Synthesis, growth, thermal, optical and mechanical properties of new organic NLO crystal: l-alanine dl-malic acid

A new organic nonlinear optical crystal, l-alanine dl-malic acid (LADLMA), has been grown from aqueous solution by the slow cooling technique. l-alanine and dl-malic acid were used in the ratio 2:1 for synthesis. Crystals of size 24×13×8 mm3 have been obtained in 26 days. Characterizations were carried out to study the structural, optical and mechanical properties of the grown crystals. Single crystal X-ray diffraction analysis shows that they belong to the orthorhombic system. To study the crystalline perfection of the grown crystals, high-resolution X-ray diffraction (HR-XRD) study was carried out. The vibrational frequencies of various functional groups have been derived from FTIR spectrum. Thermal behaviour of the crystal was investigated by TG-DTA analyses. Transmission spectrum has been recorded in the solution state and the cut-off frequency has been determined. Nonlinear optical property of the crystal has been confirmed using the Kurtz powder technique and a study of its second harmonic generation efficiency in comparison with KDP has been made. Knoop hardness test was carried out and its Young's modulus was calculated.