3.5. Population analyses and DOS plots
In this part of work, the molecular orbital population analyses were
employed to characterize the influence of the CO molecule adsorption on
the electronic structure of the simple CNT and DNTs. The energy gaps
(Eg) between the highest occupied molecular orbital
(HOMO) and the lowest unoccupied molecular orbital (LUMO) are listed in
Table 5. According to the values of energy gap of CNTs and DNTs (from
0.112 to 0.193 ev), the Eg values of simple CNT was less
than that DNTs and the highest values of Eg were found
in NCNTs. Moreover, the density of states (DOSs) plots are illustrated
in Fig. 2, to explain more about Eg and the electronic
configurations for all interactions. The changes in energy gap (ΔEg(%))
caused significant changes in electric conductivity as defined in the
equation (2).
σ ∝ exp (-Eg/2kBT) (2)
In this equation, σ is the electrical conductance, and k is the
Boltzmann’s constant 50. Thus, the reduction of
Eg in the complexes caused large changes in their
conductivities. The values of
change in energy gap (ΔEg(%))
were showed in the Table 5. These values were in the range of 3.36-42.01
eV. The larger values of ΔEg(%) were for simple CNTs (between
25.32-42.01 eV), and NCNTs (between 7.73-14.52 eV) in comparison to
SCNTs and BCNTs. These considerable values of ΔEg(%) demonstrated that
CNT have high sensitivity toward the adsorption of the CO molecule.