Thermal Stability and Structural Evolution of Li-Mg Alloys Through Atomistic Simulations

Molecular dynamics simulations were conducted to investigate the thermal stability and structural evolution of Li-Mg alloys subjected to thermal cycling between 100 K and 400 K. Alloy compositions containing 0, 5, 10, and 20 at.% Mg were analyzed using a modified embedded-atom method interatomic potential. Structural characterization was performed through radial distribution functions, Polyhedral Template Matching (PTM), and mean squared displacement (MSD) calculations. The results showed that heating promoted the temporary formation of HCP, FCC, and other local atomic environments, indicating partial loss of crystalline ordering even below the melting temperature of Li. Nevertheless, the BCC structure remained dominant for all compositions, and the structural changes were reversible during cooling. Increasing Mg concentration improved the thermal stability of the alloys by reducing the formation of non-BCC atomic structures and decreasing atomic mobility during thermal cycling. In particular, the 20 at.% Mg alloy preserved more than 90% of the BCC population throughout the simulations. In addition, the energy variations between cycles remained very small, indicating stable thermodynamic behavior during heating and cooling. These findings provide atomistic insight into the temperature-dependent behavior of Li-Mg alloys that may be useful in works related to lithium-metal battery applications.