Isostructural Phase Transition in Bismuth Oxide Chloride Induced by Redistribution of Charge under High Pressure

As one of important semiconductor photocatalysts, bismuth oxide chloride (BiOCl) crystallizes into a tetragonal matlockite structure with the space group of P4/nmm. In this work, the in situ high-pressure angle-dispersive X-ray diffraction experiments and the first-principle calculations were performed on BiOCl, in order to explore the crystal and electronic structure evolution processes upon compression. At 15.1 GPa, BiOCl undergoes a tetragonal to tetragonal isostructural phase transition and then completely transforms into a high-pressure tetragonal phase at 22.1 GPa, which adopts the same crystal structure as that of the low-pressure tetragonal phase. According to the ab initio calculation results, the redistribution of Bader charge between the Bi, O, Cl ions under high pressure induces the isostructural phase transition in BiOCl and causes the different electronic structures between the high-pressure and low-pressure phases. The pressure-induced crystal and electronic structure changes in BiOCl could be a reference to explain the mechanism of isostructural phase transition in other similar compounds upon compression.