Compression of ?-MnS (alabandite) and a new high-pressure phase

The compressibility of α-Mns (alabandite) was determined by x-ray analysis using a Mao-Bell type diamond anvil cell. The zero pressure bulk modulus (K0) is 74±2 GPa with the pressure derivative of the bulk modulus (K′o) fixed at four. Allowing (K′o) to vary yielded a statistically better fit with K0 = 88±6 GPa and k′0 = 2.2±0.6. Our data combined with the data of McCammon (1991) gave Ko = 73±1 GPa with k′o fixed at four. A fit with k′o allowed to vary yielded ko = 75±2 GPa and k′o = 3.7±0.4. Alabandite transformed from the B1 structure (NaCl-type) to an unknown high-pressure phase at 26 GPa. The high-pressure phase has lower than hexagonal symmetry and it is stable to at least 46±4 GPa.