Molecular dynamics modelling of amorphisation induced change in the mechanical properties of β-Li2TiO3

Abstract

ABSTRACT The objective of this study is to understand the effect of irradiation on the mechanical properties of Lithium metatitanate (β-) at the molecular level. Computational samples with different levels of damage are subjected to tensile and compressive loads to study changes in elastic stiffness tensor and the crushing strength. Three levels of displacement ratios are chosen; stoichiometric, where atom types are chosen at random, secondly only Lithium atoms are displaced, and finally, atoms to be displaced are chosen in the ratio 60% Li 20% O 20% Ti. Further, local structural changes due to the interaction of stress and radiation are also analysed. It is observed that for stoichiometric and 60% Li, 20% Ti and 20% O displacement cases, the material becomes isotropic at around ≃0.5 dpa. However, for explicit Li displacement, the material continued to show an anisotropic response. This observation indicates that the collapse of the Ti/O sublattice was essential for amorphisation and deteriorating stiffness. However, it was found that very small disturbances in the O/Ti sub-lattice were sufficient to cause a drastic reduction in the crushing strength. Therefore, while small damages below 0.5 dpa may not drastically change the stiffness of the material, it could alter the crushing strength significantly.