t‐Si64: A Novel Silicon Allotrope

Abstract Utilizing first principle calculations, a novel Si 64 silicon allotrope in the I 4 1 / amd space group with tetragonal symmetry (denoted as t ‐Si 64 below) is proposed in this work. In addition, also its structural, anisotropic mechanical, and electronic properties along with its minimum thermal conductivity κ min were predicted. The mechanical and thermodynamic stability of t ‐Si 64 were evaluated by means of elastic constants and phonon spectra. The electronic band structure indicates that t ‐Si 64 is an indirect band gap semiconductor with a band gap: 0.67 eV (primitive cell) compared to a direct band gap of 0.70 eV with respect to a conventional cell. The minimum thermal conductivity of t ‐Si 64 (0.74 W cm −1 K −1 ) is much smaller than that of diamond silicon (1.13 W cm −1 K −1 ). Therefore, Si−Ge alloys in the I 4 1 / amd space group are potential thermoelectric materials.