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A unitary coupled-cluster (UCC)-based self-consistent electron propagator theory (EPT) is proposed for the description of electron-detached and electron-attached states. Two practical schemes, termed IP/EA-UCC3 and IP/EA-qUCCSD, are…

Chemical Physics · Physics 2026-03-03 Yu Zhang , Junzi Liu

In the present work we report an implementation of the rank-reduced equation-of-motion coupled cluster method with approximate triple excitations (RR-EOM-CC3). The proposed variant relies on tensor decomposition techniques in order to…

Chemical Physics · Physics 2025-08-26 Piotr Michalak , Michał Lesiuk

The Born-Oppenheimer (BO) approximation is less accurate in the presence of a strong magnetic field than in the absence of a field. This is due to the complicated and unpredictable response of electronic structure to the field, especially…

Chemical Physics · Physics 2023-03-29 Tanner Culpitt , Laurens D. M. Peters , Erik I. Tellgren , Trygve Helgaker

We scrutinize the performance of different variants of equation of motion coupled cluster (EOM-CC) methods to predict electronic excitation energies and excited state potential energy surfaces in closed-shell actinide species. We focus our…

Chemical Physics · Physics 2020-02-26 Artur Nowak , Paweł Tecmer , Katharina Boguslawski

We present a new implementation of the hybrid antisymmetrized Coupled Channels (haCC) method in the framework of the tRecX [A. Scrinzi, Comp. Phys. Comm., 270:108146, 2022.]. The method represents atomic and molecular multi-electron…

Computational Physics · Physics 2024-05-02 Hareesh Chundayil , Vinay P. Majety , Armin Scrinzi

The time-dependence of multi-point observable correlation functions are essential quantities in analysis and simulation of quantum dynamics. Open quantum systems approaches utilize two-point correlations to describe the influence of an…

Quantum Physics · Physics 2025-10-27 Yoana R. Chorbadzhiyska , Peter A. Ivanov , Charlie Nation

We present algebraic diagrammatic construction theory for simulating spin-orbit coupling and electron correlation in charged electronic states and photoelectron spectra. Our implementation supports Hartree-Fock and multiconfigurational…

Chemical Physics · Physics 2025-05-12 Rajat Majumder , Alexander Yu. Sokolov

In this study, we develop a steady state and time-dependent exciton diffusion model including singlet and triplet excitons coupled with a modified Poisson and drift-diffusion solver to explain the mechanism of hyper triplet-triplet fusion…

An efficient perturbational treatment of spin-orbit coupling within the framework of high-level multi-reference techniques has been implemented in the most recent version of the COLUMBUS quantum chemistry package, extending the existing…

A novel approach to rapidly converging high-level coupled-cluster (CC) energetics in an automated fashion is proposed. The key idea is an adaptive selection of the excitation manifolds defining higher-than-two-body components of the cluster…

Chemical Physics · Physics 2023-08-25 Karthik Gururangan , Piotr Piecuch

The formulation of the time-dependent Schrodinger equation in terms of coupled-cluster theory is outlined, with emphasis on the bivariational framework and its classical Hamiltonian structure. An indefinite inner product is introduced,…

Chemical Physics · Physics 2019-04-16 Thomas Bondo Pedersen , Simen Kvaal

We present a natural orbital-based implementation of the intermediate Hamiltonian Fock space coupled-cluster method for (1,1) sector of Fock space. The use of natural orbital significantly reduces the computational cost and can…

Chemical Physics · Physics 2021-09-07 Soumi Haldar , Achintya Kumar Dutta

We describe a set of techniques for performing large scale ab initio calculations using multigrid accelerations and a real-space grid as a basis. The multigrid methods provide effective convergence acceleration and preconditioning on all…

mtrl-th · Physics 2008-02-03 E. L. Briggs , D. J. Sullivan , J. Bernholc

Simulation of 3D low-frequency electromagnetic fields propagating in the Earth is computationally expensive. We present a fictitious wave domain high-order finite-difference time-domain (FDTD) modelling method on nonuniform grids to compute…

Numerical Analysis · Mathematics 2023-02-13 Pengliang Yang , Rune Mittet

Quantum embedding schemes have the potential to significantly reduce the computational cost of first principles calculations, whilst maintaining accuracy, particularly for calculations of electronic excitations in complex systems. In this…

Materials Science · Physics 2022-03-10 Joseph C. A. Prentice

We present two improvements to the tight-binding approximation of time-dependent density functional theory (TD-DFTB): Firstly, we add an exact Hartree-Fock exchange term, which is switched on at large distances, to the ground state…

Chemical Physics · Physics 2015-10-28 Alexander Humeniuk , Roland Mitric

We have developed a new time propagation method, time-dependent adaptive sampling configuration interaction (TD-ASCI), to describe the dynamics of a strongly correlated system. We employ the short iterative Lanczos (SIL) method as the…

Chemical Physics · Physics 2025-06-23 Avijit Shee , Zhen Huang , Martin Head-Gordon , K. Birgitta Whaley

Simulation of the monodomain equation, crucial for modeling the heart's electrical activity, faces scalability limits when traditional numerical methods only parallelize in space. To optimize the use of large multi-processor computers by…

Numerical Analysis · Mathematics 2024-05-31 Giacomo Rosilho de Souza , Simone Pezzuto , Rolf Krause

We present an implementation of equation of motion coupled-cluster singles and doubles (EOM-CCSD) theory using periodic boundary conditions and a plane wave basis set. Our implementation of EOM-CCSD theory is applied to study $F$-centers in…

Materials Science · Physics 2021-02-09 Alejandro Gallo , Felix Hummel , Andreas Irmler , Andreas Grüneis

A time-dependent formulation for electron-hole excitations in extended finite systems, based on the Bethe-Salpeter equation (BSE), is developed using a stochastic wave function approach. The time-dependent formulation builds on the…

Materials Science · Physics 2015-02-11 Eran Rabani , Roi Baer , Daniel Neuhauser