Energy band structure of lithium—graphite intercalation compound

Abstract

The energy band structure for C 6Li has been calculated using a two-step procedure. In the first step the ab initio KKR method has been applied to a pseudo-muffin tin potential, where the potential within the atomic spheres is not spherically averaged. The resulting wave functions are then used to obtain the corrections to these bands resulting from the deviation of the actual interstitial potential from its volume averaged value. The results indicate a band structure composed of the energy bands of two-dimensional graphite, folded into the Brillouin zone of C 6Li, plus a metal-like band originating from the lithium s level. The minimum of the metal-like band is about 2 eV above the Fermi level, indicating sizable transfer of charge between the Li and the graphite layers. The interaction of the lithium s level with occupied carbon π and σ bands leads to a covalent contribution to interlayer bonds. However, the interaction of the Li s level with the C π levels near the Fermi level is negligible. The Fermi surface contains two electron sheets originating from the folded, two-dimensional, weakly antibonding graphite π bands.