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View article: Double-pair Coulomb and Breit photon correction to the correlated relativistic energy
Double-pair Coulomb and Breit photon correction to the correlated relativistic energy Open
The simplest, algebraic quantum-electrodynamical corrections, due to the double-negative energy subspace and instantaneous interactions, are computed to the no-pair energy of two-spin-1/2-fermion systems. Numerical results are reported for…
View article: High-precision quantum dynamics of He2 over the b 3Πg–c 3Σg+ electronic subspace by including non-adiabatic, relativistic, and QED corrections and couplings
High-precision quantum dynamics of He2 over the b 3Πg–c 3Σg+ electronic subspace by including non-adiabatic, relativistic, and QED corrections and couplings Open
Relativistic, quantum electrodynamics, and non-adiabatic corrections and couplings are computed for the b 3Πg and c3Σg+ electronic states of the helium dimer. The underlying Born–Oppenheimer potential energy curves are converged to 1 ppm (…
View article: Exact quantum dynamics of methanol: Full-dimensional <i>ab initio</i> potential energy surface of spectroscopic quality and variational vibrational states
Exact quantum dynamics of methanol: Full-dimensional <i>ab initio</i> potential energy surface of spectroscopic quality and variational vibrational states Open
The methanol molecule is a sensitive probe of astrochemistry, astrophysics, and fundamental physics. The first-principles elucidation and prediction of its rotational–torsional–vibrational motions are enabled in this work by the computatio…
View article: Rovibrational computation of H <sub>3</sub> <sup>+</sup> with permutationally invariant Pekeris coordinates
Rovibrational computation of H <sub>3</sub> <sup>+</sup> with permutationally invariant Pekeris coordinates Open
The Pekeris coordinates provide a permutationally invariant set of coordinates for H$_3^+$. They are defined as linear combinations of the three internuclear distances that automatically fulfil the triangle inequality for all non-negative …
View article: Rovibrational computations for He$_2^+$ X~$Σ_\mathrm{u}^+$ including non-adiabatic, relativistic and QED corrections
Rovibrational computations for He$_2^+$ X~$Σ_\mathrm{u}^+$ including non-adiabatic, relativistic and QED corrections Open
We report the potential energy curve, the diagonal Born-Oppenheimer, non-adiabatic mass, relativistic, and leading-order QED corrections for the ground electronic state of the helium dimer cation; the higher-order QED and finite-nuclear si…
View article: Spin-dependent terms of the Breit-Pauli Hamiltonian evaluated with an explicitly correlated Gaussian basis set for molecular computations
Spin-dependent terms of the Breit-Pauli Hamiltonian evaluated with an explicitly correlated Gaussian basis set for molecular computations Open
This work collects the spin-dependent leading-order relativistic and quantum-electrodynamical corrections for the electronic structure of atoms and molecules within the non-relativistic quantum electrodynamics framework. We report the comp…
View article: Hyperfine rovibrational states of H$_3^+$ in a weak external magnetic field
Hyperfine rovibrational states of H$_3^+$ in a weak external magnetic field Open
Rovibrational energies, wave functions, and Raman transition moments are reported for the lowest-energy states of the H$_3^+$ molecular ion including the magnetic couplings of the proton spins and molecular rotation in the presence of a we…
View article: Variational Vibrational States of Methanol (12D)
Variational Vibrational States of Methanol (12D) Open
Full-dimensional (12D) vibrational states of the methanol molecule (CH3OH) have been computed using the GENIUSH-Smolyak approach and the potential energy surface from Qu and Bowman (2013). All vibrational energies are converged better than…
View article: One-Particle Operator Representation over Two-Particle Basis Sets for Relativistic QED Computations
One-Particle Operator Representation over Two-Particle Basis Sets for Relativistic QED Computations Open
This work is concerned with two-spin-1/2-fermion relativistic quantum mechanics, and it is about the construction of one-particle projectors using an inherently two-particle, "explicitly correlated" basis representation necessary for good …
View article: Regularized relativistic corrections for polyelectronic and polyatomic systems with explicitly correlated Gaussians
Regularized relativistic corrections for polyelectronic and polyatomic systems with explicitly correlated Gaussians Open
Drachmann’s regularization approach is implemented for floating explicitly correlated Gaussians (fECGs) and molecular systems. Earlier applications of drachmannized relativistic corrections for molecular systems were hindered due to the un…
View article: Bound-State Relativistic Quantum Electrodynamics: A Perspective for Precision Physics with Atoms and Molecules
Bound-State Relativistic Quantum Electrodynamics: A Perspective for Precision Physics with Atoms and Molecules Open
Precision physics aims to use atoms and molecules to test and develop the fundamental theory of matter, possibly beyond the Standard Model. Most of the atomic and molecular phenomena are described by the quantum electrodynamics (QED) secto…
View article: QED corrections to the correlated relativistic energy: One-photon processes
QED corrections to the correlated relativistic energy: One-photon processes Open
This work is a collection of initial calculations and formal considerations within the Salpeter–Sucher exact equal-time relativistic quantum electrodynamics framework. The calculations are carried out as preparation for the computation of …
View article: Methane dimer rovibrational states and Raman transition moments
Methane dimer rovibrational states and Raman transition moments Open
Benchmark-quality rovibrational data are reported for the methane dimer from variational nuclear motion computations using an ab initio intermolecular potential energy surface reported by [M. P. Metz et al., Phys. Chem. Chem. Phys., 2019, …
View article: QED corrections to the correlated relativistic energy: one-photon processes
QED corrections to the correlated relativistic energy: one-photon processes Open
This work is a collection of initial calculations and formal considerations within the Salpeter-Sucher exact equal-time relativistic quantum electrodynamics framework. The calculations are carried out as preparation for the computation of …
View article: Vibrational infrared and Raman spectrum of HCOOH from variational computations
Vibrational infrared and Raman spectrum of HCOOH from variational computations Open
All vibrational energies of the (trans-, cis-, delocalized-) formic acid molecule are converged up to 4500 cm$^{-1}$ beyond the zero-point vibrational energy with the GENIUSH-Smolyak variational approach and using an ab initio potential en…
View article: Pre-Born-Oppenheimer Dirac-Coulomb-Breit computations for two-body systems
Pre-Born-Oppenheimer Dirac-Coulomb-Breit computations for two-body systems Open
The sixteen-component, no-pair Dirac--Coulomb--Breit equation, derived from the Bethe--Salpeter equation, is solved in a variational procedure using Gaussian-type basis functions for the example of positronium, muonium, hydrogen atom, and …
View article: The Bethe–Salpeter QED Wave Equation for Bound-State Computations of Atoms and Molecules
The Bethe–Salpeter QED Wave Equation for Bound-State Computations of Atoms and Molecules Open
Interactions in atomic and molecular systems are dominated by electromagnetic forces and the theoretical framework must be in the quantum regime. The physical theory for the combination of quantum mechanics and electromagnetism, quantum el…
View article: Pre-Born–Oppenheimer energies, leading-order relativistic and QED corrections for electronically excited states of molecular hydrogen
Pre-Born–Oppenheimer energies, leading-order relativistic and QED corrections for electronically excited states of molecular hydrogen Open
For rovibronic states corresponding to the $B$ and $B'\\ ^1\\Sigma_\\text{u}^+$\nelectronic states of the hydrogen molecule, the pre-Born--Oppenheimer\n(four-particle) non-relativistic energy is converged to a 1-3 parts-per-billion\nrelati…
View article: Lower bounds on par with upper bounds for few-electron atomic energies
Lower bounds on par with upper bounds for few-electron atomic energies Open
The development of computational resources has made it possible to determine upper bounds for atomic and molecular energies with high precision. Yet, error bounds to the computed energies have been available only as estimates. In this pape…
View article: Pre-Born–Oppenheimer energies, leading-order relativistic and QED corrections for electronically excited states of molecular hydrogen
Pre-Born–Oppenheimer energies, leading-order relativistic and QED corrections for electronically excited states of molecular hydrogen Open
For rovibronic states corresponding to the B and B′1Σu+ electronic states of the hydrogen molecule, the pre-Born–Oppenheimer (four-particle) non-relativistic energy is converged to a 1–3 parts-per-billion relative precision. The four-parti…
View article: Relativistic two-electron atomic and molecular energies using $LS$ coupling and double groups: role of the triplet contributions to singlet states
Relativistic two-electron atomic and molecular energies using $LS$ coupling and double groups: role of the triplet contributions to singlet states Open
The triplet contribution is computed to the 1 and 2 $^1S^\text{e}_0$ states of the He atom, to the $1\ ^1S^\text{e}_0$ state of the Li$^+$ and Be${^{2+}}$ ions, and to the $X\ ^1Σ_\text{g}^+$ ground state of the H$_2$ molecule by extensive…
View article: The Bethe-Salpeter QED wave equation for bound-state computations of atoms and molecules
The Bethe-Salpeter QED wave equation for bound-state computations of atoms and molecules Open
Interactions in atomic and molecular systems are dominated by electromagnetic forces and the theoretical framework must be in the quantum regime. The physical theory for the combination of quantum mechanics and electromagnetism, quantum el…
View article: Exact quantum dynamics developments for floppy molecular systems and complexes
Exact quantum dynamics developments for floppy molecular systems and complexes Open
Molecular rotation, vibration, internal rotation, isomerization, tunneling, intermolecular dynamics of weakly and strongly interacting systems, intra-to-inter-molecular energy transfer, hindered rotation and hindered translation over surfa…
View article: High-dimensional neural network potentials for accurate vibrational frequencies: The formic acid dimer benchmark
High-dimensional neural network potentials for accurate vibrational frequencies: The formic acid dimer benchmark Open
In recent years, machine learning potentials (MLP) for atomistic simulations have attracted a lot of attention in chemistry and materials science. Many new approaches have been developed with the primary aim to transfer the accuracy of ele…
View article: CH<sub>4</sub>·F<sup>−</sup> revisited: full-dimensional <i>ab initio</i> potential energy surface and variational vibrational states
CH<sub>4</sub>·F<sup>−</sup> revisited: full-dimensional <i>ab initio</i> potential energy surface and variational vibrational states Open
The automated development of a new ab initio full-dimensional potential\nenergy surface (PES) is reported for the CH$_4\\cdot$F$^-$ complex using the\nROBOSURFER program package. The new potential provides a near-spectroscopic\nquality des…
View article: Evaluation of the Bethe logarithm: from atom to chemical reaction
Evaluation of the Bethe logarithm: from atom to chemical reaction Open
A general computational scheme for the (non-relativistic) Bethe logarithm is developed opening the route to `routine' evaluation of the leading-order quantum electrodynamics correction (QED) relevant for spectroscopic applications for smal…
View article: Variational versus perturbative relativistic energies for small and light atomic and molecular systems
Variational versus perturbative relativistic energies for small and light atomic and molecular systems Open
Variational and perturbative relativistic energies are computed and compared for two-electron atoms and molecules with low nuclear charge numbers. In general, good agreement of the two approaches is observed. Remaining deviations can be at…
View article: Benchmark potential energy curve for collinear H3
Benchmark potential energy curve for collinear H3 Open
A benchmark-quality potential energy curve is reported for the H$_3$ system in collinear nuclear configurations. The electronic Schrödinger equation is solved using explicitly correlated Gaussian (ECG) basis functions using an optimized fr…