Possible New Graphite Intercalation Compounds for Superconductors and Charge Density Wave Materials: Systematic Simulations with Various Intercalants Using a van der Waals Density Functional Method

Graphite intercalation compounds (GICs) are formed by
inserting
various atoms and molecules between the layers of graphite. Among
these GICs, five structures have been reported wherein a single atom
M was intercalated into graphite. Here, the formation energies of
the GICs with these crystal structures and various M were investigated
using a van der Waals density functional method. Consequently, we
found the stable GICs for M = Sc, Y, Fr, and Ra, which are yet to
be reported. Furthermore, we found that Ra-GICs have the possibility
to exhibit a superconductivity of Tc ∼
0.07 K and that Sc- and Y-GICs have the possibility to exhibit the
charge density wave, due to the strong interaction of the electron
and lattice. This insight provides further understanding of how intercalants
and graphite interact with each other in GICs that exhibit unique
physical properties. The calculated formation energies of experimentally
reported ones showed a good agreement with the experimentally reported
stabilities, which provides insights into the synthesizing mechanism
of GICs including the new ones.