A new triclinic modification of the pyrochlore-type KOs2O6 superconductor

A new modification of KOs 2 O 6 , the representative of a new structural type (Pearson symbol a P 18, a =5.5668(1) Å, b =6.4519(2) Å, c =7.2356(2) Å, (cid:68) =65.377(3)°, (cid:69) =70.572(3)°, (cid:74) =75.613(2)° space group P -1, no.2 was synthesized employing high pressure technique. Its structure was determined by single-crystal X-ray diffraction. The structure can be described as two OsO 6 octahedral chains relating to each other through inversion and forming big voids with K atoms inside. Quantum chemical calculations were performed on the novel compound and structurally related cubic compound. High-pressure X-ray study showed that cubic KOs 2 O 6 phase was stable up to 32.5(2) GPa at room temperature.