Ion Irradiation Effects on Two-Dimensional MXene Ti₂C for Applications in Extreme Conditions: Combined Ab Initio and Monte Carlo Simulations

As an emerging category of two-dimensional (2D) materials, transition metal carbides and/or nitrides (MXenes) have attracted considerable interest for various disciplines. They exhibit unique properties typical of both metals and ceramics, rendering significant potential for harsh conditions such as in outer space and nuclear systems. In this work, using Ti 2 C as a prototype probe, we investigate the ion irradiation effects by combining ab initio and Monte Carlo simulations. We first consider the structures and energetics of various atomic vacancies in Ti 2 C. Based on binary collision approximation, a Monte Carlo approach is developed to explore the defects induced by ion bombardment. Systematic Monte Carlo (MC) simulations of different incident ions (i.e., H, He, Li, Be, B, C, N, O, F, and Ne) and selected isotopes reveal that defects are formed via primary collision and in-plane recoils, and the number of displaced atoms decreases with incident energy and increases with the atomic number of incident ions. Interestingly, Ti atoms are much easier to be knocked out than C atoms, beneficial for selective etching for nanoelectronics. We show that Ti 2 C remains metallic with vacancies of large size, indicating the high irradiation tolerance of electrical conductivity. This work not only provides fundamental insights into the irradiation response of MXenes but also paves the way for future exploration and implementation of 2D nanostructures in extreme conditions, e.g., as coatings or structural materials for nuclear reactors.