Energy levels of small titanium oxide clusters obtained from SCF calculations

The energy levels of small titanium oxide clusters [(TiO₂)₂, and (TiO₂H)₃, and (TiO₂H)₂] have been calculated using ab initio SCF methods. Both crystal and relaxed geometries have been considered. Systematic changes in the valencelevel structure resulting from geometry relaxation are found, which may be related to band-gap changes experimentally observed for small titanium oxide particles. In addition, a Ti? OH local surface state is found to be well described within a limited cluster model. © 1994 John Wiley & Sons, Inc.     

The magnetic isotopic effect for sulfur nuclei

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, p. 1195, May, 1990.     

Cation influence on the structure and electron density of water in some Men+·H2O complexes

The cation influence on the water molecule in the Li⁺·H₂O, Be²⁺·H₂O, Mg²⁺·H₂O and A1³⁺·H₂O complexes has been studied by means of quantum-mechanical ab initio calculations. A number of general trends are noted. (1) The calculated equilibrium water O-H distances increase with increasing binding energies, i.e. in the order Li⁺, Mg²⁺, Be²⁺, Al³⁺. The H-O-H angles differ by about ±1 ° from the calculated equilibrium angle for the free H₂O molecule; the variation has no systematic trend. (2) The electron density redistribution accompanying the change in the internal H₂O geometry in these complexes is considerably smaller than the redistribution brought about by the direct influence of the external field. (3) The harmonic O-H stretching force constant decreases with increased cation-water bonding. (4) The qualitative features of the density changes are very similar for the four complexes. The magnitudes of the interactions follow the relation Li⁺ < Mg²⁺ < Be²⁺ Al³⁺. An increased polarization of the H₂O molecule occurs with electron migration from the H atoms towards the O atom and an accumulation of electron charge approximately at the centre of the Meⁿ⁺—O bond, especially in Be²⁺·H₂O and A1³⁺·H₂O. An electron deficiency is found in the lone-pair region.     

Electron density of H2O in a crystalline environment

The influence of the surroundings on the water molecule m LiOH·H₂O has been studied by ab initio MO LCAO SCF techniques. The main features are an enhancement of the polarity of the molecule and a decrease in the lone-pair density.     

On R(4) symmetries in atomic structure

By defining a new rotation group in four dimensions we show that previous phase discrepancies can be accounted for. Furthermore we demonstrate that the new R(4) group is the one to be used in the study of atomic correlation.     

Conformational studies on L-serine phosphate and hydrated L-serine phosphate using ab initio SCF calculations

Ab initio MO -LCAO -SCF calculations using an STO -3G basis set were performed to find the most stable conformations of L -serine phosphate and hydrated L -serine phosphate. The most favorable conformation of L -serine phosphate is found to be one where the bond sequence O? C? C? C is trans and P? O? C? C gauche, and a very short hydrogen bond is formed between an oxygen atom of the phosphate group and a hydrogen atom of the ammonium group. For hydrated L -serine phosphate, a bridge-type hydration in which a water molecule links a phosphate oxygen and an ammonium hydrogen displays particularly low energy. In the four-hydrated L -serine phosphate anion, the most favorable conformation is such a bridged one having a rather extended configuration with regard to the bond sequences O? C? C? C and P? O? C? C.     

The structure of defect Ru4Si3

The nature of the defect structure of Ru₄Si₃ has been studied with electron diffraction and electron microscopy methods. Lattice image pictures, interpreted with histogram analysis, reveal that planar defects of chemical twinning type are common in the crystals.