Bond type in the dioxides of titanium, germanium and tin

Rutile-type compounds. IV. SiO2, GeO2 and a comparison with other rutile-type structures

“…This adds further weight to the opinion that the rutile-type oxides do not have purely ionic bonds. The results of Wackman, Hirthe & Frounfelker, (1967) and Ladd (1969) seem to contradict this conclusion. In both these papers values of Lie for TiO2 are calculated in good agreement with Uo However the authors did not attempt to prove that the lattice energy calculated by them corresponds to a minimum.…”

“…The obvious conclusion from this is that the Born model as applied by Baur (1961) is insufficient for describing the ruffle-type oxides. An advance beyond these calculations may be conceivable by using a more refined Born model (along the lines followed by Busing, 1970) but this has not been attempted by either Wackman et al (1967) or by Ladd (1969). In Fig.…”

The rutile structure of Al1-x·□xO1-3xF1 + 3x,x= 0.086

“…The reliability of the above calculation is verified by the values 2930 and 2932 kcal/mol as derived from thermodynamical data (Ladd, 1969) and computed by the author for the rutile crystal structure Ti02 assuming an amount of 10% non-ionic portion as stated by Ladd (1969). For the ordered structure AlOF we calculate 1673 kcal/mol.…”

“…To get an estimate about the energetic stability we have calculated the crystal energy for the ordered AlOF in the approach of the simple Bom-Mayer ionic model (Ladd, 1969) and assuming comparable bonding character as postulated for rutile-type structures. The reliability of the above calculation is verified by the values 2930 and 2932 kcal/mol as derived from thermodynamical data (Ladd, 1969) and computed by the author for the rutile crystal structure Ti02 assuming an amount of 10% non-ionic portion as stated by Ladd (1969).…”

Refinement of the structure of anatase at several temperatures*

“…The intensities, corrected for absorption and the Lorentz and polarization factor, were submitted to a full-matrix least-squares refinement, using a modified version of the computer program ORFLS (BuSING et al, 1962). Since the bonds in rutile are highly ionic (LADD, 1969), and since anatase is quite similar to rutile (the structural differences are only in the second-nearest neighbour coordination), form factors for Ti4+ (International tables, 1962) and 02-(SUZUKI, 1960} were used.…”