def geometric_rule(C6_A, C6_B, C12_A, C12_B):
    """
    Geometric combination rule for combining
    LJ parameters.

    Parameters:
    -----------
    C6_A:  float
    C6_B:  float
        input C6 values
    C12_A:  float
    C12_B:  float
        input C12 values

    Returns:
    --------
    float
         C6
    float
         C12
    """
    C6 = (C6_A * C6_B)**0.5
    C12 = (C12_A * C12_B)**0.5
    return C6, C12