Complete basis set limit extrapolation calculations with PNOF3

Complete basis set (CBS) extrapolated total energies have been calculated for the ground state and lowest-lying excited state with different spin of the second-row atoms (Li–Ne) using the recently developed spin-conserving PNOF3 natural orbital functional. CBS results are obtained by extrapolating power and exponential functions to the results obtained using the correlation-consistent aug-cc-pVTZ, aug-cc-pVQZ and aug-cc-pV5Z basis sets. The extrapolated total energy values are very accurate as compared to the benchmark data, and reproduce near 100% of the total energy. Interestingly, the benchmark data are lower bounds for the PNOF3 results. Finally, we have found that the calculated PNOF3 excitation energies are very accurate as comparing with both their corresponding CCSD(T, full) values and their experimental marks.