Structural, magnetic and electronic properties of CrO at multimegabar pressures.

As the only half-metallic ferromagnetic material in 3d transition metal dioxides, CrO has attracted great scientific interest from materials science to physical chemistry. Here, an investigation into the structural, magnetic and electronic properties of CrO under high pressure has been conducted by first-principles calculations based on density functional theory. Static calculations have predicted that CrO undergoes structural transitions with the sequence of rutile-type → CaCl-type → pyrite-type → → (FeP-type→) 4/ at high pressures. In addition, a transition from the ferromagnetic state to the non-magnetic state with the magnetic collapse of Cr is observed in CrO at the pyrite- transition. This transition also delocalizes the 3d electrons of Cr and leads to a metallic character of CrO. The equation of state, elasticity and band gap for each energetically favorable phase of CrO are determined. Our results not only bridge the gap about the high-pressure behavior of CrO in previous studies but also extend our understanding of its properties up to multimegabar conditions. According to previous data and present results, we further discuss and summarize the high-pressure behavior of various AO compounds. This can contribute to investigating properties of other AO compounds or exploring novel materials at high pressures.