Interactions between a water molecule and C₆₀ in the endohedral fullerene H₂O@C₆₀

Abstract

Symmetry arguments → explanation of changes in energy levels of water upon encapsulation inside C60.

Unraveling the Origin of Symmetry Breaking in H2O@C60 Endofullerene Through Quantum Computations

“…Thus, in lack of extra experimental data in Figure 5 we also present comparisons with rotational energy values from previous theoretical models available in the literature. [16,26,28,29] In particular, we have considered the electrostatic quadrupolar model, [26,28] the more recent S 6 symmetry-adapted potential model, [29] as well as the IR spectral fitting model. [16] Both earlier models [26,28,29] contain "ad-hoc" assumptions and parameters, such as considering one central H 2 O-occupied C 60 cage surrounding by twelve empty near-neighbor cages, all of them rigid with icosahedral symmetry and in P orientational orderings, with a variable water dipole moment value, or unknown free parameters chosen to reproduce results of the electrostatic model up to 12 meV, while the parameters of the spectral model [16] have been determined by fits to the synthetic experimental IR absorption spectra of solid H 2 O@C 60 samples at liquid helium temperature.…”

“…Up to date, a variety of theoretical models and scenarios have been elaborated [16,[25][26][27][28][29] to explore these experimental observations. In a series of studies, Bačić and co-workers [26,28,30,31] have performed 6D and 9D quantum calculations on translational-rotational and vibrational states of the H 2 O@C 60 system, while in order to treat the symmetry-lowering interactions, they have introduced electrostatic models involving dipole-dipole interactions between two neighbor H 2 O@C 60 , or quadrupole interactions between the charge densities of an encapsulated H 2 O molecule in a central C 60 cage surrounded by twelve empty ones.…”

“…[16] The fitting of these experimental data by a quantum mechanical model, including interactions of the H 2 O electric dipole and quadrupole moments with the electrostatic fields of the solid C 60 , has been reported, [16] and the cause of the H 2 O rotational levels splitting has been discussed in terms of effects of solid C 60 crystal field, change in H 2 O molecule geometry or translation-rotation couplings. Further, in an other recent work, symmetry arguments have been also employed [29,32] to construct a two-parameter S 6 symmetry potential, in terms of translational and rotational states of a water molecule, and additional symmetry-lowering interactions, like the intramolecular Jahn-Teller cage distortion effects, have been investigated. Such adjusted model potential has been able to match the variations in energy from selected DFT calculations, and reproduce energy splittings similar to those of the quadrupole model.…”

“…Thus, recently we have reported such computational scheme, within the multiconfiguration time-dependent Hartree (MCTDH) framework, [41,42] to perform in an efficient manner quantum dynamics calculations of any encapsulated triatomic molecule. [27,43,44] As mentioned, distinct suggestions have been reported for symmetry-lowering interaction, [3,9,16,[25][26][27][28][29] including electrostatic charge-transfer, dipoles and quadrupoles between neighbor filled or empty cages, present of impurities, as well as crystal field effects, with the origin of such reduction in symmetry (from the I h of the C 60 molecule [45] ) being of fundamental interest, whether it arises from inter-cage or intra-cage interactions or both.…”

Exclusion principle repulsion effects on the covalent bond beyond the Born–Oppenheimer approximation

“…ferent works have been carried out to analyse the change of the atomic and molecular properties as a function of the confinement, see e.g. [12][13][14][15][16][17][18][19][20][21] . Less is known for other conditions of spatial restriction in which a particular region of the space is forbidden 22,23 .…”