Recent work in the Scuseria group has shown that a single symmetry-projected Slater determinant, optimized in a variation-after-projection manner, can account for a large fraction of the electron correlation in small chemical systems. The approach is, however, not size extensive: it yields the same energy-per-particle as standard Hartree--Fock in the thermodynamic limit. Based on the generator coordinate representation of the exact wavefunction, we discuss one possible way to improve upon the single symmetry-projected Slater determinant ansatz. We consider a linear combination of (non-orthogonal) configurations optimized variationally; this yields a compact wavefunction that can be systematically improved towards the exact answer. Preliminary results indicate that this approach can yield fairly accurate results in a number of strongly correlated systems.

Compact representation of strongly correlated wavefunctions via non-orthogonal determinants obtained by symmetry breaking and restoration

246th National Meeting (2013)

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