Although the agreement between experiment and CASPT2 offers clear improvement over DFT, the bond distances are longer than what is observed for typical agreement for single-reference transitional metal complexes between DFT and experiment. Moreover, low frequency Cr-Cr stretching modes are known to exhibit significant anharmonicity. 11, Therefore, a scan of the PES along the harmonic normal mode was performed at the same level of theory as in the harmonic vibrational analysis and by including the so-called IPEA shift in the CASPT2 zeroth-order Hamiltonian. For Cr 2 (mhp) 4 and Cr 2 (dmp) 4 , the structure was displaced along the harmonic mode associated with the Cr-Cr stretching motion, Q i , in the positive and negative direction up to 3Q i . The resulting potential was fit to the fourth order polynomial,