Bound and Quasibound States of He₂H⁺ and He₂D⁺

Abstract

Bound and quasibound states of He 2 H + and He 2 D + in three dimensions have been computed by use of a time-dependent quantum-mechanical wave packet approach for total angular momentum J ) 0. Seven bound states were found for He 2 H + and 14 for He 2 D + , as compared to five for both systems by Lee and Secrest (J. Chem. Phys. 1986, 85, 6565). The potential energy surface needed for the dynamical calculation has been computed by carrying out an ab initio calculation with coupled cluster single and double excitations with perturbative triple excitations [CCSD(T)] employing d-aug-cc-PVTZ basis set. A many-body expansion function proposed by Aguado et al. (Comput. Phys. Commun. 1998, 108, 259) was fitted to the ab initio potential energy values and the resulting fit has a root-mean-square deviation of 10.8 meV (0.25 kcal/mol).

Including nuclear quantum effects into highly correlated electronic structure calculations of weakly bound systems

“…Also, previous works have shown that the vibro-rotational energy levels supported by the [He-H-He] + PES do not correspond to any particular mode but to a combination of them. 87 Focusing on the comparison with previous works using ENMO approaches, it can be noticed that our value for R X−He is quite close to that obtained in Ref. 61 using the APMO-MP2 method (see Table IV).…”

Nuclear quantum effects on the He2H+ complex with the nuclear molecular orbital approach

“…Therefore, for comparison purposes we set as reference the HeH bond distance of 1.75 a.u. calculated with CCSD(T) 1. We note that the conventional electronic structure geometries differ by only ±0.01 a.u.…”

“…Although noble gas dimers Rg 2 (Rg = He, Ne, Ar) are barely stable, with binding energy of the order of a few meV, theoretical studies have shown that the inclusion of charged species such as a proton H + results in the stabilization of the dimers 1. These complexes have attracted much attention because they not only have binding energies between hydrogen and van der Waals bonds but also are good examples of symmetric “hydrogen” bonds (the proton is centrosymmetric with respect to the heavier atoms).…”

“…These complexes have been studied using time‐dependent quantum mechanical wave packet methodologies 1, classical molecular dynamics 2, and diffusion Monte Carlo techniques 3. These studies have pointed out the importance of considering the nuclear delocalization for a proper description of the complex structure and stability.…”

“…Numerous conventional electronic structure calculations have been reported on the HeHHe + complex 1, 4, 13. There is also a NMO/MP2 level 14 study, which was only used to evaluate the efficiency of the method.…”