The ionization energies of single, double, and triple core-hole (SCH, DCH, and TCH) states were calculated for three isomers of aminophenol with the framework of density functional theory. Our calculated single core-hole ionization potentials were consistent with experiment and the previous theoretical values. Core-ionization energies via complex processes were also estimated. The difference of relaxation energy of two-site DCH (tsDCH) states can be visualized using Wagner plots. We found that the electron density of π orbitals on benzene ring are relaxed to core-vacancy sites at N,O tsDCH state.
