共查询到20条相似文献,搜索用时 131 毫秒
1.
M. Akaogi H. Takayama H. Kojitani H. Kawaji T. Atake 《Physics and Chemistry of Minerals》2007,34(3):169-183
The low-temperature isobaric heat capacities (C
p) of β- and γ-Mg2SiO4 were measured at the range of 1.8–304.7 K with a thermal relaxation method using the Physical Property Measurement System.
The obtained standard entropies (S°298) of β- and γ-Mg2SiO4 are 86.4 ± 0.4 and 82.7 ± 0.5 J/mol K, respectively. Enthalpies of transitions among α-, β- and γ-Mg2SiO4 were measured by high-temperature drop-solution calorimetry with gas-bubbling technique. The enthalpies of the α−β and β−γ
transitions at 298 K (ΔH°298) in Mg2SiO4 are 27.2 ± 3.6 and 12.9 ± 3.3 kJ/mol, respectively. Calculated α−β and β−γ transition boundaries were generally consistent
with those determined by high-pressure experiments within the errors. Combining the measured ΔH°298 and ΔS°298 with selected data of in situ X-ray diffraction experiments at high pressure, the ΔH°298 and ΔS°298 of the α−β and β−γ transitions were optimized. Calculation using the optimized data tightly constrained the α−β and β−γ transition
boundaries in the P, T space. The slope of α−β transition boundary is 3.1 MPa/K at 13.4 GPa and 1,400 K, and that of β−γ boundary 5.2 MPa/K at 18.7 GPa
and 1,600 K. The post-spinel transition boundary of γ-Mg2SiO4 to MgSiO3 perovskite plus MgO was also calculated, using the optimized data on γ-Mg2SiO4 and available enthalpy and entropy data on MgSiO3 perovskite and MgO. The calculated post-spinel boundary with a Clapeyron slope of −2.6 ± 0.2 MPa/K is located at pressure
consistent with the 660 km discontinuity, considering the error of the thermodynamic data. 相似文献
2.
Daisuke Yamazaki Eiji Ito Yoshinori Tange Takashi Yoshino Shuangmeng Zhai Hiroshi Fukui Anton Shatskiy Tomoo Katsura Ken-ichi Funakoshi 《Physics and Chemistry of Minerals》2007,34(4):269-273
In situ X-ray observations of the phase transition from ilmenite to perovskite structure in MnGeO3 were carried out in a Kawai-type high-pressure apparatus interfaced with synchrotron radiation. The phase boundary between
the ilmenite and perovskite structures in the temperature range of 700–1,400°C was determined to be P (GPa) = 16.5(±0.6) − 0.0034(±0.0006)T (°C) based on Anderson’s gold pressure scale. The Clapeyron slope, dP/dT, determined in this study is consistent with that for the transition boundary between the ilmenite and the perovskite structure
in MgSiO3. 相似文献
3.
M. Akaogi H. Yusa E. Ito T. Yagi K. Suito J. T. Iiyama 《Physics and Chemistry of Minerals》1990,17(1):17-23
ZnSiO3 clinopyroxene stable above 3 GPa transforms to ilmenite at 10–12 GPa, which further decomposes into ZnO (rock salt) plus
stishovite at 20–30 GPa. The enthalpy of the clinopyroxene-ilmenite transition was measured by high-temperature solution calorimetry,
giving ΔH0=51.71 ±3.18 kJ/mol at 298 K. The heat capacities of clinopyroxene and ilmenite were measured by differential scanning calorimetry
at 343–733 and 343–633 K, respectively. The C
p of ilmenite is 3–5% smaller than that of clinopyroxene. The entropy of transition was calculated using the measured enthalpy
and the free energy calculated from the phase equilibrium data. The enthalpy, entropy and volume changes of the pyroxene-ilmenite
transition in ZnSiO3 are similar in magnitude to those in MgSiO3. The present thermochemical data are used to calculate the phase boundary of the ZnSiO3 clinopyroxene-ilmenite transition. The calculated boundary,
相似文献
4.
Tomoo Katsura Sho Yokoshi Kazuyuki Kawabe Anton Shatskiy Maki Okube Hiroshi Fukui Eiji Ito Akifumi Nozawa Ken-ichi Funakoshi 《Physics and Chemistry of Minerals》2007,34(4):249-255
The electrical conductivity of (Mg0.93Fe0.07)SiO3 ilmenite was measured at temperatures of 500–1,200 K and pressures of 25–35 GPa in a Kawai-type multi-anvil apparatus equipped
with sintered diamond anvils. In order to verify the reliability of this study, the electrical conductivity of (Mg0.93Fe0.07)SiO3 perovskite was also measured at temperatures of 500–1,400 K and pressures of 30–35 GPa. The pressure calibration was carried
out using in situ X-ray diffraction of MgO as pressure marker. The oxidation conditions of the samples were controlled by
the Fe disk. The activation energy at zero pressure and activation volume for ilmenite are 0.82(6) eV and −1.5(2) cm3/mol, respectively. Those for perovskite were 0.5(1) eV and −0.4(4) cm3/mol, respectively, which are in agreement with the experimental results reported previously. It is concluded that ilmenite
conductivity has a large pressure dependence in the investigated P–T range. 相似文献
5.
M. Akaogi H. Kojitani H. Yusa R. Yamamoto M. Kido K. Koyama 《Physics and Chemistry of Minerals》2005,32(8-9):603-613
Phase transitions in MgGeO3 and ZnGeO3 were examined up to 26 GPa and 2,073 K to determine ilmenite–perovskite transition boundaries. In both systems, the perovskite
phases were converted to lithium niobate structure on release of pressure. The ilmenite–perovskite boundaries have negative
slopes and are expressed as P(GPa)=38.4–0.0082T(K) and P(GPa)=27.4−0.0032T(K), respectively, for MgGeO3 and ZnGeO3. Enthalpies of SrGeO3 polymorphs were measured by high-temperature calorimetry. The enthalpies of SrGeO3 pseudowollasonite–walstromite and walstromite–perovskite transitions at 298 K were determined to be 6.0±8.6 and 48.9±5.8 kJ/mol,
respectively. The calculated transition boundaries of SrGeO3, using the measured enthalpy data, were consistent with the boundaries determined by previous high-pressure experiments.
Enthalpy of formation (ΔH
f°) of SrGeO3 perovskite from the constituent oxides at 298 K was determined to be −73.6±5.6 kJ/mol by calorimetric measurements. Thermodynamic
analysis of the ilmenite–perovskite transition boundaries in MgGeO3 and ZnGeO3 and the boundary of formation of SrSiO3 perovskite provided transition enthalpies that were used to estimate enthalpies of formation of the perovskites. The ΔH
f° of MgGeO3, ZnGeO3 and SrSiO3 perovskites from constituent oxides were 10.2±4.5, 33.8±7.2 and −3.0±2.2 kJ/mol, respectively. The present data on enthalpies
of formation of the above high-pressure perovskites were combined with published data for A2+B4+O3 perovskites stable at both atmospheric and high pressures to explore the relationship between ΔH
f° and ionic radii of eightfold coordinated A2+ (R
A) and sixfold coordinated B4+ (R
B) cations. The results show that enthalpy of formation of A2+B4+O3 perovskite increases with decreasing R
A and R
B. The relationship between the enthalpy of formation and tolerance factor (
R
o: O2− radius) is not straightforward; however, a linear relationship was found between the enthalpy of formation and the sum of
squares of deviations of A2+ and B4+ radii from ideal sizes in the perovskite structure. A diagram showing enthalpy of formation of perovskite as a function of
A2+ and B4+ radii indicates a systematic change with equienthalpy curves. These relationships of ΔH
f° with R
A and R
B can be used to estimate enthalpies of formation of perovskites, which have not yet been synthesized. 相似文献
6.
Jaidong Ko Nancy E. Brown Alexandra Navrotsky Charles T. Prewitt Tibor Gasparik 《Physics and Chemistry of Minerals》1989,16(8):727-733
The phase boundary between MnTiO3 I (ilmenite structure) and MnTiO3 II (lithium niobate structure) has been determined by analysis of quench products from reversal experiments in a cubic anvil
apparatus at 1073–1673 K and 43–75 kbar using mixtures of MnTiO3 I and II as starting materials. Tight brackets of the boundary give P(kbar)=121.2−0.045 T(K). Thermodynamic analysis of this boundary gives ΔHo=5300±1000 J·mol−1, ΔSo = 1.98 ±1J·K−1· mol−1. The enthalpy of transformation obtained directly by transposed-temperature-drop calorimetry is 8359 ±2575 J·mol−1. Possible topologies of the phase relations among the ilmenite, lithium niobate, and perovskite polymorphs are constrained
using the above data and the observed (reversible with hysteresis) transformation of II to III at 298 K and 20–30 kbar (Ross
et al. 1989). The observed II–III transition is likely to lie on a metastable extension of the II–III boundary into the ilmenite
field. However the reversed I–II boundary, with its negative dP/ dT does represent stable equilibrium between ilmenite and lithium niobate, as opposed to the lithium niobate being a quench
product of perovskite. We suggest a topology in which the perovskite occurs stably at low T and high P with a triple point (I, II, III) at or below 1073 K near 70 kbar. The I–II boundary would have a negative P-T slope while the II–III and I–III boundaries would be positive, implying that entropy decreases in the order lithium niobate,
ilmenite, perovskite. The inferred positive slope of the ilmenite-perovskite transition in MnTiO3 is different from the negative slopes in silicates and germanates. These thermochemical parameters are discussed in terms
of crystal structure and lattice vibrations. 相似文献
7.
Hitoshi Yusa Masaki Akaogi Nagayoshi Sata Hiroshi Kojitani Ryo Yamamoto Yasuo Ohishi 《Physics and Chemistry of Minerals》2006,33(3):217-226
In-situ X-ray powder diffraction measurements conducted under high pressure confirmed the existence of an unquenchable orthorhombic perovskite in ZnGeO3. ZnGeO3 ilmenite transformed into perovskite at 30.0 GPa and 1300±150 K in a laser-heated diamond anvil cell. After releasing the pressure, the lithium niobate phase was recovered as a quenched product. The perovskite was also obtained by recompression of the lithium niobate phase at room temperature under a lower pressure than the equilibrium phase boundary of the ilmenite–perovskite transition. Bulk moduli of ilmenite, lithium niobate, and perovskite phases were calculated on the basis of the refined X-ray diffraction data. The structural relations among these phases are considered in terms of the rotation of GeO6 octahedra. A slight rotation of the octahedra plays an important role for the transition from lithium niobate to perovskite at ambient temperature. On the other hand, high temperature is needed to rearrange GeO6 octahedra in the ilmenite–perovskite transition. The correlation of quenchability with rotation angle of GeO6 octahedra for other germanate perovskites is also discussed. 相似文献
8.
Wenjun Yong E. Dachs A. C. Withers E. J. Essene 《Physics and Chemistry of Minerals》2007,34(2):121-127
A multi-anvil device was used to synthesize 24 mg of pure γ-Fe2SiO4 crystals at 8.5 GPa and 1,273 K. The low-temperature heat capacity (C
p) of γ-Fe2SiO4 was measured between 5 and 303 K using the heat capacity option of a physical properties measurement system. The measured
heat capacity data show a broad λ-transition at 11.8 K. The difference in the C
p between fayalite and γ-Fe2SiO4 is reduced as the temperature increases in the range of 50–300 K. The gap in C
p data between 300 and 350 K of γ-Fe2SiO4 is an impediment to calculation of a precise C
p equation above 298 K that can be used for phase equilibrium calculations at high temperatures and high pressures. The C
p and entropy of γ-Fe2SiO4 at standard temperature and pressure (S°298) are 131.1 ± 0.6 and 140.2 ± 0.4 J mol−1 K−1, respectively. The Gibbs free energy at standard pressure and temperature (ΔG°
f,298) is calculated to be −1,369.3 ± 2.7 J mol−1 based on the new entropy data. The phase boundary for the fayalite–γ-Fe2SiO4 transition at 298 K based on current thermodynamic data is located at 2.4 ± 0.6 GPa with a slope of 25.4 bars/K, consistent
with extrapolated results of previous experimental studies. 相似文献
9.
K. Kuroda T. Irifune T. Inoue N. Nishiyama M. Miyashita K. Funakoshi W. Utsumi 《Physics and Chemistry of Minerals》2000,27(8):523-532
Determination of the phase boundary between ilmenite and perovskite structures in MgSiO3 has been made at pressures between 18 and 24 GPa and temperatures up to 2000 °C by in situ X-ray diffraction measurements
using synchrotron radiation and quench experiments. It was difficult to precisely define the phase boundary by the present
in situ X-ray observations, because the grain growth of ilmenite hindered the estimation of relative abundances of these phases.
Moreover, the slow reaction kinetics between these two phases made it difficult to determine the phase boundary by changing
pressure and temperature conditions during in situ X-ray diffraction measurements. Nevertheless, the phase boundary was well
constrained by quench method with a pressure calibration based on the spinel-postspinel boundary of Mg2SiO4 determined by in situ X-ray experiments. This yielded the ilmenite-perovskite phase boundary of P (GPa) = 25.0 (±0.2) – 0.003
T (°C) for a temperature range of 1200–1800 °C, which is generally consistent with the results of the present in situ X-ray
diffraction measurements within the uncertainty of ∼±0.5 GPa. The phase boundary thus determined between ilmenite and perovskite
phases in MgSiO3 is slightly (∼0.5 GPa) lower than that of the spinel-postspinel transformation in Mg2SiO4.
Received: 19 May 1999 / Accepted: 21 March 2000 相似文献
10.
We have used Kieffer's vibrational model to calculate heat capacities and entropies for Al2O3 corundum and MgSiO3 ilmenite, using available vibrational and elastic data for these phases. The calculated heat capacity for corundum is within 1–2 percent of the experimental values between 100 K and 1,800 K, while that for MgSiO3 ilmenite is within 1–2 percent of the experimental data between 350 K and 500 K. We have calculated the heat capacity for MgSiO3 ilmenite from 50 K to 1,800 K, which extends the range of available heat capacity data for this phase. The results of this calculation suggest that there may be differences in the vibrational properties of corundum and MgSiO3 ilmenite. Finally, we have used the results of our calculation to obtain a transition entropy of near -18.8 J/mol.K for the MgSiO3 pyroxene-ilmenite reaction. 相似文献
11.
We used an in situ measurement method to investigate the phase transition of CaGeO3 polymorphs under high pressures and temperatures. A multi-anvil high-pressure apparatus combined with intense synchrotron
X-ray radiation was used. The transition boundary between a garnet and a perovskite phase at T = 900–1,650 K and P = 3–8 GPa was determined as occurring at P (GPa) = 9.0−0.0023 × T (K). The transition pressure determined in our study is in general agreement with that observed in previous high-pressure
experiments. The slope, dP/dT, of the transition determined in our study is consistent with that calculated from calorimetry data. 相似文献
12.
A new determination, using high temperature drop-solution calorimetry, of the enthalpy of transformation of MgSiO3 pyroxene to ilmenite gives H
298 = 59.03 ±4.26 kJ/mol. The heat capacity of the ilmenite and orthopyroxene phases has been measured by differential scanning calorimetry at 170–700 K; Cp of MgSiO3 ilmenite is 4–10 percent less than that of MgSiO3 pyroxene throughout the range studied. The heat capacity differences are consistent with lattice vibrational models proposed by McMillan and Ross (1987) and suggest an entropy change of -18 ± 3 J-K-1 ·mol-1, approximately independent of temperature, for the pyroxene-ilmenite transition. The unit cell parameters of MgSiO3 ilmenite were measured at 298–876 K and yield an average volume thermal expansion coefficient of 2.44 × 10-5 K-1. The thermochemical data are used to calculate phase relations involving pyroxene, -Mg2SiO4 plus stishovite, Mg2SiO4 spinel plus stishovite, and ilmenite in good agreement with the results of high pressure studies. 相似文献
13.
We present results from low-temperature heat capacity measurements of spinels along the solid solution between MgAl2O4 and MgCr2O4. The data also include new low-temperature heat capacity measurements for MgAl2O4 spinel. Heat capacities were measured between 1.5 and 300 K, and thermochemical functions were derived from the results.
No heat capacity anomaly was observed for MgAl2O4 spinel; however, we observe a low-temperature heat capacity anomaly for Cr-bearing spinels at temperatures below 15 K. From
our data we calculate standard entropies (298.15 K) for Mg(Cr,Al)2O4 spinels. We suggest a standard entropy for MgAl2O4 of 80.9 ± 0.6 J mol−1 K−1. For the solid solution between MgAl2O4 and MgCr2O4, we observe a linear increase of the standard entropies from 80.9 J mol−1 K−1 for MgAl2O4 to 118.3 J mol−1 K−1 for MgCr2O4. 相似文献
14.
M. Zhang G. J. Redhammer E. K. H. Salje M. Mookherjee 《Physics and Chemistry of Minerals》2002,29(9):609-616
Synthetic aegirine LiFeSi2O6 and NaFeSi2O6 were characterized using infrared spectroscopy in the frequency range 50–2000 cm−1, and at temperatures between 20 and 300 K. For the C2/c phase of LiFeSi2O6, 25 of the 27 predicted infrared bands and 26 of 30 predicted Raman bands are recorded at room temperature. NaFeSi2O6 (with symmetry C2/c) shows 25 infrared and 26 Raman bands. On cooling, the C2/c–P21/c structural phase transition of LiFeSi2O6 is characterized by the appearance of 13 additional recorded peaks. This observation indicates the enlargement of the unit
cell at the transition point. The appearance of an extra band near 688 cm−1 in the monoclinic P21/c phase, which is due to the Si–O–Si vibration in the Si2O6 chains, indicates that there are two non-equivalent Si sites with different Si–O bond lengths. Most significant spectral
changes appear in the far-infrared region, where Li–O and Fe–O vibrations are mainly located. Infrared bands between 300 and
330 cm−1 show unusually dramatic changes at temperatures far below the transition. Compared with the infrared data of NaFeSi2O6 measured at low temperatures, the change in LiFeSi2O6 is interpreted as the consequence of mode crossing in the frequency region. A generalized Landau theory was used to analyze
the order parameter of the C2/c–P21/c phase transition, and the results suggest that the transition is close to tricritical.
Received: 21 January 2002 / Accepted: 22 July 2002 相似文献
15.
Using density functional simulations within the generalized gradient approximation and projector-augmented wave method together
with thermodynamic modelling, the reciprocal solubilities of MgSiO3 and CaSiO3 perovskites were calculated for pressures and temperatures of the Earth’s lower mantle from 25 to 100 GPa and 0 to 6,000 K,
respectively. The solubility of Ca in MgSiO3 at conditions along a mantle adiabat is found to be less than 0.02 atoms per formula unit. The solubility of Mg in CaSiO3 is even lower, and most important, the extent of solid solution decreases with pressure. To dissolve CaSiO3 perovskite completely in MgSiO3 perovskite, a solubility of 7.8 or 2.3 mol% would be necessary for a fertile pyrolytic or depleted harzburgitic mantle, respectively.
Thus, for any reasonable geotherm, two separate perovskites will be present in fertile mantle, suggesting that Ca-perovskite
will be residual to low degree melting throughout the entire mantle. At the solidus, CaSiO3 perovskite might completely dissolve in MgSiO3 perovskite only in a depleted mantle with <1.25 wt% CaO. These implications may be modified if Ca solubility in MgSiO3 is increased by other major mantle constituents such as Fe and Al. 相似文献
16.
Unpolarized infrared (IR) reflectance spectra for MgSiO3 ilmenite taken from a single-crystal and from a densly packed polycrystalline sample possessed all eight peaks mandated by symmetry between 337 and 850 cm?1. Polarizations were inferred from intensity differences between the two samples. IR peak positions differ by up to 250 cm?1 from recent calculations, but on average are within 11%. Heat capacity C p calculated from these data by using a Kieffer-type model are within the experimental uncertainty of calorimetric measurements from 170 to 700 K. Outside this range, calculated C p is probably accurate within a few percent, based on recent results for garnets. Calculated entropy is only slightly less accurate, giving S 0 (298.15 K) as 54.1 ±0.5 J/ mol-K, which is 10% lower than recent estimates based on phase equilibria. The slope of the phase boundary between ilmenite and perovskite is used to predict S 0 (298.15 K) of perovskite as 58.7 ±1.4 J/mol-K, which is 10% lower than previous values. 相似文献
17.
The stability field of Mg3Al2Si3O12-pyrope was examined for the first time under hydrostatic pressure conditions in a CO2-laser heated diamond cell in the pressure range 21–30 GPa between 2300 and 3200 K. The phases were characterized using Raman
and fluorescence spectroscopy. With increasing pressure pyrope transforms to an ilmenite phase above ∼21.5 GPa, to perovskite
plus ilmenite above ∼24 GPa, and to perovskite above 29 GPa. The pressures of the first occurrence of perovskite in this study
are about 2 GPa above the corresponding phase boundary between end-member MgSiO3-ilmenite and perovskite. A small amount of Al2O3 coexists with perovskite up to 43 GPa, as evident from fluorescence spectra resembling those of ruby, but above 43 GPa the
entire Al2O3 content of the pyrope starting material is accommodated in the perovskite structure.
Received: 6 March 1997 / Revised, accepted: 23 July 1997 相似文献
18.
D. de Ligny P. Richet E. F. Westrum Jr J. Roux 《Physics and Chemistry of Minerals》2002,29(4):267-272
From heat capacities measured adiabatically at low temperatures, the standard entropies at 298.15 K of synthetic rutile (TiO2) and nepheline (NaAlSiO4) have been determined to be 50.0 ± 0.1 and 122.8 ± 0.3 J mol−1 K, respectively. These values agree with previous measurements and in particular confirm the higher entropy of nepheline
with respect to that of the less dense NaAlSiO4 polymorph carnegieite.
Received: 23 July 2001 / Accepted: 12 October 2001 相似文献
19.
The heat capacity (C
p
) of dmitryivanovite synthesized with a cubic press was measured in the temperature range of 5–664 K using the heat capacity
option of a physical properties measurement system and a differential scanning calorimeter. The entropy of dmitryivanovite
at standard temperature and pressure (STP) was calculated to be 110.1 ± 1.6 J mol−1 K−1 from the measured C
p
data. With the help of new phase equilibrium experiments done at 1.5 GPa, the phase transition boundary between krotite and
dmitryivanovite was best represented by the equation: P (GPa) = −2.1825 + 0.0025 T (K). From the temperature intercept of this phase boundary and other available thermodynamic data
for krotite and dmitryivanovite, the enthalpy of formation and Gibbs free energy of formation of dmitryivanovite at STP were
calculated to be −2326.7 ± 2.1 and −2,208.1 ± 2.1 kJ mol−1, respectively. It is also inferred that dmitryivanovite is the stable CaAl2O4 phase at STP and has a wide stability field at high pressures whereas the stability field of krotite is located at high temperatures
and relatively low pressures. This conclusion is consistent with natural occurrences (in Ca–Al-rich inclusions) of dmitryivanovite
and krotite, where the former is interpreted as the shock metamorphic product of originally present krotite. 相似文献
20.
Yuichi Shirako Hiroshi Kojitani Masaki Akaogi Kazunari Yamaura Eiji Takayama-Muromachi 《Physics and Chemistry of Minerals》2009,36(8):455-462
High-pressure phase transitions of CaRhO3 perovskite were examined at pressures of 6–27 GPa and temperatures of 1,000–1,930°C, using a multi-anvil apparatus. The results indicate that CaRhO3 perovskite successively transforms to two new high-pressure phases with increasing pressure. Rietveld analysis of powder X-ray diffraction data indicated that, in the two new phases, the phase stable at higher pressure possesses the CaIrO3-type post-perovskite structure (space group Cmcm) with lattice parameters: a = 3.1013(1) Å, b = 9.8555(2) Å, c = 7.2643(1) Å, V m = 33.43(1) cm3/mol. The Rietveld analysis also indicated that CaRhO3 perovskite has the GdFeO3-type structure (space group Pnma) with lattice parameters: a = 5.5631(1) Å, b = 7.6308(1) Å, c = 5.3267(1) Å, V m = 34.04(1) cm3/mol. The third phase stable in the intermediate P, T conditions between perovskite and post-perovskite has monoclinic symmetry with the cell parameters: a = 12.490(3) Å, b = 3.1233(3) Å, c = 8.8630(7) Å, β = 103.96(1)°, V m = 33.66(1) cm3/mol (Z = 6). Molar volume changes from perovskite to the intermediate phase and from the intermediate phase to post-perovskite are –1.1 and –0.7%, respectively. The equilibrium phase relations determined indicate that the boundary slopes are large positive values: 29 ± 2 MPa/K for the perovskite—intermediate phase transition and 62 ± 6 MPa/K for the intermediate phase—post-perovskite transition. The structural features of the CaRhO3 intermediate phase suggest that the phase has edge-sharing RhO6 octahedra and may have an intermediate structure between perovskite and post-perovskite. 相似文献
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