Calculations of Phonons and Phonon Dispersion in Lifep Pnictide Superconductor

Abstract

Not too long ago(2008),a new pnictide Superconductor free from arsenic was discovered–LiFeP. It belongs to the family of the so called ‘111’ type iron Superconductor. It has unique characteristics in its normal state which can be useful in understanding the unusual high temperature superconductivity observed in iron pnictide compounds. In this work,we studied LiFeP from first principles. The structure was optimised,electronic structure calculations were performed yielding lattice constants that differed only 2 − 9% from experiment. Band structure was calculated and electronic density of states showing no band gap was found. Calculations on phonon modes was also done. From observing the phonon normal modes,the FeP plane was found to be largely decoupled from the Li atoms.In some modes the P is also decoupled from the Fe plane.A small band gap of about 25cm −1 (≡ 35)K was also noticed in the phonon band structure.