I am trying to calucaled the cohesive energy density (CED) of H3O+ using COMPASS, but the value of H3O+ CED is 5.96e+010 at 353K, this is significantly larger that that of H2O (1.98e+090 at 353 K). AS we know, since the H3O+ has a positive charge, H3O+ cannot interact favorably with itself, that means the CED of H3O+ should be lower than H2O. Since the H3O+ CED is large, the density of H3O+ also reachs 1.85 g/cm3 after 500 ps NPT. I am very confused about this result. For this problem, I checked the forcefield types and charges of H3O+, COMPASS assigned h1+ forcefiled and +0.403e to H and o3 and -0.209 to O. I do not know if there is a problem with the assigned force field.