ELECTRONIC AND RELATED
PROPERTIES OF SOLIDS AND CLUSTERS
Dr. Diola Bagayoko (SUBR)
Dr. Pui-Man Lam (SUBR)
Dr. Nathan Brener (LSU)
The work of this group centers around the computation of electronic, structural, and related properties of materials.
The group and its collaborators have developed, over the last fifteen years, an extensive library of first principle computational codes. We particularly note the Cluster Calculation Package and the package for the energy band calculations (BNDPKG). A battery of auxiliary computer programs has been developed for analysis and plotting purposes. In particular, the dielectric function calculation and that of optical conductivity of solids should be noted. These auxiliary programs, using the highly accurate energy levels and wave functions, can basically compute properties of materials, including optical, magnetic, and structural properties.
Since the coding of the total energy calculation formalism by Bagayoko et al. in 19 above calculations have gained predictive capacity as opposed to a solely descriptive one. Indeed, the minima of the total energy, for various crystal geometries and magnetic structure the lattice constant is varied, lead to the prediction of stable phases. This development also afforded us the ability to investigate the effect of positive or negative pressures (hydrostatic pressures).
Brener et al. expanded the BNDPKG to the point where it can handle arbitrary geometry and several atoms per unit cell. This added capability makes it possible for us to study all materials ranging from metals to complicated oxides, including high temperature superconductors. The ability to handle all Bravais lattice is synonymous with that of investigating the effects uniaxial pressure on materials.
A singular distinction of our capabilities stems from the fact that we can not only study effects of fundamental iterations on properties of materials, but also that our ancillary programs allow us to produce experimentally verifiable and practically usable quantities. Optical transition optical conductivity, neutron and x-ray scattering form factors, phase diagrams, band mass are a few of these quantities. Densities of states, magnetic moments, and detailed electron charges are others. The cluster calculation program (CCP), by changing the size of the cluster and by varying the lattice parameter, affords unique insights on the role of short and long range interactions.
Our method employs the linear combination of atomic orbital formalism in ab-initio electron and self consistent quantum mechanical calculations. Density functional potentials and non-local are utilized in most of our calculations. They have proven themselves to be excellent representations of the many body potential that is of relevance in our work.
The synergism between this group and the ones noted elsewhere could be simply seen by noting that most properties of materials can be obtained once accurate energies and relative wave functions are available. More specifically, the phase diagram, band mass, magnetic structures to be produced by this group are directly relevant to the theoretical study and molecular dynamics simulations of Fan and Malozovsky. Further, interatomic (and pair) potential that can be explicitly derived from the output of our calculations are crucial in molecular dynamics simulations (MD). The fact that such potential be derived from X-ray data constitutes another interface between our work and that of Fan on the one hand, and experiment on the other.