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The computationally expensive evaluation and storage of high-rank reduced density matrices (RDMs) has been the bottleneck in the calculation of dynamic correlation for multireference wave functions in large active spaces. We present a…

Chemical Physics · Physics 2020-01-08 Ankit Mahajan , Nick S. Blunt , Iliya Sabzevari , Sandeep Sharma

Selected configuration interaction (SCI) methods, when complemented with a second-order perturbative correction, provide near full configuration interaction (FCI) quality energies with only a small fraction of the Slater determinants of the…

We propose a configuration-interaction (CI) representation to calculate induced nuclear fission with explicit inclusion of nucleon-nucleon interactions in the Hamiltonian. The framework is designed for easy modeling of schematic…

Nuclear Theory · Physics 2021-02-16 G. F. Bertsch , K. Hagino

We present an efficient method of inclusion of the core-valence correlations into the configuration interaction (CI) calculations. These correlations take place in the core area where the potential of external electrons is approximately…

Atomic Physics · Physics 2009-11-13 V. A. Dzuba , V. V. Flambaum

Quantum-selected configuration interaction (QSCI) utilizes an input quantum state on a quantum device to select important bases (electron configurations in quantum chemistry) that define a subspace in which to diagonalize a target…

Quantum Physics · Physics 2025-10-22 Mathias Mikkelsen , Yuya O. Nakagawa

In this work, we develop a mathematical framework for a Selected Configuration Interaction (SCI) algorithm within a bi-orthogonal basis for transcorrelated (TC) calculations. The bi-orthogonal basis used here serves as the equivalent of the…

Chemical Physics · Physics 2023-06-22 Abdallah Ammar , Anthony Scemama , Emmanuel Giner

Quantum-selected configuration interaction (QSCI) has emerged as a feasible approach for approximating electronic ground states on noisy quantum devices toward large-system demonstrations. In QSCI, Slater determinants are sampled from a…

Quantum Physics · Physics 2026-04-14 Ryota Kemmoku , Qi Gao , Shu Kanno , Kimberlee Keithley , Ikko Hamamura , Naoki Yamamoto , Kouhei Nakaji

The concept of machine learning configuration interaction (MLCI) [J. Chem. Theory Comput. 2018, 14, 5739], where an artificial neural network (ANN) learns on the fly to select important configurations, is further developed so that accurate…

Chemical Physics · Physics 2019-10-31 J. P. Coe

We present analytic gradients and derivative couplings for the simplest possible multireference configuration interaction method, CIS-1D, an electronic structure ansatz that includes all single excitations and one lone double excitation on…

Chemical Physics · Physics 2021-02-15 Hung-Hsuan Teh , Joseph E. Subotnik

Ab initio no-core configuration interaction (NCCI) calculations for the nuclear many-body problem have traditionally relied upon an antisymmetrized product (Slater determinant) basis built from harmonic oscillator orbitals. The accuracy of…

We present a novel algorithm that allows one to obtain temperature dependent properties of quantum lattice models in the thermodynamic limit from exact diagonalization of small clusters. Our Numerical Linked Cluster (NLC) approach provides…

Strongly Correlated Electrons · Physics 2007-05-23 Marcos Rigol , Tyler Bryant , Rajiv R. P. Singh

A recently proposed approach for performing electronic-structure calculations on crystalline insulators in terms of localized orthogonal orbitals is applied to the oxides of lithium and sodium, Li2O and Na2O. Cohesive energies, lattice…

Condensed Matter · Physics 2009-10-31 Alok Shukla , Michael Dolg , Peter Fulde , Hermann Stoll

Accurate ground-state energy calculations remain a central challenge in quantum chemistry due to the exponential scaling of the many-body Hilbert space. Variational Monte Carlo and variational quantum eigensolvers offer promising ansatz…

Quantum Physics · Physics 2026-03-27 Shane Thompson , Daniel Gunlycke

We discuss various ways to handle self-interaction corrections (SIC) to Density Functional Theory (DFT) calculations. To that end, we use a simple model of few particles in a finite number of states together with a simple zero-range…

Other Condensed Matter · Physics 2009-11-13 P. M. Dinh , J. Messud , P. -G. Reinhard , E. Suraud

We present a quantum-classical hybrid algorithm for calculating the ground state and its energy of the quantum many-body Hamiltonian by proposing an adaptive construction of a quantum state for the quantum-selected configuration interaction…

Quantum Physics · Physics 2024-12-12 Yuya O. Nakagawa , Masahiko Kamoshita , Wataru Mizukami , Shotaro Sudo , Yu-ya Ohnishi

We present an efficient numerical method for simulating the low-energy properties of disordered many-particle systems. The method which is based on the quantum-chemical configuration interaction approach consists in diagonalizing the…

Mesoscale and Nanoscale Physics · Physics 2009-10-31 Thomas Vojta , Frank Epperlein , Michael Schreiber

We use the recently-developed Heat-bath Configuration Interaction (HCI) algorithm as an efficient active-space solver to perform multi-configuration self-consistent field calculations (HCISCF) with large active spaces. We give a detailed…

Chemical Physics · Physics 2018-11-08 James E. T. Smith , Adam A. Holmes , Bastien Mussard , Sandeep Sharma

Two of the most widely used electronic structure theory methods, namely Hartree-Fock and Kohn-Sham density functional theory, both requires the iterative solution of a set of Schr\"odinger-like equations. The speed of convergence of such…

Chemical Physics · Physics 2024-06-06 S. Hazra , U. Patil , S. Sanvito

This paper reports an implementation of Hartree-Fock linear response with complex orbitals for computing electronic spectra of molecules in a strong external magnetic fields. The implementation is completely general, allowing for…

Chemical Physics · Physics 2019-02-01 Sangita Sen , Kai K. Lange , Erik I. Tellgren

We present efficient implementations of the multilevel CC2 (MLCC2) and multilevel CCSD (MLCCSD) models. As the system size increases, MLCC2 and MLCCSD exhibit the scaling of the lower level coupled cluster model. In order to treat large…

Chemical Physics · Physics 2020-11-25 Sarai D. Folkestad , Eirik F. Kjønstad , Linda Goletto , Henrik Koch