Gaussian Basis Sets for All-Electron Excited-State Calculations of Large Molecules

We introduce a family of all-electron Gaussian basis sets, augmented MOLOPT, optimized for excited-state calculations on large molecules. We generate these basis sets by augmenting existing STO-3G, STO-6G, and MOLOPT basis sets optimized for ground state energy calculations. The augmented MOLOPT basis sets achieve fast convergence of <i>GW</i> gaps and Bethe-Salpeter excitation energies, while maintaining low condition numbers of the overlap matrix to ensure numerical stability. For <i>GW</i> HOMO-LUMO gaps, the double-ζ augmented MOLOPT basis yields a mean absolute deviation of 60 meV to the complete basis set limit. The basis set convergence for excitation energies from time-dependent density functional theory and the Bethe-Salpeter equation is similar. We use our smallest generated augmented MOLOPT basis (aug-SZV-MOLOPT-ae-mini) to demonstrate <i>GW</i> calculations on nanographenes with 9224 atoms requiring only 34300 core hours of computational resources.