Anharmonic correlated Debye model for thermal disorder in iron-rich B2-FeAl intermetallic alloy

Abstract

The anharmonic correlated Debye model has been developed to investigate the thermal disorder in B2-type FeAl intermetallic alloy. We derive analytical expressions of the bond-stretching force constants, the Debye temperature and frequency, the atomic mean-square displacement and the first three extended X-ray absorption fine structure (EXAFS) cumulants. Numerical calculations of these thermodynamic quantities have been performed for B2-type Fe-40 at.%Al up to temperature 1300 K using the Morse potential whose parameters were derived within the Möbius lattice inversion scheme. Our research shows that the anharmonicity contributions of thermal lattice vibrations are important to the EXAFS cumulants at high temperature. The theoretical predictions are compared with available experimental data when possible to verify the developed anharmonic correlated Debye model.