Phase stability of the layered oxide, Ca2Mn3O8; probing interlayer shearing at high pressure

We have performed high–pressure neutron diffraction studies on the layered oxide, Ca2Mn3O8. Studies up to approximately 6 GPa at temperatures of 120 and 290K demonstrate that there are no structural phase transitions within this pressure range. Fits of the unit–cell volume to a Birch-Murngaham equation of state give values for the bulk modulus of 137(2) GPa and 130(2) GPa at temperatures of 290K and 120K respectively suggesting that Ca2Mn3O8 is more compressible at lower temperature. Compression along the principle axes are anisotropic on the local scale with comparison of individual bond lengths and bond angle environments demonstrating that compression is complex and likely results in a shearing of the layers.