atoms and no charge. The conformational space of this molecule is scanned by defining a regular 12x12 grid from -165º to 165º in 30º steps in the 2D space spanned by its Ramachandran angles phi and psi. The energy at each of these 144-points set is calculated using using the methods RHF and MP2, and a large number of Pople basis sets ranging from 3-21G to 6-311++G(2df,2pd). These methods are combined using the same one for the geometry optimization and the energy calculation (homolevel) or different ones (heterolevel). The dataset contains 274 grids, each one corresponding to a different homo- or heterolevel. This consists of a set of human-readable ASCII files in the output format of Gaussian 03, in folders with descriptive names and compressed using tar and gzip (i.e., you need the GNU applications tar and gzip to uncompress them). Created with Gaussian 03, Revision C.02. Readable with any text editor. This dataset is made available under the Open Database License: http://opendatacommons.org/licenses/odbl/1.0/. Any rights in individual contents of the database are licensed under the Database Contents License: http://opendatacommons.org/licenses/dbcl/1.0/, This dataset is the basis of an exhaustive published study (see https://digital.csic.es/handle/10261/35334) of more than 250 ab initio potential energy surfaces (PESs) of the model dipeptide HCO-L-Ala-NH2. The model chemistries (MCs) investigated are constructed as homo- and heterolevels involving possibly different RHF and MP2 calculations for the geometry and the energy. The basis sets used belong to a sample of 39 representants from Pople's split-valence families, ranging from the small 3-21G to the large 6-311++G(2df,2pd). The reference PES to which the rest are compared is the MP2/6-311++G(2df,2pd) homolevel, which, as far as we are aware, wss the most accurate PES in the literature at the moment of its publication. The great number of MCs evaluated has allowed us to significantly explore this space and show that the correlation between accuracy and computational cost of the methods is imperfect, thus justifying a systematic search for the combination of features in a MC that is optimal to deal with peptides. Regarding the particular MCs studied, the most important conclusion is that the potentially very cost-saving heterolevel approximation is a very efficient one to describe the whole PES of HCO-L-Ala-NH2. Finally, we show that, although RHF may be used to calculate the geometry if a MP2 single-point energy calculation follows, pure RHF//RHF homolevels are not recommendable for this problem., This work has been supported by the research projects E24/3 and PM048 (Aragón Government), MEC (Spain) FIS2006-12781-C02-01 and MCyT (Spain) FIS2004-05073-C04-01. P. Echenique was supported by a BIFI research contract., Peer reviewed