First‐P rinciples Investigations of Amorphous and Crystalline MnSb ₂ Te ₄

Crystalline Mn 1 Sb 2 Te 4 (MST), an intrinsic magnetic topological insulator, shows similarity to the ground‐s tate structure of the phase‐c hange alloy Ge 1 Sb 2 Te 4 (GST). However, the atomic structure and key physical properties of amorphous MST—crucial for phase‐c hange functionality—have not been reported to date. In this work, we investigate the amorphous and crystalline states of MST using density functional theory (DFT) and DFT‐b ased ab initio molecular dynamics (AIMD) simulations. In addition to the ordered trigonal phase, we predict the existence of a metastable cubic rocksalt‐l ikephase with a high concentration of intrinsic cation vacancies, in close analogy with rocksalt‐l ike GST. Structural analysis reveals that the short‐r ange order in amorphous MST resembles that of the rocksalt‐l ike phase, featuring defective octahedra and abundant four‐m embered rings. Furthermore, MST maintains spin polarization in both amorphous and crystalline phases and exhibits a contrast in magnetic and optical properties. These findings identify MST as a promising candidate for applications combining phase‐c hange functionality with intrinsic magnetic order.