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1.
The ternary rare‐earth germanium antimonides RE12Ge7?xSb21 (RE=La–Pr; x=0.4–0.5) are synthesized by direct reactions of the elements. Single‐crystal X‐ray diffraction studies indicate that they adopt a new structure type (space group Immm, Z=2, a=4.3165(4)–4.2578(2) Å, b=15.2050(12)–14.9777(7) Å, c=34.443(3)–33.9376(16) Å in the progression from RE=La to Pr), integrating complex features found in RE6Ge5?xSb11+x and RE12Ga4Sb23. A three‐dimensional polyanionic framework, consisting of Ge pairs and Sb ribbons, outlines large channels occupied by columns of face‐sharing RE6 trigonal prisms. These trigonal prisms are centered by additional Ge and Sb atoms to form GeSb3 trigonal‐planar units. A bonding analysis attempted through a Zintl–Klemm approach suggests that full electron transfer from the RE atoms to the anionic substructure cannot be assumed. This is confirmed by band‐structure calculations, which also reveal the importance of Ge? Sb and Sb? Sb bonding. Magnetic measurements on Ce12Ge6.5Sb21 indicate antiferromagnetic coupling but no long‐range ordering down to 2 K.  相似文献   

2.
The rare‐earth metal germanides RE2Ge9 (RE = Nd, Sm) have been prepared by thermal decomposition of the metastable high‐pressure phases REGe5 at ambient pressure. The compounds adopt an orthorhombic unit cell with a = 396.34(4) pm; b = 954.05(8) pm and c = 1238.4(1) pm for Nd2Ge9 and a = 395.46(7) pm; b = 946.4(2) pm and c = 1232.1(3) pm for Sm2Ge9. Crystal structure refinements reveal space group Pmmn (No. 59) for Nd2Ge9. The atomic pattern resembles an ordered defect variety of the pentagermanide motif REGe5 (RE = La; Nd, Sm, Gd, Tb) comprising corrugated germanium layers. These condense into a three‐dimensional network interconnected by eight‐coordinated germanium atoms. The resulting framework channels along [100] enclose the neodymium atoms. With respect to the atomic arrangement of the pentagermanides, half of the interlayer germanium atoms are eliminated in an ordered way so that occupied and empty germanium columns alternate along [001]. The rare‐earth metal atoms of both types of compounds, REGe5 and RE2Ge9, exhibit the electronic states 4f 3 and 4f 5 (oxidation state +3) for neodymium and samarium, respectively, evidencing that the modification of the germanium network leaves the electron configuration of the metal atoms unaffected.  相似文献   

3.
A series of isotypic rare‐earth metal pentagermanides including the new compound TbGe5 were prepared by high‐pressure synthesis. They crystallize in the orthorhombic space group Immm [No. 71; a = 395.70(9) pm; b = 611.1(2) pm, and c = 983.6(3) pm for TbGe5]. The crystal structure is isotypic to LaGe5 and consists of puckered germanium slabs, which sandwich a second germanium species and the rare‐earth metal atoms. At ambient pressure, the thermal decomposition of the phases REGe5 (RE = La, Nd, Sm, Gd, and Tb) proceeds via discrete intermediate steps into Ge(cF8) and thermodynamically stable germanium‐poorer phases. The investigated compounds REGe5 are paramagnetic metallic conductors, which order antiferromagnetically at low temperatures. Specific heat measurements reveal that the superconducting state of LaGe5 below Tc = 7.1(1) K is characterized by a critical field of μ0Hc2 = 0.2 T and weak electron‐phonon coupling. Density‐functional based band‐structure calculations yield a very similar electronic structure for all the isotypic REGe5 compounds. Besides a slight increase in the width of the valence band for smaller RE atoms, only minor differences are found for the two different germanium environments.  相似文献   

4.
The series of RE5Li2Sn7 (RE = Ce–Sm) compounds were synthesized by high‐temperature reactions and structurally characterized by single‐crystal X‐ray diffraction. The compounds are pentacerium dilithium heptastannide, Ce5Li1.97Sn7.03, pentapreseodymium dilithium heptastannide, Pr5Li1.98Sn7.02, pentaneodymium dilithium heptastannide, Nd5Li1.99Sn7.01, and pentasamarium dilithium heptastannide, Sm5Li2Sn7. All five compounds crystallize in the chiral orthorhombic space group P212121 (No. 19), which is relatively uncommon among intermetallic phases. The structure belongs to the Ce5Li2Sn7 structure type (Pearson symbol oP56), with 14 unique atoms in the asymmetric unit. Minor compositional variations exist, due to the mixed occupancy of Li and Sn atoms at one of the Li sites. The small occupational disorder is most evident for RE5Li2−xSn7+x (RE = Ce, Pr; x≃ 0.03), while the structure of Nd5Li2Sn7 and Sm5Li2Sn7 show no apparent disorder.  相似文献   

5.
Synthesis and Crystal Structures of Zinc Rhodium Boride Zn5Rh8B4 and the Lithium Magnesium Rhodium Borides LixMg5?xRh8B4 (x = 1.1 and 0.5) and Li8Mg4Rh19B12 The title compounds were prepared by reaction of the elemental components in metal ampoules under argon atmosphere (1100 °C, 7 d). In the case of Zn5Rh8B4 (orthorhombic, space group Cmmm, a = 8.467(2) Å, b = 16.787(3) Å, c = 2.846(1) Å, Z = 2) a BN crucible enclosed in a sealed tantalum container was used. The syntheses of LixMg5?xRh8B4 (orthorhombic, space group Cmmm, Z = 2, isotypic with Zn5Rh8B4, lattice constants for x = 1.1: a = 8.511(3) Å, b = 16.588(6) Å, c = 2.885(1) Å, and for x = 0.5: a = 8.613(1) Å, b = 16.949(3) Å, c = 2.9139(2) Å) and Li8Mg4Rh19B12 (orthorhombic, space group Pbam, a = 26.210(5) Å, b = 13.612(4) Å, c = 2.8530(5) Å, Z = 2) were carried out in tantalum crucibles enclosed in steel containers using lithium as a metal flux. The crystal structures were solved from single crystal X‐ray diffraction data. In both structures Rh atoms reside at z = 0 and all non‐transition metal atoms at z = 1/2. Columns of Rh6B trigonal prisms running along the c‐axis are laterally connected to form three‐dimensional networks with channels of various cross sections containing Li‐, Mg‐, and Zn‐atoms, respectively. A very short Li‐Li distance of 2.29(7) Å is observed in Li8Mg4Rh19B12.  相似文献   

6.
The mixed silicide‐germanides Li12Si7–xGex, Na7LiSi8–zGez, and Li3NaSi6–vGev which could serve as potential precursors for Si1–xGex materials were synthesized and characterized by X‐ray diffraction methods. The full solid solution series Li12Si7–xGex (0 ≤ x ≤ 7) is easily accessible from the elements and features preferential occupation of the more negatively charged crystallographic tetrel positions by Ge, which is the more electronegative element. In case of Na7LiSi8–zGez a broad solid solution range of 1.3 ≤ x ≤ 8 is available but the ternary silicide Na7LiSi8 could not be obtained by the tested methods of synthesis. The solubility of Ge in Li3NaSi6–vGev is highly limited to a maximum of v ≈ 0.5, and again the formally more negatively charged tetrel positions are preferred by Ge. Additionally, the two crystallographic Li positions in Li12Si7 with unusually large displacement parameters can be partially substituted by Na in Li12–yNaySi7 with 0 ≤ y ≤ 0.6. The statistical mixing of Li and Na in this solid solution contrasts the typical ordering of Li and Na in most ternary tetrelides.  相似文献   

7.
Zusammenfassung Die Verbindungen Gd(Dy, Er, Lu)6Cu8Ge8 wurden hergestellt und ihre Struktur bestimmt. Gd6Cu8Ge8 kristallisiert orthorhombisch in einem neuen Strukturtyp mita=14,000±0,008 Å,b=6,655±0,003 Å,c=4,223±0,004 Å, Raumgruppe D 2h 25 -I mmm mit 2 Gd in 2 (d), 4 Gd in 4 (e), 8 Cu in 8 (n), 4 Ge in 4 (f) und 4 Ge in 4 (h), N=1. Die Struktur ist durch Verwandtschaft zum AlB2- und CaZn5-Typ gekennzeichnet. Die anderen genannten Phasen sind dem Gd6Cu8Ge8 isotyp.
Crystal structure of Gd6Cu8Ge8, and of isotypic phases
The compounds Gd(Dy, Er, Lu)6Cu8Ge8 have been prepared and their structure has been determined. Gd6Cu8Ge8 crystallizes in a new structure type witha=14.000±0.008 Å,b=6.655±0.003 Å,c=4.223±0.004 Å, space group D 2h 25 -I mmm with 2 Gd in 2 (d), 4 Gd in 4 (e), 8 Cu in 8 (n), 4 Ge in 4 (f) and 4 Ge in 4 (h), N=1. The structure is characterized by close relationship to the AlB2 and CaZn5 structure types. The other phases mentioned above are isotypic to Gd6Cu8Ge8.


Mit 4 Abbildungen  相似文献   

8.
Binary and multicomponent intermetallic compounds based on lithium and p‐elements of Groups III–V of the Periodic Table are useful as modern electrode materials in lithium‐ion batteries. However, the interactions between the components in the Li–Ge–B ternary system have not been reported. The structure of tetralithium digermanium boride, Li4Ge2B, exhibits a new structure type, in the noncentrosymmetric space group R3m, in which all the Li, Ge and B atoms occupy sites with 3m symmetry. The title structure is closely related to the Mo2B5 and Li5Sn2 structure types, which crystallize in the centrosymmetric space group Rm. All the atoms in the title structure are coordinated by rhombic dodecahedra (coordination number = 14), similar to the atoms in related structures. According to electronic structure calculations using the tight‐binding–linear muffin‐tin orbital–atomic spheres approximation (TB–LMTO–ASA) method, strong covalent Ge—Ge and Ge—B interactions were established.  相似文献   

9.
Recently lithium phosphidogermanates were discovered as fast lithium ion conductors for potential usage as solid electrolytes in all solid-state batteries. In this context we also studied sodium phosphidogermanates since sodium ion conductors are of equal interest. Na2Ge3P3 and Na5Ge7P5 both crystallize in the monoclinic space group C2/m with unit cell parameters of a = 17.639(4) Å, b = 3.6176(7) Å, c = 11.354(2) Å, β = 92.74(3)° and a = 16.168(5) Å, b = 3.6776(7) Å, c = 12.924(4) Å, β = 91.30(3)°, respectively. Both show linearly condensed 9-atom cages of four Ge / five P and five Ge / four P atoms, respectively. These cages contain Ge–Ge bonds and form one-dimensional tubes by sharing three atoms. The parallel tubes are paired through further Ge–Ge bonds. Both structures are closely related to the one of the fibrous type of crystalline red phosphorus. A comparison with other compounds such as NaGe3P3 and GeP reveals recurring structural motifs with a broad variety of connection patterns. According to the general formula Na4+xGe6+xP6–x with x = 0 and 1, the two novel structures hint for the possibility of a variable Na content which might allow Na ion mobility.  相似文献   

10.
The quaternary germanides RE3TRh4Ge4 (RE = Ce, Pr, Nd; T = Nb, Ta) were synthesized from the elements by arc‐melting and subsequent annealing in a muffle furnace. The structure of Ce3TaRh4Ge4 was refined from single‐crystal X‐ray diffractometer data: new type, Pbam, a = 719.9(2), b = 1495.0(3), c = 431.61(8), wR2 = 0.0678, 1004 F2 values, and 40 variables. Isotypy of the remaining phases was evident from X‐ray powder patterns. Ce3TaRh4Ge4 is a new superstructure variant of the aristotype AlB2 with an ordering of cerium and tantalum on the aluminum site, whereas the honey‐comb network is built up by a 1:1 ordering of rhodium and germanium. This crystal‐chemical relationship is discussed based on a group‐subgroup scheme. The distinctly different size of tantalum and cerium leads to a pronounced puckering of the [Rh4Ge4] network, which shows the shortest interatomic distances (253–271 pm Rh–Ge) within the Ce3TaRh4Ge4 structure. Another remarkable structural feature concerns the tantalum coordination with six shorter Ta–Rh bonds (265–266 pm) and six longer Ta–Ge bonds (294–295 pm). The [Rh4Ge4] network fully separates the tantalum and cerium atoms (Ce–Ce > 387 pm, Ta–Ta > 431 pm, and Ce–Ta > 359 pm). The electronic density of states DOS from DFT calculations show metallic behavior with large contributions of localized Ce 4f as well as itinerant ones from all constituents at the Fermi level but no significant magnetic polarization on Ce could be identified. The bonding characteristics described based on overlap populations illustrate further the crystal chemistry observations of the different coordination of Ce1 and Ce2 in Ce3TaRh4Ge4. The Rh–Ge interactions within the network are highlighted as dominant. The bonding magnitudes follow the interatomic distances and identify differences of Ta bonding vs. Ce1/Ce2 bonding with the Rh and Ge substructures.  相似文献   

11.
A crystallographic study of the Si/Ge site preferences in the Si-rich regime of Gd5(SixGe1−x)4 and a crystal chemical analysis of these site preferences for the entire range is presented. The room temperature crystal structure of Gd5Si4 as well as four pseudobinary phases, Gd5(SixGe1−x)4 for x?0.6, is reported. All structures are orthorhombic (space group Pnma), Gd5Si4-type and show decreasing volume as the Si concentration increases. Refinements of the site occupancies for the three crystallographic sites for Si/Ge atoms in the asymmetric unit reveal a nonrandom, but still incompletely ordered arrangement of Si and Ge atoms. The distribution of Si and Ge atoms at each site impacts the fractions of possible homonuclear and heteronuclear Si-Si, Si-Ge and Ge-Ge dimers in the various structures. This distribution correlates with the observed room temperature crystal structures for the entire series of Gd5(SixGe1−x)4.  相似文献   

12.
New Ternary Germanides: The Compounds Ln 4Zn5Ge6 ( Ln : Gd, Tm, Lu) Three new ternary germanides were prepared by heating mixtures of the elements. Gd4Zn5Ge6 (a = 4.249(3), b = 18.663(17), c = 15.423(6) Å), Tm4Zn5Ge6 (a = 4.190(1), b = 18.410(5), c = 15.105(5) Å), and Lu4Zn5Ge6 (a = 4.179(1), b = 18.368(4), c = 15.050(3) Å) are isotypic and crystallize in a new structure type (Cmc21; Z = 4), composed of edge‐ and corner‐sharing ZnGe4 tetrahedra. The rare‐earth atoms fill channels of the Zn,Ge network running along the a axis and predominantly have an octahedral coordination of Ge atoms or a pentagonal prismatic environment of Zn and Ge atoms. The ZnGe4 tetrahedra are orientated to each other so that two of six Ge atoms form pairs, while the other ones have no homonuclear contacts. This is in accord with an ionic splitting of the formula: (Ln3+)4(Zn2+)5(Ge3–)2(Ge4–)4. LMTO band structure calculations support the interpretation of bondings derived from interatomic distances. The metallic conductivity of these compounds expected from the electronic band structure was confirmed by measurements of the electrical resistance of Tm4Zn5Ge6.  相似文献   

13.
Two new series of tetracyanamidogermanates were prepared by solid‐state reaction of appropriate amounts of REF3 (RE = rare earth), A2[GeF6] (A = alkaline), and Li2(CN2) in evacuated silica tubes. Powder X‐ray diffraction patterns of crystalline samples of KRE[Ge(CN2)4] and CsRE[Ge(CN2)4] were indexed isotypically to KRE[Si(CN2)4] and RbRE[Ge(CN2)4], respectively. Luminescence properties of Ce3+, Eu3+, and Tb3+ doped compounds and non‐linear optical properties (NLO) of KRE[Ge(CN2)4] are reported.  相似文献   

14.
The rare earth-rich cadmium compounds RE 4 TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y4RuCd (a = 1362.5(1) pm), La4RuCd (a = 1415.9(1) pm), Gd4RuCd (a = 1368.8(2) pm), La4CoCd (a = 1417.9(4) pm), Gd4CoCd (a = 1356.1(1) pm), and Gd4RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE 4 TCd compounds crystallize with the cubic Gd4RhIn type structure, space group F ${\bar 4}The rare earth-rich cadmium compounds RE 4 TCd (RE = Y, La–Nd, Sm, and Gd–Tm, Lu; T = Co, Ru, and Rh) were prepared from the elements in sealed tantalum ampoules in an induction furnace. All samples were characterized by X-ray powder diffraction. The structures of Y4RuCd (a = 1362.5(1) pm), La4RuCd (a = 1415.9(1) pm), Gd4RuCd (a = 1368.8(2) pm), La4CoCd (a = 1417.9(4) pm), Gd4CoCd (a = 1356.1(1) pm), and Gd4RhCd (a = 1368.7(1) pm) were refined from single crystal X-ray diffractometer data. The RE 4 TCd compounds crystallize with the cubic Gd4RhIn type structure, space group F 3m. The transition metal atoms have tricapped trigonal prismatic rare earth coordination. The trigonal prisms are condensed via common edges, forming a rigid three-dimensional network with adamantane symmetry. Voids in these networks are filled by Cd4 tetrahedra (304 pm Cd–Cd in Gd4CoCd) and polyhedra of the RE1 atoms. The crystal chemical peculiarities are briefly discussed. Correspondence: Rainer P?ttgen, Institut für Anorganische und Analytische Chemie, Westf?lische Wilhelms-Universit?t Münster, Correnstrasse 30, 48149 Münster, Germany.  相似文献   

15.
The compounds Li8EN2 with E = Se, Te were obtained in form of orange microcrystalline powders from reactions of Li2E with Li3N. Single crystal growth of Li8SeN2 additionally succeeded from excess lithium. The crystal structures were refined using single‐crystal X‐ray diffraction as well as X‐ray and neutron powder diffraction data (I41md, No. 109, Z = 4, Se: a = 7.048(1) Å, c = 9.995(1) Å, Te: a = 7.217(1) Å, c = 10.284(1) Å). Both compounds crystallize as isotypes with an anionic substructure motif known from cubic Laves phases and lithium distributed over four crystallographic sites in the void space of the anionic framework. Neutron powder diffraction pattern recorded in the temperature range from 3 K to 300 K and X‐ray diffraction patterns using synchrotron radiation taken from 300 K to 1000 K reveal the structural stability of both compounds in the studied temperature range until decomposition. Motional processes of lithium atoms in the title compounds were revealed by temperature dependent NMR spectroscopic investigations. Those are indicated by significant changes of the 7Li NMR signals. Lithium motion starts for Li8SeN2 above 150 K whereas it is already present in Li8TeN2 at this temperature. Quantum mechanical calculations of NMR spectroscopic parameters reveal clearly different environments of the lithium atoms determined by the electric field gradient, which are sensitive to the anisotropy of charge distribution at the nuclear sites. With respect to an increasing coordination number according to 2 + 1, 3, 3 + 1, and 4 for Li(3), Li(4), Li(2), and Li(1), respectively, the values of the electric field gradients decrease. Different environments of lithium predicted by quantum mechanical calculations are confirmed by 7Li NMR frequency sweep experiments at low temperatures.  相似文献   

16.
High‐pressure modifications of the rare earth oxide fluorides REOF (RE = Pr, Nd, Sm – Gd) were successfully synthesized under conditions of 11 GPa and 1200 °C applying the multianvil high‐pressure/high‐temperature technique. Single crystals of HP‐REOF (RE = Nd, Sm, Eu) were obtained making it possible to analyze the products by means of single‐crystal X‐ray diffraction. The compounds HP‐REOF (RE = Nd, Sm, Eu) crystallize in the orthorhombic α‐PbCl2‐type structure (space group Pnma, No. 62, Z = 4) with the parameters a = 632.45(3), b = 381.87(2), c = 699.21(3) pm, V = 0.16887(2) nm3, R1 = 0.0156, and wR2 = 0.0382 for HP‐NdOF, a = 624.38(3), b = 376.87(2), c = 689.53(4) pm, V = 0.16225(2) nm3, R1 = 0.0141, and wR2 = 0.0323 for HP‐SmOF, and a = 620.02(4), b = 374.24(3), c = 686.82(5) pm, V = 0.15937(2) nm3, R1 = 0.0177, and wR2 = 0.0288 for HP‐EuOF. Calculations of the bond valence sums clearly showed that the oxygen atoms occupy the tetrahedrally coordinated position, whereas the fluorine atoms are fivefold coordinated in form of distorted square‐pyramids. The crystal structures and properties of HP‐REOF (RE = Nd, Sm, Eu) are discussed and compared to the isostructural phases and the normal‐pressure modifications of REOF (RE = Nd, Sm, Eu). Furthermore, results of investigations by EDX and Raman measurements including quantum mechanical calculations are presented.  相似文献   

17.
Recently fast lithium ion conductors were discovered in compounds containing tetrahedral SiP48– and GeP48– units. In the context of material development for all solid state batteries the ternary Li/Ge/P phase system has been further investigated and two new lithium phosphidogermanates were discovered on the lithium poor side of the ternary composition diagram. Li2GeP2 crystallizes in space group I41/acd with unit cell parameters of a = 12.3069(1) Å and c = 19.0306(4) Å, consists of a framework of Ge4P10 supratetrahedra, and exhibits an ionic conductivity of 1.5(3)×10–7 S · cm–1 at 27 °C. LiGe3P3 crystallizes in Pbam with a = 9.8459(5) Å, b = 15.7489(7) Å, and c = 3.5995(2) Å. In LiGe3P3 Ge and P atoms form a two dimensional polyanion. The slabs consist of five- and six-membered heteroatomic rings comprising GeP4 and Ge(P3Ge) tetrahedra including homoatomic Ge–Ge bonds. A semiconducting behavior with an electronic conductivity of ∼10–4 S · cm–1 and a remarkable stability vs. air and moisture is observed.  相似文献   

18.
The rare earth‐rich compounds RE23Rh7Mg4 (RE = La, Ce, Pr, Nd, Sm, Gd) were prepared by induction‐melting the elements in sealed tantalum tubes. The new compounds were characterized by X‐ray powder diffraction. They crystallize with the hexagonal Pr23Ir7Mg4 type structure, space group P63mc. The structures of La23Rh7Mg4 (a = 1019.1(1), c = 2303.7(4) pm, wR2 = 0.0827, 1979 F2 values, 69 variables), Nd23Rh7Mg4 (a = 995.4(2), c = 2242.3(5) pm, wR2 = 0.0592, 2555 F2 values, 74 variables) and Gd23Rh6.86(5)Mg4 (a = 980.5(2), c = 2205.9(5) pm, wR2 = 0.0390, 2083 F2 values, 71 variables) were refined from single crystal X‐ray diffractometer data. The three crystallographically different rhodium atoms have trigonal prismatic rare earth coordination with short RE–Rh distances (283–300 pm in Nd23Rh7Mg4). The prisms are condensed via common edges, leading to a rigid three‐dimensional network in which isolated Mg4 tetrahedra (312–317 pm Mg–Mg in Nd23Rh7Mg4) are embedded. Temperature dependent magnetic susceptibility data of Ce23Rh7Mg4 indicate Curie‐Weiss behavior with an experimental magnetic moment of 2.52(1) μB/Ce atom, indicative for stable trivalent cerium. Antiferromagnetic ordering is evident at 2.9 K.  相似文献   

19.
The novel ternary Zintl phase Li3NaGe2 comprises alkali‐metal cations and [Ge2]4? dumbbells. The diatomic [Ge2]4? unit is characterized by the shortest Ge?Ge distance (2.390(1) Å) ever observed in a Zintl phase and thus represents the first Ge=Ge double bond under such conditions, as also suggested by the (8?N) rule. Raman measurements support these findings. The multiple‐bond character is confirmed by electronic‐structure calculations, and an upfield 6Li NMR shift of ?10.0 ppm, which was assigned to the Li cations surrounded by the π systems of three Ge dumbbells, further underlines this interpretation. For the unperturbed, ligand‐free dumbbell in Li3NaGe2, the π‐ bonding py and pz orbitals are degenerate as in molecular oxygen, which has singly occupied orbitals. The partially filled π‐type bands of the neat solid Li3NaGe2 cross the Fermi level, resulting in metallic properties. Li3NaGe2 was synthesized from the elements as well as from binary reactants and subsequently characterized crystallographically.  相似文献   

20.
The structure of lithium barium silicate, Li2BaSiO4, has been determined from synchrotron radiation powder data. The title compound was synthesized by high‐temperature solid‐state reaction and crystallizes in the hexagonal space group P63cm. It contains two Li atoms, one Ba atom (both site symmetry ..m on special position 6c), two Si atoms [on special positions 4b (site symmetry 3..) and 2a (site symmetry 3.m)] and four O atoms (one on general position 12d, and three on special positions 6c, 4b and 2a). The basic units of the structure are (Li6SiO13)5− units, each comprising seven tetrahedra sharing edges and vertices. These basic units are connected by sharing corners parallel to [001] and through sharing (SiO4)4− tetrahedra in (001). The relationship between the structures and luminescence properties of Li2SrSiO4, Li2CaSiO4 and the title compound is discussed.  相似文献   

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