Core Electron Count as a Versatile and Accurate New Descriptor for Sorting Mechanical Properties of Diverse Transition Metal Compounds

Abstract Transition‐metal light‐element compounds show superb mechanical, chemical, and thermal properties, and accurate descriptors are important to sorting targeted properties among this vast class of materials. Valence electron concentration (VEC) can track broad trends of mechanical properties, but this widely used descriptor suffers low accuracy with sorted data strongly scattered along trendlines, necessitating an improved sorting strategy. Here, elastic parameters from first‐principles calculations are examined for 81 ternary transition‐metal nitrides (TMN) in cubic structure and 81 ternary transition‐metal diborides (TMB 2 ) in hexagonal structure and identify core electron count (CEC) of the solvent atoms as a new descriptor. Combined with VEC, the composite VEC–CEC descriptor exhibits greatly improved ability to sort elastic parameters of distinct TMN and TMB 2 compounds. Unregulated property variations under the VEC description are well‐captured by CEC, which tends to enhance ductility and reduce strength at fixed VEC and rising CEC. By invoking a full‐electron consideration, the VEC–CEC descriptor accounts for the impact on bonding behaviors by both core and valence electrons with much‐improved accuracy and versatility in sorting mechanical properties of diverse TM compounds compared to many other commonly used descriptors, opening a fresh path for rational design and optimization of TM compounds with tailored performance benchmarks.