Long-period structures in titanium carbohydrides

Cubic titanium carbohydrides were prepared by quenching from 1200°C in a special regime of thermal treatment preventing hydrogen elimination from the lattice. At the lower boundary of the homogeneity range of these compounds, carbon atoms were demonstrated to randomly occupy the octahedral interstitial sites, whereas hydrogen atoms occupy the tetrahedral interstitial sites 8c in the disordered cubic structure (space group Fm3m). The carbon and hydrogen atoms in the carbohydride were found to be ordered upon annealing at 600-900°C. The crystal structure of the cubic phase is described in space group Fd3m, where the carbon atoms predominantly occupy the octahedral interstitial sites 16c, and the other carbon atoms (in an insignificant amount) and all the hydrogen atoms occupy the octahedral interstitial sites 16d. Long-period antiphase-domain structures with a period of 12 are observed in titanium carbohydrides at 450°C.