First-principles calculation on phase stability and metallization in GeH4 under pressure

Using a first-principles calculation, we investigated some possible structures of GeH4 similar to those of SiH4 investigated by Feng et al. [J. Feng, W. Grochala, T. Jaron, R. Hoffmann, A. Bergara, N.W. Aschcroft, Phys. Rev. Lett. 96 (2006) 017006] and determined their metallization pressures. It is found that GeH4 has different case with SiH4 and has lower metallization pressure. Structure T2 in germane emerges as an enthalpically competitive structure over the pressure range 55-62 GPa. The metallization pressure for GeH4 with T3 structure is about 50 GPa, which is much lower than that of 91 GPa assumed for the O3 phase of SiH4, i.e. GeH4 could be easier to be metallized than SiH4.