PHASE-TRANSITION OF SEMIFLEXIBLE LATTICE VESICLES

The existence of a crumpling transition of a three-dimensional vesicle model on the cubic lattice with fixed surface area N subject to bending rigidity kappa greater-than-or-equal-to 0 is reported. Using a Monte Carlo method, the transition characteristics of bending energy U, specific heat C, volume V, radius of gyration R and the corresponding three eigenvalues lambda(k) are discussed. The specific heat exhibits increasing and shifted maxima with increasing surface area N and decreasing bending constant kappa, respectively, which seems to indicate a continuous transition. Well above the transition point kappa(c) the conformations are comparable to compact spheres, which become on the average more oblate approaching kappa(c) from above. At kappa < kappa(c) one observes branched-polymer-like structures. A two-step transition process for the conformational transformation at finite N is proposed, and the possible existence of a unique crumpling point at kappa = kappa(c) with different scaling behavior, as compared to the rigid and the branched phases, is discussed.