A comprehensive study on structural, electronic, and spectroscopic aspects of nonlinear optical potential of 4-methylanilinium 2-carboxyacetate: A DFT approach

4-methylanilinium 2-carboxyacetate (MAC) was synthesised by solution growth method and characterized using powder X-ray diffraction (PXRD) method. The optimized geometry of MAC was obtained using the Gaussian 09 program at the B3LYP/6-311++G(d,p) level of theory. The crystal exhibited a laser damage threshold (LDT) of 1.31 GW/cm 2 , indicating its suitability for photonic applications. The surface characteristics of the grown crystal were examined through scanning electron microscope (SEM) analysis. Hirshfeld surface analysis provided assessment of interatomic interactions between atoms. Molecular electrostatic potential (MEP) analysis was conducted to confirm the proton transfer occurring during the formation of MAC. Magnetic studies using vibrating sample magnetometer (VSM) showed a magnetic susceptibility value of 2.37 × 10 -7 emu. Nonlinear optical properties evaluated using the Kurtz-Perry powder technique revealed a second harmonic generation (SHG) efficiency of 2.47 times that of KDP, while the first hyperpolarizability (β) was calculated as 3.6779 × 10 -30 esu, confirming strong nonlinear optical behavior. Frontier molecular orbital (FMO) analysis showed a HOMO-LUMO energy gap of 3.99 eV, indicating moderate chemical stability. The UV-Visible spectral analysis supported the theoretical results. Spectral analysis were carried out to examine the functional groups in the compound. The charge transfer interactions and associated stability of the molecule were analyzed through natural bond orbital (NBO) analysis. Topological analysis was employed to identify the reactive regions within the molecule.