Theoretical Studies On Electron Spin Polarization In Low-dimensional Carbon Systems Induced By Adatoms

Involved by the Pauli exclusion principle,spin polarization effects accompany the presence of unpaired electrons in the microscopic molecular system,which is also considered to be an important source of magnetism in the low-dimensional structure of pure carbon systems.We summarized previous studies about the magnetic properties in pure carbon systems,and found that the sources of these magnetic properties are basically generated by the adsorption of external carbon adatoms on the surface.These magnetic conclusions are basically obtained in one-dimensional nanotubes or two-dimensional graphenes.A common feature of these two low-dimensional structures is that they only contain hexagons surrounded by carbon atoms,so that there are only[6,6]C-C bond between two hexagons.However,as the most typical zero-dimensional fullerene,the biggest difference is that C₆₀ have not only the[6,6]C-C bond between hexagon and hexagon,but also the[5,6]C-C bond between pentagon and hexagon.In view of this,we further studied the spin-polarization properties of several pure carbon fullerenes with carbon adatoms adsorbed on[6,6]and[5,6]structures.Surprisingly,although the carbon adatom adsorbed on the[5,6]structure is spin-polarized,it can introduce a more stable non-magnetic than magnetic state due to charge transfer and electron anti-parallel occupancy.This is the first time to predict the unusual spin polarization effect in pure carbon system,and it will be helpful to understand some reasons why the experimental results can not be consistent with the theoretical results.Superatoms are a class of clusters with atomically exact orbital characteristics.Endohedral metal fullerenes based on the association of f electrons and p electrons can constitute various superatoms.Since the valence electrons of the embedded metal are all bonded to the carbon cage,the valence shell of the metal thus is fully filled.Their delocalized valence orbitals can be seen as superatomic orbitals 1S²,1P⁶,1D¹⁰,2S²...Based on the stable superatom cluster,U@C₂₈,carbon adatom defects are introduced on its surface.It is interesting to observe what will change on its electronic structure,and the interaction between adatom and pristine superatom.It can provide theoretical support for the design of new functional structures based on superatoms in the future.