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[SeCl3][GaCl4] and [TeCl3][GaCl4] show SHG intensities 3-times stronger than KDP in the visible. They are prepared at 50 °C/140 °C with quantitative yield and potentially examples of a large group of compounds with aligned tetrahedral building units.

We show, by single-crystal diffraction studies in laser-heated diamond-anvil cells, that Ca2CO4 orthocarbonate, which contains CO44− tetrahedra, can be formed already at ~20 GPa at ~1830 K, i.e., at much lower pressures than other carbonates with sp3-hybridized carbon. Ca2CO4 can also be formed at ~89 GPa and ~2500 K. This very broad P-T range suggests the possible existence of Ca2CO4 in the Earth’s transition zone and in most of the lower mantle. Raman spectroscopy shows the typical bands associated with tetrahedral CO44−-groups. DFT-theory based calculations reproduce the experimental Raman spectra and indicate that at least in the athermal limit the phase assemblage of Ca2CO4 + 2SiO2 is more stable than 2CaSiO3 + CO2 at high pressures.

Sound velocities and elastic properties of three synthetic samples of amorphous calcium carbonate (ACC), with different water contents up to 18 wt%, have been determined at high pressures, up to 20 GPa, by Brillouin spectroscopy. The experimental results show a smooth pressure-dependence of both longitudinal, vp, and transverse, vs, velocities in compression and decompression. Our results do not show any anomaly at 10 GPa, where a structural phase transition has been reported for a hydrous ACC. Instead, the anomalous behaviour of the isentropic bulk modulus, KS, and its isothermal pressure derivative, KS′, obtained in this study, with respect to the isothermal bulk modulus, KT, suggest that ACC undergoes a continuous structural evolution upon compression. The presence of 18 wt% H2O leads to a lowering of the bulk modulus up to 39% and of the shear modulus up to 38%. The values of the bulk and shear moduli for anhydrous ACC are Ka = 54(2) GPa, and Ga = 22(1) GPa, respectively. If 10 wt% CaCO3 is present in subducted carbonated oceanic crust, the phase transition from aragonite to anhydrous ACC, observed at pressures between 4 and 10 GPa and T>1000 K, would lead to a seismically detectable discontinuity in the acoustic velocities (−2.8% for vp, −4.4% for vs at 4.8 GPa).

GaSeCl5O is a new inorganic molecular compound prepared from SeO2, SeCl4, and GaCl3 at 50 °C in quantitative yield. The structure of the title compound is described by GaCl3(OSeCl2) molecules with ...

We have synthesized the orthocarbonate Sr3[CO4]O in a laser-heated diamond anvil cell at 20 and 30 GPa by heating to ≈3000 (300) K. Afterward, we recovered the orthocarbonate with [CO4]4- groups at ambient conditions. Single-crystal diffraction shows the presence of [CO4]4- groups, i.e., sp3-hybridized carbon tetrahedrally coordinated by covalently bound oxygen atoms. The [CO4]4- tetrahedra are located in a cage formed by corner-sharing OSr6 octahedra, i.e., octahedra with oxygen as a central ion, forming an antiperovskite-type structure. At high pressures, the octahedra are nearly ideal and slightly rotated. The high-pressure phase is tetragonal (I4/mcm). Upon pressure release, there is a phase transition with a symmetry lowering to an orthorhombic phase (Pnma), where the octahedra tilt and deform slightly.

Single-phase CaxSr1–xCO3 solid solutions with an aragonite structure and x = 0–1 were obtained by precipitation synthesis and characterized with respect to their structural, physical, and thermodyn...

We have synthesized the orthocarbonate Sr2CO4, in which carbon is tetrahedrally coordinated by four oxygen atoms, at moderately high pressures [20(1) GPa] and high temperatures (≈3500 K) in a diamo...

Author(s): Barkov, AY; Bindi, L; Tamura, N; Martin, RF; Ma, C; Winkler, B; Shvedov, GI; Morgenroth, W | Abstract: Fleetite, Cu2RhIrSb2, a new species of platinum-group mineral (PGM), was discovered intergrown with an Os–Ir–Ru alloy in the Miass Placer Zone (Au–PGE), southern Urals, Russia. A single grain 50 lm across was found. Osmium, ruthenium, and iridium are the main associated minerals; also present are Pt–Fe alloys, laurite, Sb-rich irarsite, Rh-rich tolovkite, kashinite, anduoite, ferronickelplatinum, heazlewoodite, PGE-bearing pentlandite and digenite, as well as micrometric inclusions of forsterite (Fo93.7), chromite–magnesiochromite, and Mg-rich edenite. In reflected light, fleetite is light gray; it is opaque, isotropic, non-pleochroic, and non-bireflectant. We report reflectance values measured in air. A mean of seven point-analyses (wavelength-dispersive spectrometry) gave Cu 13.93, Ni 8.60, Fe 0.10, Ir 28.07, Rh 7.91, Ru 1.96, Sb 39.28, total 99.85 wt.%, corresponding to (Cu1.41Ni0.58Fe0.01)R2.00(Rh0.49Ni0.36Ru0.12)R0.97Ir0.95Sb2.08 on the basis of six atoms per formula unit, taking into account the structural results. The calculated density is 10.83 g/cm3. Single-crystal X-ray studies show that fleetite is cubic, space group Fd3m (#227), a = 11.6682(8) A, V = 1588.59(19) A3, and Z = 16. A least-squares refinement of X-ray powder-diffraction data gave a = 11.6575(5) A and V = 1584.22(19) A3. The strongest five reflections in the powder pattern [d in A(I)(hkl)] are: 6.70(75)(111), 4.13(100)(220), 3.52(30)(311), 2.380(50)(422), 2.064(40)(440). Results of synchrotron micro-Laue diffraction experiments are consistent [a ¼ 11.66(2) A]. The crystal structure of fleetite was solved and refined to R ¼ 0.0340 based upon 153 reflections with Fo . 4r(Fo). It is isotypic with Pd11Bi2Se2 and best described as intermetallic, with all metal atoms in 12-fold coordination. Fleetite and other late exotic phases were formed by reaction of the associated alloy phases with a fluid phase enriched in Sb, As, and S in circulation in the cooling ophiolite source-rock. The mineral is named after Michael E. Fleet (1938–2017) in recognition of his significant contributions to the Earth Sciences.

The amidosulphates Mg(NH

Carbonates containing CO4 groups as building blocks have recently been discovered. A new orthocarbonate, Sr2CO4 is synthesized at 92 GPa and at a temperature of 2500 K. Its crystal structure was determined by in situ synchrotron single‐crystal X‐ray diffraction, selecting a grain from a polycrystalline sample. Strontium orthocarbonate crystallizes in the orthorhombic crystal system (space group Pnma) with CO4, SrO9 and SrO11 polyhedra as the main building blocks. It is isostructural to Ca2CO4. DFT calculations reproduce the experimental findings very well and have, therefore, been used to predict the equation of state, Raman and IR spectra, and to assist in the discussion of bonding in this compound., A new orthocarbonate, Sr2CO4, was synthesized under extreme pressure and temperature conditions of 92 GPa and 2500 K, respectively. The crystal structure of the compound s fully characterized in situ by synchrotron single‐crystal X‐ray diffraction and DFT calculations were employed to provide insight into its equation of state, Raman and IR spectra, and bonding. image

High-pressure single-crystal to 20 GPa and powder diffraction measurements to 50 GPa, show that the structure of Pb2SnO4strongly distorts on compression with an elongation of one axis. A structural phase transition occurs between 10 GPa and 12 GPa, with a change of space group fromPbamtoPnam. The resistivity decreases by more than six orders of magnitude when pressure is increased from ambient conditions to 50 GPa. This insulator-to-semiconductor transition is accompanied by a reversible appearance change from transparent to opaque. Density functional theory-based calculations show that at ambient conditions the channels in the structure host the stereochemically-active Pb 6s2lone electron pairs. On compression the lone electron pairs form bonds between Pb2+ions. Also provided is an assignment of irreducible representations to the experimentally observed Raman bands.

The synthesis of a novel type of carbonate, namely of the inorganic pyrocarbonate salt Sr[C

Physical review / B 105(8), 085155 (2022). doi:10.1103/PhysRevB.105.085155, Iron-bearing carbonates play an important role in Earth's carbon cycle. Owing to their stability at mantle conditions, recently discovered iron carbonates with tetrahedrally coordinated carbon atoms are candidates for carbon storage in the deep Earth. The carbonates' iron oxidation and spin state at extreme pressure and temperature conditions contribute to the redox conditions and element partitioning in the deep mantle. By laser heating FeCO$_3$ at pressures of about 83 GPa, Fe$^{3+}_4$C$_3$O$_{12}$ and Fe$^{2+}_2$Fe$^{3+}_2$C$_4$O$_{13}$ were synthesized and then investigated by x-ray emission spectroscopy to elucidate their spin state, both in situ and temperature quenched. Our experimental results show both phases in a high-spin state at all pressures and over the entire temperature range investigated, i.e., up to 3000 K. The spin state is conserved after temperature quenching. A formation path is favored where Fe$^{3+}_4$C$_3$O$_{12}$ forms first and then reacts to Fe$^{2+}_2$Fe$^{3+}_2$C$_4$O$_{13}$, most likely accompanied by the formation of oxides. Density functional theory calculations of Fe$^{2+}_2$Fe$^{3+}_2$C$_4$O$_{13}$ at 80 GPa confirm the experimental findings with both ferric and ferrous iron in high-spin state with antiferromagnetic order at 80 GPa. As the intercrystalline cation partitioning between the Fe-bearing carbonates and the surrounding perovskite and ferropericlase depends on the spin state of the iron, an understanding of the redox conditions prevalent in subducted slab regions in the lower mantle has to take the latter into account. Especially, Fe$^{2+}_2$Fe$^{3+}_2$C$_4$O$_{13}$ may play a key role in subducted material in the lower mantle, potentially with a similar role as silicate perovskite., Published by Inst., Woodbury, NY

Alkaline-earth amidosulphates and their hydrates provide not only a fascinatingly rich crystal chemistry but also an unprecedented and straightforward synthetic approach to sulphur nitride, i.e. S4N4.

Physics and chemistry of minerals 49(5), 10 (2022). doi:10.1007/s00269-022-01185-7, We performed an experiment under long-term microgravity conditions aboard the International Space Station (ISS) to obtain information on the energetics and experimental constraints required for the formation of chondrules in the solar nebula by ’nebular lightning’. As a simplified model system, we exposed porous forsterite (Mg$_2$SiO$_4$) dust particles to high-energetic arc discharges. The characterization of the samples after their return by synchrotron microtomography and scanning electron microscopy revealed that aggregates had formed, consisting of several fused Mg$_2$SiO$_4$ particles. The partial melting and fusing of Mg$_2$SiO$_4$ dust particles under microgravity conditions leads to a strong reduction of their porosity. The experimental outcomes vary strongly in their appearance from small spherical melt-droplets (∅≈ 90 µm) to bigger and irregularly shaped aggregates (∅≈ 350 µm). Our results provided new constraints with respect to energetic aspects of chondrule formation and a roadmap for future and more complex experiments on Earth and in microgravity conditions., Published by Springer, Heidelberg

GaSeCl

We have synthesized the orthocarbonate Sr

We describe the new species ognitite, NiBiTe, and a Co-rich variety of maucherite, hitherto unreported; both were discovered in the Ognit ultramafic complex of Neoproterozoic age in Eastern Sayans, Russia. The mean composition of ognitite (n = 7) is: Ni 17.05, Fe 0.07, Cu 0.14, Pd 0.14, Te 32.53, Bi 49.64, total 99.57 wt.%, corresponding to: (Ni1.11Cu0.008Fe0.005Pd0.005)Σ1.13Bi0.90Te0.97 (Σ atoms = 3 apfu). Ognitite is trigonal, space group P3m1 [R1 = 0.0276 for 81 reflections with Fo > 4σ(Fo)]. The unit-cell parameters derived from the single-crystal X-ray diffraction data are: a = 3.928(1) Å, c = 5.385(1) Å and V = 71.95(4) Å3, with Z = 1. The c:a ratio is 1.37. The powder X-ray diffraction data obtained on the same fragment used for the single-crystal study are: a = 3.9332(4) Å, c = 5.3920(6) Å and V = 72.24(1) Å3. Ognitite exhibits the brucite-type structure with edge-sharing NiTe3Bi3 octahedra forming sheets parallel to (0001). It is related to melonite, but is distinct compositionally by the extreme Bi-enrichment (melonite and its synthetic analogue contain At more than 9 wt.% Co, or ~2 apfu Co, the core of Co-rich maucherite [(Ni,Co)11As8] in a zoned crystal, which is surrounded by Co-depleted orcelite, far surpasses the norm (≤1 and up to 3.9 wt.% Co). The unit-cell parameters of the Co-rich maucherite are: a = 6.85(2) and c = 21.83(5) Å, which are based on results of synchrotron micro-Laue diffraction.The host rock consists of serpentine, clinochlore (Mg# 95–97) and skeletal chromite. We favour the metastable crystallisation of fluid-saturated globules of a sulfide–arsenide melt to explain the anomalous compositions of ore minerals at Ognit. These anomalies seem consistent with rapid cooling in a fluid-enriched system, possibly related to late-stage degassing of the magma, as reflected in a prominent metasomatic aureole at the contact with the enclosing gneissic rocks.

Modern thermodynamic assessment studies of multicomponent systems typically employ the Compound Energy Formalism (CEF) to describe phases of variable composition, which may show effects of chemical ordering. In CEF, the ordering is described by splitting a crystallographic site in which several components can substitute for each other into subsites (sublattices) and by allowing fractional occupancies of these subsites to vary. This type of component redistribution over subsites (sublattices) is classified in solid solution theories as long-range order (LRO). A well-known shortcoming of CEF is the absence of a direct description of the effects of short-range order (SRO), which do not involve a redistribution of components between sublattices, but reveal themselves in various modes of clustering. Here we show that SRO can be taken into account within CEF as an additional (fictive) LRO effect driven by an extra negative excess enthalpy term. We argue that the mathematical form of this term should be constrained such that it ensures its vanishing both in low- and high-temperature limits. Including such a term into CEF allows a significant improvement in the description of phase relations in the system of calcite-magnesite, CaCO3-MgCO3. The modified CEF model with SRO emulation is made available in the GEM-Selektor software.

We report the first direct measurements of the refractive index of silica glass up to 145 GPa that allowed quantifying its density, bulk modulus, Lorenz-Lorentz polarizability, and band gap. These properties show two major anomalies at ∼10 and ∼40 GPa. The anomaly at ∼10 GPa signals the onset of the increase in Si coordination, and the anomaly at ∼40 GPa corresponds to a nearly complete vanishing of fourfold Si. More generally, we show that the compressibility and density of noncrystalline solids can be accurately measured in simple optical experiments up to at least 110 GPa.

We have synthesized the orthocarbonate Sr

Journal of applied physics 130(10), 105303 (2021). doi:10.1063/5.0060445, The effects of ion irradiation on the surface and the subsurface of synthetic diamonds were characterized by using optical microscopy, atomic force microscopy, Raman spectroscopy, x-ray reflectivity, electron backscatter diffraction, and resistivity measurements. Irradiation experiments with 14 MeV Au$^{6+}$ ions with fluences up to 2.4 �� 10$^{15}$ ions/cm$^2$ were carried out on synthetic single crystal diamonds, grown either at high pressure or by chemical vapor deposition, and on polycrystalline samples with high boron concentrations. We show that the ion irradiation-induced changes to the surface and subsurface of diamonds are rather complex and, especially in the first few nanometers, more severe than generally considered. We establish a model describing the changes in density, defect concentration, topology, crystallinity, and bonding from the surface down to the first few micrometers of the irradiated diamond, Published by American Inst. of Physics, Melville, NY

Chondrules are thought to play a crucial role in planet formation, but the mechanisms leading to their formation are still a matter of unresolved discussion. So far, experiments designed to understand chondrule formation conditions have been carried out only under the influence of terrestrial gravity. In order to introduce more realistic conditions, we developed a chondrule formation experiment, which was carried out at long‐term microgravity aboard the International Space Station. In this experiment, freely levitating forsterite (Mg2SiO4) dust particles were exposed to electric arc discharges, thus simulating chondrule formation via nebular lightning. The arc discharges were able to melt single dust particles completely, which then crystallized with very high cooling rates of >105 K h−1. The crystals in the spherules show a crystallographic preferred orientation of the [010] axes perpendicular to the spherule surface, similar to the preferred orientation observed in some natural chondrules. This microstructure is probably the result of crystallization under microgravity conditions. Furthermore, the spherules interacted with the surrounding gas during crystallization. We show that this type of experiment is able to form spherules, which show some similarities with the morphology of chondrules despite very short heating pulses and high cooling rates., Carl Zeiss Meditec AG http://dx.doi.org/10.13039/501100002806, BIOVIA Science Ambassador program, Bundesministerium für Wirtschaft und Energie http://dx.doi.org/10.13039/501100006360, Deutsches Zentrum für Luft‐ und Raumfahrt http://dx.doi.org/10.13039/501100002946, NanoRacks LLC, DreamUp, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Dr. Rolf M. Schwiete Stiftung

Journal of applied crystallography 54(1), 287 - 294 (2021). doi:10.1107/S1600576720016039, The complete elastic stiffness tensor of thiourea has been determined fromthermal diffuse scattering (TDS) using high-energy photons (100 keV).Comparison with earlier data confirms a very good agreement of the tensorcoefficients. In contrast with established methods to obtain elastic stiffnesscoefficients (e.g.Brillouin spectroscopy, inelastic X-ray or neutron scattering,ultrasound spectroscopy), their determination from TDS is faster, does notrequire large samples or intricate sample preparation, and is applicable toopaque crystals. Using high-energy photons extends the applicability of theTDS-based approach to organic compounds which would suffer from radiationdamage at lower photon energies., Published by Wiley-Blackwell, [S.l.]

Carbonates are the major hosts of carbon on Earth's surface and their fate during subduction needs to be known to understand the deep carbon cycle. Magnesite (${\mathrm{MgCO}}_{3}$) is thought to be an important phase participating in deep Earth processes, but its phase stability is still a matter of debate for the conditions prevalent in the lowest part of the mantle and at the core mantle boundary. Here, we have studied the phase relations and stabilities of ${\mathrm{MgCO}}_{3}$ at these $P,T$ conditions, using Raman spectroscopy at high pressures ($\ensuremath{\sim}148\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$) and after heating to high temperatures ($\ensuremath{\sim}3600\phantom{\rule{0.16em}{0ex}}\mathrm{K}$) in laser-heated diamond anvil cell experiments. The experimental Raman experiments were supplemented by x-ray powder diffraction data, obtained at a pressure of 110 GPa. Density-functional-theory-based model calculations were used to compute Raman spectra for several ${\mathrm{MgCO}}_{3}$ high-pressure polymorphs, thus allowing an unambiguous assignment of Raman modes. By combining the experimental observations with the density-functional-theory results, we constrain the phase stability field of ${\mathrm{MgCO}}_{3}$ with respect to the high-pressure polymorph, ${\mathrm{MgCO}}_{3}$-II. We further confirm that Fe-free ${\mathrm{MgCO}}_{3}$-II is a tetracarbonate with monoclinic symmetry (space group $C2/m$), which is stable over the entire $P,T$ range of the Earth's lowermost mantle geotherm.

A new diffractometer is now available to the general user community at the ESRF. The new diffractometer is a side station of the high-resolution inelastic X-ray scattering spectrometer on beamline ID28 and is located in the same experimental hutch. Both instruments can be operated simultaneously. The new diffractometer combines a fast and low-noise hybrid pixel detector with a variable diffraction geometry. The beam spot on the sample is 50 µm × 50 µm, where focusing is achieved by a combination of Be lenses and a KB mirror. Wavelengths from 0.5 to 0.8 Å can be used for the diffraction experiments. The setup is compatible with a variety of sample environments, allowing studies under non-ambient conditions. The diffractometer is optimized to allow a rapid survey of reciprocal space and diffuse scattering for the identification of regions of interest for subsequent inelastic scattering studies, but can also be employed as a fully independent station for structural studies from both powder and single-crystal diffraction experiments. Several software packages for the transformation and visualization of diffraction data are available. An analysis of data collected with the new diffractometer shows that the ID28 side station is a state-of-the-art instrument for structural investigations using diffraction and diffuse scattering experiments.

Sm1-xTbxPO4 solid solutions were synthesized and extensively characterized by powder X-ray diffraction, vibrational spectroscopy, and X-ray absorption spectroscopy. At ambient conditions solid solutions up to x = 0.75 crystallize in the monazite structure, whereas TbPO4 is isostructural to xenotime. For x = 0.8 a mixture of both polymorphs was obtained. Moreover, a phase with anhydrite structure was observed coexisting with xenotime, which was formed due to mechanical stress. Selected solid solutions were investigated at pressures up to ∼40 GPa using in situ high pressure synchrotron X-ray diffraction and in situ high pressure Raman spectroscopy. SmPO4 and Sm0.5Tb0.5PO4 monazites are (meta)stable up to the highest pressures studied here. TbPO4 xenotime was found to transform into the monazite structure at a pressure of about 10 GPa. The transformation of Sm0.2Tb0.8PO4 xenotime into the monazite polymorph commences already at about 3 GPa. This study describes the reversibility of the pressure-induced (Sm,Tb)PO4 xenotime-monazite transformation.

Based on synchrotron X-ray diffraction on phase-pure samples, we revised the bulk moduli of the rhenium borides Re7B3 ( B 0 (Re7B3) = 391(5) GPa) and orthorhombic Re3B ( B 0 (orthorhombic Re3B) = 393(4) GPa) and determined the bulk modulus of monoclinic Re3B ( B 0 (monoclinic Re3B) = 390(3) GPa). These results agree well with the DFT calculations on the elastic properties. Microcalorimetry was employed to obtain thermodynamic data for Re7B3 and orthorhombic Re3B and we determined C p , 298 (Re7B3) = 210(4) J/mol, Δ H 298 0 (Re7B3) = 40558(400) J/mol, S 298 0 (Re7B3) = 267(2) J/mol K and θ D , 298 (Re7B3) = 320(2) K, as well as C p , 298 (Re3B) = 86(1) J/mol, Δ H 298 0 (Re3B) = 16950(170) J/mol, S 298 0 (Re3B) = 112(1) J/mol K and θ D , 298 (Re3B) = 329(3) K. Hardness measurements were performed for Re7B3, which gave a Vickers hardness H V (5 kgf) = 14.5(4) GPa and H V (10 kgf) = 14.1(3) GPa. Electron energy loss spectroscopy (EELS) was performed on orthorhombic Re3B and ReB2, and the experimental spectra are well reproduced by theory in terms of their absorption edges.

The new acentric indium borate InB6O9(OH)3 was synthesized in a Walker-type multianvil apparatus at extreme pressure and temperature conditions of 12.3 GPa and 1500 °C. Single-crystal X-ray diffraction provided the data for the crystal structure solution and refinement. InB6O9(OH)3 crystallizes in the orthorhombic space group Fdd2 ( Z = 8) with the lattice parameters a = 39.011(8), b = 4.4820(9), c = 7.740(2) A, and V = 1353.3(5) A3. The structure of InB6O9(OH)3 is basically built of corner-sharing BO4 tetrahedra and isolated InO6 octahedra. The presence of hydroxyl groups was confirmed with vibrational spectroscopic methods (IR and Raman). Furthermore, the second harmonic signal of an InB6O9(OH)3 powder sample yielded more than twice the intensity of quartz.

Layered doubled hydroxides (LDH), consisting of positively charged octahedral brucite-type layers and interlayer anions, have been widely studied in the last decades because of their ability to control the mobility of various anions and cations in the environment. LDH may be relevant to the safety case of nuclear waste repositories due to their retention potential of anionic radionuclide species, for example 129I or 79Se. So far few studies were dedicated to Zr incorporation into LDH, which might be a relevant secondary phase in the repository environment due to the possible corrosion of Zr-bearing nuclear materials and the presence of 93Zr, a long-lived fission and activation product, in various nuclear waste streams. The focus of our study was to synthesize and characterize Cl-bearing Mg-Al-LDH (MgxAlyZrz(OH)2Cl(2x + 3y + 4z − 2)) with different Zr-content and to evaluate their thermodynamic properties, especially their solubility as a function of temperature. The LDH were synthesized by a coprecipitation method at temperatures between 298.15 and 343.15 K, aiming at Zr/(Zr + Al) ratios of 0.1 and 0.4, respectively. Our analytical techniques combining X-ray diffraction and scanning electron microscopy indicated that up to 5 mol% Zr were incorporated into the brucite layer of the LDH. At higher Zr concentrations the precipitation of an amorphous hydrous Zr-oxide was observed. The structural uptake of Zr was lower than the value reported in literature for CO32– bearing LDH, suggesting that the interlayer anions may play a role with regard to the Zr uptake in the brucite layer. At low Zr contents, well defined crystalline LDH with the composition Mg0.72Al0.22Zr0.025(OH)2Cl0.20 were obtained at all syntheses temperatures. The solubility of this LDH decreases slightly with temperature and the stoichiometric saturation constant was found to satisfy the Van't Hoff equation. The thermodynamic properties of the Zr LDH (Gibbs free energy of formation, ΔG°f) were determined by considering an approach based on solubility data and Gibbs energy minimization and a calorimetric approach. The enthalpy of formation (ΔH°f) and the lattice entropy (S°) of the Zr-LDH were determined using calorimetric measurements to be − 1181.01 ± 4.98 kJ mol− 1 and 83.9 J mol− 1 K− 1 respectively. Considering contribution of the configurational entropy, the standard entropy, S°, was evaluated at 97 ± 7 J mol− 1 K− 1. The ΔG°f for Mg0.72Al0.22Zr0.025(OH)2Cl0.20*0.69H2O obtained from experimental measurements and that predicted by theory were evaluated at − 1046 ± 7 and − 1046 ± 13 kJ mol− 1 respectively. Thus, the combination of solubility data and Gibbs energy minimization can be considered as good alternative for the evaluation of ΔG°f of LDH.

Synthetic La $$_{1-{x}}$$ Pr $$_{{x}}$$ PO $$_4$$ monazite-type powders and ceramics with 0 $$\le$$ x $$\le$$ 1 were analysed by scanning electron microscopy, high-temperature powder X-ray diffraction, dilatometry, and plane wave ultrasound spectroscopy. Ceramics were synthesised in a two-step sintering process at 1273 and 1573 K. Final densities were up to 99.3% of the theoretical densities. Each sample shows a homogeneous distribution of grain sizes, which increase with increasing sintering temperature. Grain sizes also depend on composition, with intermediate compositions yielding the largest grains. In-situ high-temperature powder X-ray diffraction shows that the volumetric thermal expansion coefficients of the monazite powders decrease with increasing Pr content. This behavior is not observed in dilatometry measurements of the bulk samples (ceramics) because their thermal expansion mainly depends on their density. Elastic properties show the same dependence on the density.

Mg/Ti order/disorder and the lattice dynamics of orthorhombic pseudobrookite-type MgTi 2 O 5 have been studied by experiment and modeling. A mechanochemical activation by high speed ball milling allowed us to synthesize pure MgTi 2 O 5 from MgO and TiO 2 anatase at a comparatively low temperature of 1173 K. The Mg/Ti order of MgTi 2 O 5 was characterized by X-ray diffraction and Raman spectroscopy. Density functional theory calculations based on fully ordered MgTi 2 O 5 allow an assignment of all experimentally observed Raman and infrared modes and a re-evaluation of earlier findings. A standard entropy of 134.24 J mol −1 K −1 and a bulk modulus of 161(1) GPa was predicted for fully ordered MgTi 2 O 5 and is in good agreement with experimental findings based on quasi-adiabatic calorimetry of samples with different Mg/Ti ordering states and earlier high pressure studies, respectively. A linear relation of the B 1 g (5) Raman blue-shift with the Mg/Ti disorder was observed, which can be used to rapidly quantify the ordering state of MgTi 2 O 5 .

Solid state sciences 105, 106282 (2020). doi:10.1016/j.solidstatesciences.2020.106282, Pt(Cu$_{0.67}$Sn$_{0.33}$) has recently been found in a natural sample. In order to be able to characterize this new ternary compound, we synthesized it from the elements. Samples were characterized by X-ray powder diffraction, differential scanning calorimetry, thermal relaxation calorimetry, and scanning electron microscopy studies. Density functional theory-based model calculations complemented the experimental studies. Pt(Cu$_{0.67}$Sn$_{0.33}$) was already formed at a relatively low temperature of 773 K. Rietveld refinement of Pt(Cu$_{0.67}$Sn$_{0.33}$) has been carried out in CuAu-type or L1$_0$-type structure, space group , with Pt on 0,0,0 and disordered Cu and Sn on $\frac{1}{2},\frac{1}{2},\frac{1}{2}$ and Z = 1. The lattice parameters are = 2.823(1) Å, = 3.64(1) Å, and = 29.00(4) Å ; which are in good agreement with values obtained earlier on the natural sample and with the results of DFT calculations. The vibrational entropy for Pt(Cu$_{0.67}$Sn$_{0.33}$) is $S^{vib}_{298.15}$ = 79.9(7) J mol$^{−1}$ K$^{−1}$. The pressure dependence up to 36(2) GPa of the unit-cell volume and the lattice parameters and unit-cell volume have been obtained by synchrotron based powder diffraction using a diamond anvil cell. A fit of a 3-order Birch–Murnaghan equation of state to the Pt(Cu$_{0.67}$Sn$_{0.33}$) (p, V)-data results in a bulk modulus of B$_0$= 215(27) GPa and B´= 5(2)., Published by Elsevier, Amsterdam [u.a.]