Displacement threshold energy and recovery in an Al–Ti nanolayered system with intrinsic point defect partitioning

A method is established and validated using molecular dynamics (MD) to determine the displacement threshold energies as E d in nanolayered, multilayered systems of dissimilar metals. The method is applied to specifically oriented nanolayered films of Al–Ti where the crystal structure and interface orientations are varied in atomic models and E d is calculated. Methods for defect detection are developed and discussed based on prior research in the literature and based on specific crystallographic directions available in the nanolayered systems. These are compared and contrasted to similar calculations in corresponding bulk materials, including fcc Al, fcc Ti, hcp Al, and hcp Ti. In all cases, the calculated E d in the multilayers are intermediate to the corresponding bulk values but exhibit some important directionality. In the nanolayer, defect detection demonstrated systematic differences in the behavior of E d in each layer. Importantly, collision cascade damage exhibits significant defect partitioning within the Al and Ti layers that is hypothesized to be an intrinsic property of dissimilar nanolayered systems. This type of partitioning could be partly responsible for observed asymmetric radiation damage responses in many multilayered systems. In addition, a pseudo-random direction was introduced to approximate the average E d without performing numerous simulations with random directions.