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1.
Tae-Soo You 《Journal of solid state chemistry》2010,183(6):1258-214
Reported are the synthesis and the structural characterization of four new polar intermetallic phases, which exist only with mixed alkaline-earth and rare-earth metal cations in narrow homogeneity ranges. (Sr1-xCax)5In3Ge6 and (Eu1-xYbx)5In3Ge6 (x≈0.7) crystallize in the orthorhombic space group Pnma with two formula units per unit cell (own structure type, Pearson symbol oP56). The lattice parameters are as follows: a=13.109(3)-13.266(3) Å, b=4.4089(9)-4.4703(12) Å, and c=23.316(5)-23.557(6) Å. (Sr1-xCax)3In2Ge4 and (Sr1-xYbx)3In2Ge4 (x≈0.4-0.5) adopt another novel monoclinic structure-type (space group C2/m, Z=4, Pearson symbol mS36) with lattice parameters in the range a=19.978(2)-20.202(2) Å, b=4.5287(5)-4.5664(5) Å, c=10.3295(12)-10.3447(10) Å, and β=98.214(2)-98.470(2)°, depending on the metal cations and their ratio. The polyanionic sub-structures in both cases are based on chains of InGe4 corner-shared tetrahedra. The A5In3Ge6 structure (A=Sr/Ca or Sr/Yb) also features Ge4 tetramers, and isolated In atoms in nearly square-planar environment, while the A3In2Ge4 structure (A=Sr/Ca or Eu/Yb) contains zig-zag chains of In and Ge strings with intricate topology of cis- and trans-bonds. The experimental results have been complemented by tight-binding linear muffin-tin orbital (LMTO) band structure calculations. 相似文献
2.
A series of rare-earth metal–magnesium–germanides RE2MgGe2 (RE=Y, Nd, Sm, Gd–Tm, Lu) has been synthesized by reactions of the corresponding elements at high temperature. Their structures have been established by single-crystal and powder X-ray diffraction and belong to the Mo2FeB2 structure type (space group P4/mbm (No. 127), Z=2; Pearson symbol tP10). Temperature dependent DC magnetization measurements indicate Curie–Weiss paramagnetism in the high-temperature regime for all members of the family, excluding Y2MgGe2, Sm2MgGe2, and Lu2MgGe2. At cryogenic temperatures (ca. 60 K and below), most RE2MgGe2 phases enter into an antiferromagnetic ground-state, except for Er2MgGe2 and Tm2MgGe2, which do not undergo magnetic ordering down to 5 K. The structural variations as a function of the decreasing size of the rare-earth metals, following the lanthanide contraction, and the changes in the magnetic properties across the series are discussed as well. 相似文献
3.
Polycrystalline Li3Sc(BO3)2 was synthesized through the solid-state reaction, which is air-, water- and thermal-stable below about 929 °C. Its crystal structure was resolved and refined on the basis of powder X-ray diffraction data. The metal-borate framework is built up from ScO6 octahedra connected to each other by sharing common edges, corners and faces of BO3 units and LiO4 groups. Coordination surrounding of B-O in this structure, [BO3]3− group, was confirmed by an infrared absorption spectrum of an Li3Sc(BO3)2. According to the electronic structure calculated by first-principles calculations, an Li3Sc(BO3)2 is an insulator with a wide indirect energy band gap of about 4.4 eV. Considering the facile synthesis, large band gap, and thermal stability and excellent Tb3+-doped photoluminescence characteristics of this compound in general, it may be a good candidate as host of phosphors deposited on chip of the light-emitting diodes for white-color conversion. 相似文献
4.
Ivan V. Ogorodnyk Igor V. Zatovsky Vyacheslav N. Baumer 《Journal of solid state chemistry》2006,179(12):3681-3687
The single crystals of caesium magnesium titanium (IV) tri-oxo-tetrakis-diphosphate bis-monophosphate, Cs3.70Mg0.60Ti2.78(TiO)3(P2O7)4(PO4)2, crystallize in sp. gr. P-1 (No. 2) with cell parameters a=6.3245(4), b=9.5470(4), c=15.1892(9) Å, α=72.760(4), β=85.689(5), γ=73.717(4), z=1. The titled compound possesses a three-dimensional tunnel structure built by the corner-sharing of distorted [TiO6] octahedra, [Ti2O11] bioctahedra, [PO4] monophosphate and [P2O7] pyrophosphate groups. The Cs+ cations are located in the tunnels. The partial substitution of Ti positions with Mg atoms is observed. The negative charge of the framework is balanced by Cs cations and Mg atoms leading to pronounced concurrency and orientation disorder in the [P2O7] groups, which coordinate both. 相似文献
5.
A new cesium uranyl niobate, Cs9[(UO2)8O4(NbO5)(Nb2O8)2] or Cs9U8Nb5O41 has been synthesized by high-temperature solid-state reaction, using a mixture of U3O8, Cs2CO3 and Nb2O5. Single crystals were obtained by incongruent melting of a starting mixture with metallic ratio=Cs/U/Nb=1/1/1. The crystal structure of the title compound was determined from single crystal X-ray diffraction data, and solved in the monoclinic system with the following crystallographic data: a=16.729(2) Å, b=14.933(2) Å, c=20.155(2) Å β=110.59(1)°, P21/c space group and Z=4. The crystal structure was refined to agreement factors R1=0.049 and wR2=0.089, calculated for 4660 unique observed reflections with I?2σ(I), collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector.In this structure the UO7 uranyl pentagonal bipyramids are connected by sharing edges and corners to form a uranyl layer corresponding to a new anion-sheet topology, and creating triangular, rectangular and square vacant sites. The two last sites are occupied by Nb2O8 entities and NbO5 square pyramids, respectively, to form infinite uranyl niobate sheets stacking along the [010] direction. The Nb2O8 entities result from two edge-shared NbO5 square pyramids. The Cs+ cations are localized between layers and ensured the cohesion of the structure.The cesium cation mobility between the uranyl niobate sheets was studied by electrical measurements. The conductivity obeys the Arrhenius law in all the studied temperature domains. The observed low conductivity values with high activation energy may be explained by the strong connection of the Cs+ cations to the infinite uranyl niobate layers and by the high density of these cations in the interlayer space without vacant site.Infrared spectroscopy investigated at room temperature in the frequency range 400-4000 cm−1, showed some characteristic bands of uranyl ion and niobium polyhedra. 相似文献
6.
Synthesis and single crystal structures of ternary phosphides Li4SrP2 and AAeP (A=Li, Na; Ae=Sr, Ba)
Yongkwan Dong 《Journal of solid state chemistry》2007,180(2):432-439
Two new (NaSrP, Li4SrP2) and two known (LiSrP, LiBaP) ternary phosphides have been synthesized and characterized using single crystal X-ray diffraction studies. NaSrP crystallizes in the non-centrosymmetric hexagonal space group (#189, a=7.6357(3) Å, c=4.4698(3) Å, V=225.69(2) Å3, Z=3, and R/wR=0.0173/0.0268). NaSrP adopts an ordered Fe2P structure type. PSr6 trigonal prisms share trigonal (pinacoid) faces to form 1D chains. Those chains define large channels along the [001] direction through edge-sharing. The channels are filled by chains of PNa6 face-sharing trigonal prisms. Li4SrP2 crystallizes in the rhombohedral space group (#166, a=4.2813(2) Å, c=23.437(2) Å, V=372.04(4) Å3, Z=3, and R/wR=0.0142/0.0222). In contrast to previous reports, LiSrP and LiBaP crystallize in the centrosymmetric hexagonal space group P63/mmc (#194, a=4.3674(3) Å, c=7.9802(11) Å, V=131.82(2) Å3, Z=2, and R/wR=0.0099/0.0217 for LiSrP; a=4.5003(2) Å, c=8.6049(7) Å, V=150.92(2) Å3, Z=2, and R/wR=0.0098/0.0210 for LiBaP). Li4SrP2, LiSrP, and LiBaP can be described as Li3P derivatives. Li atoms and P atoms make a graphite-like hexagonal layer, . In LiSrP and LiBaP, Sr or Ba atoms reside between layers to substitute for two Li atoms of Li3P, while in Li4SrP2, Sr substitutes only between every other layer. 相似文献
7.
M.L. Foo T. He H.W. Zandbergen G. Lawes R.J. Cava 《Journal of solid state chemistry》2006,179(3):941-948
The crystal structures, synthesis and physical properties of ruthenium hollandites ALi2Ru6O12 (A=Na, K) with a new pseudo-hexagonal structure type are described. Analogous to tetragonal hollandites, the framework is made of MO6 octahedra in double chains that share corner oxygens with each other to create interstitial tunnels. The tunnels are either hexagonal or triangular in cross-section. Magnetic susceptibilities, low temperature specific heat, and electrical resistivities are reported. The data indicate that these materials are normal, low density of states metals. This new structure type can be extended from A=Group I to A=Group II ions with the synthesis of CaLi2Ru6O12 and SrLi2Ru6O12. 相似文献
8.
New uranyl vanadates A3(UO2)7(VO4)5O (M=Li (1), Na (2), Ag (3)) have been synthesized by solid-state reaction and their structures determined from single-crystal X-ray diffraction data for 1 and 3. The tetragonal structure results of an alternation of two types of sheets denoted S for ∞2[UO2(VO4)2]4− and D for ∞2[(UO2)2(VO4)3]5− built from UO6 square bipyramids and connected through VO4 tetrahedra to ∞1[U(3)O5-U(4)O5]8− infinite chains of edge-shared U(3)O7 and U(4)O7 pentagonal bipyramids alternatively parallel to a- and b-axis to construct a three-dimensional uranyl vanadate arrangement. It is noticeable that similar ∞[UO5]4− chains are connected only by S-type sheets in A2(UO2)3(VO4)2O and by D-type sheets in A(UO2)4(VO4)3, thus A3(UO2)7(VO4)5O appears as an intergrowth structure between the two previously reported series. The mobility of the monovalent ion in the mutually perpendicular channels created in the three-dimensional arrangement is correlated to the occupation rate of the sites and by the geometry of the different sites occupied by either Na, Ag or Li. Crystallographic data: 293 K, Bruker X8-APEX2 X-ray diffractometer equipped with a 4 K CCD detector, MoKα, λ=0.71073 Å, tetragonal symmetry, space group P4¯m2, Z=1, full-matrix least-squares refinement on the basis of F2; 1,a=7.2794(9) Å, c=14.514(4) Å, R1=0.021 and wR2=0.048 for 62 parameters with 782 independent reflections with I?2σ(I); 3, a=7.2373(3) Å, c=14.7973(15) Å, R1=0.041 and wR2=0.085 for 60 parameters with 1066 independent reflections with I?2σ(I). 相似文献
9.
G. Kalpana 《Journal of solid state chemistry》2007,180(5):1708-1712
Six new isostructural A2(Mo4Sb2O18) (A=Y, La, Nd, Sm, Gd and Dy) compounds have been synthesized by solid-state reactions and characterized by single crystal X-ray diffraction and spectroscopic techniques. They crystallize in C2/c space group with 4 formula units and contain A3+ cations and discrete centrosymmetric anionic (Mo4Sb2O18)6− aggregates, made of tetrahedral MoO4 and disphenoidal SbO4 moieties. They exhibit characteristic Sb3+ photoluminescence. 相似文献
10.
Tae-Soo You Jing-Tai Zhao Rainer Pttgen Walter Schnelle Ulrich Burkhardt Yuri Grin Gordon J. Miller 《Journal of solid state chemistry》2009,182(9):2430-2442
Two isoelectronic series, Eu(Ga1−xTtx)2 (Tt=Si, Ge, 0≤x≤1), have been synthesized and characterized by powder and single-crystal X-ray diffraction, physical property measurements, and electronic structure calculations. In Eu(Ga1−xSix)2, crystal structures vary from the KHg2-type to the AlB2-type, and, finally, the ThSi2-type structure as x increases. The hexagonal AlB2-type structure is identified for compositions 0.18(2)≤x<0.70(2) with Ga and Si atoms statistically distributed in the polyanionic 63 nets. As smaller Si atoms replace Ga atoms while the number of valence electrons increases, the lattice parameters, unit cell volumes, and Ga–Si distances in this phase region decrease significantly. Although aspects of X-ray diffraction results suggest puckering of the 63 nets for the Si-richest example of the AlB2-type Eu(Ga1−xSix)2, the complete experimental evidence remains inconclusive. On the other hand, in Eu(Ga1−xGex)2, six different structural types were observed as x varies. In addition to EuGa2 (KHg2-type; space group Imma) and EuGe2 (own structure type, space group P3¯m1), the ternary phases studied show four different structures: the AlB2-type for Ga-rich compositions; the YPtAs-type structure for EuGaGe; and two new structures, which are intergrowths of the YPtAs-type EuGaGe and EuGe2, for Ge-rich compositions. These two Ge-rich phases include: (1) Eu(Ga0.45(2)Ge0.55(2))2 containing two YPtAs-type motifs of EuGaGe plus one EuGe2 motif; and (2) Eu(Ga0.40(2)Ge0.60(2))2 containing one YPtAs-type motif alternating with a split site at and z=0.4798(2) with ca. 50% site occupancy by Ga and Ge along the c-axis. Magnetic susceptibilities of three Eu(Ga1−xGex)2 compounds display Curie–Weiss behavior above ca. 100 K, and show effective magnetic moments indicative of divalent Eu with a 4f7 electronic configuration, consistent with. X-ray absorption spectra (XAS). Density of states (DOS) and crystal orbital Hamilton population (COHP) analyses, based on first principles electronic structure calculations, rationalize the observed homogeneity ranges of the AlB2-type phases in both systems and the structural variations as a function of Tt content. 相似文献
11.
A2MnB′O6 (A=Ca, Sr; B=Sb, Ta) double perovskites have been synthesized and their structural and magnetic properties have been investigated. Rietveld refinement of the powder X-ray diffraction data for Sr2MnSbO6 indicated significant ordering of Mn and Sb at the B-site while all other phases showed mostly a random distribution of the B-site cations. X-ray absorption spectroscopic data established the presence of Mn in the 3+ and Sb/Ta in the 5+ oxidation states in all the phases. Magnetic susceptibility data indicated ferromagnetic correlations for all the A2MnB′O6 phases with Weiss temperatures varying from 64 to 107 K. 相似文献
12.
Xiao-Wu Lei Zhong-Ming Sun Long-Hua Li Guo-Hua Zhong Jiang-Gao Mao 《Journal of solid state chemistry》2010,183(4):920-810
The title compounds have been obtained by solid state reactions of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. Yb5Ni4Sn10 adopts the Sc5Co4Si10 structure type and crystallizes in the tetragonal space group P4/mbm (No. 127) with cell parameters of a=13.785(4) Å, c=4.492 (2) Å, V=853.7(5) Å3, and Z=2. Yb7Ni4Sn13 is isostructural with Yb7Co4InGe12 and crystallizes in the tetragonal space group P4/m (No. 83) with cell parameters of a=11.1429(6) Å, c=4.5318(4) Å, V=562.69(7) Å3, and Z=1. Both structures feature three-dimensional (3D) frameworks based on three different types of one-dimensional (1D) channels, which are occupied by the Yb atoms. Electronic structure calculations based on density functional theory (DFT) indicate that both compounds are metallic. These results are in agreement with those from temperature-dependent resistivity and magnetic susceptibility measurements. 相似文献
13.
Evgeny V. Alekseev Sergey V. Krivovichev W. Depmeier H. Katzke Evgeny V. Chuprunov 《Journal of solid state chemistry》2006,179(10):2977-2987
Three new uranyl tungstates, A8[(UO2)4(WO4)4(WO5)2] (A=Rb (1), Cs (2)), and Rb6[(UO2)2O(WO4)4] (3), were prepared by high-temperature solid-state reactions and their structures were solved by direct methods on twinned crystals, refined to R1=0.050, 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P21/n, (1): a=11.100(7), b=13.161(9), , β=90.033(13)°, , Z=8 and (2): , , , β=89.988(2)°, , Z=8. There are four symmetrically independent U6+ sites that form linear uranyl [O=U=O]2+ cations with rather distorted coordination in their equatorial planes. There are six W positions: W(1) and W(2) have square-pyramidal coordination (WO5), whereas W(3), W(4), W(5), and W(6) are tetrahedrally coordinated. The structures are based upon a novel type of one-dimensional (1D) [(UO2)4(WO4)4(WO5)2]4− chains, consisting of WU4O25 pentamers linked by WO4 tetrahedra and WO5 square pyramids. The chains run parallel to the a-axis and are arranged in modulated pseudo-2D-layers parallel to (0 1 0). The A+ cations are in the interlayer space between adjacent pseudo-layers and provide a 3D integrity of the structures. Compounds 1 and 2 are the first uranyl tungstates with 2/3 of W atoms in tetrahedral coordination. Such a high concentration of low-coordinated W6+ cations is probably responsible for the 1D character of the uranyl tungstate units. The compound 3 is triclinic, P1¯ a=10.188(2), b=13.110(2), , α=97.853(3), β=96.573(3), γ=103.894(3)°, , Z=4. There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO22+, as apical axes. Among eight W sites, the W(1), W(2), W(3), W(4), W(5), and W(6) atoms are tetrahedrally coordinated, whereas the W(7) and W(8) cations have distorted fivefold coordination. The structure contains chains of composition [(UO2)2O(WO4)4]6− composed of UO7 pentagonal bipyramids and W polyhedra. The chains involve dimers of UO7 pentagonal bipyramids that share common O atoms. The dimers are linked into chains by sharing corners with WO4 tetrahedra. The chains are parallel to [−101] and are arranged in layers that are parallel to (1 1 1). The Rb+ cations provide linkage of the chains into a 3D structure. The compound 1 has many structural and chemical similarities to its molybdate analog, Rb6[(UO2)2O(MoO4)4]. However, the compounds are not isostructural. Due to the tendency of the W6+ cations to have higher-than-fourfold coordination, part of the W sites adopt distorted fivefold coordination, whereas all Mo atoms in the Mo compound are tetrahedrally coordinated. Distribution of the WO5 configurations along the chain extension does not conform to its ‘typical’ periodicity. As a result, both the chain identity period and the unit-cell volume are doubled in comparison to the Mo analog, which leads to a new structure type. 相似文献
14.
Stanislav S. Stoyko 《Journal of solid state chemistry》2011,184(9):2360-11161
The ternary rare-earth zinc arsenides REZn1−xAs2 (RE=La-Nd, Sm) were prepared by reaction of the elements at 800 °C. Single-crystal and powder X-ray diffraction analysis revealed a defect SrZnBi2-type average structure for the La member (Pearson symbol tI16, space group I4/mmm, Z=4; a=4.0770(9) Å, c=20.533(5) Å), in contrast to defect HfCuSi2-type average structures for the remaining RE members (Pearson symbol tP8, space group P4/nmm, Z=2; a=4.0298(5)-3.9520(4) Å, c=10.222(1)-10.099(1) Å in the progression from Ce to Sm). The homogeneity range is not appreciable (estimated to be narrower than 0.6<1−x<0.7 in SmZn1−xAs2) and the formula REZn0.67As2 likely represents the Zn-rich phase boundary. The Ce-Nd members are Curie-Weiss paramagnets. LaZn0.67As2 shows activated behavior in its electrical resistivity, whereas SmZn0.67As2 exhibits anomalies in its temperature dependence of the electrical resistivity. 相似文献
15.
Mixed crystals of Li[Kx(NH4)1−x]SO4 have been obtained by evaporation from aqueous solution at 313 K using different molar ratios of mixtures of LiKSO4 and LiNH4SO4. The crystals were characterized by Raman scattering and single-crystal and powder X-ray diffraction. Two types of compound were obtained: Li[Kx(NH4)1−x]SO4 with x?0.94 and Li2KNH4(SO4)2. Different phases of Li[Kx(NH4)1−x]SO4 were yielded according to the molar ratio used in the preparation. The first phase is isostructural to the room-temperature phase of LiKSO4. The second phase is the enantiomorph of the first, which is not observed in pure LiKSO4, and the last is a disordered phase, which was also observed in LiKSO4, and can be assumed as a mixture of domains of two preceding phases. In the second type of compound with formula Li2KNH4(SO4)2, the room-temperature phase is hexagonal, symmetry space group P63 with cell-volume nine times that of LiKSO4. In this phase, some cavities are occupied by K+ ions only, and others are occupied by either K+ or NH4+ at random. Thermal analyses of both types of compounds were performed by DSC, ATD, TG and powder X-ray diffraction. The phase transition temperatures for Li[Kx(NH4)1−x]SO4x?0.94 were affected by the random presence of the ammonium ion in this disordered system. The high-temperature phase of Li2KNH4(SO4)2 is also hexagonal, space group P63/mmc with the cell a-parameter double that of LiKSO4. The phase transition is at 471.9 K. 相似文献
16.
Xiao-Wu Lei 《Journal of solid state chemistry》2011,184(4):852-858
K2Mg5−xSn3 (x=0.28) and K3Mg18Tt11 (Tt=Sn, Pb) have been synthesized by reacting the mixture of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. K2Mg5−xSn3 (x=0.28) is isostructural with Ni7−xSbQ2 (Q=Se, Te) series and features 2D corrugated [Mg5−xSn3] layers that are separated by K+ cations. The structure of K3Mg18Tt11 (Tt=Sn, Pb) is closely related to the Ho2Rh12As7 structural type and features 3D [Mg18Tt11] framework composed of 1D [Mg18Tt11] columns that are interconnected via Mg-Tt bonds, forming 1D hexagonal tunnels occupied by the K+ cations. Electronic structure calculations indicate that Mg atoms can function as either electron donor or as a participator in the network along with Tt atoms. Magnetic property measurements and band structure calculations indicate that these compounds are metallic. 相似文献
17.
Crystals of Ba5Fe5−xPtxClO13 and Ba5Co5−yPtyClO13 were prepared for x=1.31, 1.51, 1.57, 1.59 and y=0, 0.97 and 1.08 in a BaCl2 flux and investigated by X-ray diffraction methods. These compounds adopt a 10H perovskite structure built from the stacking of BaO3 and BaOCl layers in the sequence (BaO3)4(BaOCl) with space group P63/mmc. The cation sites within the trimeric unit of face-sharing octahedra are occupied by Co or Fe and Pt ions, while the tetrahedral sites formed between BaO3 and BaOCl layers are only occupied by Fe or Co. Moreover, oxygen stoichiometry indicates an average oxidation state for Co and Fe higher than +III, indicating the stabilization of Co4+ and Fe4+. 相似文献
18.
Richard E. Sykora Thomas E. Albrecht-Schmitt 《Journal of solid state chemistry》2004,177(10):3729-3734
The hydrothermal reaction of UO3, WO3, and CsIO4 leads to the formation of Cs6[(UO2)4(W5O21)(OH)2(H2O)2] and UO2(IO3)2(H2O). Cs6[(UO2)4(W5O21)(OH)2(H2O)2] is the first example of a hydrothermally synthesized uranyl tungstate. It's structure has been determined by single-crystal X-ray diffraction. Crystallographic data: tetragonal, space group I4 cm, , , Z=4, MoKα, , R(F)=2.84% for 135 parameters with 2300 reflections with I>2σ(I). The structure is comprised of two-dimensional anionic layers that are separated by Cs+ cations. The coordination polyhedra found in the novel layers consist of UO7 pentagonal bipyramids, WO6 distorted octahedra, and WO5 square pyramids. The UO7 polyhedra are formed from the binding of five equatorial oxygen atoms around a central uranyl, UO22+, unit. Both bridging and terminal oxo ligands are employed in forming the WO5 square pyramidal units, while oxo, hydroxo, and aqua ligands are found in the WO6 distorted octahedra. In the layers, four (UO2)O5 polyhedra corner share with equatorial oxygen atoms to form a U4O24 tetramer entity with a square site in the center; a tungsten atom populates the center of each of these sites to form a U4WO25 pentamer unit. The pentamer units that result are connected in two dimensions by edge-shared dimers of WO6 octahedra to form the two-dimensional [(UO2)4(W5O21)(OH)2(H2O)2]6- layers. The lack of inversion symmetry in Cs6[(UO2)4(W5O21)(OH)2(H2O)2] can be directly contributed to the WO5 square pyramids found in the pentamer units. In the structure, all of these polar polyhedra align their terminal oxygens in the same orientation, along the c axis, thus resulting in a polar compound. 相似文献
19.
Single crystals of NaCoO2 have been successfully synthesized for the first time by a flux method at 1323 K. A single-crystal X-ray diffraction study confirmed the trigonal space group and the lattice parameters , . The crystal structure has been refined to the conventional values R=1.9% and wR=2.1% for 309 independent observed reflections. The electron density distribution of NaCoO2 has been studied by the maximum entropy method (MEM) using single-crystal X-ray diffraction data obtained at 298 K. From the results of the MEM analysis, the strong covalent bonding was clearly observed between Co and O atoms, while no bonding was observed around Na atoms. We also calculated the electron density of NaCoO2 by first principles calculations. The electron density obtained experimentally is in good agreement with the theoretical one. 相似文献