DV-XαCalculation and Ultraviolet Photoelectron Spectra of Gold Trichloride-Graphite Intercalation Compound (AuCl3-GIC)

Abstract

We investigate the electronic structure of AuCl 3 graphite intercalation compounds by means of discrete variational (DV)-Xα molecular orbital calculation and ultraviolet photoelectron spectra (UPS). DV-Xα calculation of the Au 2 Cl 6 intercalate reveals the importance of relativistic effect due to the presence of heavy Au atoms. The terminal Cl 3 p orbital contributes mainly to the lowest unoccupied molecular orbital (LUMO) of Au 2 Cl 6 molecule in addition to the minor contribution of the Au 5 d component. The calculation of (Au 2 Cl 6 ) -0.5 , which is considered to be intercalate species realized in graphitic galleries through charge transfer from graphite, suggests that the Au 2 Cl 6 intercalate band is located at around the Fermi level E F as well as the graphitic π-band. As a consequence, the density of states at E F is 2-3 times larger than that expected only by the graphitic π-band, which is consistent with optical reflectance, magnetic susceptibility, and the electronic specific heat. The small hump around E F in the UPS of AuCl 3 -GIC is considered to be associated with the intercalate band. The overlap population analysis suggests the bonds between gold and chlorine atoms in Au 2 Cl 6 become weaker when the 0.5 electron transfer from graphitic π-band to Au 2 Cl 6 molecule. Therefore, the interatomic distances in the Au 2 Cl 6 molecule are found to become elongated, consistent with the experimental results of the Raman spectra.