Melting transitions of CF4 on graphite

Different melting behaviors of different solid phases of CF4 on graphite in the near-monolayer-completion region were observed with an ac heat-capacity technique. The melting transitions from the commensurate (2×2) phase and the I(S) phase, an incommensurate phase of higher density than the (2×2) phase, are found to be strongly first order. In contrast, the melting from the even-higher-density hexagonal incommensurate phase was found to be two-step melting process, similar to the melting of Ar on graphite at submonolayer coverages.