Accurate estimation of the double-bounce scattering f_d and surface scattering f_s coefficients with Freeman-Durden decomposition is still difficult. This difficulty arises because overestimation of the volume scattering energy contribution P_v leads to negative values for f_d and f_s. A generalized residual model is introduced to estimate f_d and f_s. The relationship between P_v and the residual model is analyzed. Eigenvalues computed from the residual model must be positive to explain physical scattering mechanisms. The authors employ a new volumetric scattering model to minimize P_v as calculated by several decomposition methods. It is concluded that decreasing P_v can help reduce negative energy. This conclusion is validated using actual polarimetric SAR data.