First principal studies of spectroscopic (IR and Raman, UV-visible), molecular structure, linear and nonlinear optical properties of L-arginine p-nitrobenzoate monohydrate (LANB): A new non-centrosymmetric material

Chemically Modified Quinoidal Oligothiophenes for Enhanced Linear and Third-Order Nonlinear Optical Properties

In the present investigation, quantum chemical calculations have been performed in a systematic way to explore the optoelectronic, charge transfer, and nonlinear optical (NLO) properties of different bis(dicyanomethylene) end-functionalized quinoidal oligothiophenes. The effect of different conformations (linking modes of thiophene rings) on conformational, optoelectronic, and NLO properties are studied from the best-performed dimer to octamer. The optical and NLO properties of all the selected systems (1-7) are calculated by means of density functional theory (DFT) methods. Among all the designed compounds, the largest linear isotropic (αiso) polarizability value of 603.1 × 10-24 esu is shown by compound 7 which is ∼12, ∼16, ∼9, ∼11, ∼10, and ∼4 times larger as compared to compounds 1-6, respectively. A relative investigation is performed considering the expansion in third-order NLO polarizability as a function of size and conformational modes. Among all the investigated systems, system 7 shows the highest value of static second hyperpolarizability ⟨γ⟩ with an amplitude of 7607 × 10-36 esu at the M06/6-311G** level of theory, which is ∼521, ∼505, ∼38, ∼884, ∼185, and ∼15 times more than that of compounds 1-6, respectively. The extensively larger ⟨γ⟩ amplitude of compound 7 with higher oscillator strength and lower transition energy indicates that NLO properties are remarkably dependent upon linking modes of thiophene rings and its chain length. Furthermore, to trace the origin of higher nonlinearities, TD-DFT calculations are also performed at the same TD-M06/6-311G** level of theory. Additionally, a comprehensive understanding of the effect of structure/property relationship on the NLO polarizabilities of these investigated quinoidal oligothiophenes is obtained through the inspection of Frontier molecular orbitals, the density of states (TDOS and PDOS), and molecular electrostatic potential diagrams including the transition density matrix. Hence, the current examination will not just feature the NLO capability of entitled compounds yet additionally incite the interest of experimentalists to adequately modify the structure of these oligothiophenes for efficient optical and NLO applications.

A Systematic and Comparative Analysis of Four Major Classes of DFT Functionals to Compute Linear and Nonlinear Optical Properties of Benchmark Molecules

This study spotlights the fundamental insights about the systematic and comparative analysis of four famous hybrid classes of density functional theory (DFT) methods and their efficacy to calculate the linear and nonlinear optical (NLO) polarizabilities. For this study, urea and para-nitroaniline ([Formula: see text]-NA) molecular geometries are used as prototypes to calculate their linear and NLO properties. For comparative purposes, these molecules are often used as reference organic molecules for determination of NLO response properties and there is a dire need for such a benchmark database to be utilized by the researchers. We report systematically a range of functionals including hybrid (B3LYP, PBE1PBE, BH and HLYP), meta-hybrid (M06, M06-2X, M06-HF, M06-L), long-range corrected (CAM-B3LYP, LC-BLYP, LC-B97D, LC-B97D3) and functional with dispersion correction ([Formula: see text]B97, [Formula: see text]B97X, [Formula: see text]B97XD, HSEH1PBE). These groups are evaluated and their efficiency to calculate linear and NLO properties is graphically compared with each other. Overall, there are less deviations among different functionals for calculating dipole moments of [Formula: see text]-NA and urea while these deviations enhance as one moves from dipole moment to linear polarizability and nonlinear hyperpolarizabilities. In general, if we look at the trends, the polarizability values of B3LYP, M06-L, CAM-B3LYP and HSEH1PBE are relatively large and can be compared with each other. The dispersion corrected and long-range corrected functionals show more systematic deviations. For instance, among dispersion corrected functionals, the amplitudes of dipole moments, linear polarizability and NLO polarizabilities show an increasing trend as [Formula: see text]. It is also important to note that LC-B97D and LC-B97D3 of long-range corrected functional have observed exactly the same values of all the calculated parameters. A good agreement is being observed in static first and second hyperpolarizabilities of urea (B3LYP, M06-L, M06 and HSEH1PBE) and [Formula: see text]-NA (B3LYP, M06, M06-L, CAM-B3LYP and HSEH1PBE). Thus, we believe that the current investigation will provide the benchmark data of reference NLO molecules at different methods for theoretical community and molecular level insights for experimental community to design better NLO materials for hi-tech NLO applications.

Excited state and charge transfer dynamics in gas phase molecule of CH3NH3PbI3: first-principles study

In this work, to probe the charge transfer mechanism of methylammonium lead triiodide (CH₃NH₃PbI₃), we have used density functional theory (DFT) and time-dependent density functional theory (TDDFT). We investigate ground and excited states optimized geometry, UV-vis spectrum and vibrational frequencies of CH₃NH₃PbI₃ molecule. It is observed that in an excited state, the structural change is mostly localized in PbI₃ part of the molecule. Mulliken charge analysis shows that lead (Pb) atom acquires a maximum positive charge and all iodine atoms get a negative charge. In addition to this, all the hydrogen atoms donate their charge to iodine atoms. Therefore, electron transfer from lead (Pb) and hydrogen atoms to the iodine atoms can be considered as a significant charge transfer mechanism. Vibrational frequencies are obtained and assigned with the help of hessian calculations. Vibrational mode at 225 cm^-1 is identified as the NH₃-I stretching.

Non-linear optical properties of polystyrene and polyvinyl alcohol composites with 4-methoxy-1-naphthol

The analysis of the NLO properties of 4-methoxy-1-naphthol (4M1N) reveals that this molecule has the value of polarizability tensor, α, more than 340% greater than that obtained, at the same level of theory, for urea molecule. This improvement grows to 500% when the second-order hyperpolarizability is considered. Calculations performed within LR-PCM-B3LYP/6-311+G(3d,2p) model proved that embedding of 4M1N in the polymer matrix significantly improved these results suggesting applications of 4M1N as the cheap and effective NLO material. The molecule was also studied, both theoretically and experimentally, to determine its full vibrational characterisation and structural description. Calculations were performed with HF, MP2, SVWN and B3LYP methods, in two, varying in size, basis sets, to find optimized structures, conformational isomers and UV–VIS, IR and Raman spectra. The accordance of simulated oscillation and absorption spectra with experimental ones is very good; IR values are slightly red-shifted. NBO charge distribution analysis was made to generate frontier orbitals and find most reactive parts of the molecule.

First-principles study of nitrogen-doped nanographene as an efficient charge transport and nonlinear optical material

The prospective of nitrogen doped graphene (NDG) as useful nonlinear optical (NLO) and charge transport materials is explored using first principles methods.

Role of a singlet diradical character in carbon nanomaterials: a novel hot spot for efficient nonlinear optical materials

Carbon atoms have the potential to produce a variety of fascinating all-carbon structures with amazing electronic and mechanical properties. Over the last few decades, several efforts have been made using experimental and computational techniques to functionalize graphene, carbon nanotubes and fullerenes for potential use in modern hi-tech electronic, medicinal, optical and nonlinear optical (NLO) applications. Since photons replaced electrons as a carrier of information, the field of NLO material design has drawn immense interest in contemporary materials science. There have been several reports of bridging the gap between the exciting fields of carbon nanomaterials and NLO materials by functionalizing carbon nanomaterials for potential NLO applications. In contrast to previous reports of the design of third-order NLO materials using conventional closed-shell materials, a novel strategy using open-shell diradical molecular systems has recently been proposed. Quantum chemically, diradical character is explained in terms of the instability of the chemical bonds in open-shell molecular systems. Interestingly, several carbon nanomaterials, which naturally possess open-shell singlet configurations, have recently gained momentum in the design of these classes of open-shell NLO materials with excellent NLO properties, stability and diversity. The present review establishes a systematic sequence of different studies (spanning over two decades of intense research efforts), starting from the simplest theoretical two-site diradical model, continuing to its experimental and theoretical realization in actual chemical systems, and finally applying the abovementioned model/rule to novel carbon nanomaterials to tune their NLO properties, particularly their second hyperpolarizability (γ). In the present report, we highlight several recent efforts to functionalize carbon nanomaterials by exploiting their open-shell diradical character to achieve efficient third-order NLO properties. Several issues and opportunities are discussed, including the inherited disadvantages of both experimental (the high reactivity and short life of diradical compounds) and quantum (need for multi-reference methodology) techniques when dealing with carbon nanomaterials. A comparative analysis of several quantum chemical investigations, along with contemporary experimental results, will be performed to emphasize the core issues and opportunities related to carbon nanomaterials with singlet open-shell diradical character. Thus, the present review will highlight carbon nanomaterials with diradical/biradical character for their prospective applications in the NLO field.

Molecular structure, spectroscopic (IR, Raman, Ultra Violet-Visible) and nonlinear optical investigation on DCBLPZ: A novel semiorganic NLO material

Dichlorobis(L-proline) zinc(II) (DCBLPZ) is an excellent nonlinear optical (NLO) material because of its ability to exhibit high second harmonic generation and having significant optical transparency. In this work, electro-optical properties of the titled material has been thoroughly investigated by Hartree–Fock (HF) and Density functional theory using different basis sets in C1 symmetry. The calculated geometrical parametres and vibrational frequencies were found to be in good agreement with reported experimental results. Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) studies were carried out to understand the intramolecular charge transfer within the molecule. Total dipole moment ([Formula: see text]), polarizability ([Formula: see text]), anisotropy of polarizability ([Formula: see text] and first hyperpolarizability ([Formula: see text]) values were calculated. The static first hyperpolarizability value is found to be six times higher than urea. Ultra violet-visible spectrum of DCBLPZ molecule was calculated by time-dependent density functional theory (TD-DFT) in gas phase using different functionals. The calculated value of absorption wavelength was found at 234[Formula: see text]nm using TD-B3LYP/[Formula: see text]* level of theory and was in good agreement with experimental value (230[Formula: see text]nm) than other applied methods. Our results give us flexibilty to predict about possible intramolecular charge transfer from both the chlorine atoms toward both the proline units through zinc atom in the studied metallic complex. The other important parametres such as frontier molecular orbital’s (FMO), global reactivity descriptors and molecular electrostatic potential have also been calculated and discussed.

Combined experimental and computational insights into the key features of l-alanine l-alaninium picrate monohydrate: growth, structural, electronic and nonlinear optical properties

Comprising experimental and theoretical techniques we have highlighted the key features of LALAPM for electro-optical applications