A Reduced Cost Two-component Relativistic Equation-of-Motion Coupled Cluster Method for Ionization Potential

2025/06/07 by Somesh Chamoli, Chamoli, Somesh, Malaya K. Nayak +3 · 2 citations
Materials Science · Physics and Astronomy · #Advanced Chemical Physics Studies #Atomic and Molecular Physics #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Magnetism in coordination complexes

paper · pdf · doi:10.48550/arxiv.2506.06805

openalex publication_date 2025/06/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

We report an efficient implementation of the ionization potential (IP) variant of the equation-of-motion coupled cluster (IP-EOM-CC) method based on the exact two-component atomic mean field (X2CAMF) framework, utilizing Cholesky decomposition (CD) and frozen natural spinors (FNS). The CD approximation significantly reduces memory demands, whereas the FNS approximation lowers the number of floating-point operations. Together, these techniques make the method computationally efficient for accurate relativistic IP-EOM-CC calculations of molecules containing heavy elements. The calculated IP values are almost identical to those obtained by the four-component relativistic IP-EOM-CC method. Benchmark studies show good agreement with experimental ionization energies and photoelectron spectra, demonstrating the method's reliability. The practical applicability of the approach is demonstrated by IP calculations on the medium-sized [I(H₂O)₁₂]^- complex, with 1698 virtual spinors.

Citations

• Cholesky decomposition in spin-free Dirac-Coulomb coupled-cluster calculations
• Relativistic fully self-consistent GW for molecules: Total energies and ionization potentials
• Quantum Theory of Many-Particle Systems. I. Physical Interpretations by Means of Density Matrices, Natural Spin-Orbitals, and Convergence Problems in the Method of Configurational Interaction

Cited by

• A Low Cost Relativistic Algebraic Diagrammatic Construction Method Based on Cholesky Decomposition and Frozen Natural Spinors for Electronic Ionization, Attachment and Excitation Energy Problem
• A Third-Order Relativistic Algebraic Diagrammatic Construction Method for Double Ionization Potentials: Theory, Implementation, and Benchmark

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• Two-component relativistic equation-of-motion coupled cluster for electron ionization
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• A Cholesky decomposition-based implementation of relativistic two-component coupled-cluster methods for medium-sized molecules
• Reduced-cost Relativistic Equation-of-Motion Coupled Cluster Method based on Frozen Natural Spinors: A State-Specific Approach
• Reduced-Cost Four-Component Relativistic Double Ionization Potential Equation-of-Motion Coupled-Cluster Approaches with 4-Hole--2-Particle Excitations and Three-Body Clusters