Raman spectroscopy of B12As2 under high pressure

We report a Raman spectroscopy study of B12As2 under hydrostatic pressure up to 15 GPa. Mode Grüneisen parameters were determined for the B12As2 phonon modes. Phonon modes attributed to the As–As chain have a weak pressure dependence (0.6–1.9 cm−1 GPa−1) relative to inter- and intra-icosahedral vibrations (3.4–6.6 cm−1 GPa−1). The pressure dependence of B12As2 phonon frequencies is compared to those reported for α-boron and the origin of the mode at 505 cm−1 with its weak pressure dependence is discussed.