IOSR Journal of Applied Physics (IOSR-JAP) e-ISSN: 2278-4861, PP 25-29 www.iosrjournals.org National Conference on Current Advancements in Physics 3 rd &4 th February 2017 25 | Page Department of Physics, St. John’s College, Palayamkottai-627 002, Tamilnadu, India. DOI 10.9790/4861-17002022529 Electronic, Optical and Vibrational analysis of Nitrobenzene Adsorbed on Silver Cluster U.Reeta Felscia 1 , Beulah J.M.Rajkumar 2 1 (PG & Research Department of Physics, Lady Doak College, India) 2 (PG & Research Department of Physics, Lady Doak College, India) Abstract: Interaction between nitrobenzene and silver cluster is investigated using the Density Functional Theory (DFT) at the B3PW91 level of theory. Adsorption causes a variation in the structural parameters. The charge transfer from silver cluster to nitrobenzene is identified from the plot of the molecular electrostatic potential (MEP) surface and natural population analysis (NPA). A marked enhancement in the calculated polarizability values is also obtained. Enhancement in the first order hyperpolarizability of nitrobenzene- Ag3can find applications in the design of NLO devices. Red shift in C-N stretching vibration indicates that the nitrobenzene is attached to the cluster through the nitro group. Keywords: DFT, Natural Population Analysis, Non Linear Optics, Nitrobenzene, Molecular Electrostatic Potential. I. Introduction In recent years, organic molecular systems have attracted considerable interest because the delocalization of their π-electrons makes them more potent as candidates in organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). Special interest has been paid to molecular systems of two-dimensional (2D) nonlinear acenes due to their delocalized pi electrons [1]. Researchers are showing significant interest in the study of the materials with enhanced optical nonlinearity, due to their potential applications in telecommunications, optical computing and optical information processing [2].Noble metal nanoparticles (NPs) are known to exhibit unique electrical and optical properties, which lead to their potential application in the design of new materials. Adsorption of organic ligands on metal NPs induces changes in catalytic and optoelectrical properties [3]. Several researchers have reported that nanomaterials could enhance the nonlinear optical (NLO) behavior of the molecular system [4]. Computational modeling methods are excellent tools for investigating relationships between the properties of a system and for the interpretation of experimental data. Density functional theory (DFT) is an advanced modeling technique, which is used in analyzing optimized structures, NLO properties and vibrational frequencies of molecular systems [5]. A.G.Al-Sehemi et.al have synthesized and analyzed some N, N-diacylaniline derivatives using both theoretical and experimental FTIR and NMR techniques. The effect of different substituents has been analyzed with the aid of these techniques [6]. In the current work, adsorption behavior of nitrobenzene on silver cluster is investigated using DFT approach. The geometrical, electronic, linear and nonlinear optical properties are studied. In order to gain more understanding about the adsorption process, Raman spectra are also stimulated and analyzed. II. Computational Methods Molecular geometrical properties were analyzed for nitrobenzene and its interactions with silver cluster using the DFT/B3PW91 implemented through the Gaussian 03 software [7]. The basis set 6-31G(d,p) was used for atoms in nitrobenzene. LANL2DZ was applied for Ag3 clusters, which is a well-known typical basis set for metal atoms and organometallic complexes [3]. Zero imaginary vibrational frequencies confirm a true local minimum on the potential energy surface. Investigations on the structural properties, molecular electrostatic potential (MEP), frontier molecular orbitals (FMOs) and Natural population analysis (NPA) gives an insight into the adsorption process. Further, theoretical NLO properties of the system were investigated. The Raman spectra are simulated for both nitrobenzene and nitrobenzene on silver cluster.