First-principles study on the structural and electronic properties of metallic HfH 2 under pressure

The crystal structures and properties of hafnium hydride under pressure are explored using the first-principles calculations based on density function theory. The material undergoes pressure-induced structural phase transition I 4/ mmm → Cmma → P 2 1 / m at 180 and 250 GPa, respectively and all of these structures are metallic. The superconducting critical temperature T c values of I 4/ mmm , Cmma and P 2 1 / m are 47–193 mK, 5.99–8.16 K and 10.62–12.8 K at 1 atm, 180 and 260 GPa, respectively. Furthermore, the bonding nature of HfH 2 is investigated with the help of the electron localization function, the difference charge density and Bader charge analyses, which show that HfH 2 is classified as a ionic crystal with the charges transferring from Hf atom to H.