Enabling the transition to ductile MAX phases and the exfoliation to MXenes via tuning the A element

Two-dimensional MXenes, exfoliated from their parental precursors-MAX phases, exhibit several outstanding properties and have achieved several accomplishments in a vast range of fields. Developing novel and high-performance MXenes has become a vital task in materials science, so estimating the possibilities for exfoliation is a topic positioned at the research frontier. Here, the likelihood of exfoliating 36 M(2)AC MAX phases was explored by using density functional theory. For MAX phases, the composition-dependent mechanical performances were investigated, highlighting evident trends, and, more essentially, improving MAX phases toughness, which can be achieved via modulating the A site. Two novel criteria were then introduced to assess the probability of exfoliating MXenes from MAX phases, having less complexity and lower computational cost than the prior studies. The excellent agreement provided by the new criteria with the reported results demonstrates that they are feasible, reliable as well as easily accessible. Furthermore, some key features that were previously suggested to be related to exfoliation are instead determined to be weakly correlated with it. We thus performed a detailed numerical analysis to locate representative and correlated features that are fundamental for the exfoliation. Our findings provide deep insight into the synthesis process and accelerate the discovery of new MXenes.