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We present unrestricted Hartree Fock method coupled with configuration interaction (CI) method (URHF-CI) suitable for the calculation of ground and excited states of large number of electrons localized by complex gate potentials in…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 Ramin M. Abolfath , Pawel Hawrylak

We design two variational algorithms to optimize specific 2-local Hamiltonians defined on graphs. Our algorithms are inspired by the Quantum Approximate Optimization Algorithm. We develop formulae to analyze the energy achieved by these…

Quantum Physics · Physics 2024-12-20 Kunal Marwaha , Adrian She , James Sud

We present a self-consistent approach for computing the correlated quasiparticle spectrum of charged excitations in iterative $\mathcal{O}[N^5]$ computational time. This is based on the auxiliary second-order Green's function approach [O.…

Chemical Physics · Physics 2020-10-05 Oliver J. Backhouse , George H. Booth

Achieving chemical accuracy for strongly correlated molecules is a defining milestone for first-generation, fault-tolerant quantum computers, yet the factorial growth of three, four, and six-index tensor contractions in coupled-cluster…

We develop a multi-threaded parallel coordinate descent full configuration interaction algorithm (mCDFCI), for the electronic structure ground-state calculation in the configuration interaction framework. The FCI problem is reformulated as…

Chemical Physics · Physics 2025-01-27 Yuejia Zhang , Weiguo Gao , Yingzhou Li

Accurately describing strong electron correlation in complex systems remains a prominent challenge in computational chemistry as near-term quantum algorithms treating total correlation often require prohibitively deep circuits. Here we…

Computational Engineering, Finance, and Science · Computer Science 2026-04-21 Zhanou Liu , Yuhao Chen , Yingjin Ma , Xiao He , Yuxin Deng

[Background] Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multi-reference…

Nuclear Theory · Physics 2017-01-30 W. Satula , P. Baczyk , J. Dobaczewski , M. Konieczka

The ability to efficiently and accurately calculate equilibrium time correlation functions of many-body condensed phase quantum systems is one of the outstanding problems in theoretical chemistry. The Nakajima-Zwanzig-Mori formalism coupled…

Chemical Physics · Physics 2017-04-05 Andrés Montoya-Castillo , David R. Reichman

We present the formulation and implementation of an analytical gradient algorithm for extended multiconfiguration quasidegenerate perturbation theory (XMCQDPT2) with the resolvent-fitting approximation by Granovsky. This algorithm is…

Chemical Physics · Physics 2021-08-30 Jae Woo Park

A new state specific correlation correction to configuration interaction singles (CIS) excitation energies is preseted using coupled cluster perturbation theory (CCPT). General expressions for CIS-CCPT are derived and expanded explicitly to…

Chemical Physics · Physics 2015-06-19 Jason N. Byrd , Victor F. Lotrich , Rodney J. Bartlett

The convergence property of a stochastic algorithm for the self-consistent field (SCF) calculations of electron structures is studied. The algorithm is formulated by rewriting the electron charges as a trace/diagonal of a matrix function,…

Numerical Analysis · Mathematics 2023-04-20 Taehee Ko , Xiantao Li

The multiscale model combining the multiconfigurational self-consistent field (MCSCF) method with the fully atomistic polarizable Fluctuating Charges (FQ) force field (J. Chem. Theory Comput. 2024, 20, 9954-9967) is here extended to the…

Chemical Physics · Physics 2025-11-14 Francesco Mazza , Marco Trinari , Chiara Sepali , Chiara Cappelli

We present a stable and systematically improvable quantum Monte Carlo (QMC) approach to calculating excited-state energies, which we implement using our fast randomized iteration method for the full configuration interaction problem…

Computational Physics · Physics 2023-10-03 Samuel M. Greene , Robert J. Webber , James E. T. Smith , Jonathan Weare , Timothy C. Berkelbach

We present a fully variational locally scaled self-interaction corrected (SIC) energy functional using complex optimal orbitals. This represents an important milestone for fully variational SIC energy functionals, which have been shown to…

We derive and implement analytic nuclear gradients and derivative couplings for a constrained Complete Active Space Self-Consistent Field with a small active space designed to model electron or hole transfer. Using a Lagrangian formalism,…

Computational Physics · Physics 2025-09-01 Tian Qiu , Joseph E. Subotnik

Quantum computation is one of the most promising new paradigms for the simulation of physical systems composed of electrons and atomic nuclei, with applications in chemistry, solid-state physics, materials science, and molecular biology.…

Quantum Physics · Physics 2024-11-05 Jakob Günther , Alberto Baiardi , Markus Reiher , Matthias Christandl

Over the course of the past few decades, the field of computational chemistry has managed to manifest itself as a key complement to more traditional lab-oriented chemistry. This is particularly true in the wake of the recent renaissance of…

Chemical Physics · Physics 2018-10-16 Janus J. Eriksen , Jürgen Gauss

We derive the second-order approximation (PT2) to the ensemble correlation energy functional by applying the G\"{o}rling-Levy perturbation theory on the ensemble density-functional theory (EDFT). Its performance is checked by calculating…

Computational Physics · Physics 2021-11-17 Zeng-hui Yang

We present an extension of the spin-adapted configuration-interaction method for the computation of four electrons in a quasi two-dimensional quantum dot. By a group-theoretical decomposition of the basis set and working with relative and…

Mesoscale and Nanoscale Physics · Physics 2015-06-17 Peter Kramer , Tobias Kramer

An accurate description of strong correlation is quintessential for the exploration of emerging chemical phenomena. While near-term variational quantum algorithms provide a theoretically scalable framework for quantum chemical problems, the…

Quantum Physics · Physics 2025-10-20 Arpan Choudhury , Sonaldeep Halder , Rahul Maitra , Debashree Ghosh