Unveiling the Impact of Short‐Range Order of Si─Si Dimer in 2D Si₂Te₃ from First‐Principles Calculations

Short‐range order (SRO) significantly influences material properties, but complete understanding of the effect of SRO on properties is challenging due to experimental and computational limitations. The SRO of anisotropic Si─Si dimers in Si 2 Te 3 influences significantly on electronic and optical properties so its arrangement has received wide attention. However, discrepancies between experimental observations and theoretical estimates of dimer orientations hinder understanding of the effect of SRO on the properties of Si 2 Te 3 . Density functional theory calculations are employed to identify energetically preferred dimer orientations from an SRO perspective. The results show that α‐SRO not only enhances structural stability due to optimized Si(s)─Te(p) bonding orbitals but also directly influences the material's bandgap. Furthermore, it is demonstrated that strain can control dimer orientation, tuning the bandgap by lowering the energy level of the Si(s)─Te(p) antibonding orbitals. This work deepens the fundamental understanding of Si 2 Te 3 and provides a methodology for studying SRO‐related energetics and property changes in various materials.