Paul A Johnson
@johnsontheochem.bsky.social
Strong electron correlation with Bethe Ansatz wavefunctions
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.
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.
Connections between Richardson–Gaudin states, perfect-pairing, and pair coupled-cluster theory
Slater determinants underpin most electronic structure methods, but orbital-based approaches often struggle to describe strong correlation efficiently. Geminal-
pubs.aip.org
December 17, 2025 at 4:46 PM
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.
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.
Reposted by Paul A Johnson
Reposted by Paul A Johnson
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
(ordinarily, I'd reply to a post from @titouloos.bsky.social )
arxiv.org/abs/2506.09379
Richardson-Gaudin states of non-zero seniority II: Single-reference treatment of strong correlation
Strongly correlated systems are well described as a configuration interaction of Slater determinants classified by their number of unpaired electrons. This treatment is however unfeasible. In this man...
arxiv.org
June 12, 2025 at 3:00 PM
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
(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...
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...
Richardson–Gaudin states of non-zero seniority: Matrix elements
Seniority-zero wave functions describe bond-breaking processes qualitatively. As eigenvectors of a model Hamiltonian, Richardson–Gaudin states provide a clear p
pubs.aip.org
April 3, 2025 at 2:13 PM
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...
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 😂
March 6, 2025 at 4:35 PM
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.
January 15, 2025 at 6:07 PM
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.