Temperature dependent structural and electronic properties of SrZrS₃ in distorted perovskite phase

We investigate the effect of temperature on the structure and electronic bandgap (Eg) of SrZrS₃ in its distorted perovskite (DP) (GdFeO₃ structure type) phase over the temperature range 300 - 1500 K by means of ab initio molecular dynamics in an NPT ensemble, accelerated by adaptive machine learning. The thermal expansion of this phase is observed to be atypical, with two vectors (b and c) expanding monotonously and one (a) contracting after an initial expansion. These thermally-induced structural changes in the DP phase are due to the transformation to the cubic phase (C) upon heating. This structural transformation strongly governs the Eg of the material in response to temperature. It is found that the Eg for DP decreases by ∼0.5 eV within the studied temperature range, mainly attributed to the very large atomic displacement contribution resulting from the proximity of the parent C phase. (authors)