Chemical shielding of H(2)O and HF encapsulated inside a C(60) cage

Thermal Property of Fullerene Fibers: One-Dimensional Material with Exceptional Thermal Performance

The recent groundbreaking achievement in the synthesis of large-sized single crystal C60 monolayer, which is covalently bonded in a plane using C60 as building blocks. The asymmetric lattice structure endows it with anisotropic phonon modes and conductivity. If these C60 are arranged in form of 1D fiber, the improved manipulation of phonon conduction along the fiber axis could be anticipated. Here, thermal properties of C60-fiber, including thermal transfer along the C60-fiber axis and across the interlayer interface are investigated using molecular dynamic simulations. Taking advantage of the distinctively hollow spherical structure of C60 building blocks, the spherical structure deformation and encapsulation induced thermal reduction can be up to 56% and 80%, respectively. By applying external electronic fields in H2O@C60 model, its thermal conductivity decreases up to 60%, which realizes the contactless thermal regulation. ln particular, the thermal rectification phenomenon is discovered by inserting atoms/molecules in C60 with a rational designed mass-gradient, and its maximum thermal rectification factor is predicted to ≈45%. These investigations aim to achieve effective regulation of the thermal conductivity of C60-fibers. This work showcases the potential of C60-fiber in the realms of thermal management and thermal sensing, paving the way to C60-based functional materials.

Quantum scattering of icosahedron fullerene C60 with noble-gas atoms

There exist multiple ways to cool neutral molecules. A front runner is the technique of buffer gas cooling, where momentum-changing collisions with abundant cold noble-gas atoms cool the molecules. This approach can, in principle, produce the most diverse samples of cold molecules. We present quantum mechanical and semiclassical calculations of the elastic scattering differential cross sections and rate coefficients of the C60 fullerene with He and Ar noble-gas atoms in order to quantify the effectiveness of buffer gas cooling for this molecule. We also develop new three-dimensional potential energy surfaces for this purpose using dispersion-corrected density functional theory (DFT) with counterpoise correction. The icosahedral anisotropy of the molecular system is reproduced by expanding the potential in terms of symmetry-allowed spherical harmonics. Long-range dispersion coefficients have been computed from frequency dependent polarizabilities of C60 and the noble-gas atoms. We find that the potential of the fullerene with He is about five times shallower than that with Ar. Anisotropic corrections are very weak for both systems and omitted in the quantum scattering calculations giving us a nearly quantitative estimate of elastic scattering observables. Finally, we have computed differential cross sections at the collision energies used in experiments by Han et al. (Chem Phys Lett 235:211, 1995), corrected for the sensitivity of their apparatus, and we find satisfactory agreement for C60 scattering with Ar.

First principles molecular dynamics calculations of the mechanical properties of endofullerenes containing noble gas atoms or small molecules

The mechanical properties of endofullerenes have been investigated by performing compression tests using finite temperature first principles molecular dynamics calculations. We considered various X@C₆₀ systems, with X a single noble gas atom (He, Ne, Ar, Kr, or Xe), small molecules (H₂O, CH₄), or small helium clusters. In the absence of compression, it is observed that there is no or at best a negligible effect of X on the properties of C₆₀. The compression simulations revealed several original findings. First, the influence of X on the stiffness of X@C₆₀ can be quantified, although it is at most 12% for the studied cases. Next, both energy and contact force variations as a function of strain are demonstrated to depend on X. However, this is not the case for the yield strain and for the failure mechanism of the C₆₀ shell. Finally, it is shown that the X@C₆₀ compression could bring X to be in a high stress state. In the specific cases of H₂O and CH₄ molecules, a mechanism of stress assisted dissociation is observed.

Unraveling the Origin of Symmetry Breaking in H2 O@C60 Endofullerene Through Quantum Computations

We explore the origin of the anomalous splitting of the 1₀₁ levels reported experimentally for the H₂O@C₆₀ endofullerene, in order to give some insight about the physical interpretations of the symmetry breaking observed. We performed fully‐coupled 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 C₆₀‐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 C₆₀‐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.