Intercalant ordering and lattice dynamics in stage-1 KHgC4

Neutron scattering methods were used to investigate intercalant ordering and phonon spectra in KHgC4 at 297 and 12 K. Two coexisting phases, each three dimensionally ordered, were observed in a bulk sample, with 2 × 2 and 3×2 registry of the intercalant superlattices with respect to graphite. The phonon measurements show that out-of-plane Hg vibrations have lower frequencies than in-plane intercalant motions. Accurate measurement of the C-C bond distance indicates a smaller charge transfer to C layers in KHgC4 than in MC8 (M=K,Rb,Cs).