Renormalized Internally-Contracted Multireference Coupled Cluster with Perturbative Triples
Robin Feldmann, Markus Reiher

TL;DR
This paper introduces the ric-MRCC method, combining multireference coupled cluster with renormalization techniques, achieving high accuracy in molecular energy calculations with improved stability and efficiency.
Contribution
It develops the renormalized ic-MRCC (ric-MRCC) method by adapting flow equation renormalization to nonunitary transformations and introduces approximate triples for enhanced accuracy.
Findings
ric-MRCCSD[T] matches CCSD(T) accuracy for spectroscopic constants.
The method accurately models potential energy curves of various molecules.
It offers a stable, efficient approach for multireference quantum chemistry calculations.
Abstract
In this work, we combine the many-body formulation of the internally contracted multireference coupled cluster (ic-MRCC) method with Evangelista's multireference formulation of the driven similarity renormalization group (DSRG). The DSRG method can be viewed as a unitary multireference coupled cluster theory, which renormalizes the amplitudes based on a flow equation approach to eliminate numerical instabilities. We extend this approach by demonstrating that the unitary flow equation approach can be adapted for nonunitary transformations, rationalizing the renormalization of ic-MRCC amplitudes. We denote the new approach, the renormalized ic-MRCC (ric-MRCC) method. To achieve high accuracy with a reasonable computational cost, we introduce a new approximation to the Baker-Campbell-Hausdorff expansion. We fully consider the linear commutator while approximating the quadratic commutator,…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
Taxonomy
TopicsNanocluster Synthesis and Applications · Random Matrices and Applications · Optical properties and cooling technologies in crystalline materials
