Pressure-induced phase transition and structural properties of CrO2

The structural properties and pressure-induced phase transitions of CrO2 have been investigated using the pseudopotential plane-wave method based on the density functional theory (DFT). The rutile-type (P4(2)/mnm), CaCl2-type (Pnnm), pyrite-type (Pa3), and CaF2-type (Fm-3m) phases of CrO2 have been considered. The structural properties such as lattice parameters, bulk moduli and its pressure derivative are consistent with the available experimental data. The second-order phase-transition pressure of CrO2 from the rutile phase to CaCl2 phase is 10.9 GPa, which is in good agreement with the experimental result. The sequence of these phases is rutile-type -> CaCl2-type -> pyrite-type -> CaF2-type with the phase-transition pressures 10.9, 23.9, and 144.5 GPa, respectively. The equation of state of different phases has also been presented. It is more difficult to compress with the increase of pressure for different phases of CrO2.