https://en.wikipedia.org/wiki/Combining_rules

If you don't want to test different approaches, the Lorentz-Berthelot rules should be the default choice. You can read there examples where they failed and why, and compare with your needs.

If your MD code supports the following mixing rules, you cam implement them for

LJ parameters.

mix geometric

epsilon_ij = sqrt(epsilon_i * epsilon_j)

sigma_ij = sqrt(sigma_i * sigma_j)

mix arithmetic

epsilon_ij = sqrt(epsilon_i * epsilon_j)

sigma_ij = (sigma_i + sigma_j) / 2

mix sixthpower

epsilon_ij = (2 * sqrt(epsilon_i*epsilon_j) * sigma_i^3 * sigma_j^3) / (sigma_i^6 + sigma_j^6)

sigma_ij = ((sigma_i**6 + sigma_j**6) / 2) ^ (1/6)

Thanks Ramin,

I know that mixing rule, but I don't know what's the best one for several force field utilized simultaneously in a MD Simulation?

This a big challenge!!

Please have a look at this work:

Article The effects of deviations from Lorentz–Berthelot rules on th...