  The displacive structural phase transition in a two-dimensional model solid
due to Benassi and co-workers [PRL 106, 256102 (2011)] is analyzed using Monte
Carlo simulations and finite-size scaling. The model is shown to be a member of
the two-dimensional six-state clock model universality class. Consequently, the
model features two phase transitions, implying the existence of three
thermodynamically distinct phases, namely, a low-temperature phase with
long-ranged order, an intermediate critical phase with power-law decay of
correlations, and a high-temperature phase with short-ranged order.
