Crystal structure of the pyrochlore oxide superconductor KOs$_2$O$_6$

Jun-Ichi Yamaura; Shigeki Yonezawa; Yuji Muraoka; Zenji Hiroi

doi:10.1016/j.jssc.2005.10.039

paper

Crystal structure of the pyrochlore oxide superconductor KOs $_{2}$ O $_{6}$

arXiv:cond-mat/0512683 · doi:10.1016/j.jssc.2005.10.039

Abstract

We report the single-crystal X-ray analysis of the structure of the pyrochlore oxide superconductor KOs $_{2}$ O $_{6}$ . The structure was identified as the $β$ -pyrochlore structure with space group $F d 3 ˉ m$ and lattice constant $a$ = 10.089(2)~Åat 300 K: the K atom is located at the 8 $b$ site, not at the 16 $d$ site as in conventional pyrochlore oxides. We found an anomalously large atomic displacement parameter $U_{iso}$ = 0.0735(8)~Å $^{2}$ at 300 K for the K cation, which suggests that the K cation weakly bound to an oversized Os $_{12}$ O $_{18}$ cage exhibits intensive rattling, as recently observed for clathrate compounds. The rattling of A cations is a common feature in the series of $β$ -pyrochlore oxide superconductors AOs $_{2}$ O $_{6}$ (A = Cs, Rb and K), and is greatest for the smallest K cation.

5 pages, 5 figures, to appear in J. Solid. State. Chem

Crystal structure of the pyrochlore oxide superconductor KOs2​O6​

Abstract

Crystal structure of the pyrochlore oxide superconductor KOs $_{2}$ O $_{6}$