Pressure-Induced Phase Transformations, Electronic Properties and Intermediate Phases of Chromium Dioxide

H. Öztürka, C. Kürkçüb aDepartment of Physics, Ahi Evran University, Kırşehir, 40100, Turkey bDepartment of Electronics and Automation, Ahi Evran University, Kırşehir, 40100, Turkey

Received: October 29, 2017; revised version March 11, 2019; in final form July 18, 2019

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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 P̅421m 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

DOI:10.12693/APhysPolA.136.26 topics: chromium dioxide, high pressure, phase transformation, intermediate phase