3. Solve the MP2 and IP-ADC (2) equations in the canonical Hartree-Fock basis for all the core-ionized states. Save the amplitudes to disk. 4. Loop over ionized states 4a. Retrieve the ADC (2) amplitudes and compute state-specific one-particle density matrices 4b. Generate the SS-FNO 4c. Transform the virtual MO indices of J to the SS-FNO basis ( J ). 4d. Generate the W from J , and transform the auxiliary index of J to NAF basis. 5. Solve the ground state MP2 and CCSD equations in truncated natural orbital basis.