Furthermore, we do not consider vibrational contributions in our simulations. Sources of errors in GW+BSE calculations include the DFT exchange-correlation functional used for the mean-field starting point, numerical convergence of various settings (k-point grids, number of empty states used in the GW step, the number of bands used in the BSE step), the non-self-consistency in the GW step, the plasmon pole approximation used in the GW step, the Tamm-Dancoff approximation used in the BSE step, and the static approximation for W used in the BSE step. See also Ref. for additional discussion.