PES

See here
Priroda DFT/PBE/L1

Click on ellipse to view 3D structure in popup window (run JSmol)
kcal/mol 8 - 7 - 6 - 5 - 4 - 3 - 2 - 1 - 0 - 0.00 kcal U 0.00 kcal 7.88 kcal U-Z 7.88 kcal 4.41 kcal Z 4.41 kcal