High-pressure structural, elastic and electronic properties of the scintillator host material, KMgF_3

TL;DR

This study combines theoretical calculations and high-pressure experiments to explore the structural, elastic, and electronic properties of KMgF_3, revealing its stability, brittleness, and pressure-dependent electronic gap.

Contribution

It provides a comprehensive analysis of KMgF_3's properties under pressure using density functional theory and synchrotron X-ray diffraction, which is novel for this material.

Findings

Cubic symmetry persists up to 40 GPa

Calculated properties agree with experiments

KMgF_3 is brittle and has an increasing electronic gap under pressure

Abstract

The high-pressure structural behaviour of the fluoroperovskite KMgF_3 is investigated by theory and experiment. Density functional calculations were performed within the local density approximation and the generalized gradient approximation for exchange and correlation effects, as implemented within the full-potential linear muffin-tin orbital method. In situ high-pressure powder x-ray diffraction experiments were performed up to a maximum pressure of 40 GPa using synchrotron radiation. We find that the cubic Pm\bar{3}m crystal symmetry persists throughout the pressure range studied. The calculated ground state properties -- the equilibrium lattice constant, bulk modulus and elastic constants -- are in good agreement with experimental results. By analyzing the ratio between the bulk and shear modulii, we conclude that KMgF_3 is brittle in nature. Under ambient conditions, KMgF_3 is found to be an indirect gap insulator with the gap increasing under pressure.