Prediction and synthesis of a family of atomic laminate phases with Kagomé-like and in-plane chemical ordering

Abstract

The enigma of MAX phases and their hybrids prevails. We probe transition metal (<i>M</i>) alloying in MAX phases for metal size, electronegativity, and electron configuration, and discover ordering in these MAX hybrids, namely, (V_2/3Zr_1/3)₂AlC and (Mo_2/3Y_1/3)₂AlC. Predictive theory and verifying materials synthesis, including a judicious choice of alloying M from groups III to VI and periods 4 and 5, indicate a potentially large family of thermodynamically stable phases, with Kagomé-like and in-plane chemical ordering, and with incorporation of elements previously not known for MAX phases, including the common Y. We propose the structure to be monoclinic <i>C</i>2/<i>c</i>. As an extension of the work, we suggest a matching set of novel MXenes, from selective etching of the A-element. The demonstrated structural design on simultaneous two-dimensional (2D) and 3D atomic levels expands the property tuning potential of functional materials.