def lorentz_berthelot_rule(sig_A, sig_B, eps_A, eps_B):
    """
    Lorentz-Berthelot rules for combining LJ paramters.

    Parameters
    -----------
    sig_A:  float
    sig_B:  float
        input sigma values
    eps_A:  float
    eps_B:  float
        input epsilon values

    Returns
    --------
    float
        sigma
    float
        epsilon
    """
    sig = (sig_A + sig_B)/2.0
    eps = (eps_A * eps_B)**0.5
    return sig, eps