hyperpolarizability

We theoretically investigated molecular structure, vibrational analysis, linear and nonlinear optical properties of the piperazine-1,4-diium bis 2,4,6-trinitrophenolate by employing density functional theory at several levels. To understand their linear and nonlinear optical behavior, dipole moment, polarizability, and first order hyperpolarizability β have been calculated and analysed in details. The hyper-Rayleigh scattering first hyperpolarizability, the electric field–induced second harmonic generation, and the depolarization ratios are the targeted quantities. The groups NO2, NH2, C=C, C-N, and phenolic 'O' atom were identified using theoretical vibrational analysis. The calculated of highest occupied molecular orbital, lowest unoccupied molecular orbital, and their energy gap are also presented. Global chemical reactivity descriptors and the three-dimensional molecular electrostatic potential were studied and discussed. Calculations highlight that 1°) predicted geometrical parameters show very good correlations with the corresponding experimental ones. 2°) A good correlation between the calculated and experimental vibration frequencies was also observed. 3°) A direct relationship between the energy gap and β has been obtained. 4°) The variation in β calculated confirmed the nonlinear optical activity of the studied piperazine. This work will help people understand the nonlinear optical properties of piperazine based molecules and provide guidance for the rational design of molecules with excellent optoelectronic properties.

In this paper, quantum chemical calculations were performed on urea, cinnoline, and some cinnoline derivatives (1-8) at ab initio/HF/6-311G (d, p) level of theory using Gaussian09 and Gussview05 programs. Calculated optimized molecular structure, dipole moment (μ), polarizability (α), molecular electrostatic potential (MEP), and the first order hyperpolarizability (β) for hetero-aromatics 1 to 8, and urea (as a standard molecule) in three phases (gas phase, in presence of water and ethanol) were calculated. The effects of water and ethanol as solvents were taken into account with the aid of the polarizable continuum model (IEF-PCM). The optical properties of studied molecules are increasing in presence of solvents and their values have a direct relationship with the electric constants of solvents. There is a relationship between optical property and energy of the frontier molecular orbitals (FMOs), so these orbitals and the HOMO-LUMO energy gap (ΔE) were investigated. The nonlinear optical (NLO) materials are applied in optical devices, so they are very important. Since experimentally measurement of NLO property is hard, theoretical chemistry is useful in designing new NLO materials.

During the past decades organic nonlinear optical (NLO) materials have been attracted much attention because NLO materials have potential applications in the field of optoelectroni. Experimental measurements and theoretical calculations on molecular hyper polarizability become one of the key factors in the NLO materials design. Theoretical determination of hyper ploarizability is quite useful both in understanding the relationship between the molecular structure and nonlinear optical properties. Several organic derivatives are designed with large first hyper polarizability (β). Among the interesting type of organic materials, charge transfer complexs (CTC) have recently been identified as promising NLO materials. The present study is dedicated to perform a theoretical investigation using B3LYP/6- 311G++ (d, p) level of theory, about the linear and nonlinear optical properties, represented as dipole moment (μ), α, and β of CTCs of, tetracyano quinodimethane derivatives (TCNQ, 1) and tetrathiafulualene (TTF, 2). Our aim is designing new NLO materials that can be synthesized in future.

A comprehensive study on the structural, electronic and nonlinear optical (NLO) properties of alumina nanostructures (Al2O3)n with n = 2-5 belonging to the groups III and VI dopants carried out by density functional theory. The NBO charges exhibit dopant atoms caused to the increasing charge transfer and introduces acceptor-donor model for NLO response of alumina nanostructures. Under the influence of doping S and Se, the energy gap decreases, because high energy level is formed as the new HOMO orbitals in the primary gap of pristine nanostructures. Furthermore, the results of the present study show that dopant atoms enhance NLO response in the alumina nanostructures and the greatest values are obtained for a, b0 and γtot through doping Se in Al10O15.