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We present the theory and implementation of a highly efficient relativistic third-order algebraic diagrammatic construction [ADC(3)] method based on a four-component (4c) Dirac-Coulomb (DC) Hamiltonian for the calculation of ionization…

Chemical Physics · Physics 2024-11-01 Sudipta Chakraborty , Tamoghna Mukhopadhyay , Malaya K. Nayak , Achintya Kumar Dutta

We have employed equation-of-motion coupled-cluster (EOM-CC) method in the four-component relativistic theory framework to understand roles of electron correlation effects in the $\textit{ab initio}$ estimations of electric dipole…

We report an implementation of the core-valence separation approach to the 4-component relativistic Hamiltonian based equation-of-motion coupled-cluster with singles and doubles theory (CVS-EOM-CCSD), for the calculation of relativistic…

First-principles analysis of the spectroscopic signatures of correlated quantum materials poses significant challenges due to the interplay between spin-orbit and vibronic couplings, as well as the need to describe both dynamic and static…

Strongly Correlated Electrons · Physics 2026-03-05 Teruki Matsuzaki , Liviu F. Chibotaru , Maristella Alessio , Naoya Iwahara

We present our computational implementation of the equation-of-motion (EOM) coupled-cluster (CC) singles, doubles, and triples (SDT) method for computing doubly ionized (DIP) and two-electron attached (DEA) states within Q-CHEM. These…

Chemical Physics · Physics 2025-01-14 Manisha , Prashant Uday Manohar , Anna I Krylov

We have developed an efficient scheme for the calculation of transition properties within the four-component relativistic equation-of-motion coupled-cluster (EOM-CC) method using the expectation value approach. The calculation of transition…

We present a combined imaginary-time/real-time time-dependent (TD) approach for evaluating linear absorption spectra of open-shell systems at the electron attachment (EA) and ionization potential (IP) equation-of-motion coupled-cluster…

Chemical Physics · Physics 2026-05-05 P. D. Varuna S. Pathirage , Stephen H. Yuwono , Xiaosong Li , A. Eugene DePrince

A new perturbative approach to canonical equation-of-motion coupled-cluster theory is presented using coupled-cluster perturbation theory. A second-order M{\o}ller-Plesset partitioning of the Hamiltonian is used to obtain the well known…

Chemical Physics · Physics 2015-07-09 Jason N. Byrd , Varun Rishi , Ajith Perera , Rodney J. Bartlett

We present a relativistic third-order algebraic diagrammatic construction (ADC(3)) approach for calculating double ionization potentials (DIPs). By employing the exact two-component atomic mean-field (X2CAMF) Hamiltonian in combination with…

Chemical Physics · Physics 2025-10-08 Sujan Mandal , Achintya Kumar Dutta

When a vacancy is created in an inner-valence orbital of a dimer of atoms or molecules, the resulting species can undergo interatomic/intermolecular Coulombic decay (ICD): the hole is filled through a relaxation process that leads to a…

Chemical Physics · Physics 2023-05-18 Valentina Parravicini , Thomas-C. Jagau

A subsystem approach for obtaining electron binding energies in the valence region and apply it to the case of halide ions (X$^-$, X = F-At) in water. This approach is based on electronic structure calculations combining the relativistic…

We present the implementation of relativistic coupled cluster quadratic response theory (QR-CC), following our development of relativistic equation of motion coupled cluster quadratic response theory (QR-EOMCC) [X. Yuan et al., J. Chem.…

Chemical Physics · Physics 2025-11-17 Xiang Yuan , Loïc Halbert , Lucas Visscher , André Severo Pereira Gomes

We have presented the theory, implementation, and benchmark results for the one-electronic variant of spin-free exact two-component (SFX2C1e) linear response coupled cluster (LRCCSD) theory for static and dynamic polarizabilities of atoms…

Chemical Physics · Physics 2024-05-31 Sudipta Chakraborty , Tamoghna Mukhopadhyay , Achintya Kumar Dutta

This work discusses a protocol for constructing highly accurate potential energy curves (PECs) for the lowest two states of Rb$_{2}^+$, i.e. $X\,{}^2{\Sigma}{_g^+}$ and $(1) {}^2\Sigma{_u^+}$, using an additivity scheme based on…

Atomic Physics · Physics 2022-09-21 Jan Schnabel , Lan Cheng , Andreas Köhn

We present an efficient algorithm for one- and two-component relativistic exact-decoupling calculations. Spin-orbit coupling is thus taken into account for the evaluation of relativistically transformed (one-electron) Hamiltonian. As the…

Chemical Physics · Physics 2013-05-10 Daoling Peng , Nils Middendorf , Florian Weigend , Markus Reiher

We incorporate explicit, non-perturbative treatment of spin-orbit coupling into ab initio auxiliary-field quantum Monte Carlo (AFQMC) calculations. The approach allows a general computational framework for molecular and bulk systems in…

Strongly Correlated Electrons · Physics 2023-02-16 Brandon Eskridge , Henry Krakauer , Hao Shi , Shiwei Zhang

The accurate prediction of ionization potentials (IPs) is central to understanding molecular reactivity, redox behavior, and spectroscopic properties. While vertical IPs can be accessed directly from electronic excitations at fixed nuclear…

Chemical Physics · Physics 2026-05-20 Marios-Petros Kitsaras , Johannes Tölle , Pierre-François Loos

The equation of motion coupled cluster singles and doubles model (EOM-CCSD) is an accurate, black-box correlated electronic structure approach to investigate electronically excited states and electron attachment or detachment processes. It…

Chemical Physics · Physics 2023-09-18 Loïc Halbert , Andre Severo Pereira Gomes

We have implemented noniterative triples corrections to the energy from coupled-cluster with single and double excitations (CCSD) within the 1-electron exact two-component (1eX2C) relativistic framework. The effectiveness of both the…

A relativistic coupled-cluster (RCC) theory is implemented to study electron impact excitations of atomic species. As a test case, the electron impact excitations of the $3s ~ ^2S_{1/2} - 3p ~ ^2P_{1/2;3/2}$ resonance transitions are…

Atomic Physics · Physics 2018-02-14 L. Sharma , B. K. Sahoo , P. Malkar , R. Srivastava