Thermal expansion and structure of orthorhombic CaMnO3

The structure of CaMnO3 has been studied from room temperature to 800 °C by high-resolution synchrotron X-ray powder diffraction. It is concluded that CaMnO3 remains orthorhombic in Pbnm   over the entire temperature range, with the expansion in the cell volume well fitted to the expression Vol=207.37(2)+0.00563(8)T+1.17(9)×10-6T2Vol=207.37(2)+0.00563(8)T+1.17(9)×10-6T2. The magnitude of the MnO6 tilts is estimated from the refined structural parameters and these progressively reduce as the temperate is increased.