Stability of the perovskite structure and possibility of the transition to the post-perovskite structure in CaSiO3, FeSiO3, MnSiO3 and CoSiO3 (original) (raw)
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Ab initio study of the high-pressure behavior of CaSiO3 perovskite
Physics and Chemistry of Minerals, 2005
Using density functional simulations, within the generalized gradient approximation and projectoraugmented wave method, we study structures and energetics of CaSiO 3 perovskite in the pressure range of the Earth's lower mantle (0-150 GPa). At zero Kelvin temperature the cubic ðPm " 3 mÞ CaSiO 3 perovskite structure is unstable in the whole pressure range, at low pressures the orthorhombic (Pnam) structure is preferred. At 14.2 GPa there is a phase transition to the tetragonal (I4/mcm) phase. The CaIrO 3 -type structure is not stable for CaSiO 3 . Our results also rule out the possibility of decomposition into oxides.
Effect of the incorporation of FeAlO 3 into MgSiO 3 perovskite on the post-perovskite transition
Geophysical Research Letters, 2007
Effect of the incorporation of FeAlO 3 into MgSiO 3 perovskite on post-perovskite transition was investigated in Mg 0.85 Fe 0.15 Al 0.15 Si 0.85 O 3 on the basis of high pressure and temperature in-situ X-ray diffraction experiments using a laser heated diamond anvil cell. Results demonstrate that single perovskite is stable up to 143 GPa and 2500 K and perovskite and post-perovskite coexist at 157-162 GPa and 1600-2500 K for the pressure scales by Tsuchiya (2003). Post-perovskite formed as single phase at 176-178 GPa and 1600-2600 K. The post-perovskite transition pressure in Mg 0.85 Fe 0.15 Al 0.15 Si 0.85 O 3 was much higher than that in MgSiO 3. The present experimental study indicates that the incorporation of FeAlO 3 component expands the stability region of perovskite toward high pressure. The FeAlO 3 concentration may strongly influence the thickness of the D 00 layer at the lowermost of the lower mantle.
Formation of a solid solution in the MgSiO3–MnSiO3 perovskite system
Physics and Chemistry of Minerals, 2013
Experiments using laser-heated diamond anvil cells combined with synchrotron X-ray diffraction and SEM-EDS chemical analyses have confirmed the existence of a complete solid solution in the MgSiO 3-MnSiO 3 perovskite system at high pressure and high temperature. The (Mg, Mn)SiO 3 perovskite produced is orthorhombic, and a linear relationship between the unit cell parameters of this perovskite and the proportion of MnSiO 3 components incorporated seems to obey Vegard's rule at about 50 GPa. The orthorhombic distortion, judged from the axial ratios of a/b and ffiffi ffi 2 p a=c;monotonically decreases from MgSiO 3 to MnSiO 3 perovskite at about 50 GPa. The orthorhombic distortion in (Mg 0.5 , Mn 0.5)SiO 3 perovskite is almost unchanged with increasing pressure from 30 to 50 GPa. On the other hand, that distortion in (Mg 0.9 , Mn 0.1)SiO 3 perovskite increases with pressure. (Mg, Mn)SiO 3 perovskite incorporating less than 10 mol% of MnSiO 3 component is quenchable. A value of the bulk modulus of 256(2) GPa with a fixed first pressure derivative of four is obtained for (Mg 0.9 , Mn 0.1)SiO 3. MnSiO 3 is the first chemical component confirmed to form a complete solid solution with MgSiO 3 perovskite at the P-T conditions present in the lower mantle.
The effect of pressure on the structure and volume of ferromagnesian post-perovskite
Geophysical Research Letters, 2006
We determined pressure-volume (P-V) data for (Mg 0.6 Fe 0.4)SiO 3 post-perovskite (ppv) upon decompression from 140 GPa. The data can be divided into four regions: above 95 GPa, diffraction peaks are sharp and follow a smooth and tight P-V curve; below 90 GPa, peak widths increase, and a kink develops in the P-V curve; below 60 GPa, the broadening plateaus; below 4.6 GPa, the ppv pattern disappears. This suggests that defects and stacking faults start to develop in ppv at 90 GPa and saturate at 60 GPa, and the structure disintegrates below 4.6 GPa. The volume and density of the (Mg 0.6 Fe 0.4)SiO 3 ppv is well constrained by our data at the pressures relevant to the Earth's D 00 layer. Our bulk modulus in this region is much higher than theoretical calculations for pure MgSiO 3 ppv.
Elasticity of CaSiO3 perovskite at high pressure and high temperature
Physics of the Earth and Planetary Interiors, 2006
Ab initio molecular dynamic (AIMD) simulations were performed to calculate the equation of state (EOS) of CaSiO 3 perovskite at mantle pressure-temperature conditions. At temperatures above 2000 K, even though the hydrostatic crystal structure is metrically tetragonal in the pressure range of 13-123 GPa, the symmetry of the elastic moduli is consistent with cubic symmetry. Our results show that elastic constants and velocities are independent of temperature at constant volume. Referenced to room pressure and 2000 K, we find: Grűneisen parameter is γ(V) = γ 0 (V/V 0 ) q with γ 0 = 1.53 and q = 1.02(5), and the Anderson Grűneisen parameter is given by (α/α 0 ) = (V/V 0 ) δ T in which α 0 = 2.89 × 10 −5 K −1 and δ T = 4.09(5). Using the third order Birch Murnaghan equation of state to fit our data, we have for ambient P and T, K 0 = 236.6(8) GPa, K 0 = 3.99(3), and V 0 = 729.0(6)Å 3 . Calculated acoustic velocities show the following P-T dependence: (∂ln V P /∂V) T or P = −1.9 × 10 −3 ; (∂ln V S /∂V) T or P = −1.5 × 10 −3 ; (∂ln V Φ /∂V) T or P = −2.4 × 10 −3 ; (∂ln V S /∂ln V P ) T or P = 0.79; (∂ln V S /∂ln V Φ ) T or P = 0.63, indicating that the variations in bulk modulus overpower the variations in shear modulus.
Computational study of the pressure behavior of post-perovskite phases
Aps Meeting Abstracts, 2006
Submitted for the MAR06 Meeting of The American Physical Society Computational study of the pressure behavior of post-perovskite phases RAZVAN CARACAS, Geophysical Laboratory, Carnegie Institution of Washington, RONALD COHEN, Geophysical Laboratory, Carnegie Institution of Washington-The recent discovery of the post-perovskite phase transition (CaIrO 3 structure) in MgSiO 3 has lead to theoretical and experimental investigations of silicates, germanates and oxides that could take this structure. We have employed density functional-theory to explore a series of new compounds with the post-perovskite structure under pressure. We analyze the effects of the Si substitution by tetravalent cations on the perovskite-to-post-perovskite transition and on the crystal structure of post-perovskite. Cations Ti 4+ and Zr 4+ prefer the post-perovskite structure. We also explore the sesquioxides Al 2 O 3 and Rh 2 O 3 and compare their structural evolution with the one of MgSiO 3. For Rh 2 O 3 we observe an enhancement of the ionic character of the type II structure with pressure.
Effect of pressure on the global and local properties of cubic perovskite crystals
Physica Scripta, 2011
The influence of pressure on the structural, elastic, thermal and bonding properties of four perovskite-type oxides AMO 3 is studied from the point of view of the quantum theory of atoms in molecules. Ab initio investigations are performed by means of the full-potential linear augmented plane-wave method as implemented in the wien2k code. The integrated basin charges resulting from the topological analysis of electronic density provide a partition of the bulk modulus and compressibility into atomic contributions. Special attention is paid to the nonlinear behaviour of the local bonding properties. PACS numbers: 71.15.Mb, 71.15.−m, 62.20.de, 31.15.ae (Some figures in this article are in colour only in the electronic version.)
High-temperature structural phase transitions in perovskite
Journal of Physics: Condensed Matter, 1996
High-temperature powder x-ray diffraction data are presented for CaTiO 3 perovskite between 293 and 1523 K. The temperature-dependence of superlattice intensities and cell parameters suggests a sequence of phase transitions from the room temperature orthorhombic (P bnm) structure to a tetragonal (I 4/mcm) polymorph at temperatures in the range 1373-1423 K, followed by transformation to the cubic (P m3m) aristotype at 1523 ± 10 K. The intensity of the diffuse background increases on transformation to the cubic structure and is associated with disorder (and anionic mobility) of the oxygen sub-lattice. The I 4/mcm-P bnm transition induces a large spontaneous strain, but the tetragonal spontaneous strain in the I 4/mcm phase due to the P m3m-I 4/mcm transition is small, below the resolution of this experiment. These results add weight to suggestions from recent computer simulations that orthorhombic MgSiO 3 may transform to a tetragonal (rather than a cubic) polymorph under the conditions of the Earth's mantle, in which case the effects on electrical conductivity would not be expected to be as great as for a transition to a cubic polymorph, although the consequences for elastic properties may be more significant.
Thermal equation of state of CaSiO3 perovskite
Journal of Geophysical Research, 1996
A comprehensive pressure-volume-temperature data set has been obtained for CaSiO 3 perovskite up to 13 GPa and 1600 K, using synchrotron X ray diffraction with a cubic-anvil, DIA-6 type apparatus (SAM-85). For each volume measurement, nonhydrostatic stress is determined from the relative shift in the diffraction lines of NaC1, within which the sample was embedded. Heating to above 973 K greatly reduced the strength of NaC1 (to below 0.05 GPa), making the measurements hydrostatic. At room temperature the cubic perovskite structure remains metastable at pressures as low as 1 GPa, below which the sample transforms into an amorphous phase as indicated by a large background, a marked decrease in diffraction signals, and an anomalous volume decrease of the remaining crystalline phase. Because our experimental uncertainties are significantly smaller than those in previous measurements, the new data provide a tighter constraint on the zero pressure bulk modulus for CaSiO perovskite. A new set of room temperature equation of state parameters are identified so that both our data and the diamond cell data of Mao et al. [1989] are compatible [Kr0 = 232(8) GPa, K½0 = 4.8(3), and V0 -45.58(4) •3]. Volume measurements along several isotherms under both stable and metastable pressure conditions allow isochoric and isobaric interpolations within the range of experimental pressure and temperature conditions. Analyses using various approaches yielded consistent results for (OKr/OT)e of -0.033(8) GPa K -•, and 7 1 1 (Oa/OP)r of -6.3 X 10-GPa-K-, with a zero-pressure thermal expansion a 0 of 3.0 x 10 -s K -•. The thermal pressure is found to be virtually independent of volume, and thus the Anderson-Grtineisen parameter •r-K¬ = 4.8. These results are used to predict the bulk modulus and density of CaSiO 3 perovskite under lower mantle conditions. Along an adiabat with the foot temperature of 2000 K, the density of the perovskite agrees with that of the preliminary reference Earth model (PREM) within 1% throughout the lower mantle. The bulk modulus shows a smaller pressure dependence along the adiabat; it matches that of PREM at the top of the lower mantle but is about 10% too low near the core-mantle boundary. Paper number 95JB03254, 0148-0227/96/95 J B-03254 $05.00 ZaM and Madon, 1991]. However, these phases were synthesized without the presence of the major lower mantle phases ((Mg,Fe)SiO3 perovskite and magnesiowustite) and therefore their existence in the lower mantle is questionable on petrological grounds. A recent phase equilibrium study using a more representative composition of the mantle (pyrolite) shows that A1 is mostly accommodated in (Mg,Fe)SiO3 perovskite with no separate aluminous phase observed [Irifune, 1994]. On the other hand, a number of other experimental studies indicate that the most likely calcium-bearing phase is CaSiO 3 perovskite [Ringwood and Major, 1971; Liu and Ringwood, 1975, Gasparik, 1989, 1971]. Thus the lower mantle may be composed mainly of aluminous (Mg,Fe)SiO3 perovskite, Ca-SiO 3 perovskite, and magnesiowustite, as well as 1 or 2% of other phases. Equation of state measurements of CaSiO 3 perovskite are complicated by the instability of this material. Thus it is not possible to synthesize the sample in one experiment and conduct high-pressure, high-temperature measurements in another. Rather, the synthesis experiment must be capable of giving equation of state information. Equation of state of Ca-SiO3 perovskite has been measured at ambient temperature by several groups in a diamond anvil cell [e.g., Mao et al., 1989; Tarrida and Richet, 1989; Tamai and Yagi, 1989]. Wang and Weidner [1994] reported the first in situ determination of the 661 662 WANG ET AL.: THERMOELASTICITY OF CASIO 3 PEROVSKITE zirconia fill •'%•,•'•i boron ] ,'ree",SøsXu" l i rain • •; ••boro"nitride • tubPng½carb;n • ] Saheater/, , mple chamber • Pth•aterlead Møcurf antdIsk sam le ;
Physical review, 2018
SiO 3 perovskite is the most abundant mineral of the Earth's lower mantle, and compounds with the perovskite structure are perhaps the most widely employed ceramics. Hence, they attract both geophysicists and material scientists. Several investigations attempted to predict their structural evolution at high pressure, and recent advancements highlighted that perovskites having ions with the same formal valence at both polyhedral sites (i.e., 3+:3+) define different compressional patterns when transition metal ions (TMI) are involved. In this study, in situ high-pressure synchrotron XRD measurements coupled with ab initio simulations of the electronic population of NdCrO 3 perovskite are compared with the compressional feature of NdGaO 3. Almost identical from a steric point of view (Cr 3+ and Ga 3+ have almost the same ionic radius), the different electronic configuration of octahedrally coordinated ions-which leads to a redistribution of electrons at the 3d orbitals for Cr 3+-allows the crystal field stabilization energy (CFSE) to act as a vehicle of octahedral softening in NdCrO 3 or it turns octahedra into rigid units when CFSE is null as in NdGaO 3. Besides to highlight that different electronic configurations can act as a primary effect during compression of perovskite compounds, our findings have a deep repercussion on the way the compressibility of perovskites have to be modeled.