  The calculated results of FeCl3 graphite intercalation compounds show the
detailed features. The stage-1 FeCl3-graphite intercalation compounds present
diversified electronic properties due to the intercalant. The first-principles
calculations on VASP are utilized to analyze the essential properties, such as
the geometric structures, spatial charge distributions, charge variations, band
structures and density of states. The density of states displays full
information for an explanation of the hybridizations with the special
structures van Hove singularities on it. The van Hove singularities in
graphite-related systems are very important and can provide full information
for examining the intercalation effects. The orbital-decomposed density of
states for C atoms shows that the {\pi} bondings are orthogonal to the sp2
bondings and the C-C bondings retain in the intralayer C atoms. The Fe atoms
and Cl atoms form the Fe-Cl bondings at some unique energy range, presenting
the multi-orbital hybridizations of [4s, 3dxy, 3dyz, 3dxz, 3dx2-y2, 3dz2]-[3px,
3py, 3pz]. For C-Cl and Cl-Cl bonds, the unique van Hove singularities exhibit
their coupling interactions, revealing the multi-orbital hybridizations of
[3px, 3py, 3pz]-[ 3px, 3py, 3pz] and [3s, 3px, 3py, 3pz]-[3s, 3px, 3py, 3pz],
respectively. The Fe-Cl bondings arise from multi-orbital hybridizations of
[4s, 3dxy, 3dyz, 3dxz, 3dx2-y2, 3dz2]-[ 3px, 3py, 3pz]. Due to the band
structures and density of states, the multi-orbital interactions between
intercalants and graphene layers dominate in the low-lying energy range. The
charge transfers per atom (electrons/atom) for C, Fe, Cl are -0.02 e/atom,
-0.28 e/atom and +0.46 e/atom, respectively. Thus, the C atoms in graphene
layers present as positive ones after intercalation, i.e., the graphite system
exhibit p-type doping features in agreement with previous study.
