Showing papers by "David Vanderbilt published in 1983"
TL;DR: In this article, the authors investigated the effect of the Coulomb repulsion on the bonding coordination defect in glassy Se and showed that a large negative contribution arising from interconversion between dangling-bond and threefold-coordinated structures gives rise to an overall positive $U$
Abstract: The effective Hubbard $U$ for the bonding coordination defect in glassy Se is investigated. This is accomplished by applying local-density total-energy calculations directly to charged defects in a superlattice configuration. The existence of a large negative contribution to $U$, arising from interconversion between dangling-bond and threefold-coordinated structures, is confirmed. However, a still larger Coulomb repulsion gives rise to an overall positive $U$.
36 citations
25 citations
TL;DR: In this article, a self-consistent LCAO approach is applied to the study of the C(111) ideal 1×1 and reconstructed 2×1 surfaces, and the surface states are calculated for a variety of buckled, π-bonded chain, dimerized π−bunded chain and π•bonding molecule reconstructions.
Abstract: A first principles self‐consistent LCAO approach is applied to the study of the C(111) ideal 1×1 and reconstructed 2×1 surfaces. The surface states are calculated for a variety of buckled, π‐bonded chain, dimerized π‐bonded chain, and π‐bonded molecule reconstructions. None of the models studied to date are found to be in good agreement with photoemission experiments; the theoretical occupied dangling bond surface bands are either too deep in the gap, too dispersive, or both. The dimerized π‐bonded chain model is in closest qualitative agreement with experiment.
13 citations
TL;DR: In this paper, the structural configuration of a superlattice structure containing a vacancy in trigonal Se is determined by calculating the forces, as well as the total energies, within the local-density and frozen-core approximations.
Abstract: Ab initio total-energy calculations are used to determine theoretically the structural configuration of the vacancy in trigonal Se. The method consists of calculating the forces, as well as the total energies, within the local-density and frozen-core approximations, for a superlattice structure containing a vacancy. In this way, relaxations at the vacancy can be fully taken into account, including a possible self-healing of the vacancy. A slightly relaxed symmetric version of the ideal vacancy is the lowest-energy structure found; neither asymmetric relaxation nor valence alternation appears to occur. A simple Hubbard Hamiltonian is used to analyze the spin configuration of the lowest-energy structure.
8 citations
TL;DR: In this paper, the effective Hubbard U was calculated for the interconversion of 1-fold and 3-fold bonding coordination defects in glassy Se. This was accomplished by applying local density total energy calculations directly to charged defects in a superlattice configuration.
Abstract: The effective Hubbard U is calculated for the interconversion of 1-fold and 3-fold bonding coordination defects in glassy Se. This is accomplished by applying local density total energy calculations directly to charged defects in a superlattice configuration. It is found that the defect remains 1-fold coordinated in the D − and D 0 charge states, but spontaneously forms a 3-fold center in the D + charge state. The structural relaxation energy involved in the bond switching gives rise to a sizable negative contribution to U , but a still larger Coulomb repulsion gives rise to an overall positive U . This result is not , however, inconsistent with a negative U in the compound chalcogenide glasses.
7 citations