Pressure-induced metallization of silane

Abstract

There is a great interest in electronic transitions in hydrogen-rich materials under extreme conditions. It has been recently suggested that the group IVa hydrides such as methane (CH 4), silane (SiH4), and germane (GeH 4) become metallic at far lower pressures than pure hydrogen at equivalent densities because the hydrogen is chemically compressed in group IVa hydride compounds. Here we report measurements of Raman and infrared spectra of silane under pressure. We find that SiH 4 undergoes three phase transitions before becoming opaque at 27-30 GPa. The vibrational spectra indicate the material transforms to a polymeric (framework) structure in this higher pressure range. Room-temperature infrared reflectivity data reveal that the material exhibits Drudelike metallic behavior above 60 GPa, indicating the onset of pressure-induced metallization.high pressure ͉ hydrogen-rich materials

Superconducting high-pressure phase of platinum hydride from first principles

“…10,11 Only one solid phase has been reported in the pressure range between 10 and 25 GPa with a monoclinic structure at room temperature. 12 At pressure above 60 GPa, Chen et al 13 found the pressure-induced metallization for silane by analyzing the infrared reflectivity data at room temperature.…”

Phonon Dispersion Analysis as an Indispensable Tool for Predictions of Solid State Polymorphism and Dynamic Metastability: Case of Compressed Silane

“…Experiments conducted in diamond anvil cells show that SiH 4 liquefies at 1.7 GPa and then solidifies at 4 GPa forming phase III † as evidenced by the Raman spectroscopy [4]. Upon further compression silane enters phase IV (at 6.5 GPa) and then V (at 10 GPa) [4,5].…”

“…try) [5], is stable up to 26.5 GPa [4,5]. Above this pressure SiH 4 has been reported to undergo a gradual phase transition with phase V coexisting with a new phase VI over a broad range of pressures.…”

“…Upon further compression silane enters phase IV (at 6.5 GPa) and then V (at 10 GPa) [4,5]. All these phases are molecular and insulating.…”

“…The sluggishness of this phase transformation points to large kinetic barriers which most probably originate from considerable structural difference between phases V and VI. Indeed, vibrational properties of the latter polymorph indicate that it has a polymeric structure [4] although its crystal structure has not been established. This polymorph of silane has also a small band-gap as it is opaque in visible light.…”