Papers by Keyword: Bond Order

Abstract: In this paper we present bond-order potentials (BOPs) based on the tight-binding method. The potentials have been developed for bcc non-magnetic metals of group V.B (V, Nb, Ta) and group VI.B (Cr, Mo, W) as well as for the ferromagnetic bcc iron. The testing of the transferability of BOPs involves energies of alternate structures, formation energies of vacancies and self-interstitials, transformation paths between different structures and phonon dispersion relations. An example of the application of these potentials is modeling of the structure and glide of 1⁄2<111> screw dislocations under the effect of applied shear and tensile/compressive stresses.

Abstract: The concepts of electronic stress tensor density and energy density give new viewpoints for conventional ideas in chemistry. In this paper, we introduce the electronic stress tensor and energy density and other related quantities such as tension density and kinetic energy density, which are based on quantum field theory, and show their connection to the concepts in chemistry. The topics are: (i) zero surface of the electronic kinetic energy density and size of atoms, (ii) separatrix of the tension field as a boundary surface of atoms in a molecule, (iii) interpretation of energy density based bond order as directional derivative of a total energy of a molecule regarding the bond direction, and (iv) eigenvalues of the stress tensor as tools to classify types of chemical bond.

Abstract: We study the chemical bonds of small Al clusters (Al_n, n=2-8) and hydrogenated Al clusters (Al_nH_m , n=1-8 and m=1,2) using electronic stress tensor. We calculate the bond order based on energy density for these clusters. We also study the electronic structure under the presence of electronic current by the electronic stress tensor for AlH₃ molecule.

Abstract: We report the new structures of aluminum hydrides derived from the Al4 tetrahedral cages. We perform ab initio quantum chemical calculation for these new aluminum hydrides. Our calculation of binding energies of the new aluminum hydrides reveal that stability of these hydrides increases as more hydrogen atoms are adsorbed, while stability of Al-H bonds decreases. We also calculate electronic stress tensor to evaluate the chemical bonds of these hydrides. As a result, we find that the bonds of the Al4 tetrahedral cage are strengthened as more hydrogen atoms are adsorbed on the aluminum hydrides. Our calculation of the potential energy surfaces and the regional chemical potential show that hydrogen atoms are likely to adsorb on bridge site at first.