Respective Lattice Constants Research Articles

Band gap formation in thin plates with a periodic array of resonators

A resonator assembly consisting of a two-dimensional periodic array (mass-screws) mounted to a thin homogenous plate was used to investigate the vibration characteristics of locally resonant (LR) phononic plates. The numeric simulations employed the finite element method to calculate the band structures of the proposed periodic plates and to analyze the effect of geometry parameters on the evolution of the flexural band gap behavior. To experimentally validate the predictions for these theoretical examinations, two measurements with the LR phononic plates were obtained with respective lattice constants a = 40 and 50 mm. The tested plate was clamped on one side to a shaking table to generate a plane wave, propagating in the Ox-direction. Obtained experimental measurements of the wave attenuation in this direction are in good agreement with the theoretical frequency of both complete and directional band gaps.

Optical Properties of Er3+-Doped CdIn2O4 and CdIn2O4 Crystals

CdIn2O4 and CdIn2O4:Er3+ crystals were grown by solid-state sintering of CdO and In2O3 with ErCl3. X-ray diffraction analysis revealed that CdIn2O4 and CdIn2O4:Er3+ adopt a cubic structure with respective lattice constants of a=9.1655 Å and a=9.1662 Å. The optical absorption spectra obtained near the fundamental absorption edge showed that these compounds have a direct energy band gap. The photoluminescence (PL) spectra of CdIn2O4:Er3+ acquired in the wavelength range of 630–700 nm at 294 K showed peaks in the region of 651–686 nm and eight sharp emission peaks due to the Er3+ ions. These PL peaks were attributed to radiative transitions between the split electron energy levels of the Er3+ ions occupying the In3+ sites of the CdIn2O4 host lattice.

Temperature dependent structure of spider silk by X-ray diffraction

We have investigated the structure of spider dragline silk by X-ray diffraction over a broad temperature range from room temperature up to thermal denaturation conditions. The dominating signal from the β-sheet crystallites is analyzed. Pronounced changes of scattering intensity starting at temperatures around 150 °C are observed. These changes are discussed in view of the respective lattice constants, crystal size, size distribution, crystallite number density and amino acid composition.

Studies of Monothiomalonamide and its Palladium(II) and Platinum(II) Complexes

A project related to the crystal engineering of hydrogen bonded coordination complexes has been initiated and our first results are presented here. The cis and trans forms of monothiomalonamide (LH2) have been fully characterized by vibrational spectroscopy, thermal techniques and single-crystal X-ray diffraction. The cis form crystallizes in the monoclinic space group P21/c and the trans form in the monoclinic space group C2/c. The respective lattice constants are a = 5.602(3), b = 9.055(2), c = 10.945(5)Å , β = 101.29(2)" (cis-LH2) and a = 20.336(7), b = 4.317(1), c = 12.432(5) Å, β = 92.16(1)" (trans-LH2). The new complexes [Pd(LH2)4]X2 (X = Cl, Br), [Pt(LH2)4]X2 (X = Br, I), [PdX2(LH2)2] (X = Cl, Br, I) and [PtX2(LH2)2] (X = Cl, I) were prepared and characterized by elemental analyses and spectroscopic (IR, far-IR, Raman) studies. All data are discussed in terms of the nature of bonding in conjunction with assigned structures. The LH2 molecule behaves as a monodentate ligand binding through the sulfur atom. Monomeric square planar structures are assigned for the metal complexes in the solid state; the 1:2 complexes have the trans geometry. A detailed comparison of the new complexes with the corresponding monothiooxamide complexes is also presented.

Synthesis, characterization, and structural analyses of two cyanide-bridged bimetallic complexes

The crystal structures of two bimetallic cyanide-bridged lanthanide (Ln) complexes were obtained by means of three-dimensional single-crystal X-ray diffraction techniques. The isostructural complexes (DMF)4(H2O)3LaFe(CN)6·H2O (I) and (DMF)4(H2O)3CeFe(CN)6·H2O (II) crystallize in the monoclinic system with Z=4 having respective lattice constants of a=17.660(2), 17.633(4); b=8.952(1), 8.920(2); c=20.017(2), 19.950(4)Å; and β=95.68(1), 95.72(3). In each complex, the coordination about the central lanthanide ion is eight in a square antiprism arrangement while the coordination about the iron(III) ion is six, oriented octahedrally. Molecules in the crystal lattice of each complex are held together by normal van der Waals forces and a network of hydrogen bonding. Characterization includes physical property determinations, conoscopic studies, thermal gravimetric analyses (TGA), and IR spectrometric identifications. Select geometric parameters are tabulated and a synthesis of these compounds is presented.

SYNTHESIS, CHARACTERIZATION AND STRUCTURAL ANALYSES OF THREE LANTHANIDE CYANIDE-BRIDGED COMPLEXES

Three lanthanide (Ln) complexes (DMF)4(H2O)3LnFe(CN)6 · H2O, where Ln = Er, Yb, and Lu, were structurally determined by means of three-dimensional single-crystal X-ray diffraction analysis. These systems crystallize in the centrosymmetric monoclinic space group P21/c (No. 14) with Z = 4 and respective lattice constants of a = 13.956(2), 13.952(1), 13.937(3); b = 8.867(4), 8.864(1), 8.862(2); c = 24.857(3), 24.812(2), 24.770(5) Å; and β = 96.30(1)°, 96.33(1)°, 96.30(3)°. Final least-squares full-matrix refinements based on 3499, 3367, and 2555 unique reflections yielded reliability (R) index factors of 0.071, 0.051, and 0.032, respectively. In each complex, the coordination about the central Ln ion is eight in a square-antiprism arrangement and the coordination about the Fe ions is six, oriented octahedrally. Cyanide bridging links the Ln ions to the FeC6 groups. Molecules in the crystal lattice of each complex are held together by van der Waals forces and a network of hydrogen bonding. Characterization includes physical property determinations, conoscopical studies, thermal gravimetric analyses, and IR spectrometric identifications. Selected bond lengths and angles are tabularized and a synthesis of these compounds is presented.

Preparation, characterization, and structural determination of cubic and triclinic tris (tetra-n-butylammonium) hexakisisothiocyanatoscandate (III)

Crystallographic structural refinements of the cubic (I) and triclinic (II) forms of [(n-C4H9)4N]3[Sc(NCS)6] have been carried out by means of three-dimensional single-crystal X-ray diffractometry. The cubic form crystallizes in space group Pa3 (No. 205, Z=8) and the triclinic form crystallizes in P1 (No. 2, Z=2). The respective lattice constants are a=24.630(4) Å (I) and a=12.232(2), b=12.655(3), c=22.337(4) Å, α=90.48(3), β=90.92(3), γ=96.73(3)° (II). A full-matrix least-squares refinement program yielded final reliability (R) factors of 0.088 and 0.061 based on 1078 and 4660 unique reflections, respectively. In both complexes, the molecular units consist of three separate cationic tetra-n-butylammonium groups and an independent hexakisisothiocyanatoscandium anionic group. The n-butyl ligands are coordinated tetrahedrally to the ammonium–nitrogen atoms and the near linear six thiocyanate ligands coordinate octahedrally through the nitrogen atoms to the scandium metal center atoms. Characterizations include physical property determinations and spectrometric identifications employing I.R., 1H and 13C NMR and X-ray powder analyses. Selected bond distances and angles as well as syntheses and peripheral studies are presented and discussed.

Structural determination of hexagonal and orthorhombic EuKRu(CN) 6·4H 2O

Crystallographic structural refinements of hexagonal and orthorhombic EuKRu(CN) 6·4H 2O have been carried out by means of three-dimensional single-crystal X-ray diffractometry. The hexagonal form crystallizes in the space group P6 3/ m ( Z = 2) and the orthorhombic form crystallizes in the Cmcm space group ( Z=4). The respective lattice constants are a = 7.364(1), c = 13.779(3) A ̊ and a = 7.481(1), b = 12.858(3) and c = 14.357(1) A ̊ . A full-matrix least-squares refinement program yielded final reliability ( R) factors of 0.053 and 0.032 based on 496 and 876 unique reflections, respectively. In both structures, the RuC 6 groups are octahedrally oriented. In the hexagonal form, Eu atoms are nine-coordinate, EuN 6(H 2O) 3, and in the orthorhombic form, Eu atoms are eight-coordinate, EuN 6(H 2O) 2. Cyanide bridging links these Eu groups to the RuC 6 groups in both compounds building an infinite polymeric array with cavities within the structures. The cavities are occupied by K ions and uncoordinated zeolitic-type water molecules. Important bond distances and angles are tabulated.

Structural analyses of two hexacyanoruthenate(II) complexes

Refinements of the crystallographic structures of GdKRu(CN) 6·4H 2O and TbKRu(CN) 6·4H 2O have been carried out by means of three-dimensional single-crystal X-ray diffractometry. These ruthenate(II) complexes crystallize in the orthorhombic space group Cmcm ( Z=4) with respective lattice constants of a = 7.460(2) and 7.440(2), b = 12.845(2) and 12.807(2), and c = 14.334(5) and 14.293(3) A ̊ . The structural data were anisotropically refined using a full-matrix least-squares program. The final reliability ( R) factors of 0.024 and 0.030 were based on 1070 and 1070 unique reflections for the Gd and Tb complexes, respectively. The eight-coordinated lanthanide (La) atoms are bonded to six cyanonitrogen atoms and two water molecules in a square-antiprism geometry ( D 4 d ), the LnN 6(H 2O) 2 group. The ruthenium ions are trahedrally coordinated to six cyanocarbon atoms, the RuC 6 group. Cyanide bridging links these groups to build an infinite polymeric array. Cavities within the structures are occupied by K ions and uncoordinated water molecules. The latter are within hydrogen bonding distance to the coordinated water molecules. Notable bond lengths and angles have been tabulated and infrared and thermal gravimetric studies are presented.

Structural investigations of several LnVO 4 compounds

Refinements of the crystallographic structures of SmVO 4, EuVO 4, GdVO 4 and DyVO 4 have been carried out by means of three dimensional single-crystal X-ray diffractometry. These orthovanadate compounds crystallize in the tetragonal space group 14 1/ amd (Z = 4) with respective lattice constants of a = 7.2647(9), 7.2358(7), 7.2122(7), 7.1429(8) A ̊ and c = 6.384(1), 6.362(1), 6.346(2), 6.300(2) Å. Anisotropic refinements of the structural data using a full-matrix least-squares program yielded final reliability ( R) factors of 0.026, 0.049, 0.042 and 0.041 based on 266, 273, 261 and 220 unique reflections for Ln = Sm, Eu, Gd and Dy, respectively. The lanthamide (Ln) atoms are eight-coordinated to oxygen atoms with two unique LnO bond lengths. These non-equivalent vertices form two bisphenoidal sets. A distorted triangulated dodecahedron is produced by connecting the oxygen vertices. The orthovanadate group in each compound is a distorted tetrahedron. Important crystal data, parameters, bond lengths and angles are tabulated.

Synthesis, Spectroscopic and Single-Crystal Structural Investigations of Several Mixed Metal Hexacyanocobaltate Dodecahydrates

Single crystals of Tr1.5 Zn1.5|Co(CN)6|2 · 12H2O (where divalent Tr = Cd, Mn, and Co) have been synthesized by the slow diffusion method. Each mixed metal complex crystallized in the cubic space group Fm3̄m (O5h, No. 225) with respective lattice constants of 10.5312(6), 10.3265(7), and 10.2566(14) Å. The disordered structures contain 113 molecules in each unit cell. All atoms in each system are disordered and the divalent Tr/Zn atoms are linked to the Co atoms by cyanide bridging. Anisotropic refinements of the structures using a full-matrix least-squares program yielded reliability factors of 0.038, 0.034, and 0.034, respectively. Important bond lengths are presented as well as the results from optical, thermal gravimetric, and infrared studies.

New zirconium chloride cluster phases with the stoichiometries Zr 6Cl 12Z and Zr 6Cl 14Z that are stabilized by interstitial atoms ( Z = H, Be, B, C)

The syntheses of the following compounds from Zr, Zr X 4, the interstitial Z = H, Be, B, or C, and M′Cl (where appropriate) are reported together with their respective lattice constants: Zr 6 X 12H ( X = Cl or Br), Zr 6Cl 12Be, Zr 6Br 12B, Cs 2ZrCl 6 · Zr 6Cl 12 Z ( Z = H or Be), Zr 6 X 14C ( X = Cl or Br), Zr 6Cl 14B, MZr 6Cl 14B ( M = LiCs or Tl), and CsZr 6Br 14C. A number of attempted syntheses of MZr 6Cl 14 Z phases in which other Z elements could not be encapsulated are also listed. Single-crystal X-ray diffraction data for Zr 6Cl 14C and Zr 6Cl 14B were also collected and refined ( Cmca, Z = 4, Nb 6Cl 14 structure, a = 14.091 (8), 14.243 (1)Å, b = 12.595 (5), 12.640 (2)Å, c = 11.506 (5), 11.546 (1)Å, R = 4.5, 6.1%, respectively). Both the oversized cavity available for the hydride interstitial and the consequences of a matrix effect on dimensions and stability of Zr 6 X 14C structures when X is changed from chlorine to iodine are discussed.

Crystal structures of Pr(OH) 3, Eu(OH) 3 and Tm(OH) 3

The crystal structures of Pr(OH) 3, Eu(OH) 3 and Tm(OH) 3 have been determined from single-crystal, X-ray diffraction data. The hexagonal form of these lanthanide trihydroxides crystallizes in the space group P6 3/ m( C 6 h 2) with two formula units per unit cell. The respective lattice constants for the trihydroxides of Pr, Er and Tm are a 0 = 6.456(1), 6.352(1), and 6.221(1) A ̊ and c 0 = 3.769(1), 3.653(1), and 3.503(2) A ̊ . The metal atom of each is 9-coordinate with two unique MO bond distances and three independent OO bond distances. These isotypic compounds have been refined to conventional residual index values of 0.0320, 0.0280 and 0.0199, respectively. Fluorescence and IR data were collected on each of the isomorphous compounds. Refined parameters from this investigation have been added to earlier studies on structural trends in the lanthanide trihydroxides.

The effect of pressure on A 2BX 6 halides, contrary to the effect of pressure on ABX 3 halides

The compounds Cs 2GeF 6, Rb 2SiF 6 and Cs 2ZrCl 6 with K 2PtCl 6 c-structure transform under the influence of pressure to phases with K 2MnF 6 hc-structure. The respective lattice constants of the unit cells are a = 6.124 ± 0.006 A ̊ , c = 10.021 ± 0.007 A ̊ ; a = 5.90 ± 0.02 A ̊ , c = 9.59 ± 0.03 A ̊ ; a = 7.37 ± 0.01 A ̊ , c = 12.02 ± 0.02 A ̊ . The fraction of hexagonally stacked AX 3-layers thus increases with pressure contrary to what was found for ABX 3 halides.