Strain effect on the ground-state structure of Sr2SnO4 Ruddlesden-Popper oxides

High-Pressure Behavior of Ca2SnO4, Sr2SnO4, and Zn2SnO4

“…A possible explanation for the observed phase transition is the fact that the tetragonal polymorph has been found to be a metastable polymorph, 41 with dynamical instabilities at ambient conditions which is observed due to the presence of a kinetic barrier. There are many examples of metastable oxide polymorphs reverting to the stable polymorph under a relatively low compression, as documented for example in BiPO 4.…”

“…The second is that phase coexistence is caused by stresses between grains, which induces local deviatoric stresses, a fact recently noticed by comparing HP powder XRD experiments (showing phase coexistence) and HP singlecrystal XRD experiments (not showing phase coexistence) in different oxides like FeVO 4 and BiMnO 3 at pressures as low as 3 GPa. 45,46 A possible explanation for the observed phase transition is the fact that the tetragonal polymorph has been found to be a metastable polymorph, 41 with dynamical instabilities at ambient conditions which is observed due to the presence of a kinetic barrier. There are many examples of metastable oxide polymorphs reverting to the stable polymorph under a relatively low compression, as documented for example in BiPO 4.…”

“…For a definitive answer to this question, additional experiments performed using helium as a pressure-transmitting medium are needed. The phase transition is reversible with a small hysteresis (the low-pressure phase is recovered as a single phase at 5.3 GPa), and we do not find any evidence of a transition to the orthorhombic structure described by space group Cmca predicted by previous DFT calculations 41 or to the orthorhombic phase observed at low temperatures (space group Pccn). 8 We assigned the crystal structure of the HP phase to that of the tetragonal low-temperature polymorph (space group P4 2 / ncm).…”