The coherent superposition of cation ground and excited states can produce charge migration on the femtosecond time scale. Modeling this charge migration requires information about the potential energy surfaces of the relevant cation states. CCSD can provide an accurate description of the ground state of the cation but cannot treat excited states with the same electronic symmetry as the ground state of the cation. CASSCF and CASPT2 are suitable methods but need to be customized for each molecule through the careful selection of an appropriate active space. The EOMCCSD-IP is a convenient alternative. It is a reliable "black-box" method that can be used for the ground and excited states of the cation and is similar in quality to CCSD. Haloacetylene cations have been chosen as a test case. The superposition of the X and A states of HCCX + (X = F, Cl, Br and I) results in charge migration between the CC triple bond and the halogen -type lone pair. The geometries, energies and vibrational frequencies have been calculated by CCSD/cc-pVTZ for neutral HCCX and the X state of HCCX + and by EOM CCSD-IP/cc-pVTZ for the X and A states of HCCX + . The calculated vibrational frequencies for neutral HCCX and the X and A states of HCCX cation agree very well with available experimental data. Very good agreement is found for the calculated structures, ionization potentials and frequencies for the X state computed with CCSD and EOMCCSD-IP. This demonstrates that EOMCCSD-IP is a suitable method for modeling the ground and excited states for the HCCX cations.