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![Analysis of garnet minerals. (a) The garnet structure along the [001] direction (b) Unit cell of the garnet structure showing the interconnected Ca sites forming a network for Ca diffusion. (c) Detail of the garnet structure showing three edge-sharing Ca dodecahedra. (d) Calculated energy barriers for Ca diffusion in garnet Ca 3 M 2 (SiO 4 ) 3 for M = Cr and Mn. Color code: Ca cyan, Cr/Mn blue, O red.](publication/334225890/figure/fig2/AS:777141134307330@1562296293405/Analysis-of-garnet-minerals-a-The-garnet-structure-along-the-001-direction-b-Unit.jpg)
Analysis of garnet minerals. (a) The garnet structure along the [001] direction (b) Unit cell of the garnet structure showing the interconnected Ca sites forming a network for Ca diffusion. (c) Detail of the garnet structure showing three edge-sharing Ca dodecahedra. (d) Calculated energy barriers for Ca diffusion in garnet Ca 3 M 2 (SiO 4 ) 3 for M = Cr and Mn. Color code: Ca cyan, Cr/Mn blue, O red.
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Rechargeable lithium-ion batteries dominate the consumer electronics and electric vehicle markets. However, concerns on Li availability have prompted the development of alternative high energy density electrochemical energy storage systems. Rechargeable batteries based on a Ca metal anode can exhibit advantages in terms of energy density, safety an...
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... substitutional solid solution series of silicates with the general formula X 3 Y 2 Si 3 O 12 , where X is a divalent cation (Mg, Fe, Mn, and Ca, in the most common species) in 8-fold coordination and Y is a trivalent cation (Al, Fe, and Cr, in the most common species) in 6-fold coordination 36 . The structure of these silicate garnets (Fig. 5a) consists of isolated Si tetrahedra (in grey) sharing corners with the Y octahedra (in blue) to form chains along each of the a axes of a cubic cell. The spaces between chains are occupied by the X cations (in cyan) which are coordinated by eight oxygen atoms forming a triangular dodecahedron (i.e. distorted cube). Each dodecahedron is ...
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... the Y octahedra (in blue) to form chains along each of the a axes of a cubic cell. The spaces between chains are occupied by the X cations (in cyan) which are coordinated by eight oxygen atoms forming a triangular dodecahedron (i.e. distorted cube). Each dodecahedron is linked to other three forming a 3D network of sites in the structure (see Fig. 5b). In addition to these silicate garnets, the garnet supergroup 37 also includes minerals other than silicates and even those in which the anion is not oxygen (mainly OH − groups or, more rarely, F − ). All these minerals, however, are isostructural with the most common rock-forming silicate garnets described ...
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... garnet structure possesses three-dimensional pathways for Ca diffusion; Fig. 5c shows a detail of three interconnected Ca sites. Figure 5d provides the calculated energy landscape for Ca ions hopping from one Ca site to the nearest one. A diffusing Ca ion must move from the initial site across a quadrangular face to fit in a trigonal prismatic (TP) site at the transition state. The calculated Ca-O distances in the ...
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... garnet structure possesses three-dimensional pathways for Ca diffusion; Fig. 5c shows a detail of three interconnected Ca sites. Figure 5d provides the calculated energy landscape for Ca ions hopping from one Ca site to the nearest one. A diffusing Ca ion must move from the initial site across a quadrangular face to fit in a trigonal prismatic (TP) site at the transition state. ...
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... Ằ and r(O 2− ) = 1.4 Ằ, the Ca 2+ ion seems too large for the size of the channel. Regarding the cationic repulsions, although the TP site shares a face with the octahedral chromium, the Ca-Cr 3+ distance is 2.8 Å. This means that the cationic repulsion is lower than in the pyroxene structure, in agreement with its lower energy barrier of 2.07 eV (Fig. 5). However, this barrier is still too high for Ca ...
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... An observation of structural variations associated with the chemical and temperature-driven phase transition is performed on the solid solution series LiFeGe 2 O 6 and NaFeGe 2 O 6 [8]. Some pyroxene materials have shown suitability in Ca-ion and Li-ion batteries [9,10]. Kim et al. [11] have reported the ...
Ca-based pyroxene structures have gained significant attention due to the higher abundances of calcium in the earth's crust and relatively easy synthesis process. Here, we have analyzed the structural, mechanical, elastic, thermal, and optoelectronic properties of CaMSi2O6 (M = Co, Fe, Mn) pyroxene structures in the monoclinic phase using the first-principles density functional theory (DFT) approach using CASTEP code. The lattice constants of the simulated structures in ferromagnetic (FM) orientations using GGA-WC and GGA-PBSOL were consistent with the available experimental data. Using the Born stability criteria, these structures are considered mechanically stable. These are elastically anisotropic and brittle compounds. The melting temperatures are in the order of 10³ K which symbolizes these as potential candidates for high-temperature applications. The band structure alongside the electronic density of states at the Fermi level reveals half metallicity of these structures. CaMnSi2O6 structure has a maximum half-metallic gap of around 4.60 eV. The remaining two structures have an indirect band gap in the visible photon range given as 3.14 eV, and 2.65 eV for CaCoSi2O6, and CaMnSi2O6, respectively. Observing optical and electronic properties shows that the compound holds a promising future to be utilized in the optoelectronic and plasmonic fields.
... Экспериментальные и теоретические данные о стабильности карбонатных соединений при высоком давлении и высокой температуре необходимы для лучшего понимания углеродного цикла Земли и возможности хранения СО 2 . Электронные свойства важны для разработки перезаряжаемых батарей на основе металлического Са анода [8]. Твердые растворы Ca x Cd 1-x CO 3 представляют интерес с точки зрения сорбции для удаления кадмия из водных, морских и подземных вод [9]. ...
... В двойных карбонатах указанные особенности сохраняются. Так, для двойных карбонатов кальция с магнием, цинком, кадмием и марганцем E g равна 5.11, 421, 3.68 и 2.37 eV (3.8 eV в [8]). Для карбонатов кадмия с магнием, цинком и марганцем соответственно 3.80, 3.41, 2.19 eV и для марганца с магнием и цинком 2.43, 2.34 eV. ...
Density functional theory with a PBE gradient functional and a dispersion correction D3(BJ) in the basis of localized orbitals of the CRYSTAL17 package are used to calculate crystal structure parameters, electronic and vibrational spectra, elastic constants of rhombohedral double carbonates М1М2 (СО3)2 (М1, М2: Mg, Ca, Mn, Cd, Zn) with a dolomite-type structure. The paper demonstrates the possibility for establishing the linear dependences for lattice constants, interatomic distances, elastic constants and polycrystalline moduli, wave numbers of individual vibrational modes on the radii of cations. The same possibility is shown for the dependences of the parameters of chemical bonds and formation energies on their electronegativities. The lattice parameters increase along with the average cation radius, but the elastic constants and moduli demonstrate their decrease. The highest compressibility of carbonates is predicted in the direction of the c axis, which is consistent with the nature of the chemical bond, where stronger carbon — oxygen bonds are present in the ab plane, and weaker metal — oxygen bonds are in the direction of the c axis. The formation energy of binary carbonates CaMg(CO3)2 produced from solid oxides and gaseous CO2 is equal to -2.82 eV. It is equal to -2.71 eV for CaCd(CO3)2, and -0.054 eV, 0.023 eV for simple carbonates, respectively. The resulting formulas can be used to assess and predict the physical properties of solid solutions of carbonates of variable composition.
... Within this scenario, a DFT driven research approach is clearly a powerful strategy to shortcut the meandrous that a classical trial and error method will encounter along its way. Several works [17][18][19][20] deal with the systematic search of potential positive electrodes for calcium batteries among large databases of compounds, such as the Inorganic crystal data base (ICSD), the Materials Project (MP) or the American Mineralogist Crystal Structure Database (AMCSD). From this compendium of computational results, it is concluded that the major obstacle for viable Ca-cathodes is the sluggish diffusion of Ca 2 + ions in inorganic structures. ...
Ca2MnO3.5 and CaV2O4 were found to be potentially interesting as positive electrode materials for calcium metal-based high-energy batteries with DFT-predicted average voltages of 3.7 V and 2.5 V and energy barriers for Ca migration of 1.1 eV and 0.6 eV, respectively. Both compounds were prepared by solid state reaction under reducing atmospheres. Optimum conditions to achieve Ca2MnO3.5 comprised the reduction of Ca2MnO4 under NH3 gas at 420⁰C with a flow rate of 1200 ml/min while CaV2O4 was achieved by reduction of CaV2O6 at 700 ⁰C under H2 flow. Electrochemical oxidation of Ca2MnO3.5 in lithium or calcium cells resulted in the formation of an orthorhombic phase with cell parameter (a= 5.2891(1), b= 10.551(2), c= 12.1422(1)). Operando synchrotron radiation diffraction experiments indicate that the charge compensation mechanism is not related to Ca²⁺ extraction but to intercalation of F⁻ (originated from electrolyte salt decomposition) into the anion vacancy position, as confirmed by EELS and EDS. This process was found to be irreversible. In the case of CaV2O4, oxidation induces the electrochemical extraction of calcium with the formation of an orthorhombic phase (space group Pbnm) with cell parameters a = 10.72008(9) Å, b = 9.20213(2) Å and c = 2.89418(3) Å. The process was also investigated via operando synchrotron radiation diffraction, with the oxidized phase being found to reintercalate Ca²⁺ ions upon reduction, with the formation of a solid solution. Preliminary cycling tests reveals a decrease in the polarization after the first cycle and call for further investigation of this system.
... Computational modeling based on density functional theory (DFT) and classical pair potentials shows that activation energies of Ca ion diffusion in Ca-bearing oxide materials are high, indicating the slow movement of Ca ions. 52,53 For the Ca migration, three main local hops between adjacent Ca sites were identified (refer to Fig. 2). The lowest migration barrier is 4.42 eV (path A) (refer to Table IV). ...
CaMnO3-based ceramics have been the subject of considerable research due to their potential application in solid oxide fuel cells, thermoelectric generators, and catalysis. The computational modeling technique based on the classical pair-wise potentials has allowed atomic-scale insights into the defect chemistry, diffusion of Ca²⁺ and O²⁻ ions, and solution of various dopants in this material. The Ca/Mn anti-site was found to be the most favorable intrinsic defect suggesting disorder, which would be sensitive to synthesis conditions. The second most favorable disorder in CaMnO3 involves loss of CaO, resulting in calcium and oxygen vacancies, which in turn can promote vacancy mediated self-diffusion. The activation energy for oxygen migration (1.25 eV) is much lower than that for calcium (4.42 eV). Favorable isovalent dopants on the Ca and Mn sites were found to be Fe²⁺ and Ge⁴⁺, respectively. The formation of O vacancies can be facilitated by doping of single dopants Fe²⁺ and Al³⁺ on the Mn site. Dual dopants Ni–Fe and Al–Ga on the Mn site can also facilitate the introduction of oxygen vacancies required for the vacancy assisted oxygen diffusion.
... Furthermore, calcium-bearing minerals are of interest in the development of electrode materials for rechargeable Ca-ion batteries [9]. Though CaAl 2 Si 2 O 8 was not studied for this purpose yet, theoretical investigation on other Ca-based minerals is available [10][11][12]. ...
... However, it is expected that the Ca-ion diffusion in Cabearing oxide materials would be slow due to its ion size with a double positive charge. Previous quantum mechanical simulations [10,42] analyzed the suitability of minerals as electrode materials for Ca-ion batteries and high activation energies of migration confirmed the slow diffusivity ion of Ca-ions. Atomistic simulations based on the classical pair potentials can provide useful information on diffusion pathways and activation energies as this information is generally difficult from the experiment. ...
Calcium aluminosilicate, CaAl2Si2O8, is a promising ceramic material that has found applications in several areas, such as glass production and petrology. Atomistic scale simulation techniques are used to study the intrinsic defects, Ca-ion migration paths and doping behavior in CaAl2Si2O8. The most favorable defect is the Al–Si anti-site in agreement with the experimental observation. The O-Frenkel is the second most favorable defect. The Ca-Frenkel is higher in energy only by 0.62 eV than the O-Frenkel. Long-range Ca-ion migration is observed in the ac plane with the activation energy of 2.84 eV suggesting that Ca-ion diffusion in this material is slow. The prominent isovalent dopant on the Ca site is the Sr, which was experimentally substituted on the Ca site to prevent phase transformation. The formation of Ca interstitials and oxygen vacancies is favored by Fe³⁺ doping on the Si site. The favorable tetravalent dopant on the Si site and the Al site to form Ca vacancies is the Ge.
... Other studies have shown that the replacement of Al 3+ in NaAlSi 2 O 6 by Tl 3+ results in the large bandgap reduction (from 5.32 eV to 2.05 eV) which makes this doped pyroxene a potential material in photovoltaics and optoelectronic devices [6]. Some pyroxene structures have shown applicability in Li-ion batteries [7][8][9]. Furthermore, some pyroxene structures have exhibited exotic properties have recently renewed interest in the magnetic aspect of pyroxenes, such as multiferroicity [10][11][12], ferrotoroidicity [13], spin-singlet ground states [14,15] which can lead to phosphorescence and spin-Peierls transition which leads to a magnetoelastic transition in a quasi-one-dimensional system [16]. ...
Pyroxene structures are ferromagnetic silicates that are found in abundance in the Earth's crust and upper mantle, which crystallizes in orthorhombic and monoclinic systems. Here, we present a study using first-principles density functional theory approach in analyzing the structural, physical, optical and magnetic properties of XFeSi 2 O 6 (X = Li, Na, K) pyroxenes in a monoclinic phase. The lattice parameters and lattice angles of the simulated structures in a ferromagnetic structural ordering were consistent with the available experimental data. The optical properties suggested that the structures have a high absorption of UV photons, high reflectivity for visible photons, and calculated loss function spectra show the presence of plasmon peaks near 15 eV-17 eV. The NaFeSi 2 O 6 structure was found to be ductile and the KFeSi 2 O 6 structure demonstrated an auxetic nature. All three compounds were found as ferromagnetic half-metals with a magnetic moment of 5.0μ B. These properties suggest potential applications of such pyroxenes in optoelectronics and plasmonics.
... Torres et al calculated various cobalt oxides, 1D-Ca 3 Co 2 O 6 , 2D-Ca 3 Co 4 O 9 and 3D-Ca 2 Co 2 O 5 for CIBs cathode applications and demonstrated the specific capacity to be 160, 165 and 192 mAh g −1 respectively. The calculated diffusion barrier was 0.9, 0.9 and 1.3 eV respectively [39]. ...
Two-dimensional (2D) materials have recently emerged as ideal candidates for high-capacity lithium-ion batteries anode materials because of their compelling physicochemical and structural properties. In the present study, we use first-principles calculations to investigate the performance of 2D Mg2C as anode materials for Li, Na, K and Ca-ions batteries. The calculated average open-circuit voltage are 0.37, 0.50, 0.03 and 0.06 eV for lithium-, sodium-, potassium- and calcium- ions batteries, respectively. No significant structural deformations are observed on the 2D Mg2C upon the adsorption of Li, Na, K or Ca and the metallic characteristic of the 2D Mg2C is retained. The metallic behavior of both pristine and adsorbed Mg2C ensures the desirable electric conductivity, implying the advantages of 2D Mg2C for batteries. The Na and K atoms show an extremely high diffusivity on the 2D Mg2C with a low energy barrier of 0.08 and 0.04 eV respectively, which is about an order of magnitude smaller than that of Li atom. For the Na and K atoms, the theoretical storage capacity can reach up to 1 770 mAhg-1, nearly two times that of the Li atom of 885 mAhg-1. Our study suggests that the 2D Mg2C is a promising anode material which offers a fast ion diffusion and high storage capacity.
... In general, Ca ion diffusion in Ca-bearing oxide materials is expected to be sluggish due to its ions with double positive charge. In previous theoretical simulations based on the DFT and classical pair potentials, it was shown that activation energies of Ca ion diffusion in Ca-based minerals are high, confirming the slow diffusion [49][50][51][52]. ...
Wollastonite (CaSiO3) is an important mineral that is widely used in ceramics and polymer industries. Defect energetics, diffusion of Ca ions and a solution of dopants are studied using atomistic-scale simulation based on the classical pair potentials. The energetically favourable defect process is calculated to be the Ca-Si anti-site defect cluster in which both Ca and Si swap their atomic positions simultaneously. It is calculated that the Ca ion migrates in the ab plane with an activation energy of 1.59 eV, inferring its slow diffusion. Favourable isovalent dopants on the Ca and Si sites are Sr2+ and Ge4+, respectively. Subvalent doping by Al on the Si site is a favourable process to incorporate additional Ca in the form of interstitials in CaSiO3. This engineering strategy would increase the capacity of this material.
... shown in Scheme 3, minerals can be used as electrode materials in energy applications [63][64][65][66]. For example, vermiculite was mixed with sulfur to form composites, which were used as cathodes in lithium-sulfur batteries with better cycling stabilities [66]. ...
Crystallization engineering is to design and develop solutions to the optimum conversion of the resources of nature to the uses of humankind by using crystallization. Crystallization is a cross-scale process from atoms, ions, and molecules in microscale to bulk crystals in macroscale. Fabricating nanomaterials with desired performances is an open issue with multiscale challenges during crystallization. For the innovation of crystallization engineering, geology may provide various inspirations such as structures, compositions and formation conditions, if mineral materials can be regarded as novel artificial materials. This review shows us some geo-inspirations that enable people to create and engineer novel materials with satisfactory performance.
... The broad peak centered at~25°is due to conductive carbon as mentioned above. A sharp peak at 29°is detected, which could be attributed to MnO 2 as per the literature [43][44][45]. The crystalline peak centered at~34°indexed to the (121) plane of CaMnO 3 reduces in intensity upon Ca-extraction and appears to shift to~35°, whereas other peaks also originally assigned to CaMnO 3 namely at 41.8°(220) and 60.5°(321) shift to 42°and 61.6°, respectively. ...
... It would be expected that the manganese atoms itself undergo oxidation upon Ca-removal. Han et al. have reported the mean oxidation state of manganese in CaMnO 3 as 3.8 [45], and in this case, the formation of MnO 2 upon electrochemical oxidation is possible owing to 4+ being a common manganese oxidation state. We expect this new phase to appear in the XRD profile of the oxidized electrode owing to changes in the crystal structure induced by Ca-migration and re-ordering of oxygen atoms. ...
We report on the synthesis and characterization of perovskite calcium manganese oxide (CaMnO3) as an intercalation compound for calcium ion insertion and extraction. Cyclic voltammetry measurements indicate calcium ion insertion and de-insertion into and from the CaMnO3 host. Differential capacity analysis delineates the potentials at which the insertion and extraction redox processes occur (at −0.4 V and + 0.1 V vs. Ag/Ag⁺, respectively). The insertion and extraction of calcium ions is supported by post-mortem x-ray analysis, which indicates loss of Ca²⁺ ions from the native CaMnO3 phase as well as the presence of manganese oxide phases. This study shows that perovskite calcium manganese oxide is a promising intercalation host.
