A nuclear configuration interaction approach to study nuclear spin effects: an application to ortho- and para-3He2@C60

Félix Moncada, William Quintero, Edwin Posada, Lars G.M. Pettersson, Andrés Reyes

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1 Scopus citations

Abstract

We introduce a non-orthogonal configuration interaction approach to investigate nuclear quantum effects on energies and densities of confined fermionic nuclei. The Hamiltonian employed draws parallels between confined systems and many-electron atoms, where effective non-Coulombic potentials represent the interactions of the trapped particles. One advantage of this method is its generality, as it offers the potential to study the nuclear quantum effects of various confined species affected by effective isotropic or anisotropic potentials. As a first application, we analyze the quantum states of two 3He atoms encapsulated in C60. At the Hartree–Fock level, we observe the breaking of spin and spatial symmetries. To ensure wavefunctions with the correct symmetries, we mix the broken-symmetry Hartree–Fock states within the non-orthogonal configuration interaction expansion. Our proposed approach predicts singly and triply degenerate ground states for the singlet (para-3He2@C60) and triplet (ortho-3He2@C60) nuclear spin configurations, respectively. The ortho-3He2@C60 ground state is 5.69 cm−1 higher in energy than the para-3He2@C60 ground state. The nuclear densities obtained for these states exhibit the icosahedral symmetry of the C60 embedding potential. Importantly, our calculated energies for the lowest 85 states are in close agreement with perturbation theory results based on a harmonic oscillator plus rigid rotor model of 3He2@C60.

Original languageEnglish
Article numbere202300498
JournalChemPhysChem
Volume25
Issue number4
DOIs
StatePublished - Feb 16 2024
Externally publishedYes

Funding

. FM and LGMP acknowledge financial support from the European Research Council (ERC) Advanced Grant under Project No. 101021166 – GAS‐WAT. AR acknowledges the financial support of the Office of Research of the National University of Colombia (QUIPU codes: 400000035813, 201010040226) WQ acknowledges the financial support of the ANID/Doctorado Nacional/21222021 Ph.D. fellowship. The computations were enabled by resources provided by the National Academic Infrastructure for Supercomputing in Sweden (NAISS) at the National Supercomputer Center at Linköping (NSC) partially funded by the Swedish Research Council through grant agreement no. 2022‐06725

Keywords

  • ab initio calculations
  • fullerenes
  • isotope effects
  • nuclear quantum effects
  • quantum chemistry

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