Phase Transition in a Model of Y-shaped Molecules

Increasing attention in statistical mechanics is being given to non-spherical molecules, such as polypeptide chains and protein molecules. One example is provided by immunoglobulin, which has a ``Y'' shape. In this work, we determine the phase diagram of ``Y''-shaped molecules on a triangular lattice through Monte Carlo Grand Canonical ensemble simulation, using histogram reweighting,multicanonical sampling and finite size scaling. We show that (as expected) this model is a member of the Ising universality class. For low temperatures, we implemented multicanonical sampling to induce faster phase transitions in the simulation. By studying several system sizes, we use finite size scaling to determine the two phase coexistence curve, including the bulk critical temperature, critical chemical potential and critical density.