hafnium hydride is a reversible reaction between hafnium metal and hydrogen. It is a useful chemical precursor in the manufacture of hafnium powder and for the reduction of a-alkoxy-ketones and esters.

hafnium hydride has a variety of applications in electronics, including integrated circuits and other electronic devices. It is also used in some superalloys.

Compressing hydrogen-rich hydrides is an effective method to search for exotic properties such as high-Tc superconductivity. We show that a metastable stochiometric HfH9 structure stabilized under 200 GPa and 2000 K is a potential candidate for a superconductor with Tc > 80K.

In addition to the metastable structure, our calculations show that the hydrogen atoms intercalate in the Hf-H framework. Moreover, we identify that the structure is ionic by using the difference charge density and the Bader charge analysis.

We also find that the Hf atoms form two different phases at 250 GPa and that the structure evolves from a Cmma phase to I4/mmm, Cmma, and P21/m. The Hf atoms of the P21/m phase take four 2e sites while the Hf atoms of the Cmma phase take three 2e sites.

Our calculations show that the enthalpy per HfH2 unit of I4/mmm, Cmma and P21/m is correlated to their volume (Fig. 1(b)). Unlike the Cmma and I4/mmm structures, the P21/m structure has a higher number of electron transfer and d. This is probably related to the formation of two different Hf sites. These results are a significant contribution to the study of hydrogen-rich hydrides under high pressure.

tags: Calcium nitride powder