On the other hand, vector properties can also be estimated using the reweighting MBAR estimator. As an example, We built a coarse-grained benzene model with three beads per molecule, and then parameterized the Lennard-Jones interaction between particles to reproduce the experimental RDF of liquid benzene. The loss function is the natural log of the L2-norm of the vector difference In classical force field optimizations, the Lennard-Jones parameters were always manually tuned to reproduce densities, which is not only low-efficient but also unreliable. With the help of DMFF, such process can be largely automated. Moreover, it can be done in a larger scale, with more parameters and more training data from multiple systems, thus improving the generality of the resulting force field.