Lang Jakub, Garberoglio Giovanni, Przybytek Michał, Jeziorska Małgorzata, Jeziorski Bogumił
Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
European Centre for Theoretical Studies in Nuclear Physics and Related Areas (FBK-ECT*), Strada delle Tabarelle 286, I-38123, Trento, Italy.
Phys Chem Chem Phys. 2023 Sep 13;25(35):23395-23416. doi: 10.1039/d3cp01794j.
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 - a geometry close to the minimum of the total potential energy surface - 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 , , and , the potential takes correctly into account all angular terms decaying as -l12 -m23 -n21 with + + ≤ 14 for the nonrelativistic Born-Oppenheimer energy and + + ≤ 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 works.
利用耦合簇理论和全组态相互作用方法计算了氦的非加性三体相互作用势。所得到的势包括改进的非相对论性玻恩-奥本海默能量以及主要的相对论性和核运动修正。由于轨道基组不完整，我们采用全基组外推技术确定了计算的平均绝对不确定度，结果为1.2%。对于三个氦原子形成边长为5.6玻尔的等边三角形（一种接近总势能面最小值的几何构型），我们计算得到的三体势为-90.6 mK，估计不确定度为0.5 mK。我们选择了一个为精确拟合计算得到的三体相互作用能而开发的解析函数，以正确描述三体势对于对应于三原子和原子 - 双原子碎裂通道的三聚体构型的渐近行为。对于边长分别为 、 和 的大三角形，该势正确地考虑了所有角向项，对于非相对论性玻恩 - 奥本海默能量，这些角向项按 -l12 -m23 -n21 衰减，其中 + + ≤ 14；对于玻恩 - 奥本海默修正后， + + ≤ 9。我们还开发了一个短程解析函数来描述计算得到的三体相互作用能总不确定度的局部行为。利用这两个拟合函数，我们计算了氦在很宽温度范围内的第三维里系数和声速维里系数及其不确定度。将这些计算结果与现有的实验数据以及先前的理论测定结果进行了比较。目前计算的估计不确定度比之前最佳工作中报道的不确定度小3 - 5倍。
