Pressure-induced phase transformations, electronic properties and intermediate phases of chromium dioxide

Abstract

We study pressure-induced phase transformations of chromium dioxide (CrO2) using constant pressure ab initio simulations. A first-order phase transformation from the rutile-type structure to the CaCl2-type structure is successfully observed at 220 GPa. Simulations reveal that this transformation proceeds via two intermediate phases within P421m and P21212 symmetries. Another phase transformation from this structure to the orthorhombic structure with space group Cmc21 occurs at 440 GPa. This phase transformation also proceeds via two intermediate phases within P21=c and P21 symmetries. We also study these phase transformations of CrO2 by undertaking the enthalpy calculations. We find that the phase transformation from the rutile-type structure to the CaCl2-type structure occurs around 15 GPa which is in good agreement with the experiments. Also, the phase transformation from CaCl2-type to the orthorhombic structure with space group Cmc21 is found at 105 GPa. Additionally, we predict band gaps from electronic structure calculations for obtained phases of CrO2 © 2019 Polish Academy of Sciences. All rights reserved.