We have incorporated MPI based parallelism with dynamic load balance into the Hartree–Fock and DFT modules of Q-Chem. A series of benchmark calculations consisting of both single point energy and gradient calculations were carried out to gauge the performance of the parallel modules. Calculations were carried out on two different parallel computers, namely a shared memory Silicon Graphics Origi...

We report a spin-unrestricted density functional theory(DFT) solution at the symmetric dimer structure for cluster models of Si(100). With this solution, it is shown that the symmetric structure is a minimum on the DFTpotential energy surface, although higher in energy than the buckled structure. In restricted DFT calculations the symmetric structure is a saddle point connecting the two buckled...

Density functional theory (DFT) embedding provides a formally exact framework for interfacing correlated wave-function theory (WFT) methods with lower-level descriptions of electronic structure. Here, we report techniques to improve the accuracy and stability of WFT-in-DFT embedding calculations. In particular, we develop spin-dependent embedding potentials in both restricted and unrestricted o...

We present two interatomic potentials for hydrogen in –iron based on the embedded atom method potentials for iron developed by Mendelev et al. Philos. Mag. 83, 3977 2003 and Ackland et al. J. Phys.: Condens. Matter 16, S2629 2004 . Since these latter potentials are unique among existing iron potentials in their ability to produce the same core structure for screw dislocations as density functio...

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...

first principles calculations were carried out for investigation the novel 7-hydroxycoumarinyl gallates derivatives in gas and liquid phases using density functional theory (dft) method. computational chemistry simulations were carried out to compare calculated quantum chemical parameters for gallates derivatives. all calculations were performed using dmol3 code which is based on dft. the doubl...

In this work, the optimization calculations were carried out on quetiapine hemifumarat, 4, and its analogues, 1-5. These calculations were carried out using the B3LYP/6-31G(d) level of theory. The DFT calculations clarified a boat structure for dibenzothiazepine moiety of the molecule which piperazine moiety has a chair conformation. Thermal energies (E), enthalpies (H), and free energies (G) o...

Benzyl chloride and tin powder were used to prepare dibenzyltin dichloride according to a literatureprocedure. In this study, IR spectroscopy, HOMO-LUMO energy gap, NBO analysis, polarizability,some geometrical parameters, natural charge and electrical potential of atoms, global hardness,electronic chemical potential, global electrophilicity index, and molar volume of dibenzyltindichloride were...

benzyl chloride and tin powder were used to prepare dibenzyltin dichloride according to a literatureprocedure. in this study, ir spectroscopy, homo-lumo energy gap, nbo analysis, polarizability,some geometrical parameters, natural charge and electrical potential of atoms, global hardness,electronic chemical potential, global electrophilicity index, and molar volume of dibenzyltindichloride were...

Measured and calculated band structures for the six lightest group-I and -II oxides are reported. Band structures have been measured using electron momentum spectroscopy, a technique that maps the ground-state occupied orbitals resolved both in energy and momentum. Measurements are compared with first-principles calculations carried out within the linear combination of atomic orbitals approxima...