The best overall result for the combined error of density and RCE yields the optimization using the NLP loss function, linearly decreasing WFs for the RCE and an overall balancing between density and RCE WFs of 25% to 75% (i.e. the "25-75" setup), respectively. The resulting FFParams and their corresponding errors, err dens for the density and err ener for the RCE, is shown in table . The reproduced density is (707.0 ± 4.7) kg m 3 , leading to an error of 1.0 % ± 0.67 %. For the herein used target density of 0.7 g cm 3 , that is converted to 700 kg m 3 , no error range is provided in the data's source . However, other literature, for example the Chemistry Webbook of the National Institute of Standards and Technology (NIST), report an estimated error of 0.1 % to 0.3 % for their density values . Therefore, the herein used target density is assumed to have an error less or equal to 0.3 %.