Deciphering Short-Range Order in 2D Transition Metal Dichalcogenides: From Origin to Multi-Scale Property Modulation.

Chemical short-range order (SRO) is a critical structural characteristic in multi-principal element materials, governing the global electronic properties including band gap. Yet its effect on site-resolved properties, such as magnetic moments and d-band centers, remains unclear. Here, using equiatomic 2D ternary transition metal dichalcogenides (TMDCs) exemplified by (V0.5Cr0.5)S2 and (Re0.5Ta0.5)S2, the origin and influence of SRO are unraveled via high-throughput first-principles calculations and machine learning. The results identify chemical affinity and atomic size difference as the dominant descriptors associated with SRO formation. Then, weak and strong SRO regimes are identified according to the energetic gain of SRO configurations relative to the quasi-random states. Specifically, weak SRO in (V0.5Cr0.5)S2 has negligible influence on its half-metallic character, but significantly modulates the site-resolved properties including atomic magnetic moments and d-band centers. Further, the mapping between the local atomic arrangements of (V0.5Cr0.5)S2 and the site-resolved properties is accurately described by the many-body descriptor MACE-MP extracted from the universal interatomic potential. In contrast, strong SRO in (Re0.5Ta0.5)S2 suppresses the localized mid-gap states originating from Ta_dz2 and Re_dz2/dx2-y2 orbitals, leading to a semiconducting gap. These findings establish SRO as a fundamental degree of freedom for designing the multi-scale functionalities of the materials.