DENSITY FUNCTIONAL THEORETICAL CALCULATIONS AND COMPARISONS OF PHONON DISPERSION RELATIONS OF ELEMENTAL SEMICONDUCTORS.

R. A. Amusa¹  and O. E. Oyewande²

¹Department of Science Laboratory Technology, Federal Polytechnic, Ilaro, Nigeria

²Department of Physics, University of Ibadan. Ibadan, Nigeria.

ABSTRACT

Phonon dispersion relations of semiconductor crystal frequencies at some high symmetry points were reported. A first principles method based on density functional perturbation theory (DFPT) as embedded in the Quantum Espresso (QE) simulation software was used. Appropriate equilibrium lattice constants and energy cut-offs needed for the calculations were deducted from the results of convergence tests carried out for the elements used. Effects of the local density approximation (LDA) and generalized gradient approximation (GGA) exchange correlation potentials at each of the high symmetry lines were compared. Our results of the phonon relations compare favourably well with those obtained in similar published researches. The result also showed that magnitude of phonon frequencies (both optical and acoustic) decrease from carbon to tin and in fact the ratio is 3:1 for Carbon: Silicon.

Keywords:   Quantum Espresso, dispersion relations, high symmetry points, exchange correlation potentials.