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1.
Cd(NO3)2 undergoes a phase transition at 160°C. The high temperature form is cubic and isomorphic with M(NO3)2 (M = Ba, Ca, Sr, Pb). The crystal structure of the low temperature phase has been solved by X-ray diffraction at 20°C, using 774 independent reflections collected with a 4-circle diffractometer. The dimensions of the orthorhombic unit cell are: Å, b = 15.3692 (35) Å, Z = 8, space group Pca21. The structure has been refined to the final weighted R = 0.044. The cadmium atoms are nearly in a face-centered arrangement. Each cadmium is octahedrally surrounded by six oxygen, the CdO distances varying from 2.34 to 2.46 Å. Each nitrate group belongs through its three oxygens to three different octahedra. The structural change cubic Cd(NO3)2 → orthorhombic Cd(NO3)2 is characterized by a small rotation of NO3 groups in their plane; the face-centered array of cadmium atoms is only slightly modified. The coordination of cadmium atoms changes from 12 to 6, and the approximate doubling of parameter (b) as well as the difference of symmetry can be explained by two different directions of rotation of the NO3 groups situated in the same plane. 相似文献
2.
Josep M. Oliva 《Journal of solid state chemistry》2005,178(4):1023-1029
An ab initio study on the electronic structure of the subnitrides NaBa3N, Na5Ba3N, and Na16Ba6N is performed for the first time. The NaBa3N and Na5Ba3N phases consist of infinite 1∞[NBa6/2] strands composed of face-sharing NBa6 octahedra surrounded by a “sea” of sodium atoms. The Na16Ba6N phase consist of discrete [NBa6] octahedra arranged in a body-cubic fashion, surrounded by a “sea” of sodium atoms. Our calculations suggest that the title subnitrides are metals. Analysis of the electronic structure shows partial interaction of N(2s) with Ba(5p) electrons in the lower energy region for NaBa3N and Na5Ba3N. However, no dispersion is observed for the N(2s) and Ba(5p) bands in the cubic phase Na16Ba6N. The metallic band below the Fermi level shows a strong mixing of N(2p), Ba(6s), Ba(5d), Ba(6p), Na(3s) and Na(3p) orbitals. The metallic character in these nitrides stems from delocalized electrons corresponding to hybridized 5dl6sm6pn barium orbitals which interact with hybridized 3sn3pm sodium orbitals. Analysis of the electron density and electronic structure in these nitrides shows two different regions: a metallic matrix corresponding to the sodium atoms and the regions around them and heteropolar bonding between nitrogen and barium within the infinite 1∞[NBa6/2] strands of the NaBa3N and Na5Ba3N phases, and within the isolated [NBa6] octahedra of the Na16Ba6N phase. The nitrogen atoms inside the strands and octahedra are negatively charged, the anionic character of nitrogens being larger in the isolated octahedra of the cubic phase Na16Ba6N, due to the lack of electron delocalization along one direction as opposed to the other phases. The sodium and barium atoms appear to be slightly negatively and positively charged, the latter to a larger extent. From the computed Ba-N overlap populations as well as the analysis of the contour maps of differences between total density and superposition of atomic densities, we suggest partial covalent bonding between nitrogen and barium atoms along the infinite 1∞[NBa6/2] strands and within isolated [NBa6] octahedra. 相似文献
3.
I. E. Zanin K. B. Aleinikova M. Yu. Antipin M. M. Afanasiev 《Journal of Structural Chemistry》2006,47(1):78-81
Structure of Cd3P2 (P42/nmc, a = b = 8.7390 Å, c = 12.2523 Å) has been solved and refined up to R = 3.78% using precision X-ray diffraction experimental data (λ-MoK α, graphite monochromator on a primary beam, 11529 reflections). Interatomic distances and valence angles are determined. Phosphorus forms a face-centered cubic lattice in which 3/4 tetrahedral voids are occupied by cadmium atoms in the crystal structure. The structure can be described by two equivalent models in which the positions of cadmium atoms, which occupy tetrahedral voids following the “diamond principle,” are preserved, while the remaining free and occupied voids change their places. 相似文献
4.
The complex perovskite BiMn7O12 occurs with two polymorphic structures, cubic and monoclinic. Currently their crystal structures are investigated with high-resolution synchrotron powder X-ray diffraction at room temperature. Rietveld analysis reveals unusual behavior for, respectively, the oxygen and bismuth atoms in the monoclinic and cubic phases. Bond valence calculations indicate that all the Mn atoms in both the phases are in trivalent state. Possible roles of the 6s2 lone-pair electrons of Bi3+ in BiMn7O12 are discussed in comparison with the LaMn7O12 phase that is isomorphic to monoclinic BiMn7O12. Multiple roles of the lone-pair electrons are revealed, causing (i) A-site cation deficiency, (ii) octahedral tilting, (iii) A-site cation displacement, and (iv) Mn3+ Jahn-Teller (JT) distortion. Relationships between the monoclinic and cubic phases are discussed with emphasis on the MnO2 and MnO6 local structural aspects. All Mn atoms in the monoclinic polymorph have distorted coordination consistent with JT-active Mn(III) high spin, whereas for the cubic polymorph, the B-site Mn atoms show regular octahedral coordination. 相似文献
5.
V. A. Lomovskoi B. F. Lyakhov N. Yu. Lomovskaya E. G. Belyaev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(8):1397-1402
The temperature dependences of dissipative loss spectra were studied by the internal friction method for the polycrystalline Pd system and interstitial solid solutions PdH x . Four relaxation processes related to the structural peculiarities of the crystal lattice were observed in Pd; two additional relaxation processes were observed in PdH x solid solutions. The latter were related to the mobility of hydrogen atoms in different phases of the face-centered cubic crystal structure. 相似文献
6.
7.
Danielle R. Jack Matthias Zeller Timothy R. Wagner 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(1):i6-i8
Crystals of dicalcium nitride fluoride, Ca2NF, grown from the melt have been characterized by X‐ray diffraction and were found to have a cubic () structure. Owing to ordering of N and F atoms along all three cell axes, the cell edge is doubled relative to the rocksalt‐type structure reported previously. Residual electron density at an interstitial tetrahedral site was refined as a Frenkel defect of F atoms, giving a final composition of Ca2N(F0.913)oct(F0.087)tet. 相似文献
8.
We have synthesized a new compound with formula Re4As6S3 and characterized its crystal structure by Rietveld powder diffraction methods. Re4As6S3 crystallizes in an face-centered cubic unit cell, space group (no. 216), with lattice constant a=9.8608(1) Å and Z=4. The rhenium atoms form tetrahedral clusters linked via tetrahedral arsenic clusters to produce an NaCl-type arrangement. The oxidation state of rhenium is IV and the number of electrons shared by the rhenium atoms in the cluster is 12. The structure is based on an ordered defect thio-spinel A(1−x)B2X4 where the B-type atoms form tetrahedral clusters. 相似文献
9.
H. Kohlmann G. Renaudin K. Yvon B. Harbrecht 《Journal of solid state chemistry》2005,178(4):1292-1300
The hydrogenation behavior of MgPd3 has been studied by in situ X-ray powder diffraction and by neutron powder diffraction. At room temperature and p ≈500 kPa hydrogen pressure its structure is capable of incorporating up to one hydrogen atom per formula unit (α-MgPd3H≈1), thereby retaining a tetragonal ZrAl3-type metal atom arrangement. Upon heating to 750 K in a hydrogen atmosphere of 610 kPa it transforms into a cubic modification with AuCu3-type metal atom arrangement (β-MgPd3H≈0.7). Neutron diffraction on the deuteride reveals an anion deficient anti-perovskite-type structure (β-MgPd3D0.67, a=398.200(7) pm) in which octahedral sites surrounded exclusively by palladium atoms are occupied by deuterium. Complete removal of hydrogen (480 K, 1 Pa) stabilizes a new binary modification (β-MgPd3, a=391.78(2) pm) crystallizing with a primitive cubic AuCu3-type structure. Mechanical treatment (grinding) transforms both α and β modifications of MgPd3 into a cubic face-centered solid solution Mg0.25Pd0.75 showing a random distribution of magnesium and palladium atoms. 相似文献
10.
U5Re3C8 crystallizes tetragonal in space group P4/mbm with the lattice constantsa=1 131.3(1) pm,c=330.29(7) pm,V=0.4227 nm3 andZ=2 formula units per cell. The structure was determined from single-crystal counter-data and refined to a residual ofR=0.032 for 649 structure factors and 24 variable parameters. It is of a new type with carbon atoms on three different sites with approximately octahedral environment of five uranium and one rhenium or four uranium and two rhenium atoms. The positions of the metal atoms correspond to those of a (slightly distorted) cubic body centered structure as is also found for Ho2Cr2C3, UCr4C4, UMoC2, YCoC, and U2IrC2. 相似文献
11.
A genetic algorithm (GA) coupled with a tight-binding (TB) interatomic potential is used to search for the low-energy structures of medium-sized Ni n (n = 36-40) clusters. Structural candidates obtained from our GA search are further optimized with first-principles calculations. The medium-sized nickel clusters ranging from 36 to 40 atoms are found to favor the double-icosahedron-based structures with a Ni7 core (a pentagonal bipyramidal structure) except Ni38 cluster. The lowest-energy structure of Ni38 can be considered to be a magic cluster, which is a typical face-centered cubic structure with large stability and magnetic moment. 相似文献
12.
The 15N and 31P NMR study of 2-amino 1,3-dimethyl 1,3-diaza 2-phospholanes shows that the cyclic nitrogen atoms approach a pyramidal sp3 structure and the exocyclic nitrogen atoms an sp2 structure. A determination of the factors that govern δ15N and 1J31P—15N is attempted. 相似文献
13.
Xueting Zhang Prof. Lan Hui Dengxin Yan Jinze Li Xi Chen Han Wu Prof. Yuliang Li 《Angewandte Chemie (International ed. in English)》2023,62(40):e202308968
Controlling the structure and properties of catalysts through atomic arrangement is the source of producing a new generation of advanced catalysts. A highly active and stable catalyst in catalytic reactions strongly depends on an ideal arrangement structure of metal atoms. We demonstrated that the introduction of the defect-rich structures, low coordination number (CN), and tensile strain in three-dimensional (3D) urchin-like palladium nanoparticles through chlorine bonded with sp-C in graphdiyne (Pd-UNs/Cl-GDY) can regulate the arrangement of metal atoms in the palladium nanoparticles to form a special structure. In situ Fourier infrared spectroscopy (FTIR) and theoretical calculation results show that Pd-UNs/Cl-GDY catalyst is beneficial to the oxidation and removal of CO intermediates. The Pd-UNs/Cl-GDY for methanol oxidation reaction (MOR) that display high current density (363.6 mA cm−2) and mass activity (3.6 A mgPd−1), 12.0 and 10.9 times higher than Pd nanoparticles, respectively. The Pd-UNs/Cl-GDY catalyst also exhibited robust stability with still retained 95 % activity after 2000 cycles. A defects libraries of the face-centered cubic and hexagonal close-packed crystal catalysts (FH-NPs) were synthesized by introducing chlorine in graphdiyne. Such defect-rich structures, low CN, and tensile strain tailoring methods have opened up a new way for the catalytic reaction of MOR. 相似文献
14.
A. N. Chekhlov 《Journal of Structural Chemistry》2006,47(1):71-77
X-ray spectral analysis has been applied to study the crystal structure of 4,7,13,16,21,24-hexaoxa-1-aza-10-azoniabicyclo[8.8.8]hexacosane isocyanurate of an unusual composition: [H1.2(Crypt-222)]1,2+ · [H0.8(Crypt-222)]0.8+·2(C3H2N3O3)? (I). The structure of I (space group C2/c, a = 37.840 Å, b = 13.760 Å, c = 19.456 Å, β = 91.21°, Z = 8) was solved by a direct method and refined by the full-matrix least-squares technique in the anysotropic approximation up to R = 0.119 over 6500 independent reflections measured (autodiffractometer CAD-4, λ-MoK α). The structure of I has two independent cations of 2.2.2-cryptand linked by the proximate pseudo-center of inversion and they have a rare conformation of exo-exo type, in which H atom or lone pair at both their node atoms N are directed outward their cavity. In the structure of I, all H atoms at N atoms of cations and half of H atoms of isocyanurate anions are disordered and have the populations of positions 0.7, 0.5, and 0.3. There is a developed system of interionic hydrogen bonds in the crystal structure of I. 相似文献
15.
Jun-Long Zhang Ji-Zhou Kong Ai-Dong Li You-Pin Gong Hai-Rong Guo Qing-Yu Yan Di Wu 《Journal of Sol-Gel Science and Technology》2012,64(2):269-275
Superparamagnetic face-centered cubic (fcc) FePt nanoparticles were synthesized using a polyol process. The effect of reaction temperature and molar ratio of Fe(CO)5 to Pt(acac)2 on the structure, composition and morphology of nanoparticles has been investigated. The optimum processing condition has been obtained for producing well-monodisperse fcc-phase FePt nanoparticles with the 2:1?molar ratio of Fe-Pt at 220?°C. In order to circumvent the problem of FePt particle coalescence during high temperature annealing for the L10 ordering, FePt nanoparticle/SiO2-matrix composite films have been fabricated by sol?Cgel method. The experimental results confirm that the amorphous SiO2 matrix effectively inhibits the grain growth and particle aggregation during 700?°C annealing for 1?h. Well-monodisperse face-centered tetragonal (fct) FePt particles embedded in the SiO2 matrix can be obtained with the long-range chemical order parameter S of ~0.74, indicating partially ordered L10 phase transition in FePt/SiO2 composite films. The FePt/SiO2 system exhibits a hysteretic behavior with smaller coercive field of 1,450 Oe. The incomplete phase transition from cubic deredat height maxsium (A 1-disordered phase to tetragonal L10-ordered phase) might be responsible for it. 相似文献
16.
Anion excess colorless fluorite-type strontium-yttrium chloride has been prepared. Single crystals of the SrY compound exhibit a primitive cubic lattice with a = 6.967(1)Å. Two mutually exclusive structural models for solutions, neither of which is exact, are discussed. The first is a vacancy model in which the extra charge which results from substitution of Y3+ for Sr2+ is balanced by the simultaneous removal of a Sr2+Cl? ion pair. This model requires individual ion sites to be partially occupied and nonequivalent and is strongly suggestive of vacancy ordering. Refinement in space group P1, with sites refined independenty, led to R = 0.1096. The second model describes the structure in terms of a Willis cluster of defects and includes both anion vacancies and interstitial anions. Full-matrix least squares refinement in space group Fm3m, with positions analogous to those in UO2.12 and (Ca,Y)F2.10, converged at R = 0.0633 for the 114 face-centered parent structure reflections whose |F|;2 > σ(F2). This second model is discussed in relation to a probable true solution which involves longrange order. 相似文献
17.
N,N,N??,N??-tetramethylethylenediamine is obtained by the reaction of ethylenediamine with formaldehyde and formic acid (the Eschweiler-Clarke reaction) and then alkylated with allyl chloride (or bromide) in a ratio of 1:1 or 1:2 to obtain N-allyl-N,N,N??,N??-tetramethylethylenediaminium and N,N??-diallyl-N,N,N??,N??-tetramethylethylenediaminium bromide respectively. [{C2H4N2(H+)(CH3)4(C3H5)}Cu4Cl6] (1) and [{C2H4N2(CH3)4(C3H5)2}0.5Cu2Cl1.67Br1.33] (2) ??-complexes are obtained from alcohol solutions containing an ethylenediamine derivative and copper(II) chloride by ac-electrochemical synthesis on copper wire electrodes. An XRD study of the complexes is carried out. The crystals are monoclinic; 1: P21/n space group, a = 9.0081(6) ?, b = 12.5608(7) ?, c = 16.8610(10) ?, ?? = 102.061(3)°, V = 1865.7(2) ?3, Z = 4; 2: C2/c space group, a = 14.462(2) ?, b = 12.519(1) ?, c = 12.762(2) ?, ?? = 107.861(5)°, V = 2199.1(4) ?3, Z = 8. The structure of 1 consists of infinite copper halide networks with four crystallographically independent copper atoms, one of which coordinates the double bond of the allyl group of the ligand. The [C2H4N2(H)(CH3)4(C3H5)]2+ cations are attached above and below the plane of the network. The individual fragments are bonded via an extensive system of (N)H??Cl and (C)H??Cl hydrogen bonds. The structure of 2 contains a three-dimensional copper halide framework whose cavities contain the [C2H4N2(CH3)4(C3H5)2]2+ cations that are ??-coordinated with copper(I) atoms. In both structures, the Cu(I) atom that coordinates the C=C bond has a trigonal-pyramidal coordination environment consisting of the double C=C bond of the corresponding ligand and three halogen atoms. The other Cu(I) atoms have a tetrahedral environment consisting solely of halogen atoms. The Cu-(C=C) distance is 1.958(1) ?, (1) and 1.974(1) ? (2). 相似文献
18.
Yu. V. Kokunov Yu. E. Gorbunova G. A. Razgonyaeva S. A. Kozyukhin 《Russian Journal of Coordination Chemistry》2012,38(10):657-661
Coordination compounds [Cd1.5I3(HMTA) · H2O] (I) and [CdI2(HMTA) · H2O] (II) are synthesized by the reaction of CdI2 with hexamethylenetetramine (HMTA, C6H12N4) with the 1: 1 ratio in ethanol, and their structures are determined. The crystals of compound I are triclinic, space group P $ \bar 1 $ , a = 8.027(1), b = 9.391(1), c = 10.382(1)?, ?? = 66.64(1)°, ?? = 86.18(1)°, ?? = 73.63(1)°, V = 749.2(1) ?3, ??calcd = 3.136 g/cm3, Z = 2. The crystals of compound II are triclinic, space group P $ \bar 1 $ , a =7.713(1), b = 8.192(1), c = 12.101(1)?, ?? = 80.32(1)°, ?? = 89.57(1)°, ?? = 7.30(1)°, V = 725.0(1) ?3, ??calcd = 2.402 g/cm3, Z = 2. Structure I includes two types of cadmium complexes. The Cd(1) atom is coordinated through the octahedral mode by three pairs of the I, N(HMTA), and O(H2O) atoms. The coordination polyhedron of the Cd(2) atom is a distorted tetrahedron (three I atoms and one N atom). The structure contains infinite strips consisting of tetranuclear cyclic fragments joined by the Cd(1) atoms due to the bridging iodine and nitrogen atoms. In structure II, the Cd atom is coordinated through the tetrahedral mode by two iodide ions and the N(HMTA) and O(H2O) atoms. The interaction between the complexes occurs due to hydrogen bonds O-H??N to form supramolecular chains along the direction [010]. In each HMTA molecule, one of four nitrogen atoms is a proton acceptor in the hydrogen bonds, one nitrogen atom is coordinated, and two N atoms are terminal. Compound II in the solid state has photoluminescence with maxima at 443, 470, and 518 nm. 相似文献
19.
N. V. Pervukhina S. V. Borisov S. A. Magarill V. I. Vasil’ev N. V. Kuratieva 《Journal of Structural Chemistry》2010,51(4):683-688
The crystal structure of laffittite mineral AgHg(As,Sb)S3 from the Chauvai deposit (Kyrgyzstan), containing about 10% of Sb atoms in the As3+ position, is re-determined (Aa space group, a = 7.7560(3) Å, b = 11.3340(4) Å, c = 6.6650(3) Å, β = 115.233(4)°, V =529.99(4) Å3, d = 6.078 g/cm3, Z = 4, R = 0.0229). Crystallographic analysis of the structure reveales the presence of quite regular face-centered cubic cation and anion sublattices, thus confirming the assignment of the structure to the structural type of PbS. A deviation from the octahedral coordination of cations characteristic of this type is mainly related to a mutual asymmetric displacement of the cation and anion matrices. 相似文献
20.
The NiCl2 and CoCl2 complexes with 4,5-(2-pyridylethylene)-dithio-1,3-dithiol-2-thione (L1) and 4,5-(4-pyridylethylene)-dithio-1,3-dithiol-2-thione (L2) were described. The L1 ligand shows bidentate coordination through the pyridyl N atoms and the thiol S atoms in a tetrahedral [CoCl2(L1)] complex (I) and in an octahedral [NiCl2(L1)2](MeCN)2 complex (II). The L2 ligand exhibits monodentate coordination through the pyridyl N atom in tetrahedral complexes [CoCl2(L2)2 (III) and [NiCl2(L2)2] (IV). Complexes I, III, IV in crystal state are octahedral due to extra coordination of the thione S atoms or the chloride bridges responsible for the polymeric structure. The structure of the complex II · CH2Cl2 was determined by X-ray diffraction analysis. The crystals are monoclinic, space group P21/c, a = 11.895(2) Å, b = 13.374(3) Å, c = 21.873(4) Å, β = 95.30(3)°, Z = 2. The Ni atom has quasi-tetrahedral surrounding due to two chloride ions and two L1 ligands coordinated through the pyridyl N atoms and the thiol S atoms. 相似文献