Refinement of the crystal structure of terbium arsenate TbAsO<sub>4</sub> at 77 K and 5 K by profile analysis from neutron diffraction powder data

Schäfer, Wolfgang; Will, G.; Müller‐Vogt, G.

doi:10.1107/s0567740879004210

Cited by 19 publications

(5 citation statements)

References 4 publications

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“…All calculations at the 6-311+G(3df) basis set give bond lengths close to experimental values of solid oxyanions − (Table ), with increasing deviation for oxyanions of larger charge. This discrepancy results from the larger charge difference between free oxyanion molecules and those of the solid bulk, where charge is neutralized.…”

Section: Resultssupporting

confidence: 64%

Intramolecular Bonding and Charge Distributions in XO₄(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

Boily

2002

J. Phys. Chem. A

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Intramolecular X−O bonds and charge distributions in XO4 (X = Si, P, S, Cl, and Ge, As, Se, Br) oxyanions were investigated with topological analyses of the electron density in the frameworks of the theories of atoms in molecules (AIM) and of the electron localization function (ELF). The optimized geometries and wave functions of all oxyanions were obtained at the B3LYP/6-311+G(3df) level. AIM analyses recover a significant concentration of electrons at (3,−1) bond critical points increasing from SiO4 4- (0.12 au) to ClO4 - (0.37 au) and from GeO4 4- (0.14 au) to BrO4 1- (0.27 au). Perchlorate is the only oxyanion exhibiting true shared interactions in the sense of AIM with a large and negative Laplacian of the electron density at the bond critical point. All other oxyanions are intermediate to shared and closed-shell interactions with positive values of the Laplacian of the electron density. ELF analyses tend to support the conclusions of AIM by localizing disynaptic basins between 3rd row X atoms and O with electron populations ranging from 1.56e (SiO4 4-) to 1.84e (ClO4 1-). The X−O bonds are also shown to be of donor−acceptor type. Fourth row oxyanions have highly delocalized and small disynaptic basin populations ranging from 0.27e (AsO4 3-) to 0.30e (BrO4 1-) with GeO4 4- as the only oxyanion without any formally defined disynaptic basin. The attractive forces in these oxyanions are thus mostly of electrostatic nature. All ELF disynaptic basins have strong cross-contributions with the lone pair monosynaptic valence basins of O. These latter basins contain about three electron pairs (6.12e) for ClO4 1- to about four (7.99e) for GeO4 4-. Finally, the Merz−Kollman scheme was used to determine point charges that can reproduce the electrostatic potential of the oxyanions. Their values are however notably different than those obtained by AIM.

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Section: Resultssupporting

confidence: 64%

Intramolecular Bonding and Charge Distributions in XO₄(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

Boily

2002

J. Phys. Chem. A

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“…K[Al(BH 4 ) 4 ] crystallizes in the orthorhombic space group Fddd , as the LT-TbAsO 4 prototype, with BH 4 – anions in place of oxygen atoms. The LT phase of TbAsO 4 (stable below 27.7 K) is an orthorhombic deformation of the tetragonal HT phase ( I 4 1 / amd , ZrSiO 4 type) caused by the Jahn–Teller effect.…”

Section: Resultsmentioning

confidence: 99%

The First Halide-Free Bimetallic Aluminum Borohydride: Synthesis, Structure, Stability, and Decomposition Pathway

et al. 2013

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Interaction of solid KBH 4 with liquid Al(BH 4 ) 3 at room temperature yields a solid bimetallic borohydride KAl(BH 4 ) 4 . According to the synchrotron X-ray powder diffraction, its crystal structure (space group Fddd, a = 9.7405(3), b = 12.4500(4), and c = 14.6975(4) Å) contains a substantially distorted tetrahedral [Al(BH 4 ) 4 ]− anion, where the borohydride groups are coordinated to aluminum atoms via edges. The η -coordination of BH 4− is confirmed by the infrared and Raman spectroscopies. The title compound is the first aluminum-based borohydride complex not stabilized by halide anions or by bulky organic cations. It is not isostructural to bimetallic chlorides, where more regular tetrahedral AlCl 4 − anions are present. Instead, it is isomorphic to the LT phase of TbAsO 4 and can be also viewed as consisting of two interpenetrated dia-type nets where BH 4 ligand is bridging Al and K cations. Variable temperature X-ray powder diffraction, TGA, DSC, and TGA-MS data reveal a single step of decomposition at 160°C, with an evolution of hydrogen and some amount of diborane. Aluminum borohydride is not released in significant amounts; however, some crystalline KBH 4 forms upon decomposition. The higher decomposition temperature than in chloride-substituted Li−Al (70°C) and Na−Al (

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“…The larger rare-earth (La-Nd) arsenates crystallise in the monoclinic monazite structure 8,9 while the tetragonal zircon-type structure is found for the smaller members of the series. 10 LaAsO 4 has the highest thermal stability within the LnAsO 4 series of compounds, 8 but the orthoarsenates are in general less stable than their ortho-phosphate counterparts with respect to evaporation of gaseous oxides. 11 Although the literature on the structural, vibrational, dielectric and thermodynamic properties of rare-earth arsenates is significant, [8][9][10][11][12][13][14][15][16] reports of their electrical and defect chemical properties are scarce.…”

Section: Introductionmentioning

confidence: 99%

“…10 LaAsO 4 has the highest thermal stability within the LnAsO 4 series of compounds, 8 but the orthoarsenates are in general less stable than their ortho-phosphate counterparts with respect to evaporation of gaseous oxides. 11 Although the literature on the structural, vibrational, dielectric and thermodynamic properties of rare-earth arsenates is significant, [8][9][10][11][12][13][14][15][16] reports of their electrical and defect chemical properties are scarce. 12 Pradhan and Choudhary 12 investigated the electrical conductivity of nominally undoped, polycrystalline LaAsO 4 below 200 C, which they, based on a high activation energy, attributed to transport of unspecified ionic species.…”

Section: Introductionmentioning

confidence: 99%

Hydration and proton conductivity in LaAsO₄

2012

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Refinement of the crystal structure of terbium arsenate TbAsO₄ at 77 K and 5 K by profile analysis from neutron diffraction powder data

Cited by 19 publications

References 4 publications

Intramolecular Bonding and Charge Distributions in XO₄(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

Intramolecular Bonding and Charge Distributions in XO₄(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

The First Halide-Free Bimetallic Aluminum Borohydride: Synthesis, Structure, Stability, and Decomposition Pathway

Hydration and proton conductivity in LaAsO₄

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Refinement of the crystal structure of terbium arsenate TbAsO4 at 77 K and 5 K by profile analysis from neutron diffraction powder data

Cited by 19 publications

References 4 publications

Intramolecular Bonding and Charge Distributions in XO4(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

Intramolecular Bonding and Charge Distributions in XO4(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

The First Halide-Free Bimetallic Aluminum Borohydride: Synthesis, Structure, Stability, and Decomposition Pathway

Hydration and proton conductivity in LaAsO4

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Refinement of the crystal structure of terbium arsenate TbAsO₄ at 77 K and 5 K by profile analysis from neutron diffraction powder data

Intramolecular Bonding and Charge Distributions in XO₄(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

Intramolecular Bonding and Charge Distributions in XO₄(X = Si, P, S, Cl and Ge, As, Se, Br) Oxyanions from Topological Analyses of the Electron Density

Hydration and proton conductivity in LaAsO₄