Using a recently published benchmark MP2 database of nucleic acid base trimers, the three-body contribution to the interaction energy (TBE, also termed (non)cooperativity) as a function of base composition and complex geometry is studied. In 28 out of 141 cases (or 20%), the counterpoise-corrected MP2/TZV(2df,2pd) TBE exceeds 1 kcal mol(-1). The TBE is below 1 kcal mol(-1) for all trimers in th...

Coupled-cluster theory with single and double excitations (CCSD) is a promising ab initio method for the electronic structure of three-dimensional metals, which second-order perturbation (MP2) diverges in thermodynamic limit. However, due to high cost poor convergence CCSD respect basis size, applying periodic systems often leads large set errors. In common "composite" method, MP2 used recover ...

Quantum chemistry methods exploiting density-functional approximations for short-range electron-electron interactions and second-order Møller-Plesset (MP2) perturbation theory for long-range electron-electron interactions have been implemented for periodic systems using Gaussian-type basis functions and the local correlation framework. The performance of these range-separated double hybrids has...

Density functional theory (DFT) and ab initio MP2 methods have been applied to characterize the structural features of seven different bonding isomers of copper() thiocyanate dianion complexes (Sand/or N-bonded). The DFT calculations were carried out by means of the hybrid Becke 3LYP functional, using the 6-3111G* basis set. The ab initio calculations were done at the MP2/6-3111G* theoretical ...

We present an exhaustive study of more than 250 ab initio potential energy surfaces (PESs) of the model dipeptide HCO-L-Ala-NH(2). 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, ...

Saccharopine reductase from Magnaporthe grisea, an NADPH-containing enzyme in the α-aminoadipate pathway, catalyses the formation of saccharopine, a precursor to L-lysine, from the substrates glutamate and α-aminoadipate-δ-semialdehyde. Its catalytic mechanism has been investigated using quantum mechanics/molecular mechanics (QM/MM) ONIOM-based approaches. In particular, the overall catalytic p...

The results of MNDO, AM1 and PM3 semi-empirical calculations and HF/6-31G*, MP/6-31G*, MP2/6-311+G**, and B3LYP/6-311G** and QCISD/6-31G* ab initio methods for angle strain and conjugation effects in twist-boat, boat, and half-chair geometries of (Z,Z,Z)-cycloocta-1,3,5-triene indicate that all methods, except PM3, predict wrong ordering of the conformations.

Ab initio electronic structure calculations with RHF, MP2, and CCSD(T) wave functions have been used to investigate a reaction path for the hydrosilation reaction catalyzed by divalent titanium (modeled by TiH2). Optimized structures and energies are presented. All levels of theory predict a barrierless reaction path compared to a barrier of 78 kcal/mol for the uncatalyzed reaction. The use of ...

Quantum Monte Carlo calculations with the diffusion Monte Carlo (DMC) method have been used to compute the binding energy curves of hydrogen on benzene, coronene, and graphene. The DMC results on benzene agree with both Møller-Plessett second order perturbation theory (MP2) and coupled cluster with singles, doubles, and perturbative triples [CCSD(T)] calculations, giving an adsorption energy of...