High pressure behavior of Cr$_2$O$_3$ to 62~GPa

Corundum-structured oxides are of interest for a broad range of reasons, including their mineralogical occurrences and technological uses. The high pressure behavior of Cr$_2$O$_3$ is of particular interest due to the widespread use of ruby, (Al,Cr)$_2$O$_3$, as a pressure standard in diamond anvil cells experiments. Although there have been a number of high pressure studies on Cr$_2$O$_3$, discrepancies still exist among the different data sets. Here we present synchrotron X-ray diffraction data on the structure and compressional behavior of Cr$_2$O$_3$ to 62~GPa. Although no change in crystal structure is detected within the resolution of the measurements, a change in compressional behavior occurs near 30~GPa where Cr$_2$O$_3$ changes color from red to orange.