2023/04/16 by Jakub Lang, Lang, Jakub, Giovanni Garberoglio +7
Physics and Astronomy · #Advanced Chemical Physics Studies #Atomic and Molecular Physics #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Quantum, superfluid, helium dynamics
paper · pdf · doi:10.48550/arxiv.2304.07887
openalex publication_date 2023/04/16 · openalex created_date 2023/04/21 · openalex updated_date 2026/08/01
The non-additive three-body interaction potential for helium was computed using the coupled-cluster theory and the full configuration interaction method. The obtained potential comprises an improved nonrelativistic Born--Oppenheimer energy and the leading relativistic and nuclear-motion corrections. The mean absolute uncertainty of our calculations due to the incompleteness of the orbital basis set was determined employing complete-basis-set extrapolation techniques and was found to be 1.2%. For three helium atoms forming an equilateral triangle with the side length of 5.6~bohr our three-body potential amounts to -90.6~mK, with an estimated uncertainty of 0.5~mK. An analytic function, developed to accurately fit the computed three-body interaction energies, was chosen to correctly describe the asymptotic behavior of the three-body potential for trimer configurations corresponding to both the three-atomic and the atom-diatom fragmentation channels. For large triangles with sides r12, r23, and r31, the potential takes correctly into account all angular terms decaying as r12-l r23-m r31-n with l+m+n ≤ 14 for the nonrelativistic Born--Oppenheimer energy and l+m+n ≤ 9 for the post-Born--Oppenheimer corrections. We also developed a short-range analytic function describing the local behavior of the total uncertainty of the computed three-body interaction energies. Using both fits we calculated the third pressure and acoustic virial coefficients for helium and their uncertainties for a wide range of temperatures. The results of these calculations were compared with available experimental data and with previous theoretical determinations. The estimated uncertainties of present calculations are 3-5 times smaller than those reported in the best previous work.