Ekaterina Y. Kotelevskaya, Boris B. Shkurskii, Elena A. Volkova, Vasilii O. Krivchuk, Daniil O. Poletaev, Artem R. Oganov
{"title":"Capture of lanthanum atoms by the (111) twin boundary in fluorite: a DFT study","authors":"Ekaterina Y. Kotelevskaya, Boris B. Shkurskii, Elena A. Volkova, Vasilii O. Krivchuk, Daniil O. Poletaev, Artem R. Oganov","doi":"10.1007/s00269-026-01366-8","DOIUrl":"10.1007/s00269-026-01366-8","url":null,"abstract":"<div><p>Ab initio calculations were performed to estimate the energy preference of Ca<sup>2+</sup> substitution by La<sup>3+</sup> with compensating incorporation of an additional F<sup>−</sup> ion at the (111) twin boundary of fluorite (CaF<sub>2</sub>). Model structures of polytypes and polysomes, which are periodic stacking faults within the cubic fluorite matrix, were constructed and optimized using density functional theory (DFT). Our results indicate that the twin boundary has a strong tendency to trap lanthanum cations. These findings suggest that the twin boundaries in CaF<sub>2</sub> may act as active sites for the accumulation of rare-earth elements, providing potential routes for modifying the functional properties of the materials. Conversely, addition of lanthanoids may promote growth twinning of fluorite.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148838196","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}
Kai Wang, Jingui Xu, Shijie Huang, Shanrong Zhang, Qifa Zhong, Wei Zhao, Dawei Fan
{"title":"High-temperature behavior of FeTiO3 and MgTiO3: in-situ synchrotron X-ray diffraction study","authors":"Kai Wang, Jingui Xu, Shijie Huang, Shanrong Zhang, Qifa Zhong, Wei Zhao, Dawei Fan","doi":"10.1007/s00269-026-01365-9","DOIUrl":"10.1007/s00269-026-01365-9","url":null,"abstract":"<div><p>The high-temperature volumetric and axial thermal expansion behaviors of ilmenite (FeTiO<sub>3</sub>) and geikielite (MgTiO<sub>3</sub>) were examined up to 773 K using in situ synchrotron X-ray diffraction. No phase transitions were observed within the experimental temperature range. The temperature–volume data were fitted using the Berman (1988)’s equation, yielding <i>V</i><sub>0</sub> = 316.50(3) Å<sup>3</sup> and <i>α</i><sub><i>V</i>0</sub> = 3.73(4) × 10<sup>–5</sup> K<sup>−1</sup> for FeTiO<sub>3</sub>, and <i>V</i><sub>0</sub> = 308.20(1) Å<sup>3</sup> and <i>α</i><sub><i>V</i>0</sub> = 2.95(9) × 10<sup>–5</sup> K<sup>−1</sup> for MgTiO<sub>3</sub>. In addition, axial thermal expansion analysis showed that FeTiO<sub>3</sub> has <i>a</i><sub>0</sub> = 5.0865(1) Å, <i>α</i><sub><i>a</i>0</sub> = 1.41(1) × 10<sup>–5</sup> K<sup>−1</sup>, <i>c</i><sub>0</sub> = 14.0858(4) Å, and <i>α</i><sub><i>c</i>0</sub> = 0.92(2) × 10<sup>–5</sup> K<sup>−1</sup>, while MgTiO<sub>3</sub> has <i>a</i><sub>0</sub> = 5.0585(1) Å, <i>α</i><sub><i>a</i>0</sub> = 0.85(3) × 10<sup>–5</sup> K<sup>−1</sup>, <i>c</i><sub>0</sub> = 13.9084(4) Å, and <i>α</i><sub><i>c</i>0</sub> = 1.23(3) × 10<sup>–5</sup> K<sup>−1</sup>. The results demonstrate that FeTiO<sub>3</sub> exhibits more stable volumetric expansion with increasing temperature than MgTiO<sub>3.</sub> However, FeTiO<sub>3</sub> and MgTiO<sub>3</sub> display opposite trends in axial expansion: the <i>a</i>-axis expands more than the <i>c</i>-axis in FeTiO<sub>3</sub> (<i>α</i><sub><i>a</i>0</sub>/<i>α</i><sub><i>c</i>0</sub> = 1.53), whereas in MgTiO<sub>3</sub>, the <i>c</i>-axis expands more (<i>α</i><sub><i>a</i>0</sub>/<i>α</i><sub><i>c</i>0</sub> = 0.69). These differences mainly reflect the distinct nature of the A-site cations: the 3d electrons of Fe<sup>2+</sup> affect the rigidity and thermal response of Fe–O and Ti–O bonds, while Fe-related magnetic exchange interactions and associated magnetoelastic coupling may further constrain Fe–O bond expansion and reduce the thermal expansion of FeTiO<sub>3</sub>.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751940","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}
J. B. Neto, C. H. N. Cordeiro, M. M. de Góis, J. Xavier, J. M. Soares
{"title":"Study of strontium hexaferrite prepared by solid state reaction using celestite and hematite","authors":"J. B. Neto, C. H. N. Cordeiro, M. M. de Góis, J. Xavier, J. M. Soares","doi":"10.1007/s00269-026-01364-w","DOIUrl":"10.1007/s00269-026-01364-w","url":null,"abstract":"<div><p>Strontium hexaferrite (SrM) powders were prepared by solid-state reaction using celestite and magnetite/hematite. Energy dispersive X-ray fluorescence spectrometry, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry were used for analyses. The precursor ores were purified by hand-sorting and magnetic separation. Magnetic separation yielded 75% magnetite and 25% hematite in iron ore. Strontium reached a single phase of <span>(rm SrSO_4)</span> via hand-sorting. XRD confirmed single-phase <span>(rm SrFe_{12}O_{19})</span> sample with hexagonal symmetry (space group <span>(rm P6_{3}/mmc)</span>). EDS analyse confirmed that the percentage of elements is in agreement with the expected stoichiometry for the hexaferrite phase. Initial SrM sample exhibited magnetization at maximum field of <span>(rm 56~emu/g)</span> and coercive field of <span>(rm 632~Oe)</span>. Although remanence and coercivity were lower than expected for the initial SrM sample, due to wide particle size distribution observed in SEM images, by optimizing synthesis parameters, particularly annealing at <span>(950^circ )</span>C, the coercivity increased by nearly eightfold, reaching 4.96 kOe. The sample annealed at 950 <span>(^circ )</span>C also exhibited a maximum energy product of <span>(rm (BH)_{max}approx 3.20~MGOe)</span> and an estimated magnetocrystalline anisotropy constant of <span>(rm K_1sim 3.6times 10^6~erg/cm^3)</span>. Microstructural evidence confirmed the predominance of particles in the monodomain regime, which justifies the increase in the coercive field. The results demonstrate that microstructural control is decisive for tuning the magnetic response of SrM, enabling the large-scale viability of this synthesis route for the production of high-coercivity hexaferrites, using a direct mixture of minerals instead of conventional industrial reagents.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-026-01364-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751941","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":"Simulating forsterite surfaces: localised chemistry and surface development under high temperatures","authors":"Joshua M. R. Muir, Yi Wang, Feiwu Zhang","doi":"10.1007/s00269-026-01359-7","DOIUrl":"10.1007/s00269-026-01359-7","url":null,"abstract":"<div><p>Grain boundaries are an important part of many polycrystalline mineral aggregates, possessing unique geometries and chemistries but they are often poorly understood due to the many complexities of studying such large geometrically diverse regions. In this work we shall examine the surfaces of the mineral forsterite in order to understand their controlling behaviour and mechanisms. We shall use a combination of density functional theory and both machine learning and classically trained forcefields. We find that for purposes of partitioning and surface energies most grain boundaries are similar to their constituent planar surfaces. Our main finding is that the relative energies of forsterite surfaces are highly sensitive to T and P and that their planar distributions are not static in real environments. Increasing T at low P can lead to growth of (010) surfaces while increasing T and P together can lead to the growth of (111) surfaces. In mantle conditions we predict a strong favourability of (111) surfaces that increases with depth but with large, sometimes non-monotonic shifts in the favourability of other surfaces. We also demonstrate that changing the surface distribution can lead to changes in crystal properties. The high temperature stabilisation of (010) is driven by a novel collective motion of Mg atoms along [100] channels which will also lead to a large, non-linear, anisotropic increase in grain boundary diffusion as (010) surfaces grow with temperature. We show that partitioning of water to forsterite surfaces is highly surface specific and driven by local chemistry enabling the possibility of hidden reservoirs in the Earth produced by changing surface plane distributions.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613778","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":"Laser thermal decomposition of Fe3O4 to metallic iron under vacuum: experimental and thermodynamic investigation","authors":"Xiaohu Zhang, Guangshi Li, Wenyu Xie, Changyuan Li, Zhongya Pang, Xingli Zou, Qian Xu, Xionggang Lu","doi":"10.1007/s00269-026-01356-w","DOIUrl":"10.1007/s00269-026-01356-w","url":null,"abstract":"<div><p>In-situ manufacturing and resource utilization on the lunar surface present a core challenge for establishing a sustainable lunar base, where the self-sufficiency of metal materials is particularly critical. Therefore, this study presented a novel method for extracting metallic iron from Fe<sub>3</sub>O<sub>4</sub> via laser vacuum (1.0 × 10<sup>− 3</sup> Pa) high-temperature (1930 K to 2360 K) decomposition, which could serve as a reference for in-situ metal extraction on the Moon. First, the feasibility of this approach was verified through thermodynamic calculations. Subsequently, the effects of laser power and irradiation time on the vacuum smelting process of Fe<sub>3</sub>O<sub>4</sub> were systematically investigated. The results indicated that the content of metallic iron in the product reached its maximum value (31.71%) at a laser power of 800 W and an irradiation time of 4 min. Furthermore, the distribution, morphology, and particle size of metallic iron in the product were investigated by scanning electron microscopy and X-ray computed tomography. The metallic iron was primarily enriched in the lower region of the product, presenting as aggregates of irregular fine particles. The particle size distribution was predominantly in the range of 10 to 100 μm (98%), with minor amounts in the 100 to 200 μm (1%) and 200 to 500 μm (1%) ranges.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148613620","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}
Michail Taran, Volodymyr Khomenko, Ievgen Naumenko, Jörg Nissen, Martin Kutzschbach
{"title":"On the color of a large dark-purple crystal of zircon from Afghanistan","authors":"Michail Taran, Volodymyr Khomenko, Ievgen Naumenko, Jörg Nissen, Martin Kutzschbach","doi":"10.1007/s00269-026-01352-0","DOIUrl":"10.1007/s00269-026-01352-0","url":null,"abstract":"<div><p>Optical absorption spectroscopic investigation of a zircon from Afghanistan, unique in both size and color, show evidence that it represents a new type of purple color in this mineral. By microprobe and laser ablation-inductively coupled plasm (LA-ICP-MS) mass spectrometry analyses, the material is nearly pure ZrSiO<sub>4</sub>. The contents of Nb, P, F, Na and Mn are under the detection limits in all point analyses. The mean values of K, Ca, Ti, Sm, Gd, Pb and Ho contents are below 0.001 apfu. The dark-purple, nearly black color of the zircon is thermally unstable. At annealing from 400 to 900 °C it gradually vanishes due to decrease of intensities of the high-energy absorption edge, the broad absorption bands with maxima at ~ 17,970 and 23,900 cm<sup>− 1</sup> (E⊥c) and ~ 18,620, 23,680 and 26,240 cm<sup>− 1</sup> (E||c). Intensities of the weak narrow lines of absorption, which are very likely caused by electronic spin-forbidden <i>ff</i>-transitions of uranium and REE ions, remain unchanged. The origin of the zircon is unclear. By <sup>206</sup>Pb/<sup>238</sup>U radiometric age ~ 1909 million years, it is Proterozoic.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148466211","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}
Morgan Gray, Jack Gugino, Mithun Bhowmick, Catherine Almquist, Dhanalakshmi Sellan, Mark P. S. Krekeler
{"title":"Investigating stability in shock compressed europium- and cerium-doped cryptomelane K-OMS-2 through post-shock spectroscopy and microscopy","authors":"Morgan Gray, Jack Gugino, Mithun Bhowmick, Catherine Almquist, Dhanalakshmi Sellan, Mark P. S. Krekeler","doi":"10.1007/s00269-026-01361-z","DOIUrl":"10.1007/s00269-026-01361-z","url":null,"abstract":"<div><p>Cryptomelane (K-OMS-2) (K(Mn<sup>4+</sup>, Mn<sup>2+</sup>)<sub>8</sub>O<sub>16</sub>) is a manganese-oxide mineral that is abundant in soils and rock coatings globally and is gaining importance in materials science and industrial mineralogy. The crystal structure is composed of 2 × 2 octahedra that creates a tunnel space for K<sup>+</sup>. Low-weight percent (wt%) europium (Eu)-doped, high-wt% Eu-doped, low-wt% cerium (Ce)-doped, and high-wt% Ce-doped cryptomelane were synthesized for dynamic shock compression experiments using laser-driven flyer plates. Powder X-ray diffraction (XRD), high resolution inductively coupled plasma mass spectroscopy (HR-ICP-MS), transmission electron microscopy (TEM), and Raman spectroscopy (RS) were utilized to characterize the materials pre-shock. TEM and RS analysis of post-shocked material found that high-wt% Eu- and high-wt% Ce-cryptomelane were the most resistant to shock, showing the least amount of peak changes in RS and few amorphous regions in TEM. RS and TEM indicate disorder and defects are present in both high-wt% versions, such as changes in Mn–O bond length, wavy lattice fringes, and amorphous regions near the crystal surface. This study concludes that doped cryptomelane is more resistant to shock compression than unmodified cryptomelane. This study supports the previously proposed thixotropic rebound model as the proposed mechanism for cryptomelane’s shock resistance. During the shock wave, the nanoporosity of the material allows for the material to compress as the shock wave passes through the crystals before relaxing into a similar position as the original state. The addition of higher bond strength metals appears to enhance this overall effect. The results provide context for new material applications and future molecular dynamic modeling.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-026-01361-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148466377","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}
D. A. Chareev, A. V. Tyurin, N. A. Polotnyanko, N. S. Uporova
{"title":"Thermodynamic properties of synthetic kesterite Cu2ZnSnS4","authors":"D. A. Chareev, A. V. Tyurin, N. A. Polotnyanko, N. S. Uporova","doi":"10.1007/s00269-026-01360-0","DOIUrl":"10.1007/s00269-026-01360-0","url":null,"abstract":"<div><p>This work focuses on the thermodynamic properties of the synthetic powders and crystals of kesterite, Cu<sub>2</sub>ZnSnS<sub>4</sub>, in a wide temperature range based on in-house measurements of the isobaric heat capacity using adiabatic and differential scanning calorimetry. At temperatures over 318 K coefficients of the Maier–Kelley equation in the interval from 5 to 813 K were determined, and the standard thermodynamic functions: heat capacity, entropy, enthalpy change and Gibbs energy function have been calculated. At 298.15 K, <i>С</i><sub><i>р</i></sub>° = (186.9 ± 0.4) J/(mol· K), <i>S</i>° = (263.5 ± 0.5) J/(mol· K), <i>Н°(298.15 K) - Н°(0)</i> = (37.35 ± 0.07) kJ/mol, <i>Ф</i>° = (138.1 ± 0.3) J/(mol· K). Using the literature and reference data ∆<sub><i>f</i></sub><i>G</i>°(Cu<sub>2</sub>ZnSnS<sub>4</sub>, 298.15 K) = - (460 ± 6) kJ/mol was calculated. The Debye temperature, equal to 390 K, has been calculated from the heat capacity using the fracton data processing method.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465465","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":"Linking interfacial energy estimates based on dihedral angles to grain size constraints in natural and experimental peridotites","authors":"Miki Tasaka, Haruya Aida, Yuto Sato","doi":"10.1007/s00269-026-01357-9","DOIUrl":"10.1007/s00269-026-01357-9","url":null,"abstract":"<div><p>Grain size controls diffusion, deformation, and the textural evolution of mantle rocks. Because grain growth is driven by a reduction in grain boundary energy, the relationship between grain boundary energy and grain size provides an important constraint on microstructural evolution. To better quantify this relationship, we analyzed olivine–olivine–pyroxene (ol–ol–px) dihedral angles in peridotite xenoliths from Ichinomegata (Japan) and San Carlos (USA), as well as in experimentally sintered olivine–pyroxene aggregates. In melt-free Ichinomegata peridotites, ol–ol–opx angles (≈100°) fit single normal distributions. In contrast, melt-bearing Ichinomegata peridotites yield lower-angle ol–ol–cpx triple junction populations (≈80°), which we interpret as relict ol–ol–melt triple junctions, although the distributions of dihedral angles might also reflect the combined effects of textural evolution and system conditions. The San Carlos peridotite and experimental samples yield uniform distributions with median dihedral angles of ≈100°. Moreover, the relationships between olivine grain size, secondary-phase grain size, and secondary-phase volume fraction follow the Zener equation in both natural and experimental peridotites across four orders of magnitude in olivine grain size. These findings suggest that microstructural processes, including Zener pinning, melt–rock interaction, and dynamic recrystallization, contribute to the grain-scale evolution of peridotites across both laboratory and geological scales.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-026-01357-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323891","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":"Bulk modulus and electron density distribution of high-pressure polymorphs of Fe-Ti–O minerals","authors":"Takamitsu Yamanaka, Takanori Hattori","doi":"10.1007/s00269-026-01350-2","DOIUrl":"10.1007/s00269-026-01350-2","url":null,"abstract":"<div><p>The iron-bearing Fe<sub>x</sub>Ti<sub>y</sub>O<sub>z</sub> minerals are important terrestrial materials for plate tectonics studies and paleo-magnetism in geophysics. The bulk modulus of the Fe<sub>x</sub>Ti<sub>y</sub>O<sub>z</sub> minerals, such as Fe<sub>3</sub>O<sub>4</sub> (magnetite), Fe<sub>2</sub>TiO<sub>4</sub>. (ulvöspinel), FeTiO<sub>3</sub> (ilmenite), Fe<sub>2</sub>TiO<sub>5</sub> (pseudobrookite) are related to the compressions of cation sites and vacant site. Cation site partly occupied by Ti atom shows a smaller <i>K</i><sub><i>o</i></sub> than that of only Fe atom. The compressibility increases with increasing Ti content in Fe<sub>x</sub>Ti<sub>y</sub>O<sub>z</sub>. The vacant sites in the unit cell are much larger volumes than cation sites in these four structures. The bulk moduli of these samples are very similar to those of their vacant sites. The compressibility of the cation site is much larger than those of the vacant sites. The cation distribution in the solid solutions have been carried out by neutron diffraction and X-ray diffraction studies. The Fe/Ti distribution has been examined as a function of pressure. The cation sites and vacant sites show different compressibility with increasing pressure. The cation sites of these minerals at high-pressure conditions were investigated to understand their strong electronic correlations. The crystal internal potential change under high pressure is in an equilibrium state of the external pressure by virial theorem. The structure changes such as high-low electron spin transition, Jahn–Teller effect and <i>d-p-π </i>hybridization in the Fe–O bonds are elucidated by present high-pressure experiments. The <i>d-p</i>-<i>π</i> hybridization in the octahedral cation site was discussed by molecular orbital calculation and it brings the deformation of the octahedral cation site. The deformation triggers the structure changes in the high-pressure polymorphs.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"53 3","pages":""},"PeriodicalIF":1.5,"publicationDate":"2026-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148292383","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}