Seniority-Zero Canonical Transformation Theory: Reducing Truncation Error with Late Truncation

2025/11/10 by Calero-Osorio, Daniel F., Ayers, Paul W. · 1 citation
#Chemical Physics (physics.chem-ph) #FOS: Physical sciences

paper · doi:10.48550/arxiv.2511.07580

Abstract

We show how to add the effects of residual electron correlation to a reference seniority-zero wavefunction by making a unitary transformation of the true electronic Hamiltonian into seniority-zero form. The transformation is treated via the Baker Campbell Hausdorff (BCH) expansion and the seniority-zero structure of the reference is exploited to evaluate the first three commutators exactly; the remaining contributions are handled with a recursive commutator approximation, as is typical in canonical transformation methods. By choosing a seniority-zero reference and using parallel computation, this method is practical for small- to medium-sized systems. Numerical tests show high accuracy, with errors ∼ 10^-4 Hartree.

Citations

• Seniority-zero Linear Canonical Transformation Theory
• Richardson-Gaudin states of non-zero seniority II: Single-reference treatment of strong correlation
• Singlet Geminal Wavefunctions
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Cited by

• Fanpy 2.0: Wavefunction Implementation and Analysis Tools for Flexible Ansatz Design
• Seniority-zero Linear Canonical Transformation Theory
• A new family of seniority-restricted coupled cluster methods

Related

• Seniority-zero Linear Canonical Transformation Theory
• Richardson-Gaudin states of non-zero seniority I: matrix elements
• Quantum Seniority-based Subspace Expansion: Linear Combinations of Short-Circuit Unitary Transformations for the Electronic Structure Problem
• Richardson-Gaudin states of non-zero seniority II: Single-reference treatment of strong correlation
• Jordan-Wigner Transformation for the Description of Strong Correlation in Fermionic Systems