Novel molecular hybrid geometric-harmonic-Zagreb degree based descriptors and their efficacy in QSPR studies of polycyclic aromatic hydrocarbons.

The physicochemical characteristics of polycyclic aromatic compounds critical to environmental modelling such as octanol partition coefficients, solubility, lipophilicity, polarity and several equilibrium constants are functions of their underlying molecular structures, prompting the development of mathematical models to predict such characteristics for which experimental results are difficult to obtain. We propose twelve novel descriptors derived from geometric, harmonic and Zagreb degree-based descriptors and then test the effectiveness of these descriptors on a data set consisting of 55 benzenoid hydrocarbons of environmental importance. Our computations show that the proposed descriptors have a good linear correlation and predictive power when compared to the degree and distance type descriptors. We have also derived the QSPR expressions for four properties of a large series of polycyclic aromatics arising from circumscribing coronenes and show that a scaling factor can be deduced to derive physicochemical properties of such series up to 2D graphene sheets.

Weighted Mostar indices as measures of molecular peripheral shapes with applications to graphene, graphyne and graphdiyne nanoribbons.

In this study we consider relatively new bond-additive Mostar indices that appear to provide quantitative measures of peripheral shapes of molecules. We have computed weighted Mostar, edge-Mostar and total-Mostar indices of graphene, [Formula: see text]-types of graphyne and graphdiyne, which are of considerable interest owing to their novel properties and thus find applications in a number of areas such as sensors, catalysis, chemisorption and nanomedicine. We have implemented the results to analyse the weighted Mostar indices and have obtained exact analytical expressions for the title molecules. We propose that Mostar indices together with frontier molecular orbitals, and HOMO-LUMO gaps can provide measures of chemical reactivity and analysis of peripheral molecular shapes.

Growth, thermal, dielectric and mechanical properties of L-phenylalanine-benzoic acid: a nonlinear optical single crystal.

An efficient amino acid family nonlinear optical single crystal L-phenylalanine-benzoic acid (LPB) was conveniently grown by slow evaporation technique at room temperature. The crystal system and the lattice parameters were analyzed by single crystal X-ray diffraction studies. The grown crystal has excellent transmission in the entire visible region and its lower cut-off wavelength was found to be 248 nm. The SHG efficiency of the grown crystal was found to be 1.6 times higher than that of KDP crystal. The Laser damage threshold value of LPB has been found to be 6.5 GW/cm(2). The sample was thermally stable up to 134°C. Microhardness, dielectric and AC/DC conductivity measurements were made along (001) plane and reported for the first time. Microhardness studies revealed that the sample belongs to hard nature. Frequency dependent dielectric constant was measured for different temperatures and found maximum dielectric constant of 14 for 363 K. Photoconductivity studies of LPB divulged its negative photoconducting nature.