Molecular dynamics based analysis of the threshold displacement energies in β-Li2TiO3

Abstract

The threshold displacement energies (Ed) of all atoms in β-Li2TiO3 were calculated using molecular dynamic simulations. Ed values were determined at different Wyckoff positions (4d, 4e, and 8f) across various directions, sampled every 15° of azimuthal and polar angles, and visualized through stereographic plots. The results revealed that the Ed values were highly anisotropic, with values across all Wyckoff positions ranging from 1 to 99 eV. Li atoms at 4d showed lower Ed near the equatorial line and higher values toward the poles (crystallographic c-direction), while those at 4e positions exhibited a narrower Ed range. The 8f Li showed higher Ed near the poles, similar to those Li atoms at 4d. For O atoms at 8f, Ed values were lower along the equatorial line, whereas Ti atoms displayed higher Ed values near the equatorial plane with a symmetrical distribution. Probability analysis suggested that Li atoms are more easily displaced at lower energies compared to Ti and O, with oxygen requiring the highest energy for displacement. Although Li and Ti atoms had similar minimum energies for displacement, higher energy was needed for Ti to achieve comparable defect concentrations due to its wider Ed range. The cumulative distribution function highlighted a lower likelihood of displacement for O atoms compared to Li and Ti at the same energy input.