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physics.chem-ph2026
Relativistic Dirac-Coulomb-Breit Four-Component Multireference Perturbation Theory within the Small Tensor Product Distributed Active Space Framework
Rajat Majumder, Shiv Upadhyay, Ryan A. Beck +2
We present a four-component multireference second-order perturbation theory (4C-MRPT2) within the small tensor product distributed active space (STP-DAS) framework. The formulation…
physics.chem-ph2026
Quaternion Dirac--Coulomb--Breit Integral Transformation for Relativistic Four-Component Correlated Electronic Structure Theory
Martijn Oele, Rajat Majumder, Shiv Upadhyay +5
High-accuracy correlated four-component relativistic electronic structure methods are typically formulated in terms of integrals over molecular orbital (MO). Consequently, an effic…
physics.chem-ph2026
Definitive Assessment of the Accuracy, Variationality, and Convergence of Relativistic Coupled Cluster and Density Matrix Renormalization Group in 100-Orbital Space
Shiv Upadhyay, Agam Shayit, Tianyuan Zhang +3
Accuracy, variationality, and convergence underpin the reliability of modern electronic structure methods, yet definitive benchmarks in the relativistic regime remain elusive due t…