Order to disorder transition due to entropy in layered and 2D carbides

In compositionally complex materials, there is controversy on the effect of enthalpy versus entropy on the structure and short-range ordering in so-called high-entropy materials. To help address this controversy, we synthesized and probed 40 M4AlC3 layered carbide phases containing 2 to 9 metals and found that short-range ordering from enthalpy is present until the entropy increases enough to achieve complete disordering of the transition metals in their atomic planes. We transformed all these layered carbide phases into two-dimensional (2D) sheets and showed the effects of the order vs. disorder on their surface properties and electronic behavior. This study suggests the key effect that the competition between enthalpy and entropy has on short-range order in multi-compositional materials.