Thermoelastic properties of $\alpha$-iron from first-principles

TL;DR

This study uses first-principles calculations to determine the thermomechanical properties of $ extalpha$-iron, revealing how computational strategies affect results and showing good agreement with experimental temperature dependence.

Contribution

It provides a detailed first-principles methodology for calculating elastic constants of $ extalpha$-iron, including error analysis and validation against experiments.

Findings

Zero-temperature properties are sensitive to calculation details.

Semi-local functionals yield fair to good zero-temperature elastic constants.

Temperature dependence matches experimental data up to the Curie point.

Abstract

We calculate the thermomechanical properties of $\alpha$-iron, and in particular its isothermal and adiabatic elastic constants, using first-principles total-energy and lattice-dynamics calculations, minimizing the quasi-harmonic vibrational free energy under finite strain deformations. Particular care is made in the fitting procedure for the static and temperature-dependent contributions to the free energy, in discussing error propagation for the two contributions separately, and in the verification and validation of pseudopotential and all-electron calculations. We find that the zero-temperature mechanical properties are sensitive to the details of the calculation strategy employed, and common semi-local exchange-correlation functionals provide only fair to good agreement with experimental elastic constants, while their temperature dependence is in excellent agreement with experiments in a wide range of temperature almost up to the Curie transition.