On the other hand, HS and broken-symmetry LS geometries differ with AP geometry only slightly (RMSD ∼ 0.01 -0.02Å), which suggests that AP energy correction only slightly changes the location of minima on the potential energy surface, in agreement with prior findings. This observation indicates that -at least for the test set considered here -the geometries are not very sensitive to the presence of spin contamination. As a specific example supporting this point, Fig. compares the crystal structure and optimized AP geometry for Compound 3. Overall, the three-dimensional structure remains qualitatively unchanged, but evaluation of specific internal coordinates shows a few key changes. The most notable change is in the copper-nitrogen bond distance labeled in Fig. , which decreases during geometry optimization on the AP PES by more than 0.2 Å. (The complete set of geometric parameter changes due to geometry optimization are given in Table ).