Benchmarking the Electron Affinity of Uracil

The Weizmann Bruecker doubles composite method W1BD has been applied in a benchmark study of electron attachment to the nucleobase uracil. The largest computations involved the BD method with a basis set of 760 contracted Gaussian functions, namely augh-cc-pVQZ+2df. The predictions demonstrate that the adiabatic electron affinity (AEA) of uracil is definitely positive. The most relable value for the AEA of uracil should be 0.024 ± 0.013 eV. Other high level methods such as CASPT2 and G4 theory also predict the AEA of uracil with reasonable accuracy. Both the Hartree-Fock and MP2 approaches severely underestimate the AEA. The latter two methods are not recommended for the study of electron attachment to the DNA/RNA bases. On the other hand, some commonly used Density functional theory approaches, especially, M06-2X, are promising candidates for the study of electron-DNA/RNA interactions.