Using DMFF and the ADAM optimizer in optax, we conduct such a fitting on the COCCOC dimer system, the results of which are shown in Figure . The major terms such as elec- trostatic, exchange, and dispersion interactions are well fitted, and the fitting quality of the total energy is also reasonable. The polarization and dHF terms are less accurate but they are much less important in this system anyway. More importantly, the obtained parameters show quite reasonable physical trend: for example, the B i of H1/H2 (41.9 and 45.1 nm -1 ) is larger than that of O (36.6 nm -1 ), which is then larger than that of C1/C2 (34.4 and 33.1 nm -1 ). This is exactly the reverse order of the atom sizes of the three elements (i.e., C > O > H).