Tetrahedral molecular geometry

About: Tetrahedral molecular geometry is a research topic. Over the lifetime, 1795 publications have been published within this topic receiving 30706 citations.

Large Thermal Conductivity Drops in the Diamondoid Lattice of CuFeS2 by Discordant Atom Doping

Abstract: Doping in a lattice refers to the introduction of very small quantities of foreign atoms and has a generally small effect on decreasing the lattice thermal conductivity, unlike alloying which involves large fractions of other elements and strongly enhances point defect phonon scattering. Here, we report that, by alloying only 3% of In on the Cu sites of the diamond-like lattice of CuFeS2 chalcopyrite compound (Cu1-xInxFeS2, x = 0.03) has a disproportionally large effect in reducing the lattice thermal conductivity of the compound from 2.32 to 1.36 Wm-1K-1 at 630 K. We find that In is not fully ionized to +3 when on the Cu sublattice and exists mainly in the +1 oxidation state. The 5s2 lone pair of electrons of In+ makes this atom incompatible (referred to as discordant) with the tetrahedral geometry of the crystallographic site. This causes strong local bond distortions thereby softening the In-S and Cu-S chemical bonds and introducing localized low frequency vibrations. The latter couple with the base phonon frequencies of the CuFeS2 matrix enhancing the anharmonicity and decreasing the phonon velocity, and consequently the lattice thermal conductivity. The control material in which the In doping is on the Fe3+ site of the structure at the same doping level (and found in the site-compatible In3+ state), has a far smaller effect on the phonon scattering.

Structure of Dimeric Molybdenum(VI) Oxide Species on γ-Alumina: A Periodic Density Functional Theory Study

Abstract: The structure and stability of dimeric Mo(VI) oxide species on γ-alumina are investigated with a periodic DFT approach. A large number of Mo dimers of various geometries, located on the (100) and (110) surfaces of γ-Al2O3, are modeled. The most stable dimeric species on the (100) plane are mixed dioxo−monooxo or double-monooxo species that are 3-, 4-, or 5-fold bonded to the surface. In most cases, the molybdenum atoms are pseudotetrahedrally coordinated. In the case of the (110) surface, the most stable dimeric Mo(VI) forms are double-monooxo species, which are 6- or 5-fold bonded to the support. The coordination of the molybdenum atoms is most frequently a distorted square pyramidal, but distorted octahedral or distorted tetrahedral geometry also happens. The energetic stability of the dimeric Mo(VI) species, relative to the corresponding monomeric Mo(VI) centers, is determined. On the minority (100) surface, the complex−surface interaction is moderate and the dimeric Mo(VI) species are more stable than...

Synthesis and characterization of transition metal complexes of 4-Amino-5-pyridyl-4H-1,2,4-triazole-3-thiol

Abstract: Series of coordination complexes of Ni(II), Cu(II), Zn(II), Cd(II) and Sn(II) metal with 4-amino-5-(pyridyl)-4H-1,2,4-triazole-3-thiol, as a ligand has been successfully prepared in alcoholic medium. The prepared complexes were characterized quantitatively and qualitatively by using: microelemental analysis, FTIR spectroscopy, UV-visible spectroscopy, 1H and 13C NMR, magnetic susceptibility and conductivity measurements. This triazole ligand act as bidentate that coordination to the metal ions through sulphur and amine group. According to the spectral data of the complexes a tetrahedral geometry was suggested for these complexes except Cu (II) complexes which exhibit a square structure.