Document AM-97-648 Structure and dynamics of protonated Mg2SiO4: An ab-initio molecular dynamics study Michael Haiber, Pietro Ballone, and Michele Parrinello American Mineralogist 82(9-10)913-922 Table 4. Optimized lattice parameters and atomic positions for spinel ********** * Spinel * ********** Space group: Fd3m (No.227) Atomic coordinates (using first choice of origin of the International Tables for Xray Crystallography, which puts the centre of symmetry at 1/8, 1/8, 1/8): Mg in 16(d): 5/8, 5/8, 5/8 Si in 8(a): 0, 0, 0 O in 32(e): u, u, u Positions as function of pressure: a[A] u P[kbar] 7.138598 .371500 1758.123981 7.371436 .371251 1036.523834 7.571147 .370500 617.911740 7.794777 .370260 293.656457 7.990573 .369507 95.204641 8.202244 .368604 -58.020306 8.403331 .366652 -162.279200 8.535625 .366652 -214.869330 8.678503 .365082 -260.773975