负离子配位多面体生长基元与晶体表面结构(Ⅱ)异质同构晶体表面结构：金刚石(C)与闪锌矿(ZnS)；刚玉(Al2O3)与赤铁矿(Fe2O3)；碘化镉(CdI2)与氯化镉(CdCl2)

本文研究了几种异质同构晶体的表面结构与晶体中负离子配位多面体结晶方位之间的关系,提出了晶体中各族晶面上结构花纹与负离子配位多面体在各族晶面上的显露是互相对应的关系,异质同构晶体中的负离子配位多面体的结构形式、联结方式和结晶方位是完全相同的。故晶体的表面结构花纹亦完全一致,而且晶体的结晶形貌也是十分相似的。     

Structural analysis of anodic alumina films

Structures of amorphous anodic alumina films have been investigated by the X-ray radial distrubution function and the correlation method. The amorphous anodic alumina films are considered to contain AlO₅ coordination polyhedra as well as AlO₄ tetrahedra and AlO₆ octahedra. Two types of conformation are taken into account by the correlation method; one (model A) is the conformation in which the above coordination polyhedra are arranged in a similar way to that found in the crystalline modifications of γ-Al₂O₃ within a short range of r < 4.5 Å and the other (model B) is the conformation in which coordination polyhedra are randomly arranged. The final model formed by mixing these two conformations (model A and B) in 1 : 1 ratio describes quantitatively the observed scattering intensity curves of the amorphous anodic alumina films.     

Distortion of V<Superscript><Emphasis Type="Italic">z</Emphasis>+</Superscript>O<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> coordination polyhedra and parameters of the bond valence model for V-O bonds in inorganic crystals

The dependences of average V-O distances in inorganic compounds of vanadium of different valence on the degree of distortion of coordination polyhedra have been obtained by careful statistical treatment of modern structural data banks. Values of bond lengths in undistorted (regular) polyhedra are recommended. Theoretical analysis of the statistical data made it possible to calculate the most likely values of the parameters of the bond valence model: the interatomic distance for the single (two-electron) bond, corresponding to the single valence, and the bond softness parameter. Calculations of the sums of bond valences for some complicated cases (different coordination numbers, mixed vanadium valence) confirmed reliability of the recommended parameters.     

晶体表面结构和负离子配位多面体生长基元

本文讨论了晶体表面结构和负离子配位多面体结晶方位的关系.指出了晶体表面结构,显示了负离子配位多面体在晶体生长过程中的结晶轨迹.因此,运用负离子配位多面体生长基元理论模型,晶体的生长机制可以通过对晶体表面结构的分析得以解释.     

Geometrical model of the structure of the heterocomplex compound [Cr(OCN2H4)6]3+[Co(DH)2(NO2)2] 3 − ⋅ 2H2O

The structural organization of the new heterocomplex compound with carbamide has been considered on the basis of division of the crystal space into Dirichlet polyhedra of the system of Delone points (centers of the complex ions). It is demonstrated that the coordination numbers for all domains (Dirichlet domains) of the complex ions in the structure obey the “rule of fourteen,” whereas the polyhedra providing the structural organization of the crystal are distorted Fedorov cuboctahedra.     

Short range order in powder of amorphous anodic yttrium oxide

The characteristics of the short-range order in a powder of amorphous yttrium oxide obtained by anodic oxidation are determined by the Finbak-Warren method. It is established that the first coordination number equals seven. Amorphous oxide is built by irregular coordination polyhedra characteristic of the hexagonal and monoclinic modifications of yttrium oxide.     

熔体温度对负离子配位多面体生长基元聚集体结构的影响

据Na2SiO3与BaB2O4晶体和熔体的高温拉曼光谱测试结果综合分析后提出:熔体的温度对负离子配位多面体生长基元相互联结的聚集体结构有影响.在高温熔体中,高电价、离子半径小的阳离子配位多面体往往孤立存在.当熔体过冷度大时,孤立的负离子配位多面体顶角上的氧与低电价、离子半径大的阳离子配位构成大维度的聚集体.同质异构晶体的熔体拉曼谱都显示出相同的孤立负离子配位多面体振动峰.     

Hg X n coordination polyhedra (X = F, Cl, Br, and I) in crystal structures

The crystallochemical analysis of 188 structures containing 252 crystallographic kinds of Hg(II) atoms in Hg X _n coordination polyhedra (X = F, Cl, Br, and I) has been performed by the method of intersecting spheres with the use of Vorono-Dirichlet polyhedra. It was found that halogen atoms surrounded by Hg(II) atoms are characterized by the coordination numbers from 3 to 8. It was demonstrated that, at the unvarying nature of the X atoms, the average Hg-X interatomic distance increases by 0.13–0.57 Å with an increase of the coordination number, whereas the average radius of spheres with the volume equal to that of the Vorono-Dirichlet polyhedron of a Hg atom is either independent of the coordination number (at X = F) or varies with it only by about 0.02–0.07 Å (at X = Cl, Br, and I). This allows the approximation of mercury atoms in the crystal structures by soft (deformable) spheres of a constant volume. Some results obtained in the analysis of the topology and the geometry of [Hg_m X _n ] ^z?-complexes in crystal structures are also presented.     

负离子配位多面体生长基元和晶体形貌

本文运用负离子配位多面体生长基元理论模型讨论了负离子配位多面体在异质同构和同质异构晶体中的结晶方位和其形态之间的关系,发现晶体的生长习性与负离子配位多面体在不同面族上相互联结的稳定性密切相关.负离子配位多面体以顶角相联最稳定,以边相连次之,以面相连最不稳定.同时,本文用负离子配位多面体生长基元理论模型对极性晶体ZnO和ZnS的生长习性也做了一定的解释.     

Neutron and X-ray scattering studies of Li2O–TeO2–V2O5 glasses

Neutron and X-ray scattering studies of (Li₂O)_x–(TeO₂)₂–V₂O₅ glasses with x = 0, 1 and 2, obtained by melting and subsequent cooling in air to room temperature, have been performed. Reciprocal space data have been Fourier transformed into real space yielding the radial distribution functions. Nearest and next neighbor peaks have been analyzed using a least-squares fitting method which suggests the presence of both TeO₃ and TeO₄ coordination polyhedra, the fivefold coordination of lithium and mixture of 6, 5 and 4 coordination numbers of vanadium. These results are discussed in relation to the electronic and ionic conductivity properties.     

Evolution of the calcium hydroxyapatite crystal structure under plasma deposition and subsequent reducing treatment

The structure of hydroxyapatite plasma coatings on a titanium substrate has been investigated by the X-ray Rietveld method. The hydroxyapatite crystal structure in plasma-deposited samples is characterized by strong distortions of its main element (tetrahedral PO₄ cluster) and coordination calcium polyhedra, as well as calcium deficit in the Ca2 site; however, these features do not change the main motif of the hydroxyapatite structure. The bond distortions in PO₄ clusters are estimated by the Bauer method. It is shown that hydrothermal treatment leads to the almost complete recovery of the hydroxyapatite structure.     

Molecular dynamics simulation of high-pressure densification of fluorozirconate glass

Molecular dynamics simulations have been performed for a fluorozirconate glass and its model crystals in order to investigate the mechanism of the peculiar high-pressure densification phenomenon of the glass. All the polymorphs and the pressure-induced phase-transition of the model crystals were satisfactorily reproduced. The changes in the density, the F⁻ coordination number and the connectivity of ZrF_n polyhedra during the compression-decompression process are investigated under the glassy state. The density increases under high pressure, accompanying the increases in the coordination number and the connectivity. The effect of annealing treatment near T_g is also investigated. The effect was significant around 20 GPa, around which a maximum was found in the treatment-pressure dependence of density after decompression, only for the samples with the annealing treatment before decompression.     

Specific structural features of copper(II) complexonates with nitrilotriacetate anions: A review

The specific structural features of copper(II) complexes with nitrilotriacetate anions (H_n Nta, n = 0?2) are considered with due regard for the original results and data available in the literature. The structural features and the degree of distortion of copper coordination polyhedra (such as a (4 + 1) elongated square pyramid, a trigonal bipyramid, a (4 + 2) symmetric elongated tetragonal bipyramid, and a (4 + 1 + 1) asymmetric elongated tetragonal bipyramid) are discussed. Criteria for identification of five-vertex copper(II) polyhedra of the general formula Cu(H_n Nta)X (n = 0?2; X = Cl, Br, N, O) are proposed for the cases of a distorted square pyramid, a distorted trigonal bipyramid, and a polyhedron intermediate between them. The modes of coordination of H_n Nta ^{3 ? n} ligands with a mctal arc described in terms of crystal chemical formulas.     

The structures and vibrational spectra of crystals and glasses in the silica-alumina system

Solar furnace melting and fast-quench techniques have been used to prepare SiO₂Al₂O₃ glasses to high alumina content (near 60 mol% Al₂O₃), which have been studied by Raman spectroscopy. These spectra may not be simply interpreted. The structures of crystalline compounds in the SiO₂Al₂O₃ system are discussed in relation to their vibrational spectra. On the basis of this discussion and other considerations, a structural model for the silica-alumina glass system is proposed, which is consistent with the stable or metastable immiscibility suggested along this join. The essential features of this model include a modified silica structure at low alumina content, and “structure-broken” regions at high alumina compositions, with silicon in tetrahedral coordination, but aluminium assuming a variety of bonding geometries. These are proposed to include aluminate tetrahedra with higher polymerization than simple corner-sharing, and less well-defined polyhedra of higher average coordination number.     

共生晶体Mn2Hg4(SCN)12和MnHg(SCN)4的形成

采用恒温蒸发法从水溶液中生长Hg2+、Mn2+为双配位中心的SCN- 的配合物晶体.生长液中Hg2+含量较SCN-适当过量的条件下,出现Mn2Hg4(SCN)12晶体和MnHg(SCN)4晶体共生现象.MnHg (SCN)4晶体中Hg2+只与SCN-配位,Mn2+只与NCS-配位,而Mn2Hg4(SCN)12晶体中部分Hg2+可以同时与SCN-和NCS-配位体结合,并且部分SCN-同时和2个Hg2+结合成桥式结构.Mn2Hg4(SCN)12晶体中Mn2+的配位数由MnHg(SCN)4晶体中的4配位增大为5配位和6配位.Mn(NCS)4-6 和Mn(NCS)3-5 配位多面体的存在使Mn2Hg4(SCN)12晶体的颜色比MnHg(SCN)4晶体的颜色浅.     

Specific features of nonvalent interactions in orthorhombic perovskites

It is established that isostructural orthorhombic perovskites ABO₃ (sp. gr. Pnma in different systems, no. 62, Z = 4), depending on the specificity of nonvalent interactions (which determine the combinatorial-topological type of the Voronoi-Dirichlet polyhedra (VDPs) of four basis atoms), are divided into ten different stereotypes. It is shown by the example of 259 perovskites belonging to the DyCrO₃ stereotype that VDP characteristics can be used to quantitatively estimate the distortion of BO₆ octahedra, including that caused by the Jahn-Teller effect. It is found that one of the causes of the distortion of the coordination polyhedra of atoms in the structure of orthorhombic perovskites is heteroatomic metal-metal interactions, for which the interatomic distances are much shorter than the sum of the Slater radii of A and B atoms.     

Structural chemistry of oxoperoxo complexes of vanadium(V): A review

This paper presents a review of the structural features of monomeric, dimeric, and polymeric oxoperoxo complexes of vanadium(V). The structural manifestations of the trans effect of multiply bonded oxo and peroxo ligands in pseudooctahedral oxo monoperoxo complexes of vanadium(V) are compared. The dependence of the geometric parameters of the structural fragment V(O₂)_n (n = 1, 2) (V-O, O-O bond lengths; OVO angles) on the type of coordination seven-vertex polyhedron (pseudooctahedron, n = 1; pseudotrigonal bipyramid, n = 2) of the metal atom is analyzed. Regular distortions of the coordination polyhedra of vanadium atoms (pseudooctahedron, pseudotrigonal bipyramid, pseudotetragonal pyramid, pseudotetrahedron) are considered.     

Synthesis and Crystal Structure of bis [2-(3-(2-((2-Hydroxybenzylidene) Amino)Ethyl)Oxazolidin-2-yl)Phenol]Cerium (IV) 1,4-Dioxane Monosolvate

The metal complex, bis [2-(3-(2-((2-hydroxybenzylidene)amino)ethyl) oxazolidin-2-yl)phenol]cerium(IV) 1,4-dioxane monosolvate was synthesized and characterized by infrared, ¹H NMR, elemental analysis, single-crystal, and powder X-ray diffraction. The coordination polyhedra of cerium shows a distorted square-antiprismatic geometry. No classical hydrogen bonds were observed. The crystal packing was influenced by weak C-H···O (intermolecular) and van der Waals interactions.     

Aquanitrilotris(methylenephosphonato)dirubidium [Rb<Subscript>2</Subscript>(H<Subscript>2</Subscript>O){μ<Superscript>12</Superscript>-NH(CH<Subscript>2</Subscript>PO<Subscript>3</Subscript>H)<Subscript>3</Subscript>}]: Synthesis and structure

Aquanitrilotris(methylenephosphonato)dirubidium is a 3D coordination polymer with a layer structure. Space group \(P\bar 1\), Z = 2; a = 8.0380(3) Å, b = 9.0522(4) Å, and c = 10.7837(4) Å; α = 113.252(4)°, β = 105.391(3)°, and γ = 96.182(3)°. Rb atoms populate two symmetrically inequivalent positions with c.n. = 8 and 10; significant difference in O–Rb–O angles in the coordination polyhedra is indicative of the ionic type of Rb–O bonds. In the crystal packing, molecules are connected by not only coordination bonds but hydrogen bonds as well.     

Morphogenesis of crystal structures in the discrete modeling of packings

Within the framework of the discrete modeling of molecular packings, a metric approach to the investigation of the mechanisms of crystal formation is proposed. This method is based on the construction of a combination of polyhedra in a space in which the space division into polyhedra (or the periodic packing of polyhedra) is specified by the multistage addition to the initial “seeding” polyhedron set of this division (packing) of the adjacent polyhedra. Crystal growth is modeled using the constructions of bounding boxes in the division of the plane into polyominoes and the three-dimensional space, into polycubes. The formation of phenomenological polygons (polyhedra) in the growth of periodic structures is revealed and theoretically grounded.