To compare GEO with GEO and get a feeling how the errors in geometric parameters translate into GEO, we use the HCN molecule. The CCSD(T)(full) method is taken as a reference with the aug'-cc-pCV5Z basis set [cc-pCV5Z for the hydrogen atom and aug-cc-pCV5Z for the other two atoms 18 ], and (full) indicates that all electrons are included in the correlation treatment.