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.