Synthesis and structural analysis of nonstoichiometric ternary fulleride K Ba CsC .

The existence of cation-vacancy sites in fullerides might lead to long-range ordering and generate a new vacancy-ordered superstructure. The purpose of this work is to search whether or not long-range ordering of vacant tetrahedral sites, namely superstructure emerges in nonstoichiometric K Ba CsC fulleride. Therefore, K Ba CsC with cation-vacancy sites is synthesized using a precursor method to avoid inadequate stoichiometry control and formation of impurity phases within the target composition. For this purpose, first, phase-pure K C , Ba C and Cs C precursors are synthesized. Stoichiometric quantities of these precursors are used for further reaction with C to afford K Ba CsC . Rietveld analysis of the high-resolution synchrotron X-ray powder diffraction data of the precursors and K Ba CsC confirms that K C , Ba C and Cs C are single-phase and they crystallize in a body-centered-cubic structure ( 3) as reported in the literature. The analysis also shows that K Ba CsC phase can be perfectly modeled using a face-centered cubic structure. No new peaks appear which could have implied the appearance of a superstructure. This suggests that there is no long-range ordered arrangement of vacant tetrahedral sites in K Ba CsC .