N. Shanthi

Realistic tight-binding model for the electronic structure of II-VI semiconductors

We analyze the electronic structure of group II-VI semiconductors obtained within linearized muffin-tin-orbital approach in order to arrive at a realistic and minimal tight-binding model, parametrized to provide an accurate description of both valence and conduction bands. It is shown that a nearest-neighbor

Electronic structure of Millerite NiS

{\mathrm{sp}}^{3}{d}^{5}

ELECTRONIC EXCITATION SPECTRA FROM AB INITIO BAND-STRUCTURE RESULTS FOR LAMO3 (M = CR,MN,FE,CO,NI)

model is fairly sufficient to describe the electronic structure of these systems over a wide energy range, obviating the use of any fictitious

Electronic structure of

{s}^{*}

LaCrO_3,LaMnO_3

orbital. The obtained hopping parameters obey the universal scaling law proposed by Harrison, ensuring transferability to other systems. Furthermore, we show that certain subtle features in the bonding of these compounds require the inclusion of anion-anion interactions in addition to the nearest-neighbor cation-anion interactions.

and

We investigate the electronic structure of Nickel sulphide (NiS) in the millerite phase using electron spectroscopic measurements and band structure as well as model Hamiltonian calculations. While band structure calculations are found to be relatively more successful in describing the experimental valence band spectrum of this highly conducting phase compared to the hexagonal phase of NiS, cluster calculations including electron correlation effects are found to be necessary for the description of certain features in the experimental spectra, indicating the importance of correlation effects even in a highly metallic system. The electronic parameter strengths obtained from these calculations confirm that the millerite NiS is a highly covalent pd metal. The comparative study of hexagonal and millerite forms of NiS, provides the information concerning the evolution of the spectral function in a pd metal as a function of covalency.

LaFeO_3

We present calculated electron excitation spectra for the LaMO3 series (M=Cr-Ni) obtained within ab-initio band structure calculations for the real geometric and magnetic structures. The calculated results show good agreement with the experimentally obtained spectra. This suggests that the transition metal-transition metal interactions via the oxygen atom play an important role in determining the spectroscopic features and indicates a smaller value of U/t than has been believed so far. The present approach undermines the importance of multiplet interactions which otherwise play an important role within various single impurity models.

from ab initio spin-polarized calculations

The electronic structures of the

Estimates of electronic interaction parameters for LaMO3 compounds (M=Ti-Ni) from ab-initio approaches

LaMO_3

Electronic structure of

series are discussed on the basis of ab initio band-structure calculations within the local spin-density approximation, which correctly predicts the insulating and magnetic structures in each case. The band dispersions obtained along various symmetry directions were mapped onto those calculated with a nearest-neighbour tight-binding model within a least-squared-error procedure, providing estimates for the various hopping strengths as well as the intra-atomic exchange strength in each case.