Structure and nonlinear optical property analysis of L-Methioninium oxalate: a DFT approach

Infrared and FT-Raman spectra of the nonlinear optical material l-Methioninium Oxalate were recorded and analyzed. The optimized geometry, first-order hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of density functional theory method. The detailed interpretation of the vibrational spectra was carried out with the aid of normal coordinate analysis followed by scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions leading to its nonlinear optical activity and charge delocalization were analyzed using natural bond orbital technique. Mulliken atomic charge and molecular electrostatic potential are also predicted. HOMO-LUMO energy gap value suggests the possibility of charge transfer within the molecule. The thermodynamic properties at different temperatures are also calculated.