Li adsorption was also performed on similarly defected single vacancy
and Stone-Wales defective graphene substrates and it was found that in
the case of both pristine graphene and SW graphene, the Li binding
energies were much lower than the cohesive energy of lithium, thus
showing the superiority of silicene over graphene as a viable substrate.
These results can be seen in the supplementary information in Fig S3.
In order to understand the electronic interaction between the lithium
atom and the silicene substrate, the projected density of states (pDOS)
of the Li(s) and Li(p) orbitals along with the Si(p) orbitals for the
different Si atoms in the SV silicene and SW silicene systems were
plotted. The pDOS plots can be observed in Fig. 5 and confirm the
electronic interaction that takes place between the Li atom and the Si
atoms respectively. An overlap between the Li orbitals with the Si(s)
orbital can be seen from -10 to -8 eV along with overlap just before and
after the Fermi level which indicates strong chemical adsorption of the
Li adatom onto the surface. The extent of the overlap can be seen to be
greater, especially in the region from -8 to -4 eV in the SV silicene
system which indicates stronger electronic interactions and hence
stronger binding energies compared to the SW silicene system. The
symmetric nature of the Li bonding can also be observed via the pDOS
plots of the Si (25) and Si (27) atoms for the SV silicene system shown
in Fig. 5c which completely overlap with one another. This coupled with
the same Si-Li bond length in these atoms indicate that the Li atoms
bonds similarly to both the atoms in the SV silicene system. Similar
behaviour can be observed in the interactions of Li with atom 23 and 33
in the SW silicene system which are also alike in nature.