Synthesis and characterization of Hg metal-doped C-60

Synthesis of the new fulleride HgxC60 Was achieved inside an evacuated ampo ule filled with metallic Hg and C-60 powder kept at 500 degrees C for sever al months. A heat capacity anomaly is observed at 232.3 K, reminiscent of t he ordering transition of pristine C-60 but With reduced transition enthalp y. Weakly shifted F-1u infrared bands suggest lack of Hg-C-60 charge transf er. The structure at 300 K is as in pristine C-60 but with a measurable lat tice expansion consistent with Hg intercalation in octahedral sites. This l attice expansion induces downshift of the ordering transition and weak disp lacement of infrared bands. (C) 2000 Elsevier Science B.V. All rights reser ved.