Knoop microhardness studies were carried out on anthracene single crystals. The hardness vs load plot shows two peaks, one at 5g and another at 17·5 g having hardness values 13·0 kg/mm² and 11·4 kg/mm² respectively. The present observation shows that the$$(20\bar 1)[010]$$ dislocations split into partials.

Microhardness anisotropy in single crystals of anthracene and phenanthrene has been observed by the Knoop indentation technique. The Knoop hardness variation with respect to the [010] direction shows opposite trends. Both these crystals have the same crystal structure and space group. The present observations are explained in terms of orientation and disposition of molecules in the unit cells.

Good quality, non-hygroscopic and transparent crystals of organic benzimidazole L-tartrate (BILT) were grown successfully with a slow evaporation method. The powder X-ray diffraction patterns were analysed with Powder-X software which confirms the monoclinic crystal structure. The charge distribution, transport mechanism and intramolecular bonding mechanism have been investigated with the help of natural bond orbital analysis and molecular electrostatic potential diagram. The presence of various functional groups was confirmed with the help of FTIR–ATR response. The values were compared with the values obtained from computational output with the help of Gaussian software. The crystalline quality was further analysed with UV–visible spectral analysis. The lower cut-off wavelength of 288 nm and further optical parameters like band gap, change in refractive index with wavelength and extinction coefficient values support the usage of the material for optoelectronic devices. With band gap of 4.2 eV, the reactivity of material has been observed with the HOMO and LUMO study. The TGA and DTA analyses confirm the thermal stability of the material up to 192$^{\circ}$C. The lower dielectric constant and lower dielectric loss support the usage of the material for an NLO device. The hopping motion and Joncher’s power law parameters were also obtained. The material decomposes in single-phase which observes in a range of 180–250$^{\circ}$C. The second harmonic generation capacity of the material is found to be 2.69 times that of the KDP with the help of Kurtz and Perry powder technique.