Phase stability and physical properties of Ta5Si3 compounds from first-principles calculations,

TL;DR

This study uses first-principles calculations to analyze the phase stability, electronic structure, and thermophysical properties of Ta5Si3 compounds, predicting phase transformation temperatures and bonding characteristics.

Contribution

It provides a comprehensive first-principles analysis of Ta5Si3 phases, including stability, electronic, elastic, and thermodynamic properties, with predictions aligning closely with experimental data.

Findings

D8l phase is the low-temperature stable structure.

Bonding in Ta5Si3 is predominantly covalent.

Predicted phase transformation temperature is 2303.7K.

Abstract

We present a study of the thermodynamic and physical properties of Ta5Si3 compounds by means of density functional theory based calculations. Among the three different structures (D8m, D8l, D88), the D8l structure (Cr5B3-prototype) is the low temperature phase with a high formation enthalpy of -449.20kJ/mol, the D8m structure (W5Si3-prototype) is the high temperature phase with a formation enthalpy of -419.36kJ/mol, and the D88 structure (Mn5Si3-prototype) is a metastable phase. The optimized lattice constants of the different Ta5Si3 compounds are also in good agreement with the experimental data. The electronic density of states (DOS) and the bonding charge density have also been calculated to elucidate the bonding mechanism in these compounds and the results indicate that bonding is mostly of covalent nature. The elastic constants of the D8m and D8l structures have been calculated together with the different moduli. Finally, by using a quasiharmonic Debye model, the Debye temperature, the heat capacity, the coefficient of thermal expansion and the Gr\"uneisen parameter have also been obtained in the present work. The transformation temperature (2303.7K) between the D8m and the D8l structures has been predicted by means of the Gibbs energy, and this predicted temperature (2303.7K) is close to the experimental value (2433.5K).