Finally, all of the results discussed above were calculated at a single screened cutoff of 20 Ryd. We performed similar calculations using a second screened cutoff of 10 Ryd because screened cutoff impacts the size of the polarizability and thus the subspace basis set. Comparison of Figures and shows that the fraction of subspace eigenvalues/vectors needed to achieve similar errors in the RPA correlation energy is smaller for the larger screened cutoff. This is simply because the larger screened cutoff increases the basis set size, thus reducing the need to retain as many subspace eigenvalues/vectors. Nevertheless, the 20 Ryd results are more relevant because we show in the Computational Details section that accurate extrapolated RPA correlation energies can be obtained using screened cutoffs near 20 Ryd.