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A new polymorph of the β-modification of N,N′-di(pyridin-2-yl)formamidine that is more thermodynamically stable than the known α-modification is obtained. The crystal of β-modification contains hydrogen bonded molecular dimers with a skewed geometry. Therefore, the space group is not centrosymmetric – P42. This geometry is a result of the molecular E-syn,syn conformation in crystals of the β-phase, which differs from the E-anti,syn conformation in the α-phase. The number of crystallographically non-equivalent molecules (8) in the β-modification is unusually large for organic compounds. The structure of the packing is analyzed, and it is shown that the centers of dimers follow the sites of a distorted body-centered cubic pseudo-lattice (Ат ≈ 10 A, αт = 90°) with a 16 times decreased unit cell volume. Reasons for symmetry violations causing modulations are considered.

We propose a technique for the refinement of unit cell parameters (UCPs) using a single crystal diffractometer equipped with a flat-panel area detector. The technique is based on choosing Kα1 components of X-ray radiation when processing diffraction reflections. The capabilities of the technique are demonstrated on [NiEn3]MoO4 single crystals. In two independent experiments, the difference between 2θexp and 2θcalc did not exceed 0.02° while the reproducibility of unit cell parameters was at least 0.008 A.

The phase composition of the interaction product of zinc acetate with hydrogen peroxide in a dispersed aqueous phase of a reverse micellar solution based on oxyethylated Brij 30 surfactant and decane as a dispersion medium is analyzed by powder X-ray diffraction (XRD). Along with ZnO2 nanoparticle, the isolated product is found to contain needle-like microcrystals that, according to the single crystal XRD analysis, are zinc lactate dihydrate [Zn(lact)2(H2O)2]: a = 6.0196(3) A, b = 11.9068(4) A, c = 14.3878(7) A, Z = 4, space group P212121. The coordination environment of the Zn atom is a distorted octahedron: Zn–О distances are 2.051(2)-2.099(3) A, ∠О–Zn–О bond angles are 76.16° and 76.14°. Chelate rings are bent along the О…О line at 22.18° and 11.54°. The Hirshfeld surface (complex sphericity 0.79, asphericity 0.16) is constructed and intermolecular contacts are analyzed. A comparative crystal chemical analysis with the known [Zn(lact)2(H2O)2]·H2O structure is performed.

Mossbauer spectroscopy is used to study the characteristic features of the crystal lattice dynamics in powdered single crystals of Fe1.75V0.25BO4 warwickite in the temperature range of 4.2–505 K. The Debye temperature (ΘD = 260 K) is determined from the temperature dependence of the probability of the Mossbauer effect in the thin absorber approximation. It is found that the electron delocalization related to the fast electronic transfer between neighboring Fe3+ and Fe2+ cations takes place in the temperature range of 260−505 K. As a result, iron cations exhibiting the mixed valence (Fe2.5+) arise. This process correlates with a change in the elastic properties of the lattice. Such correlation leads to a sharp decrease in the recoil-free absorption of γ‑ray photons by the crystal lattice in the range of 260–400 K.

The Cu(hfac)2 complex with a paramagnetic ligand 2-(1-ethyl-imidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L5Et) was synthesized in the form of two polymorphs: α-[Cu(hf...

The study addresses layer-by-layer formation processes and properties of gold nanoparticle films deposited from reverse micellar solutions of Brij 30 surfactant on rigid glass and flexible polymer (PET) substrates. The films are of interest for transparent electronics and optical sensorics. The spectrophotometric studies of film formation revealed linear relationships between the extinction of growing film at definite wavelengths and the number of nanoparticle deposition cycles, and their parameters were determined. The effects of concentrations of gold and 1,2-ethanedithiol as an interlayer linker in the initial solutions on the film growth were elucidated. Data on the composition, morphology, optical spectra, and surface resistance of gold nanoparticle films, and changes of these characteristics during heat treatment in air and in boiling ethanol were gained using X-ray diffractometry, scanning electron and atomic force microscopy, UV-Vis spectroscopy, and electrical resistance measurements.

Two crystal structures containing [Pd(NH3)4]2+ cations and $$\text{WO}_4^{2-}$$ and $$\text{W}_7\text{O}_{24}^{6-}$$ anions are studied. For the [Pd(NH3)4]WO4 structure at 150 K the following crystallographic data are obtained: a = 7.4626(3) A, c = 15.5718(8) A, space group I41/amd, V = 867.20 A3, Z = 4. With increasing temperature to 400 K, the unit cell parameters change in different directions: a increases by 0.032 A, c decreases by 0.036 A. The total increase in the unit cell volume is 5 A3. In a range of 150 K to 400 K, the observed W-O distances decrease by 0.019 A from 1.778(18) A to 1.759(3) A. For the [Pd(NH3)4]3W7O24·4.4H2O structure at 298 K the crystallographic data are as follows: a = 8.3409(2) A, b = 22.2654(6) A, c = 10.5450(3) A, β = 104.449(1)°, space group P21/m, V = 1896.41 A3, Z = 2. In the heptatungstate anion the shortest are the W—O distances with the terminal O atoms (1.731–1.745 A). The distances to the bridging O atoms connecting two W atoms are 1.930–2.406 A; those connecting three W atoms are 1.882–2.234 A, and those connecting four W atoms are 2.192–2.220 A. It is shown that the [Pd(NH3)4]3W7O24·4.4H2O structure has a pseudohexagonal motif in the a direction. The thermal decomposition of the salts is performed in the presence of LiH in the He atmosphere at 1273 K. The ex situ powder X-ray diffraction study reveals the formation of Pd–W alloys.

The crystal structure of [CuEn3]MoO4 (En is ethylenediamine) is studied in a range 100–390 K. The crystallographic data at 100 K are as follows: a = 27.5808(9) A, c = 9.9043(4) A, space group $$P\overline 3 $$ , V = 6524.8(4) A3, Z = 18. The coordination of copper atoms is a distorted square bipyramid. In three crystallographically independent cations. four short Cu-N distances are 2.041(2)–2.093(2) A, two long ones in a trans position are 2.397(2)–2.496(2) A (at 200 K these intervals are 2.039(4)–2.148(4) A and 2.332(2)–2.461(4) A respectively). In a range from 200 K to 298 K, the transition occurs to the space group $$P\overline 3 $$ c1 (a = 15.9992(6) A, c = 9.9385(4) A, V = 2203.17(19) A3, Z = 6) and the Cu-N distances are aligned: 2.086(6) A, 2.162(7) A, 2.273(8) A. At 390 K the Jahn-Teller effect disappears and the Cu-N distances are 2.153(4) A (a = 9.2785(14) A, c = 10.0035(18) A, $$P\overline 3 $$ 1c, V = 745.8(3) A3, Z = 2). It is shown that with increasing temperature from 100 K to 320 K the average Mo-O distances decrease from 1.766 A to 1.699 A. The ex situ powder X-ray diffraction study of the formation process of metal and carbide phases is performed during [CuEn3]MoO4 thermal decomposition in the He atmosphere in the presence of LiH. Starting from 973 K, a mixture of Mo2C and the fcc phase based on the Cu structure (a ≈ 3.65 A) forms.

Two complex salts with heptatungstate anions and [Pd(NH3)4]2+ and Na+ cations are synthesized. In the structure of Na2[Pd(NH3)]5(W7O24)2·16H2O (a = 11.5703(3) A, b = 12.4653(4) A, c = 14.8201(5) A, α = 69.733(1)°, β = 97.231(1)°, γ = 75.816(1)°, space group P-1, V = 1937.8(1) A3, Z = 1), the Na+ cations link heptatungstate anions into dimers; the Na…O distances are 2.321–2.446 A. In the structure of Na[Pd(NH3)4]2(HW7O24)·7H2O (a = 11.1113(8) A, b = 17.9869(12) A, c = 17.8140(13) A, β = 96.974(2)°, space group P21/n, V = 3533.9(4) A3, Z = 4), the bridging Na+ cations link hydroheptatungstate anions into zigzag chains; the Na…O distances are 2.291–2.724 A.

In this work, we study the effect of fluorosubstitution on the crystal structure of phthalocyanines of copper, cobalt, and vanadyl and analyze the correlations between the structure and volatility ...

Separation of structurally similar components from their mixtures is one of the most promising applications of metal-organic frameworks (MOFs). A high efficiency of such molecular sieving requires fine tuning of the MOF structure. In this work, we investigate subtle metal- and temperature-induced changes in window dimensions of zeolitic imidazolate frameworks (ZIF-8(Zn) and ZIF-67(Co)) and apply such structural tuning for efficient separation of xylene isomers (p-, m-, and o-xylenes). The use of Co instead of Zn favorably modifies window geometry: it accelerates the diffusion of all components by a factor of 2-3 while maintaining closely the same separation efficiency as that of ZIF-8(Zn). Outstanding selectivity above 18:1 and faster isolation of demanded p-xylene from the ternary mixture using ZIF-67(Co) have been demonstrated at room temperature, opening new horizons for its energy-efficient xylene separation. More generally, our findings suggest the prospective ways to tune various MOFs for target liquid-state separations.

The Fe–C system, which is widely used to grow commercial high-pressure–high-temperature diamond monocrystals, is rather complicated due to the formation of carbides. The carbide Fe3C is a normal run product, but the pressure at which Fe7C3 carbide becomes stable is a subject of discussion. This paper demonstrates the synthesis of Fe7C3 carbide and its detailed study using single-crystal and powder X-ray diffraction, as well as electron probe micro-analysis and scanning electron microscopy. The experiments were performed using a multiple-anvil high-pressure apparatus of `split-sphere' (BARS) type at a pressure of 5.5 GPa and a temperature of 1623 K. Our results show that in the Fe–C system, in addition to diamond, a phase that corresponds to the Fe7C3 carbide was synthesized. This means that both carbides (Fe7C3 and Fe3C) are stable at 5.5 GPa. Two crystal phases are described, Fe14C6 and Fe28C12−x . Fe14C6 is based on the well known rhombic structure of Fe7C3, while Fe28C12−x has a different packing order of Fe6C polyhedrons. The results obtained in this study should be taken into account when synthesizing and growing diamond at high pressures and temperatures in metal–carbon systems with a high iron content, as well as when conducting experimental studies on the synthesis of diamond directly from carbide.

The crystal structure of [CuEn3]WO4 (En is ethylenediamine) is studied in the temperature range 100–390 K. Crystallographic data at 100 K are: a = 27.6903(8) A, c = 9.9405(3) A, space group P3, V = 6600.8(4) A3, Z = 18. Copper atomic coordination is a distorted square bipyramid. Four short Cu–N distances are within 2.038(5)–2.110(6) A; two long distances are within 2.374(8)–2.514(7) A. The lengths of N–H…O interionic contacts lie within 1.96–2.17 A. A temperature elevation makes the Cu–N distances equal: at 298 K they are within 2.066(2)–2.256(3) A(a = 16.0391(8) A, c = 9.9608(6) A, space group P3c1, V = 2219.1(3) A3, Z = 6), and at 390 K they are 2.151(6) A(a = 9.2986(10) A, c = 10.0520(14) A, P31c, V = 752.7(2) A3, Z = 2). In the range from 100 K to 390 K the average W–O distances decrease from 1.776 A to 1.734 A. Hirshfeld surfaces of complex cations are analyzed. It is shown that with increasing temperature the number of interionic N–H…O contacts decreases. The [CuEn3]WO4 phase is found to be unstable and on storing in air it transforms into [CuEn2](WO4)·2H2O.

The paper presents the results of experimental studies on the synthesis of carbide Fe 7 C 3 at 5,5 GPa. It was found that carbide Fe 3 C and several polytypes of carbide Fe 7 C 3 are formed together with diamond when the system is cooled. It is believed that Fe 7 C 3 carbide may be a component of the Earth’s inner core. The obtained results indicate that carbide Fe 7 C 3 in the form of polytypic modifications under natural conditions could be formed at relatively low pressures at the stage of differentiation of the Earth.

Metal-organic frameworks (MOFs) are the promising nanomaterials for separation of molecules with close dimensions and structures, such as various types of isomers. The efficiency of separation can be greatly enhanced if the apertures of the nanosized windows, controlling the diffusion of a particular molecule inside the cavities, are fine-tuned by external stimuli. We report the new approach for precise measurement of window sizes in ZIF-8 MOF and employ it in efficient separation of xylenes, which is of high practical importance. For this sake, we synthesized ZIF-8 with embedded stable nitroxides in the pores and applied electron paramagnetic resonance spectroscopy for in situ kinetic measurement of the diffusion of various guest molecules through the material. Slight variation of temperature within 298-333 K allowed tuning of the windows and reaching optimum conditions for separation of

The crystal structural characteristics of the [NiEn3]MoO4 complex salt (En is ethylenediamine) at 90 K are as follows: space group $$P\overline 3 ,\;a = 15.9307\left( 9 \right)\;\acute{\mathring{\mathrm{A}}} ,\;c = 9.9238\left( 6 \right)\;\acute{\mathring{\mathrm{A}}} ,\;V = 2181.1\left( 3 \right)\;{\acute{\mathring{\mathrm{A}}} ^3},\;Z = 6,\;{d_{\rm{x}}} = 1.822\;{\rm{g/c}}{{\rm{m}}^{\rm{3}}}$$ , Ni-N is $$2.1182\left( {12} \right) - 2.1498\left( {11} \right)\;\acute{\mathring{\mathrm{A}}} ,$$ ∠Ni-N-N is 80.76(4)-82.27(4)°. According to the differential scanning calorimetry data in a range from 295 K to 310 K, there is a thermal anomaly with peaks at T1 = 299.6 K and T2 = 304.7 K. The crystal structural characteristics at 320 K are as follows: space group $$P\overline 3 \,1c,\;a = 9.2491\left( 4 \right)\;\acute{\mathring{\mathrm{A}}} ,\;c = 9.9713\left( 4 \right)\;\acute{\mathring{\mathrm{A}}} ,\;V = 738.72\left( 7 \right)\;{\acute{\mathring{\mathrm{A}}} ^3},\;Z = 2,\;{d_x} = 1.794\;{\rm{g/c}}{{\rm{m}}^3}$$ , Ni-N is $$2.1302\left( {14} \right)\;\acute{\mathring{\mathrm{A}}} $$ , ∠N-Ni-N is 80.96(8)°. With increasing temperature from 90 K to 320 K a decrease in the average Mo-O distance from $$1.769\;\acute{\mathring{\mathrm{A}}} $$ to $$1.725\;\acute{\mathring{\mathrm{A}}} $$ is observed in the structure. The comparative analysis of the interionic N-H…O and C-H…O contacts is carried out. The ex situ powder X-ray diffraction study of the formation process of metal and carbide phases by the [NiEn3]MoO4 thermal decomposition in the presence of LiH in the He atmosphere is performed. At the temperature of 1323 K a Mo2C and MoNi4 phase mixture forms in the first minute. With increasing keeping time the Ni2Mo4Cx phase forms.

The formation of metallic and carbide phases during the thermal decomposition of a mixture of the coordination compound [NiEn3]WO4 (En = ethylenediamine) and LiH in a He atmosphere has been studied by X-ray diffraction. The results demonstrate that heat treatment of the mixture at 410°C for 10 min leads to the formation of a Ni(Cx) interstitial solid solution based on the HCP Ni lattice and a W1 –xNix substitutional solid solution based on the BCC W lattice. Starting at 510°C, a Ni1 –xWx solid solution based on the FCC Ni lattice is also formed. The double carbide Ni2W4Cx appears at 660°C, and Ni6W6Cx forms at 860°C. Under similar conditions (700°C, He), the thermal decomposition of a mixture of NiWO4 and LiH leads to the formation of W and an FCC Ni1 –xWx (x ~ 0.12) solid solution.

For the first time, lonsdaleite-rich impact diamonds from one of the largest Popigai impact crater (Northern Siberia) with a high concentration of structural defects are investigated under hydrostatic compression up to 25 GPa. It is found that, depending on the nature of a sample, the bulk modulus for lonsdaleite experimentally obtained by X-ray diffraction in diamond-anvil cells is systematically lower and equal to 93.3-100.5% of the average values of the bulk moduli of a diamond matrix. Density functional theory calculations reveal possible coexistence of a number of diamond/lonsdaleite and twin diamond biphases. Among the different mutual configurations, separate inclusions of one lonsdaleite (001) plane per four diamond (111) demonstrate the lowest energy per carbon atom, suggesting a favorable formation of single-layer lonsdaleite (001) fragments inserted in the diamond matrix. Calculated formation energies and experimental diamond (311) and lonsdaleite (331) powder X-ray diffraction patterns indicate that all biphases could be formed under high-temperature, high-pressure conditions. Following the equation of states, the bulk modulus of the diamond (111)/lonsdaleite (001) biphase is the largest one among all bulk moduli, including pristine diamond and lonsdaleite.

Rhodium(III) octahedral complexes with amine and chloride ligands are the most common starting compounds for preparing catalytically active rhodium(I) and rhodium(III) species. Despite intensive study during the last 100 years, synthesis and crystal structures of rhodium(III) complexes were described only briefly. Some [RhClx(NH3)6-x] compounds are still unknown. In this study, available information about synthetic protocols and the crystal structures of possible [RhClx(NH3)6&minus, x] octahedral species are summarized and critically analyzed. Unknown crystal structures of (NH4)2[Rh(NH3)Cl5], trans&ndash, [Rh(NH3)4Cl2]ClH2O, and cis&ndash, [Rh(NH3)4Cl2]Cl are reported based on high quality single crystal X-ray diffraction data. The crystal structure of [Rh(NH3)5Cl]Cl2 was redetermined. All available crystal structures with octahedral complexes [RhClx(NH3)6-x] were analyzed in terms of their packings and pseudo-translational sublattices. Pseudo-translation lattices suggest face-centered cubic and hexagonal closed-packed sub-cells, where Rh atoms occupy nearly ideal lattices.

Materialia 14, 100920 (2020). doi:10.1016/j.mtla.2020.100920, Hcp-Ir$_{0.24}$Ru$_{0.36}$Os$_{0.40}$ and fcc-Ir$_{0.84}$Ru$_{0.06}$Os$_{0.10}$ ternary alloys as well as binary hcp-Ir$_{0.33}$Ru$_{0.67}$ and fcc-Ir$_{0.75}$Ru$_{0.25}$ ones were prepared using thermal decomposition of [Ir$_x$Ru$_{1-x}$(NH$_3$)($_5$)Cl][OsyIr$_{(1-y)}$Cl$_6$] single-source precursors in hydrogen flow below 1070 K. These single-phase alloys correspond to ternary and binary peritectic phase diagrams and can be used as synthetic models for rare iridosmine minerals. Thermal decomposition of parent bimetallic precursor [Ir(NH$_3$)($_5$)Cl][OsCl$_6$] has been investigated using in situ powder X-ray diffraction in inert and reductive atmospheres. In reductive atmosphere, [Ir(NH$_3$)($_5$)Cl][OsCl$_6$] forms (NH$_4$)($_2$) [OsCl$_6$] as crystalline intermediate; Ir from its cationic part is reduced by hydrogen with a formation of defect fcc-structured metallic particles; the final product is a metastable hcp-Ir$_{0.5}$Os$_{0.5}$ alloy. In inert atmosphere, the salt decomposes at higher temperature without a formation of any detectable crystalline intermediates; two-phase fcc+hcp mixture forms directly above 800 K. Room temperature compressibility up to 50 GPa has been studied for all prepared alloys in diamond anvil cells. Investigated ternary and binary alloys do not show any phase transitions upon compression at room temperature. In contrast with other investigated ultra-incompressible refractory alloys with osmium and iridium, hcp-Ir$_{0.33}$Ru$_{0.67}$, fcc-Ir$_{0.75}$Ru$_{0.25}$ binary and fcc-Ir$_{0.84}$Ru$_{0.06}$Os$_{0.10}$ ternary alloys show higher compressibility in comparison with pure metals. Fcc-Ir0.75Ru0.25 alloy shows several magnetic phase transitions (at approx. 3.4 K, 135 K and 233 K) that could be related to different magnetic phases., Published by Elsevier, Amsterdam

Thermal decomposition of (NH4)2[OsxPt1-xCl6] as single-source precursors for Os–Pt binary alloys has been investigated under ambient and high pressure up to 40 GPa. Thermal decomposition of mixed-metal (NH4)2[OsxPt1-xCl6] precursors in hydrogen atmosphere (reductive environment) under ambient pressure results in formation of β-trans-[Pt(NH3)2Cl2] and α-trans-[Pt(NH3)2Cl2] crystalline intermediates as well as single and two-phase Os–Pt binary alloys. For the first time, direct thermal decomposition of coordination compound under pressure has been investigated. A formation of pure metallic alloys from single-source precursors under pressure has been shown. Miscibility between fcc- and hcp-structured alloys has been probed up to 50 GPa by in situ high-pressure X-ray diffraction. Miscibility gap between fcc- and hcp-structured alloys does not change its positions with pressure up to at least 50 GPa.

The synthesis method for [NiEn3]WO4 complex salt is described. Data of single crystal X-ray diffraction at 115 K are: space group $$p\bar 3$$ , a = 15.9633(5) A, c = 9.9446(4) A, V = 2194.6(1) A3, Z = 6, dx = 2.210 g/cm3, Ni–N is 2.120(2)-2.149(2) A, ∠N–Ni–N is 80.69(7)-82.28(7)°. From the differential scanning calorimetry data it is found that a phase transition occurs at 269 K. The crystal structural characteristics at 298 K are as follows: space group $$p\bar 31c$$ , a = 9.2641(3) A, c = 9.9817(3) A, V = 741.89(4) A3, Z = 2, dx = 2.179 g/cm3, Ni–N is 2.128(2) A, ∠N–Ni–N is 81.05(12)°. The phase transition is shown to correspond to the disordering of tungstate anions over three positions. The comparative analysis of N–H…O and C–H…O interionic contacts is performed.

A change in the coordination of the copper atom in the crystal structure of [CuEn3]CrO4 (En is ethylenediamine) in studied in the range 150–300 K. According to the single crystal X-ray diffraction (XRD) data at 150 K, the single crystal has a complicated twining character based on the triclinic cell (a = 9.027(2) A, b = 13.335(3) A, c = 13.339(3) A, α = 71.77(3)°, β = 70.53(3)°, γ = 70.42(3)°) composed of two crystallographically independent [CuEn3]2+ complex cations. The coordination of copper atoms is a distorted square bipyramid; four short Cu–N distances lie in the range 2.049-2.082 A; two long ones are 2.415 A and 2.470 A. According to the differential scanning calorimetry (DSC) data, near 218 K there is a phase transition. The single crystal XRD experiment performed at 250 K (a = 15.6992(19) A, c = 9.7573(13) A, V = 2082.6(6) A3, space group P $$\bar 3$$ c1 (No. 165), Z = 6) shows that chromate anions are disordered over three positions about the с axis, and Cu–N distances are 2.120-2.177 A. According to the DSC data, on further heating the structure undergoes yet another two alterations (260 K and 270 K) due to the disordering of oxygen atoms of chromate anions and the subsequent equalization of Cu–N distances. At 300 K in the structure (a = 9.0778(6) A, c = 9.7715(5) A, V = 697.4 A3, space group P $$\bar 3$$ c (No. 163), Z = 2) all Cu–N distances are 2.155 A, and chromate anions are disordered over six positions about the с axis. A comparative crystal chemical analysis of the packing of the studied structures is carried out.

Annulation of the two pyrimidine rings with anthraquinone through the simple condensation of the 1,5-diiodoanthraquinone with guanidine was employed to build 1,3,7,9-tetraazaperylene framework functionalized by NH2, C=O, aliphatic and alkoxy-groups. The properties of the synthesized 1,3,7,9-tetraazaperylenes were studied by cyclic voltammetry, optical and luminescence spectroscopy and DFT-calculations. Remarkably, the vacuum-deposited thin film of 1,3,7,9-tetraazaperylene functionalized by 2-ethylhexyloxy groups demonstrated photoluminescence quantum yield as high as 55%, which is even higher than that for toluene solution (33%).

The graphitization process of impact diamonds in the helium atmosphere at 1900–1960 °C is investigated. It is shown that when an impact diamond particle with a large number of lonsdaleite defects is kept at 1900 °C for 1 min, ~5 wt.% of graphite are formed (in the paralle experiment with a particle without lonsdaleite defects the graphite formation is not observed). With an increase in the temperature to 1930 °С and 1940 °С the graphite amount increases to 70 wt.% and 80 wt.% respectively. In both cases, a mixture of two graphite phases forms: the first is turbostratic graphite with d002 = 3.38 A; the second is compressed graphite with d002 = 3.21 A. On heating a particle to 1960 °C graphite is formed in which the layer packing contains a large amount of defects and is a mixture of 2Н and 3R polytypes (the ratio 40:60) with a small degree of turbostratic disordering.

The crystal structures of [CuL2](ReO4)2 and [NiL2](ReO4)2 (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane) are studied. The crystal structural data for [CuL2](ReO4)2, C16H32CuN4O8Re2: a = 13.5523(7) A, b = 9.3446(4) A, c = 18.4410(9) A, V = 2335.38(19) A3, space group Pbca, Z = 4, dx = 2.402 g/cm3; the copper atom coordination C–N of (2×)1.973(5) A and (2×)2.008(5) A, the additional coordination Cu…O of (2×)2.642 A. The crystal structural data for [NiL2](ReO4)2, C16H32NiN4O8Re2: a = 8.9308(2) A, b = 14.3479(3) A, c = 18.6501(4) A, β = 91.492(1)°, V = 2388.98(9) A3, space group P21/c, Z = 4, dx = 2.334 g/cm3; the nickel atom coordination Ni–N of 1.889(4)-1.917(3) A, the additional coordination Ni…O of 2.750(3) A.

The results of experimental synthesis of carbide Fe7C3 at 5.5 GPa are presented. It is found that carbide Fe3C and several polytypes of carbide Fe7C3 are formed along with diamond during cooling of the system. It is considered that the Fe7C3 phase is a component of the Earth’s inner core. Our results indicate that polytypic carbide modifications could have been formed under natural conditions at relatively low pressures during differentiation of the Earth.

The structure of [ZnEn3]CrO4 (En is ethylendiamine) complex salt is determined. It is demonstrated that at room temperature the crystallographic characteristics are as follows: а = 9.0942(4) A, с = 9.7673(4) A, space group Р-31с (No. 163). Contrary to [ZnEn3]SO4, disordered chromate anions participate in its formation. When [ZnEn3]CrO4 is heated in a hydrogen atmosphere up to 700 °C, zinc chromite spinel is formed (а = 8.328 A, space group Fd-3m), which has a complex nanocrystalline structure.

The crystal structure of [NiEn3]CrO4 (En is ethylendiamine), C6H24CrN6NiO4 is studied: a = 9.0408(5) A, c = 9.7466(4) A, V = 689.92(8) A3, space group P63/mmc, Z = 2, d x = 1.704 g/cm3, Ni–N 2.133(9) A, ∠N–Ni–N 82.4(5)°. The thermal properties are determined. When it is heated in a hydrogen atmosphere, a mixture of nanocrystalline Ni and Cr2O3 powders with coherent scattering regions of 59 nm and 90 nm respectively is formed. It is demonstrated that thermal decomposition products consist of pseudomorphic particles that inherit the sizes and shapes of initial [NiEn3]CrO4 single crystals.

Acta materialia 139, 236 - 243 (2017). doi:10.1016/j.actamat.2017.08.012, The formation of the hcp-Ir$_{0.70}$Re$_{0.30}$ alloy from the single-source precursor (NH4)2[Ir$_{0.70}$Re$_{0.30}$Cl$_6$] upon heating in hydrogen atmosphere can be associated with the formation of two intermediates: a crystalline iridium-based intermediate and a fcc-structured alloy. Ir–Re alloys show lower thermal expansion coefficients and smaller compressibility in comparison with individual metals. The high-temperature high-pressure treatment of hcp-Ir$_{0.70}$Re$_{0.30}$ alloy enable us to probe the Ir–Re pressure dependent phase diagram. The miscibility gap between hcp and fcc alloys slightly shifts towards the rhenium side below 4 GPa. Above 4 GPa, the miscibility gap does not drift with pressure and narrows with compression. The electrocatalytic activity of Ir–Re alloys has been tested for methanol oxidation in acidic water solution. Ir–Re alloys show higher electrocatalytic activity in comparison with pure Ir and Re, which makes them perspective candidates for fuel cells application. The highest electrocatalytic activity has been obtained for the two-phase Ir$_{0.85}$Re$_{0.15}$ composition., Published by Elsevier Science, Amsterdam [u.a.]

An approach for the substantiated choice of the indexing procedure of a diffraction pattern is described. The technique is based on a combined use of powder X-ray diffraction data in Bragg–Brentano schemes and 2D GIXD of mainly oriented polycrystalline samples.

High-entropy alloys containing 5 and 6 platinum group metals have been prepared by thermal decomposition of single-source precursors non requiring high temperature or mechanical alloying. The prepared Ir 0.19 Os 0.22 Re 0.21 Rh 0.20 Ru 0.19 alloy is the first example of a single-phase hexagonal high-entropy alloy. Heat treatment up to 1500 K and compression up to 45 GPa do not result in phase changes, a record temperature and pressure stability for a single-phase high-entropy alloy. The alloys show pronounced electrocatalytic activity in methanol oxidation, which opens a route for the use of high-entropy alloys as materials for sustainable energy conversion.