t-Se has a quasi-one-dimensional crystal structure, whereby trigonal helical chains oriented along the c-axis are packed together to give a trigonal lattice with space group P3 1 21 (Fig. ). Our computational setup results in bulk lattice parameters of a = 4.34 Å and c = 4.96 Å, closely matching the room temperature experimental values of a = 4.37 Å and c = 4.95 Å.