Upon repeating for each occupied level, most naturally in a localized representation, and using similar arguments to Kapuy's zeroth in the Fock and 2nd order in correlation approximation, we suggest that this is an appropriate non-iterative way to find a set of antibonding orbitals in 1:1 correspondence with the bonding orbitals. This approach may be contrasted with Sano's suggestion to obtain the virtual orbital with maximum repulsion from the bonding orbital by solving the eigenvalue problem for each orbital using K i rather than T i . Inclusion of orbital denominators in Eq. 9 provides a clear physical meaning of the antibonding orbital as having strongest pair correlation amplitude with its parent bonding orbital. As will be demonstrated numerically later, this property also dramatically improves basis set convergence relative to the Sano definition.