High-pressure structural study of α -Mn: Experiments and calculations

Manganese, in the $\ensuremath{\alpha}$-Mn structure, has been studied using synchrotron powder x-ray diffraction in a diamond anvil cell up to 220 GPa at room temperature combined with density functional calculations. The experiment reveals an extended pressure stability of the $\ensuremath{\alpha}$-Mn phase up to the highest pressure of this study, in contrast to previous experimental and theoretical studies. On the other hand, calculations reveal that the previously predicted hcp Mn phase becomes lower in enthalpy than the $\ensuremath{\alpha}$-Mn phase above 160 GPa. The apparent discrepancy is explained due to a substantial electron transfer between Mn ions, which stabilizes the $\ensuremath{\alpha}$-Mn phase through the formation of ionic bonding between monatomic ions under pressure.