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These are the results for calculation of the energy of the 3 stereoisomers with HF methode, spin=restricted, ans the basis set 6-21G.
| Form | Energy |
| RR | -1194.71529844 |
| SS | -1194.71529844 |
| meso | -1194.71784298 |
So the form RR and SS have exactly the same energy, but there is a difference of energy between them and the meso form of around 2.5 millihartrees, and it is already a significant difference.