Theoretical double-core-hole spectroscopy of cytosine tautomers

Highlights: • Double-core-hole spectroscopy was applied to cytosine. • Theoretical calculations were performed at the density functional theory level. • The differences among tautomers were visualized using a Wagner plot. - Abstract: Double-core-hole potentials of cytosine tautomers were calculated within the framework of the density functional theory. The differences between the relaxation energies of these tautomers were visualized using a Wagner plot. Relationship of molecular structure with relaxation energies among tautomers was discussed.