Robustness of the I4 symmetry energy coefficient

In this paper we investigate the ${I}^{4}$ symmetry energy coefficient $[I=(N\ensuremath{-}Z)/A]$ extracted from a few popular mass models, and their corresponding databases improved, respectively, by the radial basis function (RBF) approach and the RBF with odd-even corrections. Our results show that the linear correlation between our resultant ${I}^{4}$ symmetry energy coefficients (denoted by ${c}_{4}^{(\mathrm{V})}$) and the corresponding root-mean-square deviations from experimental masses of these theoretical databases is very robust. Interestingly, the extrapolated values of ${c}_{4}^{(\mathrm{V})}$ using the above three versions of databases are consistent with each other.