High-pressure phase transformations between the polymorphic forms I, II, III, and IIIb of CaCO3 were investigated by analytical in situ high-pressure high-temperature …
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Calcite, CaCO 3, undergoes several high pressure phase transitions.We report here the crystal structure determination of the CaCO 3-III and CaCO 3-VI high-pressure polymorphs obtained by single-crystal synchrotron X-ray diffraction. This new technical development at synchrotron beamlines currently affords the possibility of collecting single-crystal data suitable …
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Raman scattering spectra of calcite at different pressure points up to 19.4 GPa upon compression at the atmospheric temperature. (a) 0.5-5.7 GPa; (b) 8.5-19.4 GPa.
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Increasing temperature at ambient pressure is known to induce an order–disorder transition into a calcite-type phase (SG R (bar{3}) c, Z = 6), with mutual Ca and Mg cationic exchange (Reeder and Wenk 1983; Antao et al. 2004).The effect of pressure on this order–disorder transition was shown to be negligible (Hammouda et al. 2011)bined high …
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4 Center for High Pressure Science and Technology Advanced Research, Beijing 100193, China 5Skolkovo Institute of Science and Technology, 3 Nobel Street, Moscow 143026, Russia ... pressure, CaCO3 successively adopts five phases (calcite R-3c, aragonite Pnma, low-pressure P21/c, post-aragonite Pmmn, and high-pressure P21/c). As shown in Fig.
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In addition to calcite II and III, high-pressure and high-temperature phases labeled calcite IV and V were found and these phases are generally called calcite disorderly, owing to the orientational disorder of the CO3–2 [22–26,21].
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Fig. 3 shows the constant-pressure specific heat of aragonite at 0 GPa, as compared to experimental data (Litasov et al., 2017), as well of the high-pressure phases P2 1 /c-l, post-aragonite, and P2 1 /c-h, computed with LDA, GGA, and optB86b-vdW. Those results show that the optB86b-vdW provides the best description of these properties.
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The Raman spectra of calcite, Mg‐calcite, and dolomite were measured under ambient and high pressure–temperature (P‐T) conditions using a hydrothermal diamond anvil cell, for the purpose of ...
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Dense and strong calcite (CaCO 3) ceramics were prepared by room-temperature cold sintering with the aid of water and high pressure of up to 900 MPa.Under atmospheric pressure, calcite is barely soluble in water. However, the microstructure evolution and stress-strain analysis during cold sintering revealed that the dissolution-precipitation, plastic …
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For the stability of single carbonate under high-pressure and high-temperature conditions, dolomite CaMg(CO 3 ) 2, magnesite MgCO 3, and calcite CaCO 3 can survive in the deep Earth mantle [26 ...
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Raman spectra of magnesite (MgCO 3) and infrared spectra of the highest pressure meta-stable phase of calcite (designated calcite-III) are presented to pressures of 34 and 32 GPa, respectively.We document that both phases persist at 300 K to the highest pressures of these measurements. Our results for magnesite are similar to previous data on dolomite, in that the …
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In effect, smaller cations tend to stabilize the calcite structure to high-pressure conditions. Indeed, the calcite-III structure, which both calcite and dolomite convert to under pressure, includes the presence of two different octahedrally-coordinated cation sites, one of which is considerably distorted (Smyth and Ahrens, 1997). It is ...
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The Raman spectra of calcite, Mg-calcite, and dolomite were measured under ambient and high pressure–temperature (P-T) conditions using a hydrothermal diamond anvil cell, for the purpose of developing new pressure sensors suited for experiments investigating the physicochemical properties of carbonate minerals.By fitting the Raman vibrational frequencies …
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The geometry of the carbonate unit within the high-pressure phase is likely closer to trigonal symmetry than in the calcite-III structure, and the C-O bond is probably longer than in the lower ...
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Elastic properties of three high pressure polymorphs of CaCO 3 are investigated based on first principles calculations. The calculations are conducted at 0 GPa–40 GPa for aragonite, 40 GPa–65 GPa for post-aragonite, and 65 GPa–150 GPa for the -h-CaCO structure, respectively. By fitting the third-order Birch–Murnaghan equation of state (EOS), the values of bulk modulus …
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The room-temperature Raman spectra of aragonite, magnesite and dolomite have been recorded up to 30 GPa and 25 GPa, respectively and no phase changes were observed during compression, unlike calcite. The effect of temperature on the room-pressure Raman spectra of calcite, aragonite, magnesite and dolomite is reported up to 800–1100 K. The measured …
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We document the presence of a high pressure phase transition in metastable calcite-III using infrared spectroscopy. The post-calcite-III transition initiates at a pressure of 15.5 (±2) GPa, and is completed between 25 and 30 GPa.
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Here, we report on the experimental XRD and Raman investigation of calcite which has been saturated and temperature annealed in an H 2 medium at high pressures up to 110 GPa. We find that H 2 incorporates in the calcite lattice in an atomic form at room temperature starting from the lowest pressure studied, demonstrated by the lattice expansion and …
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Semantic Scholar extracted view of "CaCO3-III and CaCO3-VI, high-pressure polymorphs of calcite: Possible host structures for carbon in the Earth's mantle" by M. Merlini et al.
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Abstract. The high-pressure response of the cell parameters of calcite, CaCO 3, has been investigated by single crystal X-ray diffraction.The unit cell parameters have been refined from 0 to 1.435 GPa, and the linear and volume compressibilities have been measured as β a =2.62(2) × 10-3 GPa-1,β c =7.94(7) × 10-3 GPa-1, β v =13.12 × 10-3 GPa-1.The bulk modulus has been …
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In this work, we use first-principles atomistic calculations based on density functional theory to investigate the first phase transition that occurs when pressure and temperature are …
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The transition temperature of calcite-aragonite decreases with pressure at low pressure from 1.5 to 2.4 GPa but increases with pressure at high pressure from 2.4 to 12 GPa . This is inconsistent with Bridgman (1939), Hess et al. (1991), and especially Suito et al. (2001) .
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Calcite-III was always found to exist at pressures above 20 kbar at room temperature. It was often observed that calcite-I transformed directly to calcite-III with increasing pressure and that calcite-III always reverted directly to calcite-I with decreasing pressure, without the appearance of calcite-II in either case. The Raman spectra of ...
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High-pressure phase transformations and Raman spectra of calcite at room temperature were studied using single crystals in a diamond-anvil cell under hydrostatic presswe. Calcite …
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In this study, two separate high pressure-temperature XRD experiments using either NaCl or KCl as the pressure medium have confirmed that CaCO 3-VII is stable up to 2,300 K between 23 and 38 GPa ... Some …
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In-situ powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra were measured on the natural crystals of calcite (Ca0.996Mg0.004CO3), dolomite (Ca0.497Mg0.454Fe0.046Mn0.003CO3) and magnesite (Mg0.988Ca0.010Fe0.002CO3), with a temperature up to 796 K. The thermal expansion coefficients were evaluated for these …
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Here, based on high-pressure-temperature experiments, the authors present a reversible temperature-induced transition from aragonite to amorphous CaCO3. ... K. Structural evolution of calcite at ...
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Calcite pseudomorphs after aragonite were recorded throughout the high-pressure marbles of the Basal Unit (Evia Island, Greece). The pseudomorphs form a columnar microstructure oriented normal to the foliation, which developed at peak metamorphic conditions within the stability field of aragonite.
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