Measurement of Electrical Resistance and Raman Spectrum of α-Boron under High Pressure

The electrical resistance and Raman spectrum of α-boron were measured under high pressures. A logarithmic drop in the resistance and blackening of the color were observed under pressure; however, the temperature dependence of the resistance did not become metallic even at pressures up to 112 GPa. Clear bending in the ρ( P ) curves, which may correspond to the structural change, were observed at 40–50 GPa. However, there was no significant change in the Raman spectrum between 300 and 1300 cm -1 up to 80 GPa, which indicates that α-boron keeps its icosahedron-based structure.