Molecular dynamics study of FeCo phase transitions and thermal properties based on an improved 2NN MEAM potential

A semi-empirical potential in line with the second nearest-neighbor modified embedded-atom method (2NN MEAM) formalism has been improved for the Fe-Co interactions intended to reproduce the different thermal phases stability. Fundamental structural and elastic properties are correctly reproduced. Point defects have been included in the fitting to improve the thermodynamic characteristics. Molecular dynamics simulations using this potential predict melting temperatures which aligns with experimental data and is the first potential showing a temperature-induced B2 to L10/hcp transformation. A disorder transformation is observed by diffusing vacancies at different temperatures and quantified by the long-range order parameter. The potential is also applied to thin films of the metastable L10 structure by using a face-centered cubic buffer, which can predict the good stability and energetical results comparable to ab initio calculations. The potential proves useful to study the thermal effects of different FeCo phases in bulk and multilayer films.