Pressure-induced structural and electronic transitions in InTeI

Based on crystal structural search and ab initio calculations, we report pressure-induced structural and electronic phase transitions for the semiconductor indium tellurium iodine (InTeI). We have found two structures belonging to the same space group of InTeI at high pressure (labeled as P4/nmm-I and P4/nmm-II, respectively), where P4/nmm-II is metastable. Our calculation results show that the ambient P2(1)/c phase transforms to a tetragonal P4/nmm-I phase at about 15 GPa, characterized by the appearance of metallization and superconductivity with T-c of around 7 K. Besides, band-structure calculations suggest that the InTeI system undergoes a pressure-induced electronic phase transition from a direct to indirect band gap in the P2(1)/c phase. On the application of atomic substitution, the superconducting temperature T-c of InTeI can be further raised to around 9.7 K if the iodine atoms are replaced by the lighter chlorine atoms in the P4/nmm-I phase. The results pave the way for applying of Indium tellurohalide in optoelectronic devices and demonstrate a method that adjusts electronic properties by pressure or atomic substitution.