arXiv subjects

Carlos Jimenez-Hoyos

Publications and source records attributed to Carlos Jimenez-Hoyos.

6 recordsLinked to original sources

arXiv2026

Strictly Localized Molecular Orbitals: Non-Orthogonal Local Orbitals Built with Chemical Intuition

We propose the use of an a priori localization method based on separating the molecule into fragments to generate a wavefunction suitable for post Hartree-Fock methods. A quasi-Newton approach utilizing Thouless rotation is developed to optimize the strictly localized molecular orbitals(sLMO). We discuss the properties of the sLMO-HF wavefunction and compare it to the tail deleted a posteriori localization methods that are usually done in preparation of post Hartree-Fock methods. We then discuss the effects of choosing different fragmentation patterns and basis sets.

physics.chem-ph↗

arXiv2026

Utilizing a Perturbative Inverse of the Hamiltonian to Improve Lanczos Diagonalization

The use of the shifted inverse Hamiltonian in the Lanczos algorithm is examined. We present a perturbative inverse and demonstrate that the Krylov subspace formed from it is better suited to approximating the ground state wavefunction compared with the Hamiltonian itself. We further demonstrate that the perturbative inverse provides an adequately accurate approximation to the inverse Hamiltonian at second order. Naturally, the quality of the results depend on the quality of the initial guess, here we use the Hartree-Fock, CISD, MP-PT1, and EN-PT1 wavefunctions. Lastly, we examine the scaling of the method where we find that accurate results can be found for similar cost as PT5.

physics.chem-ph↗

arXiv2026

Examining Convergence of Cluster Perturbation Theory and Cluster Coupled Cluster for J1-J2 Heisenberg Spin Lattices

In previous work, it was shown that using the cluster mean field(cMF) wavefunction as the zeroth order wavefunction for perturbation theory and coupled cluster produces a reasonable approximation for the J 1-J 2 Heisenberg model in the thermodynamic limit(TDL). However, this work was limited to cPT4 and cCCSD. The central claim of cMF is that it takes strongly correlated systems and makes them weakly correlated so that PT weakly correlated methods can be used. To confirm that this claim is true, it is important to show that the PT and CC series converge. In this paper, we extend the previous calculations to cPT7 and cCCSDTQ5 where we show that the energy is converging. We also discuss how to perform cluster based calculations efficiently in the thermodynamic limit, which is crucial for these more expensive calculations.

cond-mat.str-el↗

arXiv2026

Examination of Cluster Based Methods to Fermionic Systems

We present the cluster mean field(cMF) and its extensions into perturbation theory(cPT) and coupled cluster(cCC) methods for fermionic systems. We discuss how the commutation rules for fermionic systems modifies the method as well as other computational details. We then perform calculations on the Hubbard model and a few select conjugated molecules to demonstrate the efficacy of the method. We will also use these examples to compare cluster methods to CAS-SCF.

physics.chem-ph↗

arXiv2020

Ground-state properties of the hydrogen chain: insulator-to-metal transition, dimerization, and magnetic phases

Accurate and predictive computations of the quantum-mechanical behavior of many interacting electrons in realistic atomic environments are critical for the theoretical design of materials with desired properties, and require solving the grand-challenge problem of the many-electron Schrodinger equation. An infinite chain of equispaced hydrogen atoms is perhaps the simplest realistic model for a bulk material, embodying several central themes of modern condensed matter physics and chemistry, while retaining a connection to the paradigmatic Hubbard model. Here we report a combined application of cutting-edge computational methods to determine the properties of the hydrogen chain in its quantum-mechanical ground state. Varying the separation between the nuclei leads to a rich phase diagram, including a Mott phase with quasi long-range antiferromagnetic order, electron density dimerization with power-law correlations, an insulator-to-metal transition and an intricate set of intertwined magnetic orders.

cond-mat.str-el↗

arXiv2017

Towards the solution of the many-electron problem in real materials: equation of state of the hydrogen chain with state-of-the-art many-body methods

We present numerical results for the equation of state of an infinite chain of hydrogen atoms. A variety of modern many-body methods are employed, with exhaustive cross-checks and validation. Approaches for reaching the continuous space limit and the thermodynamic limit are investigated, proposed, and tested. The detailed comparisons provide a benchmark for assessing the current state of the art in many-body computation, and for the development of new methods. The ground-state energy per atom in the linear chain is accurately determined versus bondlength, with a confidence bound given on all uncertainties.

physics.comp-ph↗