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Int. J. Electroactive Mater. 5 (2017) 31-41

Molecular Structure, Frontier Orbital Analysis and Vibrational Assignments of a Nematic Liquid Crystal: 4-n-ethyl-4´-cyanobiphenyl

Sugriva Nath Tiwari1*, Dipendra Sharma1*, Manoj Kumar Dwivedi2

1Physics, DDU Gorakhpur University, Gorakhpur, Gorakhpur, Uttar Pradesh, India
2Physics, Banaras Hindu University, Varanasi, U.P., India

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Abstract : Molecular structure and thermodynamical properties of 4-n-ethyl-4´-cyanobiphenyl, which is the second homologue of 4-n-alkyl-4´-cyanobiphenyl liquid crystal series, have been reported. The molecular geometry has been optimized by ab-intio HF/6-31G(d,p) as well as DFT B3LYP/6-31G(d,p) methods using GAMESS program. The molecular electrostatic potential surface has been scanned with 0.001electron/bohr3isodensity surface. HOMO, LUMO energies,ionization potential, electron affinity,electronegativity, global hardnessand softness parameters of the liquid crystal molecule have been determined. Thermodynamic properties of the molecule such as internal energy, entropy, enthalpy, Gibbs free energy have been reported. Further, vibrational assignments of the molecule, carried out using ab-intio HF/6-31G(d,p) as well as DFT B3LYP/6-31G(d,p) techniques, have been compared and discussed.

Keywords : Liquid crystal,GAMESS,MEP,HOMO,LUMO,Vibrational assignment