Mn3O4 at high pressure: a diamond-anvil cell study and a structural modelling
Paris, Eleonora; Ross Il, Charles R.; Olijnyk, Helmut
published: Feb 13, 1992
manuscript accepted: Aug 20, 1991
manuscript received: Nov 16, 1990
ArtNo. ESP147050401018, Price: 29.00 €
Abstract The phase transition and compressibility of Mn3O4 have been investigated at room temperature with X-ray diffraction diamond-anvil cell experiments up to 38.7 GPa. At pressures below 10 GPa a tetragonal phase is present, having the hausmannite structure, whereas at higher pressure the hausmannite phase transforms into an orthorhombic marokite-like phase with a volume reduction of 8.7%. The calculated density varies between 4.83 and 5.15 g/cm3 for the hausmannite structure from room pressure up to 10 GPa, and between 5.33 and 6.24 g/cm3 for the marokite-like structure in the range 1bar-38.7 GPa. Compressibility determination (BO′ = 4) gives a bulk modulus 137 ± 3.8 GPa for Mn3O4-hausmannite and 166.6 ± 2.7 GPa for Mn3O4-marokite. Structural modelling of both phases indicates, at increasing pressures, an overall decrease of polyhedral volumes and an increase of the regularity of the sites. The phase transition results in an increase of the quadratic elongation, suggesting that it takes place when, in the hausmannite structure, the Mn3+ octahedral site becomes too regular and incompatible with the presence of the Jahn-Teller effect.