Physics and Chemistry of Minerals最新文献

{"title":"Features of the defect-impurity composition of diamonds from the northern Istok and Mayat placers (Yakutia) according to EPR, IR, and luminescence data","authors":"V. A. Nadolinny,&nbsp;O. P. Yurjeva,&nbsp;M. I. Rakhmanova,&nbsp;A. Yu. Komarovskikh,&nbsp;V. S. Shatsky","doi":"10.1007/s00269-022-01227-0","DOIUrl":"10.1007/s00269-022-01227-0","url":null,"abstract":"<div><p>Diamonds from placers in the northern provinces of the Siberian Platform attract attention not only due to the unsolved problem of their sources but also due to the variety of properties they exhibit. In this work, electron paramagnetic resonance (EPR), infrared (IR), and photoluminescence (PL) methods were used to study cuboid diamonds from Istok (25 diamonds of Ib-IaA type) and dodecahedron diamonds from Mayat (21 diamonds of IaAB type) placers. The main impurity defects in the crystals studied are nitrogen, nitrogen-titanium, and oxygen-containing centers. The total amount of nitrogen in the form of C (P1 in EPR nomenclature), A, and B centers ranges from 34 to 903 ppm. For 19 out of 25 crystals from the Istok placer, the N3 titanium-related center is observed in the EPR spectra, but only one optical system with zero-phonon line (ZPL) at 635.7 nm is detected in the PL spectra in most cases. It can be assumed that the absence of an accompanying system with ZPL at 440.3 nm is due to its quenching by other centers in these crystals. For 12 out of 21 crystals from the Mayat placer, photoluminescence of oxygen-containing centers in the region of 600–800 nm in the form of a series of equidistant bands with an interval of ~ 31 meV was revealed. A comparison of the EPR and PL data has shown that this red broad band is not correlated with titanium-nitrogen paramagnetic centers OK1 and N3. Thus, the results obtained for diamond crystals from the Istok and Mayat placers show no connection between the N3 and OK1 paramagnetic centers and band in the 600–800 nm region, which questions the presence of oxygen in the structure of the N3 and OK1 centers. The nickel-nitrogen centers were found in crystals from the Mayat placer testifying about the peridotitic paragenesis of these diamonds.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"50 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4639739","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectral variability of the uranyl silicates uranophane-α and uranophane-β: polymorphism and luminescence","authors":"Martin Stark,&nbsp;Markus Noller","doi":"10.1007/s00269-022-01225-2","DOIUrl":"10.1007/s00269-022-01225-2","url":null,"abstract":"<div><p>The luminescence of the uranyl cation UO₂²⁺ depends on the local crystalline environment and is sensitive to structural influences. Steady-state photoluminescence emission spectra of the related uranyl silicates uranophane-α, uranophane-β, sklodowskite and haiweeite from various locations are presented and discussed in the light of structure–property relation. The four mineral species were chosen for their close relationships: uranophane-α and uranophane-β are polymorphs and share the underlaying topology with sklodowskite. Haiweeite, with different topology, shares the composing elements Ca, U, Si, O with uranophane, while in sklodowskite Mg replaces Ca. All species show some variability in their spectra, parameterized as a variation of the centroid wavelength. Those variations are linked to defects and structural disorder, relevant in studies of uranyl speciation and migration. We present empiric spectra of the four mineral species with the least influence of structural disorder. As an unexpected feature, a prominent—partly dominating—double peak structure occurs in the case of uranophane-α only, while it is absent in the spectra of the other species. Considering a model of luminescent transitions in the uranyl ion in more detail, this observation is discussed in the light of the polymorphism of uranophane. We show evidence that variable amounts of uranophane-β phase embedded in uranophane-α are possibly at the origin of this spectral signature. Growth of those uranophane-β clusters might be induced by defects in the uranophane-α lattice and further promoted by the polymorphism of uranophane.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"50 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01225-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4073363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compressibilities along the magnetite–magnesioferrite solid solution","authors":"C. Melai,&nbsp;T. Boffa Ballaran,&nbsp;L. Uenver-Thiele,&nbsp;A. Kurnosov,&nbsp;A. I. Chumakov,&nbsp;D. Bessas,&nbsp;D. J. Frost","doi":"10.1007/s00269-022-01217-2","DOIUrl":"10.1007/s00269-022-01217-2","url":null,"abstract":"<div><p>To calculate the thermodynamic properties of recently discovered high-pressure mixed valence iron oxides in the system Fe–Mg–O, information on the equation of state of precursor inverse spinel phases along the magnetite–magnesioferrite join is needed. The existing equation of state data, particularly for magnesioferrite, are in poor agreement and no data exist for intermediate compositions. In this study, the compressibility of nearly pure magnesioferrite as well as of an intermediate <span>({{mathrm{Mg}}_{0.5}}^{vphantom{2+}}mathrm{Fe}_{0.5}^{2+}{mathrm{Fe}}_{2}^{3+}{mathrm{O}}_{4}^{vphantom{2+}})</span> sample have been investigated for the first time up to approximately 19 and 13 GPa, respectively, using single-crystal X-ray diffraction in a diamond anvil cell. Samples were produced in high-pressure synthesis experiments to promote a high level of cation ordering, with the obtained inversion parameters larger than 0.83. The room pressure unit cell volumes, <i>V</i>₀, and bulk moduli, <i>K</i>_<i>T</i>0, could be adequately constrained using a second-order Birch–Murnaghan equation of state, which yields <i>V</i>₀ = 588.97 (8) ų and <i>K</i>_<i>T</i>0 = 178.4 (5) GPa for magnesioferrite and <i>V</i>₀ = 590.21 (5) ų and <i>K</i>_<i>T</i>0 = 188.0 (6) GPa for the intermediate composition. As magnetite has <i>K</i>_<i>T</i>0 = 180 (1) GPa (Gatta et al. in Phys Chem Min 34:627–635, 2007. https://doi.org/10.1007/s00269-007-0177-3), this means the variation in <i>K</i>_<i>T</i>0 across the magnetite–magnesioferrite solid solution is significantly non-linear, in contrast to several other Fe–Mg spinels. The larger incompressibility of the intermediate composition compared to the two end-members may be a peculiarity of the magnetite–magnesioferrite solid solution caused by an interruption of Fe²⁺–Fe³⁺ electron hopping by Mg cations substituting in the octahedral site.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"50 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01217-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4378139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correction: Overview of HPCAT and capabilities for studying minerals and various other materials at high-pressure conditions","authors":"Arunkumar Bommannavar,&nbsp;Paul Chow,&nbsp;Rich Ferry,&nbsp;Rostislav Hrubiak,&nbsp;Freda Humble,&nbsp;Curtis Kenney-Benson,&nbsp;Mingda Lv,&nbsp;Yue Meng,&nbsp;Changyong Park,&nbsp;Dmitry Popov,&nbsp;Eric Rod,&nbsp;Maddury Somayazulu,&nbsp;Guoyin Shen,&nbsp;Dean Smith,&nbsp;Jesse Smith,&nbsp;Yuming Xiao,&nbsp;Nenad Velisavljevic","doi":"10.1007/s00269-022-01218-1","DOIUrl":"10.1007/s00269-022-01218-1","url":null,"abstract":"","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"49 12","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01218-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4912972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oxidation processes and thermal stability of actinolite","authors":"Constanze Rösche,&nbsp;Naemi Waeselmann,&nbsp;Nadia Petrova,&nbsp;Thomas Malcherek,&nbsp;Jochen Schlüter,&nbsp;Boriana Mihailova","doi":"10.1007/s00269-022-01223-4","DOIUrl":"10.1007/s00269-022-01223-4","url":null,"abstract":"<div><p>Understanding the thermal behaviour of iron-containing amphiboles (AB₂C₅T₈O₂₂W₂, C₅ = <i>M</i>(1)₂<i> M</i>(2)₂<i> M</i>(3)) at atomic-level scale may have important implications in several fields, including metamorphic petrology, geophysics, and environmental sciences. Here, the thermally induced oxidation and decomposition of actinolite are studied by in situ high-temperature Raman spectroscopy and complementary thermogravimetric/mass-spectrometry analyses as well as X-ray diffraction of the products of amphibole decomposition. The effect of ^CFe²⁺ on dehydrogenation/dehydroxylation is followed by comparing the results on actinolite with those for tremolite. We show that mobile charge carriers, namely polarons (conduction electrons coupled to FeO₆ phonons) and H⁺ cations, exist in actinolite at elevated temperatures ~ 1150–1250 K. The temperature-induced actinolite breakdown is a multistep process, involving (i) delocalization of <i>e</i>⁻ from ^CFe²⁺ as well as of H⁺ from hydroxyl groups shared by Fe-containing <i>M</i>(1)<i>M</i>(1)<i>M</i>(3) species, which, however, remain in the crystal bulk; (ii) dehydrogenation and ejection of <i>e</i>⁻ between 1250 and 1350 K, where actinolite can be considered as “oxo-actinolite”, as H⁺ also from hydroxyl groups next to ^{<i>M</i>(1,3)}(MgMgMg) configurations become delocalized and mostly remain in the crystal bulk; (iii) complete dehydroxylation and consequent structure collapse above 1350 K, forming an Fe³⁺-bearing defect-rich augitic pyroxene. The dehydrogenation of tremolite occurs at 1400 K, triggering immediately a disintegration of the silicate double-chain into single SiO₄-chains and followed by a rearrangement of the amphibole octahedral strips and ^BCa²⁺ cations into pyroxene-type octahedral sheets at 1450 K. The result of tremolite decomposition is also a single-phase defect-rich clinopyroxene with an intermediate composition on the diopside–clinoenstatite join.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"49 12","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01223-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5174064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of P–V equation of state of a natural clinoptilolite using high-pressure powder synchrotron X-ray diffraction","authors":"Andrew C. Strzelecki,&nbsp;Stella Chariton,&nbsp;Cody B. Cockreham,&nbsp;Michael T. Pettes,&nbsp;Vitali Prakapenka,&nbsp;Bethany A. Chidester,&nbsp;Di Wu,&nbsp;Chris R. Bradley,&nbsp;Garrett G. Euler,&nbsp;Xiaofeng Guo,&nbsp;Hakim Boukhalfa,&nbsp;Hongwu Xu","doi":"10.1007/s00269-022-01224-3","DOIUrl":"10.1007/s00269-022-01224-3","url":null,"abstract":"<div><p>Characterization of the behavior of zeolites at high pressures is of interest both in fundamental science and for practical applications. For example, zeolites occur as a major mineral group in tuffaceous rocks (such as those at the Nevada Nuclear Security Site), and they play a key role in defining the high-pressure behavior of tuff in a nuclear explosion event. The crystal structure, Si/Al ratio, and type of pressure-transmitting media (PTM) used in high-pressure experiments influence the compressional behavior of a given zeolitic phase. The heulandite-type (HEU) zeolites, including heulandite and clinoptilolite, are isostructural but differ in their Si/Al ratios. Thus, HEU-type zeolites comprise an ideal system in unraveling the effects of Si/Al ratio and type of PTM on their pressure-induced structural behavior. In this study, we performed in situ high-pressure angle-dispersive powder synchrotron X-ray diffraction (XRD) experiments on a natural HEU zeolite, clinoptilolite, with a Si/Al ratio of 4.4, by compressing it in a diamond anvil cell (DAC) up to 14.65 GPa using a non-penetrating pressure-transmitting medium (KCl). Unit cell parameters as a function of pressure up to 9.04 GPa were obtained by Rietveld analysis. Unit cell volumes were fit to both a second and a third-order Birch–Murnaghan equation of state. The mean bulk modulus (<i>K</i>₀) determined from all the fittings is 32.7 ± 0.9 GPa. The zero-pressure compressibility of the <i>a-</i>, <i>b-</i>, and <i>c</i>-axes for clinoptilolite are 10.6 (± 0.8) × 10^–3 GPa^–1, 5.3 (± 0.7) × 10^–3 GPa^–1, and 17.1 (± 1.8) × 10^–3 GPa^–1, respectively. The pressure–volume equations of states of this type of zeolite are important for characterizing high-pressure behavior of the broader family of microporous materials and for developing reliable geophysical signatures for underground nuclear monitoring.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"49 12","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4624546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-pressure behavior of gasparite-(Ce) (nominally CeAsO4), a monazite-type arsenate","authors":"Francesco Pagliaro,&nbsp;Paolo Lotti,&nbsp;Davide Comboni,&nbsp;Tommaso Battiston,&nbsp;Alessandro Guastoni,&nbsp;Patrizia Fumagalli,&nbsp;Nicola Rotiroti,&nbsp;G. Diego Gatta","doi":"10.1007/s00269-022-01222-5","DOIUrl":"10.1007/s00269-022-01222-5","url":null,"abstract":"<div><p>The high-pressure behavior of the natural arsenate gasparite-(Ce) [Ce_0.43La_0.24Nd_0.15Ca_0.11Pr_0.04Sm_0.02Gd_0.01(As_0.99Si_0.03O₄)] from the Mt. Cervandone mineral deposit (Piedmont Lepontine Alps, Italy), has been studied by in situ single-crystal synchrotron X-ray diffraction up to 22.01 GPa. Two distinct high-pressure ramps have been performed, using a 16:3:1 methanol:ethanol:water solution and helium as <i>P</i>-transmitting fluids, respectively. No phase transition occurs within the pressure range investigated, whereas a change in the compressional behavior has been observed at ~ 15 GPa. A second-order Birch-Murnaghan EoS was fitted to the <i>P-V</i> data, leading to a refined bulk modulus of 109.4(3) GPa. The structural analysis has been carried out on the basis of the refined structure models, allowing the description of the deformation mechanisms accommodating the bulk compression in gasparite-(Ce) at the atomic scale, which is mainly controlled by the compression of the Rare Earth Elements coordination polyhedra, while the AsO₄ tetrahedra behave as a quasi-rigid units. A micro-Raman spectroscopy analysis, performed at ambient conditions, suggests the presence of hydroxyl groups into the structure of the investigated gasparite-(Ce).</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"49 12","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01222-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"4627361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Compositional effects in the liquid Fe–Ni–C system at high pressure","authors":"Esther S. Posner,&nbsp;Gerd Steinle-Neumann","doi":"10.1007/s00269-022-01219-0","DOIUrl":"10.1007/s00269-022-01219-0","url":null,"abstract":"<div><p>We performed molecular dynamics simulations based on density functional theory to systematically investigate the Fe–Ni–C system including (1) pure Fe and Ni; (2) binary Fe–Ni, Fe–C, and Ni–C; and (3) ternary Fe–Ni–C liquid compositions at 3000 K and three simulation volumes corresponding to pressure (<i>P</i>) up to 83 GPa. Liquid structural properties, including coordination numbers, are analyzed using partial radial distribution functions. Self-diffusion coefficients are determined based on the atomic trajectories and the asymptotic slope of the time-dependent mean-square displacement. The results indicate that the average interatomic distance between two Fe atoms (<i>r</i>_Fe–Fe) decreases with <i>P</i> and is sensitive to Ni (<i>X</i>_Ni) and C (<i>X</i>_C) concentration, although the effects are opposite: <i>r</i>_Fe–Fe decreases with increasing <i>X</i>_Ni, but increases with increasing <i>X</i>_C. Average <i>r</i>_Fe–C and <i>r</i>_Ni–C values also decrease with increasing <i>X</i>_Ni and generally remain constant between the two lowest <i>P</i> points, corresponding to a coordination change of carbon from ~ 6.8 to ~ 8.0, and then decrease with additional <i>P</i> once the coordination change is complete. Carbon clustering occurs in both binary (especially Ni–C) and ternary compositions with short-range <i>r</i>_C-C values (~ 1.29 to ~ 1.57 Å), typical for <i>r</i>_C-C in diamond and graphite. The self-diffusion results are generally consistent with high-<i>P</i> diffusion data extrapolated from experiments conducted at lower temperature (<i>T</i>). A subset of additional simulations was conducted at 1675 and 2350 K to estimate the effect of <i>T</i> on diffusion, yielding an activation enthalpy of ~ 53 kJ/mol and activation volume of ~ 0.5 cm³/mol.\u0000</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"49 11","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01219-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5509059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phase diagrams of Fe–Si alloys at 3–5 GPa from electrical resistivity measurements","authors":"Meryem Berrada,&nbsp;Richard A. Secco","doi":"10.1007/s00269-022-01220-7","DOIUrl":"10.1007/s00269-022-01220-7","url":null,"abstract":"<div><p>One of the most extensively investigated properties of Fe is electrical resistivity (<i>ρ</i>) which features several well-established temperature (<i>T</i>) dependent characteristics. Based on systematic data for Fe and Fe–Si alloys and guidance from the 1 atm diagram, the <i>T-X</i> (composition <i>X</i>) phase diagram can be obtained at constant pressure (<i>P</i>) by plotting maps of constant <i>ρ</i> contours, proposed herein to be called ‘iso-ohms’, maps of constant <i>δρ/δT</i>, as well as maps of variations of exponent <i>x</i> in power law fits to <i>ρ(T</i>^<i>x</i><i>)</i>. Electrical resistivity measurements of Fe-(≤ 17wt%)Si alloys are available at 3–5 GPa and up to liquid temperatures. This study provides a new approach to mapping high <i>P</i>–<i>T</i> structural phase diagrams in the Fe-rich region of the Fe–Si system at moderate pressures and may be used for other compositions. Maps of iso-ohms suggest the α phase is the less resistive phase followed by <i>α</i>₂, <i>α</i>₁, η + α₁, and ε + α₁. Above ~ 11 wt% Si, the ε + α₁ displays a higher <i>ρ</i> than the liquid phase. This is discussed in terms of <i>s</i> and <i>d</i> electron scattering. Maps of constant <i>δρ/δT</i> emphasize the magnetic transition and boundary between the ε + α₁ and η + α₁ phases, while variations of exponent <i>x</i> outline the α₂ region. The Fe–Si system is of interest to the cores of the moon and Mercury.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"49 11","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-022-01220-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5060224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stable compounds in the CaO-Al2O3 system at high pressures","authors":"Ekaterina I. Marchenko,&nbsp;Artem R. Oganov,&nbsp;Efim A. Mazhnik,&nbsp;Nikolay N. Eremin","doi":"10.1007/s00269-022-01221-6","DOIUrl":"10.1007/s00269-022-01221-6","url":null,"abstract":"<div><p>Using the evolutionary crystal structure prediction algorithm USPEX, we showed that at pressures of the Earth’s lower mantle (24-136 GPa) CaAl₂O₄ is the only stable calcium aluminate. At pressures above 7.0 GPa it has the CaFe₂O₄-type structure with space group <i>Pnma</i>. This phase is one of the prime candidate aluminous phases in the lower mantle of the Earth. We show that at low pressures 5CaO • 3Al₂O₃ (C₅A₃) with space group <i>Cmc</i>2₁, CaAl₄O₇ (with space group <i>C</i>2/<i>c</i>) and CaAl₂O₄ (space group <i>P</i>2₁/<i>m</i>) are stable at pressures of up to 2.1, 1.8 and 7.0 GPa, respectively. The previously unknown structure of the orthorhombic \"CA-III\" phase is also found in our calculations. This phase is metastable at 0 K and has a layered structure with space group <i>P</i>2₁2₁2.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"49 11","pages":""},"PeriodicalIF":1.4,"publicationDate":"2022-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5064312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}