CASSCF quality dissociations with MP2 cost. Single-reference perturbation theory with Perfect-Pairing reference. The excitations are correlated but everything is simple to compute. arxiv.org/abs/2605.31582

Université Laval: Canada Impact+ Research Chairs in Nanostructured Materials Chemistry https://chempostingscanada.blogspot.com/2026/02/universite-laval-canada-impact-research.html

Work with @titouloos.bsky.social @marm314.bsky.social : PP is an independent pair model with a reference Hamiltonian. The corresponding PT2 correction \approx pCCD. Here, seniority-zero correction only in the valence. The real correction coming soon.

arxiv.org/abs/2510.06144 #compchem

arxiv.org/abs/2507.02160 #compchem

Very short follow-up after the ridiculous part I. Short excitation-based CI of RG states converges quickly. (ordinarily, I'd reply to a post from @titouloos.bsky.social ) arxiv.org/abs/2506.09379

Finally. This was quite a struggle. In short: can add missing structure from a seniority-zero state with single-reference methods. Parts 2 and 3 to come. pubs.aip.org/aip/jcp/arti...

Scheduling a meeting at 6:30, google calendar assumes it's in the evening 😂

Seniority-based CI works well for strongly correlated systems at an exponential cost. The goal here is to replace it with a short excitation-based CI of correlated states. Here all the required matrix elements are computed. In every case, a single linear algebra operation per pair of states.