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

Abstract

We explore the origin of the anomalous splitting of the 1 01 levels reported experimentally for the H 2 O@C 60 endofullerene, in order to give some insight about the physical interpretations of the symmetry breaking observed. We performed fullycoupled quantum computations within the multiconfiguration time-dependent Hartree approach employing a rigorous procedure to handle such computationally challenging problems. We introduce two competing physical models, and discuss the observed unconventional quantum patterns in terms of anisotropy in the interfullerene interactions, caused by the change in the off-center position of the encapsulated water molecules inside the cage or the uniaxial C 60 -cage distortion, arising from noncovalent bonding upon water's encapsulation, or exohedral fullerene perturbations. Our results show that both scenarios could reproduce the experimentally observed rotational degeneracy pattern, although quantitative agreement with the available experimental rotational levels splitting value has been achieved by the model that considers an uniaxial elongation of the C 60 -cage. Such finding supports that the observed symmetry breaking could be mainly caused by the distortion of the fullerene cage. However, as nuclear quantum treatments rely on the underlying interactions, a decisive conclusion hinges on the availability of their improved description, taken into account both endofullerene and exohedral environments, from forthcoming highly demanding electronic structure many-body interaction studies.

Confining CO2 inside sI clathrate‐hydrates: The impact of the CO2–water interaction on quantized dynamics

“…In these computations the quantitative description has been achieved by solving numerically the multidimensional, fully coupled Schröndinger equation of the nuclear motion of the guest molecule, 56 by employing the multiconfiguration time-dependent Hartree (MCTDH) method. 58,59 Nevertheless, the accuracy of these and other predictions from rigorous theoretical investigations on the quantum dynamics of nanoconfined molecules inside cavities [60][61][62][63][64][65][66] highly relies on the quality of the potential energy surface (PES) employed in the calculations.…”

Computational Energy Spectra of the H2O@C70 Endofullerene

“…By means of different models that include the breaking of the icosahedral symmetry of the system its energy level structure has been calculated and the experimental energy gap of 4 cm −1 has been reproduced. There is still a rich debate about the nature of the processes involved in this splitting that remains an open discussion [30–36] …”

“…There is still a rich debate about the nature of the processes involved in this splitting that remains an open discussion. [30][31][32][33][34][35][36] However, there are only a few of theoretical studies of the H 2 O@C 70 system. In the seminal article of Williams & Whitehead [29] it was predicted that the water molecule is stable inside the cavity of the C 70 as the endohedral energy of the system has been found lower compared to its exohedral one.…”