Interactions between hydrogen and silane at high pressure

Understanding the behavior of hydrogen-rich systems at extreme conditions has significance to both condensed matter physics and applied research areas like hydrogen storage. We report the high-pressure study of the SiH$_{4}$-H$_{2}$ binary system at 300K in a diamond anvil cell. Raman measurements indicate significant intermolecular interactions between H$_{2}$ and SiH$_{4}$. We found that H$_{2}$ vibron frequency is significantly softened with the presence of SiH$_{4}$ for the fluid phase compared with pure H$_{2}$ fluid at the same pressures. In contrast, the Si-H stretching modes of SiH4 shift to higher frequency in the mixed fluid compared with pure SiH$_{4}$. Pressure induced solidification of the H$_{2}$-SiH$_{4}$ fluid shows a binary eutectic point at $\sim$ 72 mol\% H$_{2}$ and $\sim$ 6.1 GPa, above which the fluid crystallizes into a mixture of two nearly end-member solids. We were able to superpressurize the sample above the eutectic pressure before complete crystallization, indicating extended metastability. The properties of the two nearly end-member solids will also be presented.