PEMODELAN DOPING NITROGEN DALAM CARBON NANOTUBE (6,0) DENGAN TEORI FUNGSI KERAPATAN; THE MODELLING OF NITROGEN DOPING IN CARBON NANOTUBE (6,0) BY USING DENSITY FUNCTIONAL THEORY

Azra, Fajriah, Harno Dwi Pranowo

2015 | Tesis | FMIPA

Nitrogen doping in Carbon Nanotube (CNT) is a way to modify the structure of CNT in order to produce CNT that has appropriate electronic property. The modelling of nitrogen doping in CNT with chirality (6,0) is aimed at giving theoretical information about the effect of nitrogen doping toward the structure and electronic property of CNT. That information is really needed to predict the direction and experiment condition in CNT synthesis with nitrogen doping. The modelling was done by using Density Functional Theory (DFT) method at the level of hybrid theory Becke 3, Lee-Yang-Parr (B3LYP). The modelling was also done through atom carbon substitution with atom nitrogen that builds graphite-like and pyridine-like structure. The substitution of atom carbon with atom nitrogen was done randomly. The concentration of nitrogen dopan in CNT which build graphite-like structure is 2,37% and 4,73%, and for pyridinelike is 2,42% and 4,83%. The effect of nitrogen doping toward structure and electronic property of CNT was done by using the structure parameter measurement (diameter, bond length, cohesive energy, and dipole moment) and the parameter of electronic property (Density of State (DOS), gap width between HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) energy, ionization potential, electron affinity, hardness, bonding vibration energy, and electron excitation energy) CNT (6,0) in pure condition and with nitrogen doping. The result of this research states that the energy gap between HOMO and LUMO at CNT is effected by the length, diameter and chirality of the tube. Nitrogen doping in CNT causes the diameter increase (from 4,82 Å becomes 4,83 – 4,85 Å), dipole moment (from 0,0 Debye becomes 0,21 – 3,36 Debye), cohesive energy (from 260,97 kkal/mol becomes 1401,73 – 2580,98 kkal/mol), the gap width between HOMO and LUMO energy (from 0,43 eV becomes 0,64 – 1,88 eV), ionization potential (from 3,65 eV becomes 3,82 – 4,71 eV), hardness (from 0,21 eV becomes 0,32 – 0,94 eV), bonding vibration energy and electron excitation, it also increases the CNT stability. Nitrogen doping in CNT decreases DOS at Fermi area (from 0,5 becomes 0,3 and 0), Fermi energy (from 3,43 eV becomes 3,50 – 3,81 eV), and electron affinity (from 3,22 eV becomes 3,18 – 2,58 eV). The variation of nitrogen dopan in CNT has an effect toward CNT electronic property. If the concentration becomes higher, the stability and gap energy becomes lower. The width of energy gap is 1,72 & 1,88 eV; 1,55 & 1,79 eV; 1,39 & 1,50 eV; and 0,64 eV gradually for dopan concentration 2,37%; 2,42%; 4,73 and 4,83%.

Kata Kunci : Carbon Nanotube (CNT); doping; density functional theory; electronic property.