Pressure-induced spin collapse of octahedrally coordinated Mn3+ in the tetragonal hydrogarnet henritermierite Ca3Mn2[SiO4](2)[O4H4]

Article

关键词: X-RAY-DIFFRACTION;    NEUTRON POWDER DIFFRACTION;    AB-INITIO;    SILICATE GARNETS;    VIBRATIONAL-SPECTRUM;    STATE;    TRANSITION;    SPECTROSCOPY;    KATOITE;    IRON;   

DOI  :  10.1103/PhysRevB.92.014117

来源: SCIE

【 摘 要 】

The high-pressure behavior of natural henritermierite garnet with close to end-member composition Ca3Mn2[SiO4](2)[O4H4] was studied at pressures up to 80 GPa using single-crystal synchrotron x-ray diffraction, Raman spectroscopy, and quantum-mechanical calculations based on density functional theory. An isosymmetric phase transition was observed in the pressure range between 55 and 70 GPa, which is associated with a gradual high-spin to low-spin electronic transition in Mn3+ and a pronounced reduction of the Jahn-Teller distortion of the Mn3+O4(OH)(2) octahedra. In the high-pressure phase the Jahn-Teller distortion is totally suppressed and the Mn3+ is in a low-spin configuration. Experimental structural data before and after the phase transition are in excellent agreement with the theoretically predicted structural compression of the high-spin and low-spin phases, respectively. While the overall unit-cell volume is reduced by about 1.5% across the phase transition, a collapse of about 4-5% of the MnO6 octahedral volume is observed. The high-spin phase shows a bulk modulus B = 101(1) GPa and its pressure derivative B' = 4.5(1). The bulk moduli of the coordination polyhedra are B-MnO6 = 178(2) GPa, B-Ca1O8 = 101.2(5) GPa, B-Ca2O8 = 88.4(8) GPa, B-SiO4 = 337(5) GPa, and B-O4H4 = 29(1) GPa for the high-spin phase. Mode Gruneisen parameters range between 0.34 and 0.94. The computed spin-pairing energy is approximate to 3.6 eV at 0 GPa.

【 授权许可】

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