First-principles calculations based on density functional theory have been done on the technologically important liquid crystalline material azobenzene. The orthorhombic structure of azobenzene has been simulated and the structural parameters have been found out. Structures of Ortho-fluorinated and Para-fluorinated azobenzene have also been simulated. Electron density of states (EDOS) have been computed in all the three cases which exhibits a narrow band gap and are looking similar to that of a semiconductor in all the three cases. Dielectric constant of the material has been computed and it has been observed that the value of dielectric constant decreases due to fluorination. Phonon modes computed in all the three cases show that the structure is very much stable in all the three cases.