Defect Landscape and Stability of High-Entropy Carbides

Abstract

High-entropy carbides (HECs) can be stabilized as single-phase solid-solution microstructures by kinetically trapping a “high-entropy state” under ambient conditions; however, such microstructures may represent metastable states rather than true thermodynamic equilibrium. Here, we investigate the thermodynamic stability of HECs using an integrated theoretical–experimental framework. Density functional theory calculations of carbon vacancy formation energies reveal two distinct energy landscapes, from which we hypothesize that rugged profiles correspond to reduced effective configurational entropy and promote multiphase microstructures, whereas smoother profiles are indicative of higher configurational entropy and stabilize single-phase microstructures. High-power impulse magnetron sputtering synthesis validates these predictions, showing single-phase HECs in the as-deposited state due to kinetic barriers, whereas postdeposition annealing induces phase segregation in compositions exhibiting rugged energy landscapes. Furthermore, machine-learning-derived descriptors enable systematic mapping of these energy landscapes, providing a predictive pathway to accelerate understanding of defect profile and its critical role in delineating phase stability in HECs.