Equations of state of α-SiC (6H) and βʹ-Mg2Si1.1 from single-crystal X-ray diffraction data and novel high-pressure magnesium silicide Mg2Si7

Abstract SiC and (Fe, Mg)-silicide are candidate phases forming under reducing conditions in the Earth planetary interiors. However, structural studies of Mg 2 Si at high pressure their thermal stability presently lacking. In this work, we applied single-crystal X-ray diffraction a diamond anvil cell determined equations state α -SiC (6H) β ʹ-Mg 1.1 up to 60 40 GPa, respectively, yielding bulk moduli 226.0(4) 56(1) GPa. We also report formation novel orthorhombic 7 phase upon laser heating ~ 45 GPa 2000 °C [ Pbam , = 7.16(1) Å, b 12.490(3) c 2.6545(3) V 237.5(3) Å 3 ]. The structure compound contains layers formed by irregular 12-member silicon rings, which arranged channels filled with both atoms. No signs were detected releasing DAC, suggests that is unstable ambient conditions.