Density functional theory investigation of electronic structure and muon hyperfine interaction in isolated adenine and thymine

In DFT calculation, a basis set is an important factor in determining the quality of results, especially for hyperfine interaction where changes in the local geometry and electronic structure can have a big impact. The use of extensive basis sets is always desirable and is expected to produce better results. However, for DNA molecules of more than 10 base-pairs, all-electron geometry optimization calculation using large basis sets such as 6-311++G(d,p) is prohibitively difficult even on a supercomputer. An alternative is to use smaller basis sets such as 6-31G which is used in this work. Thus, the objective of the work reported here is to determine whether 6-31G basis set is suitable to be used to study muon hyperfine interaction in short DNA molecule. It is found that in comparison with 6-311++G(d,p), 6-31G does not change the ranking of muon sites stability in isolated adenine and thymine. Furthermore, the 6-31G calculated muon HFCCs are slightly closer to the experimental values.