Effect of screening on the carbonKVVAuger line shape of alkali-metal — intercalated graphite

The $\pi$-electron bands of graphite and alkali-metal — intercalated graphite compounds are modeled by a 109-atom-cluster calculation. With the use of relevant parameters determined from linear combination of atomic orbitals $X\alpha$ calculations on ${\mathrm{C}}_2$, both the initial and final states of the Auger (and x-ray emission) process are calculated for a graphite layer having two different densities of $\pi$ electrons, and the effects of screening are addressed. The orthogonalized-final-state rule of Davis and Feldkamp for x-ray emission is extended to the Auger effect. The results indicate that the transition density of states at the Fermi level is increased relative to the final-state density of states, and this finding qualitatively explains the large high-kinetic-energy peak intensity seen in the C $\mathrm{KVV}$ Auger spectra of ${\mathrm{C}}_6$Li and ${\mathrm{C}}_8$Cs.