We describe fully quantum, time-independent scattering calculations of the F+H2-->HF+H reaction, concentrating on the HF product rotational distributions in v'=3. The calculations involved two new sets of ab initio potential energy surfaces, based on large basis set, multireference configuration-interaction calculations, which are further scaled to reproduce the experimental exoergicity of the ...

Algorithms for the efficient calculation of two-electron integrals in the newly developed mixed ramp-Gaussian basis sets are presented, alongside a Fortran90 implementation of these algorithms, RampItUp. These new basis sets have significant potential to (1) give some speed-up (estimated at up to 20% for large molecules in fully optimised code) to general-purpose Hartree-Fock (HF) and density f...

The isomer shift for the 23.87 keV M1 resonant transition in the (119)Sn nucleus is calibrated with the help of ab initio calculations. The calibration constant alpha((119)Sn) obtained from Hartree-Fock (HF) calculations (alpha(HF)((119)Sn) = (0.081+/-0.002)a(0)(-3) mm/s) and from second-order Moller-Plesset (MP2) calculations (alpha(MP2)((119)Sn) = (0.091+/-0.002)a(0)(-3) mm/s) are in good agr...

We present and discuss results of the calculations for BaTiO3 and SrTiO3 surface relaxation with different terminations using a semi-empirical shell model (SM) as well as ab initio methods based on Hartree-Fock (HF) and Density Functional Theory (DFT) formalisms. Using the SM, the positions of atoms in 16 near-surf ace layers placed atop a slab of rigid ions are optimized. This permits us deter...

Detailed investigation of the tautomerism of oxazolidines, thiazolidines and selenazolidines substituted at positions 2 and 4 by hydroxy and amino groups was carried out by calculations at HF and MP2 levels of theory and NMR spectroscopy. The relative stabilities of the tautomers of the heterocycles were calculated in gas phase and in solvents CHCl3 and DMSO utilizing the PCM method. The ab ini...

structural and magnetic properties of purine and pyrimidine nucleotides (cmp, ump, dtmp, amp, gmp, imp) were studied at different levels of ab initio molecular orbital theory. these calculations were performed at the hartree-fock level and density functional b3lyp methods. geometries were fully optimized by following cs symmetry restrictions. the standard 6-31g** basis set which includes polari...

First-principles quantum calculations for anharmonic vibrational spectroscopy of three protected dipeptides are carried out and compared with experimental data. Using hybrid HF/MP2 potentials, the Vibrational Self-Consistent Field with Second-Order Perturbation Correction (VSCF-PT2) algorithm is used to compute the spectra without any ad hoc scaling or fitting. All of the vibrational modes (135...

Broken-symmetry density functional theory (BS-DFT) calculations are assessed for redox energetics [Cu(SCH3)2]1-/0, [Cu(NCS)2]1-/0, [FeCl4]1-/0, and [Fe(SCH3)4]1-/0 against vertical detachment energies (VDE) from valence photoelectron spectroscopy (PES), as a prelude to studies of metalloprotein analogs. The M06 and B3LYP hybrid functionals give VDE that agree with the PES VDE for the Fe complex...

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.

We review electronic structure calculations of finite-length semiconducting carbon nanotubes using time-dependent density functional theory (TD-DFT) and the time dependent Hartree-Fock (TD-HF) approach coupled with semi-empirical AM1 and ZINDO Hamiltonians. We specifically focus on the energy splitting, relative ordering, and localization properties of optically active (bright) and optically fo...