Structural study of SnO at high pressure

We have studied the structural behaviour of tin monoxide (SnO) by energy dispersive X-ray diffraction (EDXRD) and EXAFS in a pressure range up to 51 GPa. We found a shear stress induced phase transition to an orthorhombically distorted structure under non hydrostatic conditions. Besides this we observed no phase transition of SnO up to the highest pressure of this study. SnO shows strong anisotropy in compression. The a  -axis is rather incompressible with a linear stiffness coefficient of Ka0=306(6)GPa whereas the stiffness of the c-  axis is Kc0=43(2)GPa. The bulk modulus of SnO is K0=35(1)GPa and its derivative K0′=6.1(2). A possible disproportionation of SnO to SnO2 and Sn at ambient temperature under high pressure is also discussed.