Facile phase transition to β- from α-SnSe by uniaxial strain

We investigate the phase transition between uniaxially strained α- and β-SnSe using density functional theory calculations and suggest that uniaxial strain can enable a facile phase transition to the β phase. Increasing the interlayer spacing along the a-axis and, more effectively, applying compressive strain in the corrugated direction along the c-axis in α-SnSe are found to decrease the β-phase energy with respect to α. Where the phase transition temperature T_c of unconstrained SnSe is 800 K, the T_c of a-axis +2.6% tensile strained α-SnSe is estimated to be 600 K, while the T_c of c-axis −3.8% compressive strained α-SnSe is estimated to be 400 K. The uniaxial strain engineering can lower the optimal operation temperature of SnSe-based thermoelectric applications.