Space Group R3m Research Articles

Cd3(IO3)(IO4)F2·0.1CdO: A Nonlinear-Optical Crystal with the Introduction of Fluoride into Iodate Containing Both [IO3]- and [IO4]3- Groups.

A new d10 transition-metal iodate fluoride, namely, Cd3(IO3)(IO4)F2·0.1CdO, was successfully designed and synthesized via the mid-infrared hydrothermal method. It crystallizes in the polar space group R3m and features the coexistence of the [IO3]- and [IO4]3- groups. Cd3(IO3)(IO4)F2·0.1CdO has a strong second-harmonic-generation response of about 3.0 times that of KDP(KH2PO4), large birefringence (0.133 at 546.1 nm), and a wide energy band gap (4.00 eV). In addition, the power laser damage threshold (LDT) measurement indicated that it possesses a high LDT of 84.29 MW/cm2, which is about 30 times that of AgGaS2. These superior properties showed that Cd3(IO3)(IO4)F2·0.1CdO may be an excellent nonlinear-optical crystal for visible and mid-infrared application.

DyFe2O4: A new trigonal rare-earth ferrite grown by molecular-beam epitaxy

Using epitaxial stabilization, we synthesized single-phase (001)-oriented thin films of DyFe2O4+x on (111) MgAl2O4 substrates by molecular-beam epitaxy. The metastable DyFe2O4 polymorph formed is isostructural to known trigonal ferrimagnetic RFe2O4 phases with space group R3m, where R = Ho to Lu. The epitaxial DyFe2O4 thin films have two in-plane orientation relationships: [100] DyFe2O4 || 211 MgAl2O4 plus a twin variant related by a 60° in-plane rotation. DyFe2O4 is not bulk stable and has never been synthesized before. Indeed, it has been predicted to be on the edge energetically of what may be possible to stabilize. The fact that the RFe2O4 phase is stable for all elements leading up to dysprosium (Ho–Lu) leads us to believe that DyFe2O4 could be a “remnant metastable phase,” one which, given the right thermodynamic conditions, could become the lowest free energy phase. We find that although we are able to get structurally very close to R3m DyFe2O4, the films are not stoichiometric as they have an increased c lattice parameter, indicative of extra oxygen as is sometimes seen in other RFe2O4 phases. The unintended surplus oxygen opens questions regarding what may be achievable using such tricks as epitaxial stabilization to access metastable phases and whether this indeed constitutes “remnant metastability.”

Deconvoluting the Magnetic Structure of the Commensurately Modulated Quinary Zintl Phase Eu11-xSrxZn4Sn2As12.

The structure, magnetic properties, and 151Eu and 119Sn Mössbauer spectra of the solid-solution Eu11-xSrxZn4Sn2As12 are presented. A new commensurately modulated structure is described for Eu11Zn4Sn2As12 (R3m space group, average structure) that closely resembles the original structural description in the monoclinic C2/c space group with layers of Eu, puckered hexagonal Zn2As3 sheets, and Zn2As6 ethane-like isolated pillars. The solid-solution Eu11-xSrxZn4Sn2As12 (0 < x < 10) is found to crystallize in the commensurately modulated R3 space group, related to the parent phase but lacking the mirror symmetry. Eu11Zn4Sn2As12 orders with a saturation plateau at 1 T for 7 of the 11 Eu2+ cations ferromagnetically coupled (5 K) and shows colossal magnetoresistance at 15 K. The magnetic properties of Eu11Zn4Sn2As12 are investigated at higher fields, and the ferromagnetic saturation of all 11 Eu2+ cations occurs at ∼8 T. The temperature-dependent magnetic properties of the solid solution were investigated, and a nontrivial structure-magnetization correlation is revealed. The temperature-dependent 151Eu and 119Sn Mössbauer spectra confirm that the europium atoms in the structure are all Eu2+ and that the tin is consistent with an oxidation state of less than four in the intermetallic region. The spectral areas of both Eu(II) and Sn increase at the magnetic transition, indicating a magnetoelastic effect upon magnetic ordering.

Temperature-induced structural phase transitions in RERhSn (RE = Y, Gd-Tm, Lu)

Abstract The structures of the equiatomic stannides RERhSn with the smaller rare earth elements Y, Gd-Tm and Lu were reinvestigated on the basis of temperature-dependent single crystal X-ray diffraction data. GdRhSn crystallizes with the aristotype ZrNiAl at 293 and 90 K. For RE = Y, Tb, Ho and Er the HP-CeRuSn type (approximant with space group R3m) is already formed at room temperature, while DyRhSn adopts the HP-CeRuSn type below 280 K. TmRhSn and LuRhSn show incommensurate modulated variants with superspace groups P31m(1/3; 1/3; γ) 000 (No. 157.1.23.1) (γ = 3/8 for TmRhSn and γ = 2/5 for LuRhSn). The driving force for superstructure formation (modulation) is a strengthening of Rh–Sn bonding. The modulation is expressed in a 119Sn Mössbauer spectrum of DyRhSn at 78 K through line broadening.

Arrheniusite-(Ce), CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11, a New Member of the Vicanite Group, from the Östanmossa Mine, Norberg, Sweden

ABSTRACT Arrheniusite-(Ce) is a new mineral (IMA 2019-086) from the Östanmossa mine, one of the Bastnäs-type deposits in the Bergslagen ore region, Sweden. It occurs in a metasomatic F-rich skarn, associated with dolomite, tremolite, talc, magnetite, calcite, pyrite, dollaseite-(Ce), parisite-(Ce), bastnäsite-(Ce), fluorbritholite-(Ce), and gadolinite-(Nd). Arrheniusite-(Ce) forms anhedral, greenish-yellow translucent grains, exceptionally up to 0.8 mm in diameter. It is optically uniaxial (–), with ω = 1.750(5), ε = 1.725(5), and non-pleochroic in thin section. The calculated density is 4.78(1) g/cm3. Arrheniusite-(Ce) is trigonal, space group R3m, with unit-cell parameters a = 10.8082(3) Å, c = 27.5196(9) Å, and V = 2784.07(14) Å3 for Z = 3. The crystal structure was refined from X-ray diffraction data to R1 = 3.85% for 2286 observed reflections [Fo &amp;gt; 4σ(Fo)]. The empirical formula for the fragment used for the structural study, based on EPMA data and results from the structure refinement, is: (Ca0.65As3+0.35)Σ1(Mg0.57Fe2+0.30As5+0.10Al0.03)Σ1[(Ce2.24Nd2.13La0.86Gd0.74Sm0.71Pr0.37)Σ7.05(Y2.76Dy0.26Er0.11Tb0.08Tm0.01Ho0.04Yb0.01)Σ3.27Ca4.14]Σ14.46(SiO4)3[(Si3.26B2.74)Σ6O17.31F0.69][(As5+0.65Si0.22P0.13)Σ1O4](B0.77O3)F11; the ideal formula obtained is CaMg[(Ce7Y3)Ca5](SiO4)3(Si3B3O18)(AsO4)(BO3)F11. Arrheniusite-(Ce) belongs to the vicanite group of minerals and is distinct from other isostructural members mainly by having a Mg-dominant, octahedrally coordinated site (M6); it can be considered a Mg-As analog to hundholmenite-(Y). The threefold coordinated T5 site is partly occupied by B, like in laptevite-(Ce) and vicanite-(Ce). The mineral name honors C.A. Arrhenius (1757–1824), a Swedish officer and chemist, who first discovered gadolinite-(Y) from the famous Ytterby pegmatite quarry.

The Phase Transition and Photoluminescence Properties of (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ Solid-Solution Phosphors

A series of color-tunable (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ (0 ≤ x ≤ 9) phosphors are designed by using mineral-inspired structural design strategy and synthesized by solid-state reaction. The mineral structure β-Ca3(PO4)2-type compounds, Ca9Mg1.5(PO4)7 and Sr9Mg1.5(PO4)7 are chosen as structural prototypes. Both of them are hexagonal structure but have different space groups. The former has R3c space group, while the latter possesses R3m space group. When Ca9Mg1.5(PO4)7 compound is used as maternal materials, the powder X-ray diffraction results demonstrate that the successive substitution of Ca2+ with Sr2+ ions expands and distorts the lattice parameters and unit cell volume of Ca9Mg1.5(PO4)7 compound, rendering phase transition from the (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ (phase 1, 0 ≤ x < 3) with R3c space group to (Ca9−x Sr x )Mg1.5(PO4)7:Eu2+ (phase 2, 5 < x ≤ 9) with R3m space group. The phase transition causes noticeable spectral redshift from the original blue-violet emission of x = 0 to bright yellow emission of x = 9 sample. Importantly, at x = 1, a bright white-light emission with a full width at half maximum of ∼255 nm is discovered in Ca8SrMg1.5(PO4)7:Eu2+ phosphor, which is beneficial to achieve phosphor-converted white-light-emitting diodes with high color-rendering index. These findings indicate that the mineral-inspired structural design strategy is very helpful for the development of new phosphors.

Celleriite, ☐(Mn22+Al)Al6(Si6O18)(BO3)3(OH)3(OH), a new mineral species of the tourmaline supergroup

Abstract Celleriite, ☐(Mn22+Al)Al6(Si6O18)(BO3)3(OH)3(OH), is a new mineral of the tourmaline supergroup. It was discovered in the Rosina pegmatite, San Piero in Campo, Elba Island, Italy (holotype specimen), and in the Pikárec pegmatite, western Moravia, Czech Republic (co-type specimen). Celleriite in hand specimen is violet to gray-blue (holotype) and dark brownish-green (co-type) with a vitreous luster, conchoidal fracture, and white streak. Celleriite has a Mohs hardness of ~7 and a calculated density of 3.13 and 3.14 g/cm3 for holotype and its co-type, respectively. In plane-polarized light in thin section, celleriite is pleochroic (O = pale violet and E = light gray-blue in holotype; O = pale green and E = colorless in co-type) and uniaxial negative. Celleriite has trigonal symmetry: space group R3m, Z = 3, a = 15.9518(4) and 15.9332(3) Å, c = 7.1579(2) and 7.13086(15) Å, V = 1577.38(9) and 1567.76(6) Å3 for holotype and co-type, respectively (data from single-crystal X-ray diffraction). The crystal structure of the holotype specimen was refined to R1 = 2.89% using 1696 unique reflections collected with MoKα X-ray intensity data. Structural, chemical, and spectroscopic analyses resulted in the formulas: x ( ◻ 0.58 N a 0.42 ) Σ 1.00 Y ( M n 1.39 2 + F e 0.16 2 + M g 0.01 A l 1.14 F e 0.01 3 + L i 0.28 T i 0.01 ) Σ 3.00 Z A l 6 [ T ( S i 5.99 A l 0.01 ) Σ 6.00 O 18 ] ( B O 3 ) 3 ( O H ) 3 w [ ( O H ) 0.65 F 0.03 O 0.32 ] Σ 1.00 ( for holotype ) and x ( ◻ 0.51 N a 0.49 ) Σ 1.00 Y ( M n 0.90 2 + F e 0.50 2 + A l 1.36 F e 0.04 3 + L i 0.17 Zn 0.04 ) Σ 3.00 Z A l 6 [ T ( S i 5.75 B 0.25 ) Σ 6.00 O 18 ] ( B O 3 ) 3 ( O H ) 3 w [ ( O H ) 0.35 F 0.17 O 0.48 ] Σ 1.00 ( for co-type ) Celleriite is a hydroxy species belonging to the X-site vacant group of the tourmaline supergroup. The new mineral was approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association, proposal no. 2019-089. In the Rosina pegmatite, celleriite formed an overgrowth at the analogous pole of elbaite–fluorelbaite–rossmanite crystals during the latest stage of evolution of pegmatite cavities after an event of a pocket rupture. In the Pikárec pegmatite, celleriite occurs as an intermediate growth sector of elbaite, princivalleite, and fluor-elbaite.

Different structural evolutions of inorganic perovskite CsGeI3

The structural evolution of CsGeI3 and octahedral distortion in CsSnxGe1−xI3 perovskites.

Odikhinchaite, Na9Sr3[(H2O)2Na]Ca6Mn3Zr3NbSi (Si24O72)O(OH)3(CO3)·H2O, a New Eudialyte-Group Mineral from the Odikhincha Intrusion, Taimyr Peninsula, Russia

The new eudialyte-group mineral, odikhinchaite, was discovered in a peralkaline pegmatite vein hosted by melteigite at the Odikhincha ultrabasic alkaline–carbonatite intrusion, Taimyr Peninsula, Krasnoyarsk Krai, Russia. Associated minerals are orthoclase, albite, aegirine, cancrinite, ancylite-(Ce), catapleiite, and wadeite. Odikhinchaite occurs as dense rosette-like aggregates up to 11 mm across, consisting of split lamellar individuals. The mineral is translucent to transparent, deep purple, with vitreous luster. Odikhinchaite is brittle, with uneven fracture; distinct cleavage on (001) is observed. Hardness determined by the micro-indentation method is equal to 430 kgf/mm2; the Mohs hardness is 5. D(meas.) is 2.97(1) g·cm−3, D(calc.) is 3.04 g·cm–3. Odikhinchaite is optically uniaxial (–), ω = 1.638(2), ε = 1.630(2). The IR spectrum shows the presence of the IVMn2+O4 polyhedra, H2O molecules and CO32– anions. The chemical composition is (electron microprobe, H2O determined by the modified Penfield method, CO2 determined by selection sorption of gaseous annealing products; wt%): Na2O 9.25, K2O 0.59, CaO 12.77, MnO 5.49, FeO 0.75, MgO 0.24, La2O3 0.38, Ce2O3 0.39, Nd2O3 0.15, Al2O3 0.07, SiO2 44.80, ZrO2 11.13, TiO2 0.07, Nb2O5 4.17, Cl 0.69, CO2 0.90, H2O 2.22, –O = Cl –0.16, total 99.72. The crystal structure was solved using single-crystal X-ray diffraction data. Odikhinchaite is trigonal, space group R3m; the unit-cell parameters are: a = 14.2837(2) Å, c = 30.0697(3) Å, V = 5313.04(12) Å3. The new mineral is isostructural with other 12-layered members of the eudialyte group with the space group R3m. Its crystal chemical formula is (Z = 3): {N1(Na2.58Ca0.42)N2[Na2.37Ca0.51(H2O)0.12]N3(Sr2.00K0.45Na0.35REE0.20)N4Na3N5[(H2O)1.8Na1.2]}{ZZr3M1Ca6M2(Mn2.49Fe2+0.51)[M3Nb(OH)1.82O1.18](M4SiOH)[Si3O9]2[Si9O27]2X1[(CO3)0.53Cl0.47]X2[(H2O)0.6(O,F)0.4]XM4(CO3)0.15. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 11.42 (64) (101), 4.309 (41) (205), 3.405 (53) (131), 3.208 (45) (208, 036), 3.167 (44) (217), 2.978 (100) (315), 2.858 (86) (404).

A Facile Synthesis Method of BiSb Nanoparticles for Thermoelectric Applications

BiSb nanoparticles were synthesized by solvothermal method. The synthesized material having a trigonal structure with space group R3m was confirmed through X-ray diffraction pattern. The Williamson-Hall method was employed to analyze the lattice stress and micro-strain produced in the BiSb nanoparticles. On the prepared material surface morphology studies were carried out using HR-SEM with EDXA. UV-visible absorption spectrum shows a wide absorption peak at 287 nm and the estimated band gap value is at Eg = 1.6 eV (from Tauc plot). The values of remanent polarization Pr = 0.156 μC/cm2, saturation polarization Ps = 0.253 μC/cm2, and coercive electric field Ec = 13.5 kV/cm obtained from the loop were close to the value. The BiSb nanoparticles exhibit semi-metallic-reported characteristics. This material is useful for thermoelectric power generation applications.

Li2Eu3Br2[BO3]2: A New Europium(II) Halide Oxoborate with Yellow Luminescence

The europium(II) oxoborate Li2Eu3Br2[BO3]2 featuring lithium and bromide ions was synthesized by the reaction of Eu2O3 with Li[BH4] as lithium‐ and boron‐ as well as EuBr3 as bromide‐source at 750 °C for 24 h in silica‐jacketed sealed niobium capsules. The yellow, air‐stable and yellow fluorescent compound crystallizes in the trigonal space group R3m (a = 1049.06(7) pm, c = 2993.1(3) pm, c/a = 2.853, Z = 12). The two crystallographically distinguishable Eu2+ cations show either an eightfold coordination as bicapped trigonal prism ([EuO6Br2]12–) or a ninefold coordination as monocapped square antiprism ([EuO5Br4]12–). All oxygen atoms stem from isolated triangular [BO3]3– anions and the Li+ cations reside in octahedral voids provided by both oxygen atoms and Br– anions.

Crystal structure of Ag-exchanged levyne intergrown with erionite: Single-crystal X-ray diffraction and Molecular Dynamics simulations

Abstract The modification of natural zeolites via ion exchange is an efficient technique used to improve their performances and tune their properties for specific applications. In this study, a natural levyne-Ca intergrown with erionite was fully exchanged by Ag+ and its structure [with idealized chemical composition Ag6(Si,Al)18O36·18H2O] was investigated by combining a theoretical and experimental approach. Single-crystal X-ray diffraction data demonstrated that Ag-levyne maintained the R3m space group, characteristic of the natural levyne. Ag ions distribute over partially occupied sites along the threefold axis and, differently from the pristine material, at the wall of the 8-membered ring window of the lev cavity. The lack of ~30% of Ag ions that could not be located by the structural refinement is ascribed to the strong disorder of the extraframework occupants. The structural results obtained by Molecular Dynamics simulations are in overall agreement with the experimental data and showed that, on average, Ag+ is surrounded by ~2 H2O and 1 framework oxygen at distances between 2.43 and 2.6 Å. Molecular Dynamics trajectories indicate that the occurrence of silver inside the D6R cage depends on the water content: silver occupancy of D6R cages is estimated to be 83, 30, and 0% when the structure contains 3, 2.5, and 2 H2O per Ag ion, respectively. The cation-exchange process, as demonstrated by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) spectrometry, affects the intergrown erionite as well. A structural characterization of the Ag-erionite phase (with dimension &amp;lt;100 μm) was possible by means of a CuKα micro-focus source: structure solution pointed to P63/mmc space group, indicating no change with respect to natural erionite. In agreement with previous studies, K ions in the cancrinite cage could not be exchanged, whereas Ag+ is found in the eri cavity.

Two Mixed-Anion Units of [GeOSe3] and [GeO3S] Originating from Partial Isovalent Anion Substitution and Inducing Moderate Second Harmonic Generation Response and Large Birefringence.

Highly polarizable mixed-anion structural building units (SBUs) have been demonstrated as promising candidates for high-performing optical crystals. In this work, two new mixed-anion SBUs of [GeOSe3] and [GeO3S] are first designed through partial isovalent substitution of chalcogen atoms by O atoms in the classical [GeQ4] (Q = S, Se) tetrahedra. On the basis of these SBUs, two new quaternary oxychalcogenides, Sr3Ge2O4Se3 and SrGe2O3S2, are successfully synthesized. Sr3Ge2O4Se3 crystallizes in the noncentrosymmetric space group R3m and possesses unique zero-dimensional [Ge2O4Se3]6- units consisting of highly distorted [GeOSe3] tetrahedra and [GeO4] tetrahedra through a shared O atom. It displays intriguing potential as an infrared nonlinear optical material with a wide band gap (2.96 eV) and moderate second harmonic generation intensity (0.8 × AgGaS2). SrGe2O3S2 belongs to the centrosymmetric space group P21/c and features 2∞[Ge2O3S2]2- layers formed by the corner-shared [GeO3S] tetrahedra. Moreover, the large birefringence of SrGe2O3S2 (calculated Δn = 0.22-0.17 from 0.4 to 4.0 μm) gives it a potential as a birefringent material. Theoretical calculations revealed the crucial effects of mixed-anion [GeOSe3] and [GeO3S] units on the moderate second harmonic generation response and large birefringence. The discovery of new mixed-anion SBUs of [GeOSe3] and [GeO3S] will guide the exploration of new functional oxychalcogenides.

Boranes: The Boron Subhydride B104.67H3 with a Distorted β-Boron Crystal Structure.

A single crystal of the boron subhydride B104.67(4)H3 was serendipitously obtained while attempting to synthesize β-boron. An accurate crystal structure analysis revealed a distorted β-boron framework with the noncentrosymmetric space group R3m. We have found one interstitial site occupied by boron. The site related by inversion remains empty. The distortions of the framework result in ideal environments for the interstitial boron atom, and for the three hydrogen atoms at bridging positions between icosahedral B12 groups, they result in ideal B-H distances of 1.33 Å. B104.67(4)H3 is a borane with the lowest amount of hydrogen recorded to date, and it is the first compound with a noncentrosymmetrically distorted β-boron framework.

Structural, Electrical, and Electrochemical Characterization of Li1.2Ni0.6−xMgxCo0.3O2 Cathode Materials for Application in Lithium-Ion Batteries

Lithium-rich nickel cobalt magnesium oxide cathode materials with varying concentrations of nickel and magnesium have been synthesized using a solid-state reaction (SSR) method. The structural properties of the as-synthesized cathode materials were analyzed by x-ray diffraction (XRD), confirming their α-NaFeO2 layered structure in space group R3m. Scanning electron microscopy (SEM) study revealed the cube-like hexagonal structure of the prepared materials. Electrochemical impedance spectroscopy (EIS) was carried out in the frequency range from 1 Hz to 7 MHz with a voltage amplitude of 10 mV. At ambient temperature, the direct-current (DC) conductivity was found to be the highest for the Li1.2Ni0.6Co0.3O2 cathode material with a value of 3.64 × 10−4 S/cm. Various conducting mechanisms are proposed for the prepared cathode materials based on Jonscher’s power law. The activation energy is seen to increase with increasing Mg concentration, which helps to produce a defect-less or ordered homogeneous structure. Furthermore, the value of the power-law exponent n is found to decrease with increasing Mg concentration. For the Li1.2Ni0.3Mg0.3Co0.3O2 sample, the n value decreases with increasing temperature and is found to be less than 1 at higher temperatures, indicating the orderliness of the system. Cyclic voltammetry (CV) measurements confirmed that Mg substitution delayed the oxidation and reduction processes, thus enhancing the operating voltage of the electrochemical cell.

Establishing magneto-structural relationships in the solid solutions of the skyrmion hosting family of materials: GaV4S8\u2212ySey

The GaV4S8−ySey (y = 0 to 8) family of materials have been synthesized in both polycrystalline and single crystal form, and their structural and magnetic properties thoroughly investigated. Each of these materials crystallizes in the Fbar{4}3m space group at ambient temperature. However, in contrast to the end members GaV4S8 and GaV4Se8, that undergo a structural transition to the R3m space group at 42 and 41 K respectively, the solid solutions (y = 1 to 7) retain cubic symmetry down to 1.5 K. In zero applied field the end members of the family order ferromagnetically at 13 K (GaV4S8) and 18 K (GaV4Se8), while the intermediate compounds exhibit a spin-glass-like ground state. We demonstrate that the magnetic structure of GaV4S8 shows localization of spins on the V cations, indicating that a charge ordering mechanism drives the structural phase transition. We conclude that the observation of both structural and ferromagnetic transitions in the end members of the series in zero field is a prerequisite for the stabilization of a skyrmion phase, and discuss how the absence of these transitions in the y = 1 to 7 materials can be explained by their structural properties.

Lingbaoite, AgTe3, a new silver telluride from the Xiaoqinling gold district, central China

Abstract Lingbaoite, AgTe3, is a new silver telluride discovered in the S60 gold-bearing quartz vein, Xiaoqinling gold district, central China. The new mineral is named after Lingbao city, the municipality of which covers a major part of the Xiaoqinling gold district. Lingbaoite is only microscopically visible and occurs within pyrite as small composite inclusions (&amp;lt;50 μm) that commonly consist of lingbaoite, sylvanite, and chalcopyrite, and locally of bornite, galena, altaite, and stützite. The largest lingbaoite grain is about 30 × 12 μm in size. At least two stages of gold and telluride mineralization are recognized in the lingbaoite-bearing sample set. The first stage is characterized by the deposition of lingbaoite, native tellurium, and sylvanite, within the commonly observed mineral assemblages of lingbaoite + sylvanite + chalcopyrite and sylvanite + native tellurium + stützite. The second stage is characterized by the deposition of Bi-bearing minerals and native gold, within the commonly observed mineral assemblages of rucklidgeite + altaite + volynskite ± hessite ± petzite and rucklidgeite + gold ± altaite. Lingbaoite is opaque and exhibits no internal reflections. In plane-polarized reflected light, lingbaoite shows a creamy yellow reflection color. The calculated density is 7.06 g/cm3. Seventeen WDS spot analyses from 17 different lingbaoite grains gave an empirical formula of Ag0.946Fe0.134Cu0.008Pb0.003 Te2.841S0.067. When considering Ag and Te as the only two essential structural components, the empirical formula is Ag1.00Te3.00. The EBSD and SAED data confirm the structural identity of lingbaoite and synthetic AgTe3. Synthetic AgTe3 is trigonal, space group R3m, with a = 8.645 Å, c = 5.272 Å, V = 341.2 Å3, and Z = 3. The unit-cell parameters of lingbaoite are: a = 8.60 (5) Å, c = 5.40 (18) Å, V = 346 (9) Å3, and Z = 3. Synthetic AgTe3, and by analog lingbaoite, can be viewed as silver-stabilized cubic tellurium, which is an ordered (1:3 Ag:Te) analog of the α-polonium structure (i.e., simple cubic crystal structure). Synthetic AgTe3 becomes a stable phase at above 0.4 GPa, but can also occur in a metastable state at atmospheric pressure. Lingbaoite probably formed through the cooling of polymetallic melt droplets within the hydrothermal system. Lingbaoite and associated minerals (e.g., sylvanite, native tellurium) reveal a previously unrecognized but perhaps common magmatic-hydrothermal process in the Xiaoqinling gold district, which precedes the precipitation of native gold, suggesting that gold mineralization in the Xiaoqinling gold district involves multiple superimposed processes of gold enrichment.

Electrochemical Effects of Yttrium(Y) Doping on Rich-Nickel Cathode Materials for Lithium Ion Batteries

Rich-nickel layered oxides are regarded as one of the most promising cathode materials for the next generation of high energy lithium-ion batteries due to its high discharge specific capacity. However, the practical application of the materials is limited by poor cyclic stability. In order to solve this severe problem, the spherical precursor Ni0.85Co0.075Mn0.075(OH)2 cathode materials are synthesized through co-precipitation, then Yttrium(Y) is added to synthesize high nickel layered oxides Li(Ni0.85Co0.075Mn0.075)0.98Y0.02O2 during crystallization by solid-state reaction at a certain calcination temperatures under oxygen atmosphere to improve the electrochemical properties of materials in this study. The microstructure, particle morphology and electrochemical properties of the materials are characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), constant current charge and discharge, cyclic voltammetry(CV), respectively. The XRD results show that both two samples are corresponding to the layered α-NaFeO2 structure with R3m space group, while the c/a ratio and the unit cell volume increased with the addition of Yttrium. As the unit cell size increases, the volumes of Li-ion transport pathways also increase, which further promote lithium diffusion rate in the channel and facilitate Li+ intercalation/de-intercalation. And the SEM results demonstrated that both precursor materials were spherical secondary particles formed by the aggregation of primary scale-like particles, and the particle size gradually decreased with the addition of yttrium. The CV determination results show that both materials have two pairs of redox peaks. Still ,the redox peak of the doped material is broader and without the sharpness of the original one. In addition to this, the doped sample exhibits the excellent electrochemical performance with first discharge specific capacity with 193.34 mAh·g-1 and capacity retention of 85.83% after 100 cycles at 0.5C, while the original material LiNi0.85Co0.075Mn0.075O2 has higher first discharge capacity of 195.86 mAh·g-1, and the capacity retention in the 100 cycles of original was only 78.06%. In a word, the results showed that Y-doping could significantly improve the cyclic stability of LiNi0.85Co0.075Mn0.075O2 due to it promoted the diffusion channel of Li+ and inhibited the side reactions between samples and electrolyte. Figure 1

Strong hydrogen bonding in a dense hydrous magnesium silicate discovered by neutron Laue diffraction.

A large amount of hydrogen circulates inside the Earth, which affects the long-term evolution of the planet. The majority of this hydrogen is stored in deep Earth within the crystal structures of dense minerals that are thermodynamically stable at high pressures and temperatures. To understand the reason for their stability under such extreme conditions, the chemical bonding geometry and cation exchange mechanism for including hydrogen were analyzed in a representative structure of such minerals (i.e. phase E of dense hydrous magnesium silicate) by using time-of-flight single-crystal neutron Laue diffraction. Phase E has a layered structure belonging to the space group R 3 m and a very large hydrogen capacity (up to 18% H2O weight fraction). It is stable at pressures of 13-18 GPa and temperatures of up to at least 1573 K. Deuterated high-quality crystals with the chemical formula Mg2.28Si1.32D2.15O6 were synthesized under the relevant high-pressure and high-temperature conditions. The nuclear density distribution obtained by neutron diffraction indicated that the O-D dipoles were directed towards neighboring O2- ions to form strong interlayer hydrogen bonds. This bonding plays a crucial role in stabilizing hydrogen within the mineral structure under such high-pressure and high-temperature conditions. It is considered that cation exchange occurs among Mg2+, D+ and Si4+ within this structure, making the hydrogen capacity flexible.

Electronic and elastic properties of rhombohedral GeTe: Exfoliation energy of a monolayer from (111) surface

In the present study, the electronic and elastic properties of rhombohedral germanium telluride (GeTe) - a low temperature phase (space group R3m), have been reported using density functional theory with Rabe Rappe Kaxiras Joannopoulos ultrasoft pseudopotentials. The calculated results are in good agreement with the experimentally reported results. The exfoliation energy for a GeTe monolayer from the (111) surface of bulk GeTe has been calculated with a much lesser computation cost and the results show that ∼0.66 J/m2 energy is required to lift off a GeTe monolayer and also suggests the study to minimize the exfoliation energy to enhance the feasibility of the formation of GeTe monolayer.