High-pressure behavior of alpha-boron studied on single crystals by X-ray diffraction, Raman and IR spectroscopy

Abstract : In the present study single crystals of rhombohedral alpha-B were investigated under pressure to 60 GPa by means of single-crystal X-ray diffraction. The bulk modulus of alpha-B was found to be K=224(7) GPa (K'=3.0(3)). Measurements of interatomic distances as a function of pressure revealed that the intericosahedral two-center two-electron (2c-2e) bonds are almost as stiff as some of intraicosahedral ones. The three-center two-electron (3c-2e) intericosahedral bonds show much higher compliance compared to other bonds in alpha-B. The vibrational properties of alpha-B under pressure were investigated by Raman spectroscopy at pressures up to 160 GPa and IR spectroscopy at pressures up to 53 GPa.