The crystal structure of BaCuO2 at 193 K

The crystal structure of BaCuO2 has been determined at 193 K by a single crystal X-ray study. The crystal used was the same as that in an earlier study at room temperature and was obtained as a parasitic phase during preparation of YBa2Cu3O7. The compound crystallizes in the cubic space group Im3m with a 18.319(3) A. The non stoichiometric formula now got is Ba0.92Cu1.06O2.14, that of the part with completely occupied positions Ba0.92Cu0.88O1.63, that of the part with partially occupied positions Cu0.18O0.51. 8806 reflections were collected and the structure was refined to Rw = 0.074 based on F2 of 922 unique reflections, R1 = 0.037 (for 557 reflections with vertical stroke Fvertical stroke > 4σ(F)). The results for the part with completely occupied positions confirm earlier structure determinations. The structure for the partially occupied atomic positions is different from all earlier given results in a few details. (orig.)