Journal of Computational Chemistry

The XYG3-type doubly hybrid (xDH) functionals are nonvariational in both the hybrid density functional part and the second-order perturbation part, each of which requires formally a coupled-perturbed Kohn–Sham equation to be solved for analytic gradients. An implementation is reported here which combines the two parts by defining a total Lagrangian such that only a single set of the Z-vector equations need to be solved. Test calculations are provided to demonstrate the satisfactory performance of the xDH functionals for geometry optimizations.

Accurate theoretical estimation of protein–ligand interaction is vitally important for the rational design of an effective drug. In this work, we have developed a nonfitting protein–ligand interaction scoring function based on divide and conquer strategy and first-principles methods. Good correlations on applications to cyclin-dependent kinase 2 and p21-activated kinase 1 inhibitor databases are found between the calculated scores and the experimental inhibitor efficacies with the square of correlation coefficient R² of 0.76–0.89.

O1s core-electron binding energies of electrophilic and nucleophilic oxygens important for olefin epoxidation on silver surface were investigated by the symmetry-adapted-cluster configuration-interaction (SAC-CI) method combined with the dipped adcluster model (DAM). The experimental information and our theoretical results indicate that Oelec is the atomic oxygen adsorbed on the fcc site of Ag(111) and that Onuc is the one on the reconstructed added-row site of Ag(110).

A set of exchange-correlation functionals, including BLYP, PBE0, B3LYP, BHandHLYP, CAM-B3LYP, LC-BLYP, and HSE, has been used to determine static and dynamic nonresonant (nuclear relaxation) vibrational (hyper)polarizabilities for a series of polymethineimine oligomers containing up to eight monomer units. These functionals are assessed against reference values obtained using the MP2 and CCSD methods.

A newly developed HF-3c quantum chemical protocol combines a Hartree- Fock/small basis set calculation with three physically plausible atom-pair wise correction terms. It yields good results for non-covalent interactions, geometries of organic molecules, supramolecular complexes and small proteins. For most test cases its accuracy approaches DFT-D3/large basis set quality, but obtained at a tiny fraction of computational cost and can hence be applied to large molecular systems as an alternative to semiempirical methods.