An ab initio calculation of the barrier to internal rotation in ethane using a minimum basis of Slater‐type atomic orbitals is reported. Electron correlation is partly taken into account by a second‐order perturbation method. It decreases the barrier by 0.13 kcal/mol with respect to the SCF value of Pitzer or 0.17 kcal/mol with respect to another set of bond orbitals. These small lowerings are discussed in terms of localized orbitals.

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