THEORY OF STRUCTURAL, ELECTRONIC, VIBRATIONAL, AND SUPERCONDUCTING PROPERTIES OF HIGH-PRESSURE PHASES OF SULFUR

Pseudopotential ab initio calculations are performed for three high-pr essure phases of sulfur (bco, beta-Po, and bcc). These calculations yi eld a value of around 550 GPa for the transition pressure of the beta- Po to bcc transformation; however, we do not reproduce the reported bc o to beta-Po phase transition. Ab initio calculations of the phonon sp ectrum and the electron-phonon interaction for the bcc phase of sulfur are also done using the frozen phonon method. The results predict tha t the bcc phase of sulfur is a metal with very low resistivity and a s uperconducting transition temperature of 15 K.