New high-pressure phase relations in CaSnO3

High-pressure phase stabilities of the CaSnO 3 system were investigated using density functional theory static lattice energy calculations. We have identified six phase changes in this system: perovskitepost-perovskite, post-perovskite-B2+cotunnite in CaSiO 3 , B1-B2 in CaO, cassiterite-pyrite, pyriteorthorhombic-I, and orthorhombic-I-cotunnite in SnO 2 . Our results demonstrate a new high-pressure phase sequence of perovskite → post-perovskite → B2 + cotunnite. The post-perovskite transformation occurs at ~12 GPa with ~2.5% volume reduction and then it decomposes into the oxide mixture of B2 CaO and cotunnite SnO 2 at ~70 GPa with 8.1% volume reduction. The results also predict a few percent bulk velocity variations across these phase changes.