Chromium-driven severe lattice distortion in high-entropy diboride ceramics

High-entropy diboride (HEB 2 ) ceramics are promising materials due to their exceptional mechanical and thermal properties, especially for extreme environments. While lattice distortion is known as a key strengthening mechanism in these systems, how to effectively tune atomic-scale lattice distortion remains elusive. Here we demonstrate, via density functional theory (DFT) based first-principles calculations and special quasi-random structure analysis of 132 HEB 2 compositions (spanning 9-, 8-, 6-, and 5-cation systems), that Cr induces the largest lattice distortion, with mean lattice distortion reaching ∼ 0.15 Å. In contrast, Ti, Zr, Hf, Nb, and Ta show only limited distortions (∼ 0.03 Å), while V, Mo, and W exhibit intermediate distortion levels of ∼ 0.04 Å. Furthermore, a qualitative correlation is observed between the local density of states at the Fermi level N ( E f ) and the degree of elemental lattice distortion, with elements exhibiting higher N ( E f ) showing more pronounced distortions. These findings shed light on the underlying electronic mechanisms driving lattice distortions and offer new perspectives for designing high-entropy boride materials with tailored properties for high-performance applications.