Mechanical and thermal properties of monazite LaPO₄ under pressure

¹ Materials Modelling Centre, University of Limpopo, South Africa
² Advanced Materials Division, MINTEK, South Africa
³ The South African Nuclear Energy Corporation SOC Ltd. (Necsa), South Africa

^* Corresponding author: lmotsomone@gmail.com

Abstract

Monazite-La (LaPO4) is considered the first constituent of the rare-earth orthophosphate group and has received a considerable scientific interest owing to its notable physical characteristics, such as its optical emissivity and its ability to withstand radiation damage and corrosion when exposed to molten glass. This material is deemed suitable for the extended- term containment of radioactive nuclear waste. This study investigates the influence of pressure on the mechanical and thermal properties of Monazite- La within the pressure range of 0 to 100 gigapascals (GPa) through the utilization of the density functional theory (DFT) approach. At 0 GPa, it was shown that the lattice parameters exhibited a significant level of concurrence with experimental findings to within 3%. Furthermore, it has been observed that the structure exhibits mechanical stability up to a pressure of 100 GPa. Additionally, this paper will also address the concepts of heat capacity, and thermal expansion. The findings provide enhanced insights into the mechanical and thermal properties of Monazite-La when subjected to pressure.