Benchmark four-component relativistic density functional calculations on Cu2, Ag2, and Au2

Optimization of basis functions with the analytical gradient method is implemented at the level of four-component relativistic density functional theory (DFT). The basis set requirements for the molecular spectroscopic constants (i.e., bond length, dissociation energy, vibrational frequency, and parallel component of the dipole polarizability tensor) of Cu2, Ag2 and Au2 are investigated, indicating that including up to g-type functions in the basis set is sufficient, whereas the effects of higher angular momentum functions are negligibly small. The basis set limit results are estimated and should be taken as benchmark for calibration of other density functional calculations, in particular, those using the same exchange-correlation functionals.