Simulation of X-ray photoelectron spectra (XPS) by fc-CVS-EOM-IP-CC (frozen-core core-valence-separation equation-of-motion coupled-cluster method for ionization potentials):

• EOM-IP-CC: the ground state is treated at the CC level and the ionized states are accessed by applying an ionization operator to the ground-state wavefunction. Excited states are accessed by MOM.

• FC approximation: omitting core-core and core-valence correlation in the ground state.

• CVS scheme: the EOM states are represented in a restricted Fock space spanned the many-electron determinants with at least one occupied core orbital index.