Phase behavior of linear heterogeneous trimers on a square lattice.

Monte Carlo simulations in the grand canonical ensemble, the multiple-histogram analysis and finite-size scaling techniques have been used to study a phase behavior of trimer BAB on a square lattice. The systems with the same energies u(AA) = u(BB) and different strengths of interactions between unlike segments are considered. The AB-contacts are energetically unprofitable. There are two phase transitions: the first-order vapor-liquid transition and the second-order structural transition in the supercritical fluid. The phase diagram topology depends on the energy u(AB). The crossover between the tricritical point phase diagram topology and the critical end phase diagram topology is found. It is demonstrated that the transition to the ordered strip-like phase is non-universal.