Titanium lattice symmetry

In the layer lattice of a, 7, or 6 TiCls, each Ti atom is bonded to three other Ti atoms through six bridged Cl atoms (404). The local symmetry of the Ti atoms is D3 so that each titanium... 

J.M. Popa et al. described the preparation of a titanium containing silicalite from a reaction mixture having a very low pH (6.5 - 7.5) and containing fluoride anions [26]. The crystalline product obtained by this method had a monoclinic symmetry. No evidence was given to support the presence of titanium in lattice position. 

Titanium h.f.s. are resolved (500) at 77°K in Ti + doped Al(acac)8. The symmetry here is and the large trigonal distortion (S = 2000-4000 cm ) increases the spin-lattice relaxation time so that resonance is observed at 77°K. The electron is in the a- d 2) orbital in contrast with most other cl ions. Titanium h.f.s. are observed on the F-center line in H2-reduced BaTiOs 664). 

Tables 1.8 and 1.9 and Fig. 1.21 give some reference data on the values of the thermal coefficient of linear expansion for oxides, refractory, and ceramic materials [100-102]. Crystals with a cubic lattice (CaO, MgO) have equal values of linear coefficients of expansion along aU axes. The typical linear coefficients of thermal expansion for such materials are 6-8 x 10 and increase with the temperature up to 10-15 X 10 K . Anisotropic crystals with low symmetry have different values of linear coefficients of thermal expansion along different axes, but with a temperature increase, this difference becomes smaller. Materials with strong chemical bonds (silicon carbide, titanium diboride, diamond) have low values of linear coefficients of thermal expansion. However, these materials have high values of Debye characteristic temperature (values of the linear coefficients of thermal expansion grow below the Debye temperature and are almost constant above it).

In another example, at temperatures >393 K, barium titanate has the perovskite structure, which is simple cubic with all of the symmetry elements of the cubic lattice, so its point group is Oh or m3m. As the temperature is reduced to its Curie temperature, the lattice contracts and the oxygen ions on the faces of the cube squeeze the titanium ion in the center of the cube so that it is displaced in one direction while the oxygen ions are displaced in the opposite direction, destroying the inversion symmetry as well as the mirror symmetry about the central plane and the rotational symmetry about several of... 

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