Many of the challenges in popular electronic structure methods for molecules are related to the (de)localization of electrons over the different subsystems in the compounds. We show how incorporating suitable constraints on the quantum many-body wavefunction can

(1) lead to accurate electron (spin)localization in bond dissociation processes, as described by Yang's flat-plane conditions, and

(2) accurately capture static electron correlation via artificial spin-symmetry breaking/restoration in the Generator Coordinate Method framework.

Joint work with Amir Ayati (UNB), Xeno De Vriendt, Guillaume Acke, Patrick Bultinck (Ghent University) and Hugh Burton (Oxford)