First-principles calculations of structural, electronic, and optical absorption properties of CaCO3 Vaterite

Medeiros, S.K.; Albuquerque, E.L.; Maia, F. F.; Caetano, E. W. S.; Freire, V. N.

doi:10.1016/j.cplett.2006.12.051

Cited by 57 publications

(26 citation statements)

References 26 publications

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“…Aragonite is metastable and can be transformed to calcite. Vaterite is the least stable CaCO 3 form, and consequently was not studied thoroughly (Bischoff, 1969;Medeiros et al, 2007). The rate of transformation of aragonite to calcite at 323-373 K is proportional to the square of reaction time in aqueous solution (Bischoff, 1969).…”

Section: Independent Species Phases and Chemical Reactionsmentioning

confidence: 99%

Coupled phase and aqueous species equilibrium of the H2O–CO2–NaCl–CaCO3 system from 0 to 250°C, 1 to 1000bar with NaCl concentrations up to saturation of halite

Duan

2008

Geochimica et Cosmochimica Acta

139

102

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Section: Independent Species Phases and Chemical Reactionsmentioning

confidence: 99%

Coupled phase and aqueous species equilibrium of the H2O–CO2–NaCl–CaCO3 system from 0 to 250°C, 1 to 1000bar with NaCl concentrations up to saturation of halite

Duan

2008

Geochimica et Cosmochimica Acta

139

102

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“…In the first strategy, the orthorhombic (Pbmn) crystal structure proposed by Meyer (1960) was used. This crystal structure does not allow the structural disorder of the CO 3 2À groups, which simplifies the simulation (de Medeiros et al, 2007). In the second strategy, the hexagonal P6 3 /mmc crystal structure given by Kamhi (1963) was used.…”

Section: Methodsmentioning

confidence: 99%

The role of sulfate groups in controlling CaCO3 polymorphism

Fernández-Dı́az¹,

Fernández-González²,

Prieto³

2010

Geochimica et Cosmochimica Acta

140

100

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The nucleation and growth of CaCO 3 phases from aqueous solutions with SO 4 2À :CO 3 2À ratios from 0 to 1.62 and a pH of $10.9 were studied experimentally in batch reactors at 25°C. The mineralogy, morphology and composition of the precipitates were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and microanalyses. The solids recovered after short reaction times (5 min to 1 h) consisted of a mixture of calcite and vaterite, with a S content that linearly correlates with the SO 4 2À :CO 3 2À ratio in the aqueous solution. The solvent-mediated transformation of vaterite to calcite subsequently occurred. After 24 h of equilibration, calcite was the only phase present in the precipitate for aqueous solutions with SO 4 2À:CO 3 2À 6 1. For SO 4 2À :CO 3 2À > 1, vaterite persisted as a major phase for a longer time (>250 h for SO 4 2À :CO 3 2À = 1.62). To study the role of sulfate in stabilizing vaterite, we performed a molecular simulation of the substitution of sulfate for carbonate groups into the crystal structure of vaterite, aragonite and calcite. The results obtained show that the incorporation of small amounts (<3 mole%) of sulfate is energetically favorable in the vaterite structure, unfavorable in calcite and very unfavorable in aragonite. The computer modeling provided thermodynamic information, which, combined with kinetic arguments, allowed us to put forward a plausible explanation for the observed crystallization behavior.

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“…Considering the interest in the CaXO 3 (X = C, Si, Ge, Sn, Pb) class of materials [9,[15][16][17][18][19][20][21][22], first principles calculations of the structural, electronic, and optical properties were performed by our research group for all the CaCO 3 polymorphs (calcite [23], aragonite [24], and vaterite [25]), for triclinic CaSiO 3 [26], orthorhombic CaGeO 3 [27], CaSnO 3 [28], and CaPbO 3 [29]. The calculated band structures suggest an overall trend of the minimal band gap energy to decrease, with some oscillation, according to the sequence CaCO 3 calcite ð$ 5:0 eVÞ !…”

mentioning

confidence: 99%

CdXO3 (X = C, Si, Ge, Sn, Pb) electronic band structures

Barboza

Henriques

Albuquerque

et al. 2009

Chemical Physics Letters

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a b s t r a c tElectronic properties for a set of CdXO 3 (X = C, Si, Ge, Sn, Pb) crystals were investigated using the density functional theory (DFT) formalism considering both the local density and generalized gradient approximations, LDA and GGA, respectively. Hexagonal CdCO 3 and triclinic CdSiO 3 have indirect main energy band gaps while orthorhombic CdGeO 3 and CdSnO 3 exhibit direct interband transitions. Orthorhombic CdPbO 3 has a very small indirect band gap. The Kohn-Sham minimum electronic band gap oscillates as a function of the X ns level, changing from 2.94 eV (hexagonal CdCO 3 ; LDAÞ to 0.012 eV (orthorhombic CdPbO 3 ; LDA).Ó 2009 Elsevier B.V. All rights reserved.CdXO 3 (X = C, Si, Ge, Sn, Pb) crystals exhibit several polymorphs and have a wide range of applications. Starting with CdCO 3 , nanoparticles were synthesized through the sonochemical method [1], and shape-controlled hydrothermal synthesis of single-crystalline hexagonal CdCO 3 nanowires, nanobelts, nanorolls, and other onedimensional nanostructures was achieved [2], with the possibility of transforming them into oriented nanoporous CdO. An aragonitetype phase was also found for CdCO 3 by Liu and Lin [3]. Cadmium silicate (CdSiO 3 ), on the other hand, is used as a host matrix for rare-earth doping, allowing for the production of multicolored long-lasting phosphorescence materials [4]. X-ray diffraction data for CdSiO 3 samples revealed a phase structure similar to that of pseudowollastonite CaSiO 3 (JCPDS 35-0810). A survey on the reported unit-cell parameters and space groups for pseudowollastonite CaSiO 3 published by Yang and Prewitt [5] mentions several works favoring either monoclinic or triclinic symmetries. Due to the resemblance between the pseudowollastonite CaSiO 3 and CdSiO 3 , Lei et al. [6] have argued that the crystal structure of the latter is expected to be an one-dimensional chain of edge-sharing SiO 4 tetrahedra.Cadmium germanate ðCdGeO 3 Þ at room temperature and atmospheric pressure has a complex structure resembling the pyroxenoids. Four CdGeO 3 polymorphs in the temperature range from 600°C to 1200°C and varying pressure up to 12 GPa were found by Susaki [7]. The pyroxenoid phase ðCdGeO 3 IÞ is transformed successively into garnet ðCdGeO 3 IIÞ, ilmenite (CdGeO 3 III, hexagonal) and perovskite (CdGeO 3 IV, orthorhombic with increasing pressure. The orthorhombic perovskite phase has Pbnm symmetry, with each germanium (coordination number IV) atom connected to six oxygen atoms, forming a tridimensional array of GeO 6 tilted octahedra with cadmium atoms inserted between them [8]. In order to understand the mechanisms behind the stabilization of the various perovskite crystals, CdGeO 3 , CaGeO 3 , CaSiO 3 , MgSiO 3 and other ABO 3 structures have been investigated [9]. Cadmium stannate ðCdSnO 3 Þ is a semiconducting oxide with gas-sensing properties [10][11][12], and experimental electronic energy band gap of 3.0 eV. Refinement of the CdSnO 3 structure confirms that it is a distorted orthorhombic perovskite, isostructura...

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First-principles calculations of structural, electronic, and optical absorption properties of CaCO3 Vaterite

Cited by 57 publications

References 26 publications

Coupled phase and aqueous species equilibrium of the H2O–CO2–NaCl–CaCO3 system from 0 to 250°C, 1 to 1000bar with NaCl concentrations up to saturation of halite

Coupled phase and aqueous species equilibrium of the H2O–CO2–NaCl–CaCO3 system from 0 to 250°C, 1 to 1000bar with NaCl concentrations up to saturation of halite

The role of sulfate groups in controlling CaCO3 polymorphism

CdXO3 (X = C, Si, Ge, Sn, Pb) electronic band structures

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