Full-dimensional quantum calculations of the vibrational states of ${\rm H}_5^+$H5+

Abstract

Full-dimensional quantum calculations of the vibrational states of H5(+) have been performed on the accurate potential energy surface developed by Xie et al. [J. Chem. Phys. 122, 224307 (2005)]. The zero point energies of H5(+), H4D(+), D4H(+), and D5(+) and their ground-state geometries are presented and compared with earlier theoretical results. The first 10 low-lying excited states of H5(+) are assigned to the fundamental, overtone, and combination of the H2-H3(+) stretch, the shared proton hopping and the out-of-plane torsion. The ground-state torsional tunneling splitting, the fundamental of the photon hopping mode and the first overtone of the torsion mode are 87.3 cm(-1), 354.4 cm(-1), and 444.0 cm(-1), respectively. All of these values agree well with the diffusion Monte Carlo and multi-configuration time-dependent Hartree results where available.

Rotation/Torsion Coupling in H5+, D5+, H4D+, and HD4+ Using Diffusion Monte Carlo

“…We also compare our results to those obtained from multiconfigurational time-dependent Hartree (MCTDH) calculations, 31 vibrational configuration interaction (VCI) calculations obtained using the reaction path version of MULTIMODE, 32 and full CI (FCI) calculations. 33 We believe that the 33 cm −1 shift in the zero-point energy calculated using the basis set DMC approach reflects an incomplete treatment of the coupling between the torsion and the other vibrational degrees of freedom. In particular, this approach neglects couplings between the torsion and displacements of the central proton from the vector that connects the centers of mass of the outer H 2 units, R ⃗ in Figure 1.…”

Modelling rotations, vibrations, and rovibrational couplings in astructural molecules – a case study based on the H+5 molecular ion

“…These reduced-dimensional Hamiltonians replace the full-dimensional (12D) rovibrational Hamiltonian and are used to provide physical insight into the motions of the atoms of H + 5 . The vibrational and rovibrational levels of H + 5 have been computed both by variational nuclear motion [29,30,32,33] and diffusion Monte Carlo (DMC) [31,34,35] techniques. The full-and reduced-dimensional variational computations performed by three of the present authors [18] utilised the GENIUSH algorithm and code [36][37][38].…”

The role of large-amplitude motions in the spectroscopy and dynamics of ${\rm H}_5^+$H5+

“…The proton delocalization is reflected in the low frequency of this vibrational mode as has been seen in both experimental and a variety of theoretical studies of the vibrational spectrum of H + 5 . 11,[13][14][15][16][17][18][19][20] In a recent study, we demonstrated that this proton hopping vibration is strongly coupled to the dissociation coordinate in H + 5 . 14 The third process is more complicated than the first two.…”

“…This choice of coordinates has been employed in many of the studies on H + 5 of Prosmiti and co-workers 16,17,19,20 as well as by Fàbri et al 34 In the second set of Jacobi coordinates, the dissociation coordinate S is defined as the vector that connects H 2 and H + 3 , and the remaining coordinates are designated by s i . Such coordinates were used by Song et al 18 and provide a more appropriate description of H + 5 as it dissociates. It should be noted that, as they are defined in Fig.…”