High-pressure elasticity, shear-mode softening and polymorphism in MnO

Webb, Sharon L.; Jackson, Ian; Gerald, J. D. Fitz

doi:10.1016/0031-9201(88)90061-1

Cited by 38 publications

(36 citation statements)

References 34 publications

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“…Their data indicated no suggestion of a structural phase transition to the maximum pressure attained. Based on this observation, in conjunction with a theoretical lattice model developed by Seino (1982) incorporating magnetic exchange coupling, Jeanloz and Rudy tentatively concluded that the C44 soft mode behavior observed in the results of Webb et al (1983Webb et al ( , 1988) most likely reflected magnetic interactions between Mn ions. However, the maximum pressure reached in the Jeanloz and Rudy (1987) study is well below the upper range of the revised B1 ~ B2 transition (~90 GPa) later predicted by Webb et al (1988).…”

Section: Introductionmentioning

confidence: 84%

“…Conversely, the work of Webb et al (1983Webb et al ( , 1988 and Jeanloz and Rudy (1987) describe the pressure dependence of the elastic behavior of MnO at 300 K. As yet, however, the combined effects of both pressure and temperature have not been evaluated. Such data are required to assess the temperature behavior of the B1--,B2 phase transition in the approach followed by Webb etal.…”

Section: Introductionmentioning

confidence: 90%

“…However, the occurrence of a PM~AFM transformation in MnO in this pressure range at 300 K is complicated by the tendency of NaC1-type compounds to transform from the B1 phase to a B2 (CsC1) structure at high pressure. In this regard, ultrasonic measurements on MnO to 3.0 GPa by Webb et al (1988) have indicated strong shear mode softening for C44. Because C44 mode softening appears to occur as a precursor to both PM~AFM and B1--,B2 phase transitions, Webb et al (1988) were unable to definitively ascribe the behavior they observed to either of these possibilities.…”

Section: Introductionmentioning

confidence: 95%

“…In this regard, ultrasonic measurements on MnO to 3.0 GPa by Webb et al (1988) have indicated strong shear mode softening for C44. Because C44 mode softening appears to occur as a precursor to both PM~AFM and B1--,B2 phase transitions, Webb et al (1988) were unable to definitively ascribe the behavior they observed to either of these possibilities. Extrapolating the data of Bloch et al (1980) and their own results according to the B1 ~ B2 stability criterion for C44/K with pressure proposed by Demarest et al (1977), they constructed a very tentative phase diagram that predicts the occurrence of both transitions at about 50-90 GPa when the temperature is 300 K.…”

Section: Introductionmentioning

confidence: 95%

“…Of particular emphasis has been the systematic relationship between elastic properties and phase transitions (e.g. Sumino et al 1980;Jeanloz and Rudy 1987;Webb et al 1988;Manghnani 1989). Each of the transition metal oxides has been demonstrated to undergo a paramagnetic to antiferromagnetic (PM ~ AFM) phase transformation with decreasing temperature at ambient pressure.…”

Section: Introductionmentioning

confidence: 99%

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Pressure and temperature dependence of the elastic properties of synthetic MnO

Pacalo

Graham

1991

Phys Chem Minerals

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Abstract. The adiabatic elastic stiffness constants of synthetic single-crystal MnO were measured in this study using pulse superposition interferometry. Data were obtained up to 1.0 GPa in pressure and over the temperature range 273 to 473 K. As a result, we were able to determine the complete set of second-order stiffness moduli (C~]) and their pressure and temperature derivatives, as well as higher-order properties for selected modes. Relevant results for the adiabatic bulk modulus are: KS= 155.1 +0.8 GPa;(~Ks/~P)r=4.70+_0.13; and, (~KS/~T)v=-0.0203_+0.0009 GPa/K. Our results for the second-order moduli are generally consistent with the data from previous studies. However, relative to the estimated uncertainties, small and systematic discrepancies appear to characterize the data set. The available evidence indicates that the differences result from microstructural variations (in particular, microcracks and Mn30 4 inclusions) between the synthetic MnO specimens used in different investigations. The pure shear mode C44 exhibits anomalous soft-mode behavior with both temperature (the ambient derivative is positive) and pressure (the ambient derivative is negative). In both cases the C4~ data trends appear to primarily reflect the influence of Mn -Mn magnetoelastic interactions associated with the onset of a paramagnetic-antiferromagnetic (PM --> AFM) phase transition.

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Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Pressure and temperature dependence of the elastic properties of synthetic MnO

Pacalo

Graham

1991

Phys Chem Minerals

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Poisson's Ratio and Auxetic Properties of Natural Rocks

Motra

et al. 2018

JGR Solid Earth

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Here we provide an appraisal of the Poisson's ratios (υ) for natural elements, common oxides, silicate minerals, and rocks with the purpose of searching for naturally auxetic materials. The Poisson's ratios of equivalently isotropic polycrystalline aggregates were calculated from dynamically measured elastic properties. Alpha‐cristobalite is currently the only known naturally occurring mineral that has exclusively negative υ values at 20–1,500°C. Quartz and potentially berlinite (AlPO4) display auxetic behavior in the vicinity of their α‐β structure transition. None of the crystalline igneous and metamorphic rocks (e.g., amphibolite, gabbro, granite, peridotite, and schist) display auxetic behavior at pressures of >5 MPa and room temperature. Our experimental measurements showed that quartz‐rich sedimentary rocks (i.e., sandstone and siltstone) are most likely to be the only rocks with negative Poisson's ratios at low confining pressures (≤200 MPa) because their main constituent mineral, α‐quartz, already has extremely low Poisson's ratio (υ = 0.08) and they contain microcracks, micropores, and secondary minerals. This finding may provide a new explanation for formation of dome‐and‐basin structures in quartz‐rich sedimentary rocks in response to a horizontal compressional stress in the upper crust.

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Deformation of Earth Materials: Six Easy Pieces

Evans

Dresen

1991

Reviews of Geophysics

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Detailed knowledge of rheology is critical to understanding tectonic processes. Laboratory experiments to determine the strength of rocks have provided quantitative bounds on the strength of the crust and mantle. This knowledge has allowed computation of large scale deformation in the asthenosphere, given guidance in interpreting field structures, and improved our knowledge of the earthquake process. Progress has been particularly rapid in some areas: the effect of point defect chemistry on high temperature strength; the effect of water on rock strength, recrystallization and grain boundary processes; deformation processes in two‐phase materials; the application of linear elastic fracture mechanics; and the physics of rock friction and instability. Further progress requires increased knowledge of the effect of fluids and fluid flow on strength; of the ways in which chemical reactions and deformation interact, and of the physics and kinetics of deformation mechanisms

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High-pressure elasticity, shear-mode softening and polymorphism in MnO

Cited by 38 publications

References 34 publications

Pressure and temperature dependence of the elastic properties of synthetic MnO

Pressure and temperature dependence of the elastic properties of synthetic MnO

Poisson's Ratio and Auxetic Properties of Natural Rocks

Deformation of Earth Materials: Six Easy Pieces

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