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DF: Fachverband Dielektrische Festkörper
DF 8: Multiferroics III (jointly with MA, DS, KR, TT)
DF 8.6: Vortrag
Dienstag, 27. März 2012, 10:45–11:00, EB 301
First principles study of Mn2O3 under pressure: Competition between Jahn-Teller distortion and charge disproportionation — •Carmen Quiroga and Rossitza Pentcheva — Dept. of Earth and Environmental Sciences, University of Munich
Contrary to most sesquioxides, which naturally occur in the corundum structure, Mn2O3 has a complex crystal structure corresponding to an orthorhombically distorted bixbyite [1], associated with the presence of the Jahn-Teller active Mn3+ cation. It has been suggested that the Jahn-Teller effect is inhibited under pressure, which could induce a phase transition to the corundum structure [2], from where the general transformation sequence of sesquioxides to perovskite and post-perovskite should follow. So far, however, only the post-perovskite has been reported experimentally above 27 GPa [3].
Using density functional theory calculations including an on-site Coulomb repulsion term, we explore the stability of the ambient phase α-Mn2O3 (Pbca) and candidate high-pressure polymorphs: corundum (R3c), perovskite phases of Rh2O3 II (Pbcn) and GdFeO3 (Pbnm) type and post-perovskite (Cmcm). In particular we focus on the effect of pressure on the charge, spin and structural degrees of freedom. Parallels to the pressure induced phase transitions in MnTiO3 are discussed.
Funding by DFG SPP1236 (PE883/8-1) is acknowledged.
[1] S. Geller. Acta Crystallogr. B27, 821 (1971).
[2] C.T. Prewitt et al. Inorg. Chem. 8, 1985 (1969).
[3] J. Santillán et al. Geophys. Res. Lett. 33, L15307 (2006).