The carbon nanotubes (CNTs) in a zigzag (4, 0) shape before and after substituted with F, Cl, and Br atoms were used as a basic computer model depending on the Quantum Espresso package DFT process (in the present work. This method demonstrated that the electronic structure, bandgap, total energy, FTIR spectrum, Raman spectrum, and depolarization spectrum can all being calculated. The simulated res...