Lattice dynamics of KNi2Se2

TL;DR

This study combines first-principles calculations and Raman scattering experiments to analyze the lattice dynamics of KNi2Se2, revealing phonon modes and structural differences from related compounds.

Contribution

It provides the first detailed lattice dynamics analysis of KNi2Se2 using both computational and experimental methods, highlighting its unique vacancy ordering behavior.

Findings

Three Raman active modes observed experimentally

Calculated phonon frequencies match experimental data

No vacancy ordering in KNi2Se2 unlike its iron counterpart

Abstract

We report the first principle calculations of the lattice dynamics of KNi$_{2}$Se$_2$ together with the Raman scattering study.\ We have observed three out of four Raman active modes predicted by the factor group analysis. Calculated phonon frequencies are in good agreement with experimental findings.\ Contrary to its iron counterpart (K$_x$Fe$_{2-y}$Se$_2$), K$_{0.95}$Ni$_{1.86}$Se$_2$ does not show vacancy ordering.