Evaluation of intermolecular distance and binding energy (BE) of van der Waals complex/cluster at ab initio level of theory is computationally demanding when many monomers are involved. Starting from MP2 energy, we reached a two-step evaluation method of BE of van der Waals complex/cluster through reasonable approximations; BE = BE(HF) + sum Mi> Mj{BE (Mi- Mj)(MP2 or MP2.5) - BE(Mi-Mj)(HF)} whe...

We have examined the performance of semiempirical quantum mechanical methods in solving the problem of accurately predicting protein-ligand binding energies and geometries. Firstly, AM1 and PM3 geometries and binding enthalpies between small molecules that simulate typical ligand-protein interactions were compared with high level quantum mechanical techniques that include electronic correlation...

MP2 and CCSD(T) complete basis set (CBS) limit relative electronic energies (DeltaE(e)) have been determined for eight low-lying structures of the water hexamer by combining explicitly correlated MP2-R12 computations with higher-order correlation corrections from CCSD(T) calculations. Higher-order correlation effects are quite substantial and increase DeltaE(e) by at least +0.19 kcal mol(-1) an...

A combined computational and (13)C NMR study was used to investigate the formation of mixed aggregates of 1-methoxyallenyllithium and lithium chloride in tetrahydrofuran (THF) solution. The observed and calculated chemical shifts, as well as the calculated free energies of mixed aggregate formation (MP2/6-31+G(d)), are consistent with the formation of a mixed dimer as the major species in solut...

The conformational landscape of phenylisoserine (PhIS) was studied. Trial structures were generated by allowing for all combinations of single-bond rotamers. Based on the B3LYP/aug-cc-pVDZ calculations 54 conformers were found to be stable in the gas phase. The six most stable conformers were further optimized at the B3LYP/aug-cc-pVTZ and MP2/aug-cc-pVDZ levels for which characteristic intramol...

The Soa bitter-sensitivity and Prp salivary-protein loci map to distal mouse chromosome six. No recombination has been found between sucrose octaacetate (SOA)-avoidance phenotype and PRP haplotype in any mouse population. Soa and Prp, therefore, are either very near each other or identical. To assess the latter possibility, two type-A, proline-rich protein genes (MP2 and M14), situated approxim...

We developed a new first principles potential for the cytosine dimer. The ab initio calculations were performed with a DFT-SAPT combination of the symmetry-adapted perturbation method and density functional theory, and fitted to a model site-site functional form. The model potential was used to predict cluster structures up to cytosine hexamers. The global cluster structure optimizations showed...

The atomic orbital basis set limit is approached in periodic correlated calculations for solid LiH. The valence correlation energy is evaluated at the level of the local periodic second order Møller-Plesset perturbation theory (MP2), using basis sets of progressively increasing size, and also employing "bond"-centered basis functions in addition to the standard atom-centered ones. Extended basi...

ab initio calculations at the density functional theory (dft) and the second-order møller−plessetperturbation theory levels with 6-31+g(d), 6-31g(d) basis sets for non-metal atoms and lanl2dzfor metal have been performed for the adsorption of dimethyl methylphosphonate (dmmp) on znoby gaussisn 98 program. the calculated rotational constants by b3lyp/6-31g(d) are in moreagreement with the experi...