Thermoelectric Power of Different Phases and States of Silicon at High Pressure

The thermoelectric properties of silicon in its high-pressure and metastable (upon decompression) phases in the pressure range up to similar to 25 GPa were investigated. Experimental data were obtained using designed high-pressure cells with sintered diamond anvils. Band-structure calculations based on density functional theory were performed to explain the thermoelectric properties. In particular, it has been established that the nonnegligible positive values of the thermoelectric power S found for the high-pressure "metal" phases of silicon may be well explained by s-d electron scattering. Qualitative agreement between the experimental data and the results of the calculations has been achieved for the known silicon polymorphs named Si-III, Si-V, and Si-XI.