Ceramics-Silikáty 26, (1) 7 - 13 (1982)

The crystal structure of a model-system clinopyroxene of approximate 72 mole % diopside-28 mole % CaTiAl₂O₆ solid solution was refined. The space group is C2/c, cell parameters a = 9.781(5), b 8.856(4), c = 5.331(3) 10^-10 m, β = 106.06 (5)°. The problem of Ti⁴⁺ location was solved by the least-squares refinement and difference Fourier syntheses to an R-value 6.1 %. The Ti⁴⁺ presumably occupy the M1 site but a small part of Ti⁴⁺ is placed in the tetrahedraly coordinated positions. These results are confirmed by the increase of T-O2 interatomic distance. With respect to crystallisation of cast basalt products, TiO₂ is not suitable as a nucleation admixture because of its "solubility" in clinopyroxenes.