Beardsley, T.M.Spencer, R.K.W.Matsen, M.W.2019-12-062019-12-062019-11-12https://doi.org/10.1021/acs.macromol.9b01904http://hdl.handle.net/10012/15292Field-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. Although FTS work well for ultrahigh molecular weights, they have struggled with experimentally relevant values. Here, we consider FTS for two-component (i.e., AB-type) melts, where the composition field fluctuates but the saddle-point approximation is still applied to the pressure field that enforces incompressibility. This results in real-valued fields, thereby allowing for conventional simulation methods. We discover that Langevin simulations are one to two orders of magnitude faster than previous Monte Carlo simulations, which permits us to accurately calculate the order-disorder transition of symmetric diblock copolymer melts at realistic molecular weights. This remarkable speedup will, likewise, facilitate FTS for more complicated block copolymer systems, which might otherwise be unfeasible with traditional particle-based simulations.enArticle