On the Structure of Tetralead(II) Complexes with OH Bridges

2004 ◽  
Vol 69 (11) ◽  
pp. 2045-2054 ◽  
Author(s):  
Martin Breza ◽  
Stanislav Biskupič
Keyword(s):  
Oxygen Atom ◽  
Electronic Structures ◽  
Apical Position ◽  
Hartree Fock ◽  
Central Oxygen ◽  
Total Charges

Using Hartree-Fock, B3LYP and MP2 treatments, the optimal geometries and corresponding electronic structures of tetrahedral [Pb4(μ3-OH)n]q and [Pb4O(μ3-OH)n]q-2 complex cations with total charges q = 8 - n , n = 2, 3, 4, are investigated. After OH- removal, the central oxygen atom in [Pb4O(μ3-OH)4]2+ is shifted to the apical position in [Pb4O(μ3-OH)3]3+ whereas the [Pb4(μ3-OH)2]6+ and [Pb4O(μ3-OH)2]4+ complex cations are unstable. Direct Pb-Pb and O-O interactions are weakly antibonding in all the systems under study. The clusters are held together exclusively by relatively weak Pb-O bonds. A higher stability of the complex cations with a larger number of OH- bridges may be confirmed.

On the Stability of Hydroxo-Dilead(II) Complex Cations

2003 ◽  
Vol 68 (12) ◽  
pp. 2377-2385 ◽  
Author(s):  
Martin Breza ◽  
Stanislav Biskupič
Keyword(s):  
Aqueous Solutions ◽  
Electronic Structures ◽  
Hartree Fock ◽  
The Stability ◽  
Total Charges

Using Hartree-Fock, B3LYP and MP2 treatments, the optimal geometries and corresponding electronic structures of various isomers of [Pb2(OH)n]q complex cations with total charges q = 4 - n, n = 1, 2, 3, are investigated. [Pb(μ-OH)Pb]3+ seems to be the most stable whereas [Pb(μ-OH)Pb(OH)]2+ and [Pb(μ-OH)Pb(OH)2]+ are unstable (because additional non-bridging hydroxyl weakens the neighboring Pb-Oμ and Oμ-Hμ bonds). Direct Pb-Pb and Oμ-Oμ interactions are weakly antibonding in all the systems under study. The clusters are held together exclusively by relatively weak Pb-O bonds. Non-measurable concentrations of [Pb(μ-OH)Pb]3+ in aqueous solutions might be explained by its reaction with OH- yielding preferably unstable [Pb(μ-OH)Pb(OH)]2+ species.

On the Structure of Boat-Shaped Hexalead(II) Cations with OH Bridges

2004 ◽  
Vol 69 (11) ◽  
pp. 2055-2067 ◽  
Author(s):  
Martin Breza ◽  
Stanislav Biskupič
Keyword(s):  
Electronic Structures ◽  
Water Solutions ◽  
Hartree Fock ◽  
Total Charges

Using Hartree-Fock, B3LYP, and MP2 treatments, the optimal boat-shaped geometries and corresponding electronic structures of [Pb6Om(μ3-OH)n]q complex cations with total charges q = 12 - 2m - n, m = 0 or 1, n = 6 or 8, are investigated. Whereas the [Pb6(μ3-OH)6]6+ cation is unstable, the remaining structures preserve C2v symmetry. Direct Pb-Pb interactions are weakly antibonding in all the systems under study. The clusters are held together exclusively by relatively weak Pb-O bonds. The effects of central O and two additional μ3-OH bridges in [Pb6O(μ3-OH)8]2+ are not fully cooperative. [Pb6O(μ3-OH)6]4+ and [Pb6(μ3-OH)8]4+ may coexist in water solutions in comparable concentrations.

PERIODIC HARTREE–FOCK CALCULATION OF THE OXIDATION OF Si(111)

1999 ◽  
Vol 06 (06) ◽  
pp. 1031-1036 ◽  
Author(s):  
PHILIPPE SONNET ◽  
LOUISE STAUFFER ◽  
CHRISTIAN MINOT
Keyword(s):  
Oxygen Atom ◽  
Local Minimum ◽  
Atomic Oxygen ◽  
Potential Surface ◽  
Early Stage ◽  
Heat Of Adsorption ◽  
Molecular Adsorption ◽  
Hartree Fock

We present Hartree–Fock calculations of the adsorption of oxygen on a Si(111)-(2×2) surface, which models the Si(111)-(7×7) structure, including its two main sites (adatom and rest atom sites). In the most stable configurations, molecules dissociate leading to atomic oxygen bridging the adatom backbonds. The molecular adsorption is less favorable. The dioxygen, however, is a local minimum of the potential surface in two cases: (i) in the "grif" geometry; (ii) bridging between a rest atom and an adatom. It then represents a possible precursor for the early stage of oxidation. The presence of an oxygen atom already adsorbed on the surface enhances the heat of adsorption of other oxygen (atomic or molecular) on the same site.

Darstellung und Kristallstruktur von Lithiumozonid-Ammoniakat (1/5) LiO3 · 5 NH3/Synthesis and Crystal Structure of Lithiumozonide-Ammonia (1/5) LiO3 · 5 NH3

1999 ◽  
Vol 54 (11) ◽  
pp. 1345-1349 ◽  
Author(s):  
Wilhelm Klein ◽  
Martin Jansen
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Cation Exchange ◽  
Liquid Ammonia ◽  
Boiling Temperature ◽  
Synthesis And Crystal Structure ◽  
Central Oxygen

Lithium ozonide has been synthezised starting from cesium ozonide via cation exchange in liquid ammonia and crystallizes at -78°C as an ammoniate, LiO3 · 5NH3. The coarse, ruby red crystals decompose above the boiling temperature of ammonia and are extremely sensitive to moisture. The crystal structure of L iO3 · 5NH3 (P c21n; a = 1231.9(5), b = 637.4(2), c = 1104.8(4) pm; Z = 4; R1 = 4.57%; 1318 independent reflections) consists of lithium tetramine complexes, ozonide anions and non coordinating ammonia molecules. With respect to the arrangement of the complex cations and of the anions there is similarity to the WC type of structure. The central oxygen atom of the ozonide anion is disordered.

Refinement of the structure of Mg2As2O7

1970 ◽  
Vol 48 (6) ◽  
pp. 890-894 ◽  
Author(s):  
C. Calvo ◽  
K. Neelakantan
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Least Squares ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Cell Dimensions ◽  
Central Oxygen ◽  
R Value ◽  
Unit Cell Dimensions

The crystal structure of Mg2As2O7 has been refined by full matrix least squares procedures using 587 observed reflections. The structure of Mg2As2O7 is of the thortveitite type, as reported by Łukaszewicz, with space group C2/m and unit cell dimensions a = 6.567(2) Å, b = 8.524(4) Å, c = 4.739(1) Å, β = 103.8(1)°, and Z = 2. The As—O—As group in the anion appears to be linear but the central oxygen atom undergoes considerable disorder in the plane perpendicular to this group. The AsO bond distances uncorrected for thermal motion are 1.67 Å for the As—O(—As) bond and 1.66 and 1.65 Å for the terminal As—O bonds. The final R value obtained is 0.088.

THE CRYSTAL STRUCTURE AND PHASE TRANSITIONS OF β-Zn2P2O7

1965 ◽  
Vol 43 (5) ◽  
pp. 1147-1153 ◽  
Author(s):  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Oxygen Atom ◽  
Bond Angle ◽  
Thermal Motion ◽  
Mirror Plane ◽  
Red Emission ◽  
Space Group ◽  
Central Oxygen ◽  
Cation Coordination

β-Zn2P2O7 crystallizes in the C2/m space group with lattice parameters a = 6.61 ± 0.01 Å, b = 8.29 ± 0.01 Å, c = 4.51 ± 0.01 Å, β = 105.4° ± 0.2° and z = 2. The anion, P2O7−4, is centered with its mirror plane coinciding with the mirror plane of the space group. The central oxygen atom, however, shows high anisotropic thermal motion and thus it appears that the P—O—P bond angle is linear only as a result of thermal averaging. The cations are found on twofold axes in irregular sixfold coordination and these ZnO6 groups share three edges with neighboring cations. This cation coordination is, therefore, consistent with that predicted from the red emission of β-Zn2P2O7:Mn++.

Crystal structure of Cd2V2O7

1967 ◽  
Vol 45 (20) ◽  
pp. 2297-2302 ◽  
Author(s):  
P. K. L. Au ◽  
C. Calvo
Keyword(s):  
Crystal Structure ◽  
Oxygen Atom ◽  
Lattice Parameters ◽  
The Other ◽  
Distorted Octahedron ◽  
Thermal Activity ◽  
Space Group ◽  
Bond Angles ◽  
Central Oxygen ◽  
Oxygen Atoms

Cadmium pyrovanadate crystallizes in the C2/m space group with lattice parameters a = 7.088(5) Å, b = 9.091(5) Å, c = 4.963(5) Å, β = 103°21(5)′, and z = 2. This crystal is an isostructure of the mineral thortveitite and thus the anion consists of a pair of centrosymmetrically related corner-sharing VO4 tetrahedra while the cation resides within a distorted octahedron of oxygen atoms. The anion has a linear V—O—V group, but, as with the isostructural pyrophosphates, the central oxygen atom shows an anomalously high thermal activity. The V—O bond distances are 1.76 Å for the inner bond and 1.70 Å for the terminal bond. The bond angles about the anion and cation are similar to those found for the other analogues of thortveitite.

scholarly journals On topological materials as photocatalysts for water splitting by visible light

2021 ◽  
Author(s):  
Ahmad Ranjbar ◽  
Hossein Mirhosseini ◽  
Thomas D Küehne
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
Water Oxidation ◽  
Electronic Structures ◽  
Density Functional ◽  
Band Edge ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Hartree Fock ◽  
Topological Materials

Abstract We performed virtual materials screening to identify promising topological materials for photocatalytic water splitting under visible light irradiation. Topological compounds were screened based on band gap, band edge energy, and thermodynamics stability criteria. In addition, topological types for our final candidates were computed based on electronic structures calculated by means of hybrid density functional theory including exact Hartree-Fock exchange. Our final list contains materials which have band gaps between 1.0 eV and 2.7 eV in addition to band edge energies suitable for water oxidation and reduction. However, the topological types of these compounds calculated with the hybrid functional differ from those reported previously. To that end, we discuss the importance of computational methods for the calculation of atomic and electronic structures in materials screening processes.

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