Order-disorder transition for diblock copolymer melts using field-theoretic simulations

Field-theoretic simulations (FTS) provide fluctuation corrections to self-consistent field theory (SCFT) by simulating its field-theoretic Hamiltonian rather than applying the saddle-point approximation. Here, we apply FTS to AB diblock copolymer melts, where the composition field fluctuates via Langevin dynamics but the saddle-point approximation is still applied to the pressure field that enforces incompressibility. The order-disorder transition for diblock copolymer melts is evaluated for a high invariant polymerization index of N = 10⁴. Consistent with experiment, we find direct transitions between disorder and gyroid and between disorder and Fddd.