We study the phase behavior of single homopolymers in a simplehydrophobic/hydrophilic off-lattice model with sequence independent localinteractions. The specific heat is, not unexpectedly, found to exhibit apronounced peak well below the collapse temperature, signalling a possiblelow-temperature phase transition. The system size dependence at this maximum isinvestigated both with and without the local interactions, using chains with upto 50 monomers. The size dependence is found to be weak. The specific heatitself seems not to diverge. The homopolymer results are compared with thosefor two non-uniform sequences. Our calculations are performed using the methodsof simulated and parallel tempering. The performances of these algorithms arediscussed, based on careful tests for a small system.
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