  We study the two-dimensional +/-J Ising model, three-state Potts model and
four-state Potts model, by the numerical transfer matrix method to investigate
the behaviour of the sample-to-sample fluctuations of the internal energy on
the Nishimori line. The result shows a maximum at the multicritical point in
all the models we investigated. The large sample-to-sample fluctuations of the
internal energy as well as the existence of a singularity in these fluctuations
imply that the bond configuration (or, equivalently, the distribution of
frustrated plaquettes) may be experiencing a non-trivial change of its
behaviour at the multicritical point. This observation is consistent with the
picture that the phase transition at the multicritical point is of
geometry-induced nature.
