The Effect of Doping on The Physical Properties of Graphene

Abstract

The presents research focuses on a theoretical study of structural and electronic properties of pure 
graphene sheet and then adding different number of N2 atoms . The calculations are carried out using the 
density functional theory(DFT) was used with hybrid functional B3LYP/6-31G level of theory to 
investigate the proposed structures. Gauss View 5.0.8 program was used to design the structures of pure 
and doped graphene sheets. These structures are relaxed by employing the PM6 semi- empirical method 
with the hybrid functional B3LYP-DFT at Gaussian 09 package of programs. The results of the structural 
properties of the studied graphene sheets observed that good relaxation of the structures, the values of 
C-C,C=C, C⚍C and C-H bonds in pure graphene sheets remain in the same ranges of the carbon rings 
structures . These calculations are included the total energy, High Occupied Molecular Orbital HOMO 
and Low Unoccupied Molecular Orbital LUMO energies, forbidden energy gap, ionization energy and 
electron affinity, electrochemical hardness, electronic softness. The result of the total energy of the studied doping graphene sheets is a reflection of the binding energy of each structure and indicates to 
that these structures have good relaxation, and the effect of adding N2 atoms in pure graphene sheet on 
the total energy of the molecule is effective. We showed all doping graphene sheets have small forbidden 
energy gap, but it vibrates depending on the length and number of each sheet and position of N2 atoms 
in the sheets. The ionization energy IE and electron affinity EA of the doping graphene sheets are slightly 
decrease with decreasing the length of the sheets. And all doped graphene sheets have low values of IE 
and EA in comparison with the pure. Also, we showed that all the pure and doped graphene sheets have 
low electrochemical hardness H and high electronic softness S. High electronic softness is the main 
future as a sign for that band gap of the structure goes to be rather soft.