  The practically unlimited high-dimensional composition space of high-entropy
materials (HEMs) has emerged as an exciting platform for functional materials
design and discovery. However, the identification of stable and synthesizable
HEMs and robust design rules remains a daunting challenge due to the difficulty
in determining composition/structure-specific enthalpy and entropy
contributions to the stability and formation of HEMs. In this work, using
first-principles calculations, we find that (i) the stability and miscibility
of HEMs strongly depend on the formation enthalpy of the HEM relative to the
most stable completing phase rather than on the conventionally-viewed
enthalpies of mixing over all possible competing phases, and (ii) the entropy
forming ability of a HEM can be measured from the defect formation energy
spectrum of tens of substitutional defects in ordered binary compounds,
involving no sampling over numerous alloy configurations. Based on these
findings, we propose a highly predictive Mixed Enthalpy-Entropy Descriptor
(MEED), which enables the rational high-throughput first-principles design and
screening of new HEMs over large chemical spaces. Applying the MEED to two
structurally distinct material systems (i.e., 3D rocksalt carbides and 2D
layered sulfides), not only all experimentally reported HEMs within each system
are successfully identified, but a universal cutoff criterion for assessing
their relative synthesizability also revealed. In addition, tens of new high
entropy carbides and 2D high-entropy sulfides are also predicted. They have the
potential for a wide variety of applications such as coating in aerospace
devices, energy conversion and storage, and flexible electronics.
