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Abstract:
The effect of pressure on the superconducting transition temperature
(T-c) of the Ca-intercalated graphite compound CaC6 has been
investigated up to similar to 16 kbar. T-c is found to increase under
pressure with a large relative ratio Delta T-c/T-c of approximate to
0.4%/kbar. Using first-principles calculations, we show that the
positive effect of pressure on T-c can be explained within the scope of
electron-phonon theory due to the presence of a soft phonon branch
associated with in-plane vibrations of the Ca atoms. The implications
of the present findings for the current debate about the
superconducting mechanism in graphite intercalation compounds are
discussed.