Space Group P3m1 Research Articles

The structural, elastic, optoelectronic properties and hydrogen storage capability of lead-free hydrides XZrH3 (X: Mg/Ca/Sr/Ba) for hydrogen storage application: A DFT study

Perovskite hydrides are promising materials for hydrogen capacity application to achieve the US DOE on-board criteria. We have investigated novel perovskite hydrides XZrH3 (X: Mg/Ca/Sr/Ba) for H2 storage and transportation applications. In this study we investigates the physical properties of XZrH3 light materials for solid-state hydrogen storage application by incorporating the DFT framework with the CASTEP code. We have theoretically examined the structural, mechanical, electronic, optical, and hydrogen storage properties of these materials. The selected compounds were fully relaxed and optimized in the cubic phase space group Pm-3 m. Structural phase stability was confirmed through thermodynamic, and mechanical analyses. Mechanical properties, evaluated based on Poisson’s ratio, the Puagh’s ratio, and Cauchy pressure, indicate the ductile behavior with a preference for ionic bonding. The electronic structure analysis reveals the metallic behavior of these materials. Optical calculations were also performed to provide additional insights into the physical properties of H2 compounds. The gravimetric hydrogen storage capacities were calculated as 2.55, 2.25, 1.66, and 1.31 wt% for MgZrH3, CaZrH3, SrZrH3, And BaZrH3 hydrides respectively. The identified properties of XZrH3 suggest that these materials could significantly enhance hydrogen storage systems, with potential integration into existing energy technologies, offering a pathway toward more efficient and sustainable hydrogen-based solutions.

Enhanced functionalities of isovalently substituted 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) relaxor piezoceramics synthesized via air quenching

The isovalently substituted lead-free binary solid solution, 0.67(Bi1-xLaxFe0.97Ga0.03O3)-0.33(BaTiO3) (BF-BT) (x ≤ 0.07), has been synthesized by solid state ceramic method via air quenching sintering. FTIR and XRD along with Rietveld structure refinement confirmed a pure perovskite phase with a pseudocubic structure (space group Pm3‾m) for developed compositions. SEM revealed a dense microstructure with fine grain size (<1.5 μm) and minimal porosity. XPS analysis reveals predominantly Bi+3 and Fe+3 states, along with oxygen vacancies (VO··). Ferroelectric studies demonstrated a maximum remanent polarization (Pr) of 12.3 μC/cm2 and coercive field EC of 30.95 kV/cm for La3+ concentration of x = 0.03. Overall decrement in Pr can be attributed to dipolar defect-induced random fields reducing the activation barrier for domain nucleation. Leakage current measurement reveals improved resistivity (∼108 Ω cm) up to an applied field of 30 kV/cm. Dielectric measurements unveiled two frequency-dependent anomalies in temperature dependence above room temperature, indicative of diffuse phase transitions. The Vogel-Fulcher model depicted an increasing freezing temperature (from 465 K for x = 0.01–551 K for x = 0.07) and decreasing activation energy (from ∼0.61 eV to 0.07 eV) with increasing La3+ concentration. The estimated diffuseness parameter around ∼2 suggested relaxor behavior. Doping with La resulted in increased dielectric permittivity at 10 kHz (from 4100 to 24066), showcasing the efficacy of site engineering in augmenting the functional properties of BF-BT for high-temperature dielectric and transducer applications.

Magnetic structure of the noncentrosymmetric magnet Sr2MnSi2O7 through irreducible representation and magnetic space group analyses.

Magnetic structures of the noncentrosymmetric magnet Sr2MnSi2O7 were examined through neutron diffraction for powder and single-crystalline samples, as well as magnetometry measurements. All allowed magnetic structures for space group P421m with the magnetic wavevector qm = (0, 0, ½) were refined via irreducible representation and magnetic space group analyses. The compound was refined to have in-plane magnetic moments within the magnetic space group Cmc21.1'c (No. 36.177) under zero field, which can be altered to P212121.1'c (No.19.28) above μ0H = 0.067 (5) T to align induced weak-ferromagnetic components within one layer on the ab plane. All refined parameters are provided following the recent framework based upon the magnetic space group, which better conveys when exchanging crystallographic information for commensurate magnetic structures.

Phase relations in the La2O3-ZrO2-HfO2 system at 1250 °C and 1500 °C

In the present study, the phase equilibria in the ternary system La2O3-ZrO2HfO2 have been studied in the whole concentration range. In the course of the study, isothermal sections of the phase diagram of the system were constructed at temperatures of 1500 and 1250 °C. The obtained results indicate the no new phase formation in the studied system. It was found that in the La2O3-ZrO2HfO2 ternary system at temperatures of 1500 and 1250 °C, solid solutions are formed on the basis of monoclinic (M, space group P21/C) HfO2 and tetragonal (T, space group P42/nmc) modifications of ZrO2, solid solutions based on a hexagonal modification (A, space group P3m1) of La2O3, and an ordered phase with a pyrochlore-type structure of La2Zr2О7 (La2Hf2О7) (Py, space group Fd-3 m). The system studied is characterized by the formation of a continuous series of solid solutions with a pyrоchlore-type structure. A decrease in temperature from 1500 °C to 1250 °C leads to the shift of the three-phase region, containing solid solutions based on a pyrochlore-type structure of Ln2Zr2О7 (Ln2Hf2О7), monoclinic M-HfO2, and tetragonal T-ZrO2, towards the concentration area with higher ZrO2 content and also to an increase in the extent of the solid solution based on the monoclinic modification M-HfO2.

The Influence of Lanthanum Admixture on Microstructure and Electrophysical Properties of Lead-Free Barium Iron Niobate Ceramics.

This article presents the research results of lead-free Ba1-3/2xLax(Fe0.5Nb0.5)O3 (BFNxLa) ceramic materials doped with La (x = 0.00-0.06) obtained via the solid-state reaction method. The tests of the BFNxLa ceramic samples included structural (X-ray), morphological (SEM, EDS, EPMA), DC electrical conductivity, and dielectric measurements. For all BFNxLa ceramic samples, the X-ray tests revealed a perovskite-type cubic structure with the space group Pm3¯m. In the case of the samples with the highest amount of lanthanum, i.e., for x = 0.04 (BFN4La) and x = 0.06 (BFN6La), the X-ray analysis also showed a small amount of pyrochlore LaNbO4 secondary phase. In the microstructure of BFNxLa ceramic samples, the average grain size decreases with increasing La content, affecting their dielectric properties. The BFN ceramics show relaxation properties, diffusion phase transition, and very high permittivity at room temperature (56,750 for 1 kHz). The admixture of lanthanum diminishes the permittivity values but effectively reduces the dielectric loss and electrical conductivity of the BFNxLa ceramic samples. All BFNxLa samples show a Debye-like relaxation behavior at lower frequencies; the frequency dispersion of the dielectric constant becomes weaker with increasing admixtures of lanthanum. Research has shown that using an appropriate amount of lanthanum introduced to BFN can obtain high permittivity values while decreasing dielectric loss and electrical conductivity, which predisposes them to energy storage applications.

Photoluminescence and energy transfer studies in the Sm3+ and Eu3+ co-doped Sr2ZnSi2O7 red-emitting phosphors

In this study, we utilized a high-temperature solid-state reaction method to synthesize the red-emitting phosphors, namely Sr2ZnSi2O7:Sm3+ and Sr2ZnSi2O7:Sm3+/Eu3+. Characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX) revealed that the crystal structure of the as synthesized Sr2ZnSi2O7 samples aligned with the standard JCPDS no. 00-039-0235, featuring small irregularly shaped particles having a tetragonal structure with space group P-421m and space group number 113. The band gap values were determined using diffuse reflectance spectral (DRS) data. Photoluminescence (PL) emission spectra indicated efficient excitation of Sr2ZnSi2O7:Sm3+ and Sr2ZnSi2O7:Sm3+/Eu3+ phosphors under near-ultraviolet light (λex = 404 nm). The PL intensity of Eu3+ ions increased with increasing the concentration of Eu3+ ions, leading to a decrease in the PL intensity of Sm3+ ions. The energy transfer mechanism from Sm3+ to Eu3+ ions is mainly driven by dipole-dipole (D-D) interaction, as predicted using Dexter Reisfeld's approximation. As the concentration of Eu3+ ions increased, there was a reduction in the photoluminescence (PL) decay lifetimes. This decline affirmed the presence of the energy transfer (ET) mechanism from Sm3+ to Eu3+ ions, reaching a maximum transfer efficiency of around 23.11 % in the Sr2ZnSi2O7:Smx/Euy (x = 1.5, y = 5 mol%) phosphor. Computed CIE parameters under UV excitation showed a gradual shift towards the deep red region with increase in Eu3+ concentration. For Sr2ZnSi2O7: Smx/Euy (x = 1.5, y = 5 mol%) phosphor, the CIE color coordinates and color purity were (0.60120, 0.39485) and 95.62 %, respectively. These findings highlight the potential of the synthesized phosphors as solid-state emitters for warm white LED applications, featuring a low color-correlated temperature (CCT) value of 1724 K when stimulated with UV chips.

High-temperature Néel skyrmions in Fe3GaTe2 stabilized by Fe intercalation into the van der Waals gap

Two-dimensional (2D) van der Waals (vdW) magnets that exhibit ferromagnetism at ambient temperature show great promise for spintronic applications. However, until now, only a few pristine or doped 2D magnets have demonstrated the ability to host non-collinear spin textures, thereby limiting their potential applications. Here we directly observe Néel-type skyrmions in the metallic vdW magnetic compound Fe3GaTe2 (FGaT) up to temperatures well above room temperature (≈340 K) in the absence of any external magnetic field. We show that the presence of defects in the structure of FGaT make its structure acentric and therefore compatible with hosting skyrmions that would otherwise not be possible. Indeed, in this regard it is very similar to the closely related compound Fe3GeTe2 (FGT), whose structure with the same space group P3m1 is also realized by defects. Interestingly, however, FGaT accommodates a significantly higher concentration of Fe within the vdW gaps, likely accounting for its enhanced Curie temperature (TC). In addition to the Néel skyrmions observed in the temperature range of 250–340 K, we also detect type-I and -II Bloch-type skyrmionic bubbles in the temperature range of 100–200 K due to an enhanced magnitude of dipole-dipole interactions relative to the Dzyaloshinskii-Moriya exchange interaction. Self-intercalation is thus a highly interesting property of vdW magnets that considerably modifies their fundamental properties.

Exploring innovative applications of Sr2MgSi2O7:Fe3+ luminescent system in surface-triggered fingerprint divergence and cheiloscopy screening

In this study, we employ a cost-effective combustion method to synthesize (1–11 mol %) Fe3+ doped Sr2MgSi2O7 nanophosphors (SMSO NPs) and conduct a comprehensive investigation into their structural and luminescent properties. The impact of iron concentration on the structural and optical characteristics is thoroughly analysed, revealing a tetragonal crystal structure with space group P-421m through Rietveld refinement and X-ray Diffraction (XRD) patterns. Scanning electron microscopy showcases the random dispersion of agglomerated particles with non-uniform dimensionality. Energy Dispersive X-ray analysis (EDS) assesses the nominal composition of Sr, Mg, Si, Fe, and O, while X-ray Photon Spectroscopy (XPS) confirms the direct incorporation of Fe3+ ions into the SMSO lattice. Photoluminescence (PL) emission spectra exhibit a deep red emission band at 718 nm. The residual luminescence intensity of SMSO:7Fe3+ at 200 °C is 91 %. Under 365 nm UV light, the optimized SMSO:7Fe3+ NPs displays easily identifiable levels I-III fingerprints (FPs) features with good resolution and contrast. The resilient luminescence and nano-regime of the phosphor reveal well-defined type I–V groove patterns in latent lip prints (LLPs) on various non-porous surfaces, unaffected by background interference or colour distraction. This study highlights SMSO:7Fe3+ NPs as a promising option for individualizing and detecting latent fingerprints (LFPs) and lip prints (LPs).

Thermoelectric properties and thermal transport in two-dimensional GaInSe3 and GaInTe3 monolayers: A first-principles study

We here report the electronic structure calculation of GaInSe3 and GaInTe3 monolayers with the P3m1 (no. 156) space group. The electronic structure and thermoelectric properties of the monolayers are calculated through the Vienna Ab initio Simulation Package and BoltzTraP2 codes. The dynamic and thermodynamic stabilities were verified by calculating their phonon spectra and simulating ab initio molecular dynamics. The monolayers were found to have a direct bandgap, with both PBE + SOC and HSE06 + SOC potentials. The lattice thermal conductivity of GaInTe3 monolayer calculated using Phono3py code shows ultra-low values due to enhanced phonon–phonon scattering. Combining electrical and thermal transport, the values have been evaluated. Importantly, the p-type GaInTe3 has excellent thermoelectric properties at 700 K, with a zT value of 2, indicating that the p-type GaInTe3 has potential application in the field of thermoelectricity.

Phase structure of the ceramic samples of the BiScO3–PbTiO3–PbMg⅓Nb⅔O3 system near the morphotropic phase boundary studied by the Rietveld method

Abstract An X-ray diffraction study of ceramic samples of the BiScO3–PbTiO3–PbMg⅓Nb⅔O3 system with compositions close to the morphotropic phase boundary was carried out at room temperature. The existence of wide areas of solid solutions has been established. The symmetry of the PbTiO3-based solid solutions is tetragonal (space group P4mm). The symmetry of the PbMg⅓Nb⅔O3-based solid solutions is cubic (space group Pm3‾m). Near the BiScO3 side, the solid solutions are rhombohedral (space group R3m). During the morphotropic phase transition from the cubic solid solutions to the tetragonal ones, additional phases appear. If a tetragonal phase prevails ((1 − 2x)BiScO3–xPbTiO3–xPbMg⅓Nb⅔O3 x = 0.46; (1 − 2x)BiScO3–1.1xPbTiO3–0.9xPbMg⅓Nb⅔O3 x = 0.45 and 0.42), a satisfactory model is a model with a minority cubic phase (space group Pm3‾m). If a cubic phase prevails ((1 − 2x)BiScO3–1.1xPbTiO3–0.9xPbMg⅓Nb⅔O3 x = 0.39 and 0.36; (1 − 2x)BiScO3–0.8xPbTiO3–1.2xPbMg⅓Nb⅔O3 x = 0.4), a model with a minority monoclinic phase (space group Cm) or with two minority phases: tetragonal (space group P4mm) and monoclinic (space group Cm) is satisfactory.

Structural, mechanical and electronic properties and phase transitions in superhard BC1-xNx: A first-principles study

First-principles investigations of the stability, mechanical properties, electronic and phonon structures, as well as molecular dynamics simulations of temperature- and pressure-induced phase transitions in boron carbonitrides, BC1-xNx, for x = 1.0 (C0), 0.75 (C1), 0.5 (C2), 0.25 (C3) and 0.0 (C4), were carried out. The plausible mechanisms of the phase transitions in BNs were proposed and the transformation paths were established for the h → w, r → c, c → r and w → h’ transitions, where h’ was the new hP4-187 phase (space group P-6m2, #187). The non-layered C0–C3 compounds transformed into the layered ones at 2000–3000 K. The new BC1-xNx structures are brittle materials and exhibit the best combination of hardness (23.1–60.8 GPa) and fracture toughness (4.03–5.23 MPa m1/2). The C1–C4 structures are metallic, except for three compounds: C1-oP8-25 and C4-tP8-136 are semi-metals, and C4-mP8-10 is a semiconductor with a very narrow bandgap of 0.2 eV.

Rashba spin-splitting and spin Hall effect in Janus monolayers Sb2XSX’ (X, X’= S, Se, or Te; X ≠ X’)

The combined influence of spin–orbit coupling and spatial inversion asymmetry leads to an enhancement of electronic properties, including Rashba spin-splittings as well as spin Hall effect. Recent research has shown the possibility to create two-dimensional Janus materials with inherent structural asymmetry. In this work, the structural stability, piezoelectricity, electronic properties, and intrinsic spin Hall conductivity of quintuple-layer atomic Janus Sb2XSX’ (X, X’ = S, Se, Te; X ≠ X’) monolayers are investigated using first-principles calculations within the framework of density functional theory. They demonstrate relatively high in-plane piezoelectric coefficients (d22) and also possess out-of-plane piezoelectric coefficients (d31), which is due to the breaking of inversion symmetry in the crystal structure with the space group P3m1. Large Rashba parameters are obtained in Janus Sb2XSX’ monolayers, especially high for Sb2S2Te (1.62 eV Å) and Sb2SeSTe (1.33 eV Å) due to strong spin–orbit coupling. Moreover, Rashba-like spin-splitting is also observed in the edge-states as well, which is highest for Sb2SeSTe with 2.17 eV Å. Furthermore, Sb2S2Te and Sb2SeSTe monolayers reveal a significantly high Berry curvature (65.59 and 61.05 Bohr2), spin Berry curvature (−118.4 and −120.6 Bohr2), and spin Hall conductivity (1.8 and 1.6 e2/h). Our results suggest that Janus Sb2S2Te and Sb2SeSTe monolayers could be an excellent platform for multifunctional electronic applications.

Investigation of Zinc and Chromium Substitution Nickel-rich LiNi1−x−yZnyCrxO2 Cathode Materials to Improve the Redox Reaction of Lithium-ion Battery: A First-principles Study

First-principles calculations are employed to investigate the structural, electronic, magnetic, thermoelectric, and electrochemical characteristics of Nickel-rich layered cathodes by substitution of Zn and Cr such as LiNi1−x−yZnyCrxO2 (with x = 0.00, 0.16 and 0.32, y = 0.00 and 0.16). The structure of pure LiNiO2 and substituted are organized in a trigonal arrangement inside the P3m1 space group. Using PBE-GGA approximation, the spin-polarized calculation of pure LiNiO2 in a spin-down channel exhibits a band gap of 0.48 eV. Whereas, Zn and Cr substitution results in the band gap reduction to zero, and metallic behavior is observed. Electronic charge density calculation Ni(Zn, Cr)-O reveals covalent bonding. In electrochemical investigation, by the increasing substitution concentration of Zn and Cr in LiNi1−x−yZnyCrxO2 significant improvements are observed at 4.65–3.89 V potential with a good theoretical discharge capacity of 48–246 mAhg−1. The exchange constants N∘α and N∘β demonstrate negative values that validate the ferromagnetic nature of substituted material. The thermoelectric parameters have been determined using the BoltzTraP code and the highest ZT value of 0.35 is obtained for LiNi0.52Zn0.16Cr0.32O2. These results offer a new perspective on the potential of doping techniques for Nickel-rich cathode materials, providing helpful insight for the development of high-performance cathodes for Lithium-ion battery applications.

Prediction of high-temperature superconductors at ambient pressure with diamond-like structures: B2CX (X = N, P).

In recent years, the superconducting properties of materials with diamond-like structures have attracted widespread attention. The superconducting transition temperature (Tc) of most diamond-like structures is relatively low, and there has been little research on the superconductivity of ternary diamond-like materials. Here, based on first-principles calculations, we predict B2CX (X = N, P) with P3m1 space group, and reveal that they all exhibit phonon-mediated superconductivity at ambient pressure, with Tc range from 44.3 to 46.1 K, which is higher than most diamond-like superconductors. The coupling between metallic σ electrons and softened E phonon (B-C stretching modes) contributes greatly to their superconductivity. Our work provides an important theoretical basis for the experimental design and synthesis of ternary high-temperature superconductors with diamond-like structures.

Broken Inversion Symmetry in Van Der Waals Topological Ferromagnetic Metal Iron Germanium Telluride.

Inversion symmetry breaking is critical for many quantum effects and fundamental for spin-orbit torque, which is crucial for next-generation spintronics. Recently, a novel type of gigantic intrinsic spin-orbit torque is established in the topological van der Waals(vdW) magnet iron germanium telluride. However, it remains a puzzle because no clear evidence exists for interlayer inversion symmetry breaking. Here, the definitive evidence of broken inversion symmetry in iron germanium telluride directly measured by the second harmonic generation (SHG) technique is reported. The data show that the crystal symmetry reduces from centrosymmetric P63/mmc to noncentrosymmetric polar P3m1 space group, giving the threefold SHG pattern with dominant out-of-plane polarization. Additionally, the SHG response evolves from an isotropic pattern to a sharp threefold symmetry upon increasing Fe deficiency, mainly due to the transition from random defects to ordered Fe vacancies. Such SHG response is robust against temperature, ensuring unaltered crystalline symmetries above and below the ferromagnetic transition temperature. These findings add crucial new information to the understanding of this interesting vdW metal, iron germanium telluride: band topology, intrinsic spin-orbit torque, and topological vdW polar metal states.

Novel High-Temperature Modification of Belomarinaite KNaSO4: Crystal Structure and Thermal Order–Disorder Phase Transitions

Belomarinaite KNaSO4 (space group P3m1, a = 5.6072(3), c = 7.1781(4) Å and Z = 2) has been studied by high-temperature single crystal X-ray diffraction. The K and Na atoms are disordered, and M1(1c) and M2(1b) sites merge into an M1(2d)(K50%/Na50%) site with increasing temperature, and novel translationsgleiche phase transition of belomarinaite KNaSO4 (P3m1 → P-3m1) was revealed at 123 °C. Then, the temperature increase leads to phase transition of P3¯m1-polymorph of KNaSO4 to α-KNaSO4 (P63/mmc) at 446 °C, and sodium and potassium atoms in K1(1a) and Na1(1b) sites merged into an M4(2a)(K50%/Na50%) site. Crystal structures of KNaSO4 were refined at 300, 500 and 750 °C to R1 = 0.057, 0.056 and 0.048, respectively. The BVS maps and bond-valence energy landscape (BVEL) have been calculated, and the probability of the Na+ migration has been predicted using structural data for belomarinaite at 25 °C. The Na+ ion migration can occur at 2.14 eV in the ab plane and 2.80 eV along the c axis at 25 °C.

Zeolitic germanosilicate analogue to pharmacosiderite crystallized in an acidic medium

Zeolites are typically synthesized in alkaline or fluoride-containing near-neutral media. Sophisticated organic structure-directing agents have been investigated for such systems with the aim of discovering materials with unprecedented structures and properties for novel technical applications. In contrast, zeolite crystallization in strongly acidic media has yet to be explored. This study demonstrates that a zeolitic silicate phase crystallizes from acidic gels using trimethylamine as an organic additive with the composition 1 SiO2:0.3 TMA:0.3 HCl: 0.15 HF:55 H2O:(0.1–0.4) GeO2. This phase has an interrupted four-connected framework analog to the octahedron/tetrahedron-mixed framework of the mineral family pharmacosiderite. In comparison to the pharmacosiderite-type HK3(Ge7O16)(H2O)4, the four GeO6-octahedra forming the central [HGe4O4O12]-cluster are replaced by four SiO4-tetrahedra in a [Si4O6(OH)2.89]-unit in the new phase. However, the structure is distorted and may contain connectivity and point defects; thus, healing by the occasional incorporation of GeO6-units is necessary. The refined unit cell has a cubic symmetry, space group P-43m (#215), with a = 7.7005(1) Å. Acidic-medium synthesis is a useful way to find new zeolites that move in a fundamentally different direction from sophisticated organic structure-directing agents.

Galeite, Na15(SO4)5ClF4, and Schairerite, Na21(SO4)7ClF6: Phase Transitions, Thermal Expansion and Thermal Stability

In this study, galeite, Na15(SO4)5ClF4 and schairerite, Na21(SO4)7ClF6 were investigated via in situ single-crystal X-ray diffraction in the temperature range of 300–750 K. Galeite and schairerite are trigonal, P31m, a = 12.1903(2), c = 13.9454(2) Å, V = 1794.69(6) Å3, and Z = 3 (R1 = 0.0273, 300 K) for galeite and a = 12.1859(3), c = 19.3080(6) Å, V = 2483.04(14) Å3, and Z = 3 (R1 = 0.0334, 300 K) for schairerite. The crystal structures of galeite and schairerite are based upon frameworks consisting of alternating face- and corner-sharing fluorine- and chlorine-centered octahedra. Galeite and schairerite can be attributed to 5H (galeite) and 7H (schairerite) antiperovskite polytypes, respectively. It was observed that schairerite undergoes at least one reversible phase transition before it starts to lose its crystallinity at 750 K. This phase transition occurs in the temperature range of 550–600 K. The high-temperature modification of schairerite is trigonal, with the centrosymmetric space group P-3m1 and the unit-cell parameters a = 7.0714(2), c = 19.5972(7) Å, V = 848.66(6) Å3, and Z = 1. Galeite is stable up to 600 K. The crystal structures of minerals expand anisotropically, and, in both cases, the strongest thermal expansion was parallel to the modules of face-sharing anion-centered octahedra. The structural complexity analysis showed that galeite is complex (695.175 bits/cell) and that the LT-modification of schairerite is very complex (1064.990 bits/cell), whereas its HT-modification is intermediate in complexity (256.755 bits/cell). The complexities of LT- and HT-polymorphs of schairerite are consistent with the general observations regarding structures with positional disorder: complexity decreases with increasing temperature, and simpler polymorphs have lower physical density.

Crystal structure and electrochemical hydrogenation of HoNiIn1-xAlx (x = 0-1) solid solution

The influence of the substitution of indium by aluminum in HoNiIn compound at 873 K was investigated in the full concentration range by means of powder X-ray diffraction and EDX analysis. The formation of continuous solid solution was determined and changes of the unit cell parameters were calculated: HoNiIn1.0–0Al0–1.0 (ZrNiAl-type structure, space group P-62m, a = 0.74343(4)–0.69959(6) nm and c = 0.37472(3)–0.38289(4) nm, V = 0.17936(2)–0.16229(3) mn3). The best discharge capacity after electrochemical hydrogenation studies of HoNiIn1-xAlx solid solution is observed for battery prototypes with HoNiIn0.2Al0.8- and HoNiIn0.4Al0.6-based electrodes.

Honeycomb Constructs in the La-Ni Intermetallics: Controlling Dimensionality via p-Element Substitution.

The new ternary compounds La15Ni13Bi5 and La9Ni8Sn5 were obtained by arc melting under argon from appropriate amounts of the elements and subsequent annealing at 800 °C for 2 weeks. Single-crystal X-ray diffraction reveals that they represent two new structure types: La15Ni13Bi5 crystallizes in the hexagonal space group P62m [hP33, a = 14.995(3), c = 4.3421(10) Å, V = 845.5(4) Å3, Z = 1] and La9Ni8Sn5 in P63/m [hP88, a = 23.870(15), c = 4.433(3) Å, V = 2187(3) Å3, Z = 4]. The crystal structures of both compounds are characterized by hexagonal honeycomb-based motifs formed by Ni and Sn that extend along the c axis. The building motif with its three-blade wind turbine shape is reminiscent of the organic molecule triptycene and is unprecedented in extended solids. First-principles calculations have been performed in order to analyze the electronic structure and provide insight into chemical bonding. They reveal significant electron transfer from La to Ni and the respective p-element, which supports the formation of the polyanionic Ni-p-element network. DFT calculations suggest paramagnetic-like behavior for both compounds, which was confirmed by magnetic measurements.