Growth, electronic absorption and vibrational spectral analysis of semiorganic nonlinear optical material potassium acid phthalate: A scaled quantum mechanical force field study

The spectroscopic properties of the crystallized semiorganic nonlinear optical molecule Potassium Acid Phthalate (KAP) have been recorded and analyzed by FT-IR, Raman and UV techniques. The spectra were interpreted with the aid of normal coordinate analysis following structure optimizations and force field calculations based on density functional theory (DFT) at the B3LYP/6-311+G(d,p) level of theory. Normal coordinate calculations were performed using the DFT force field corrected by a recommended set of scaling factors yielding fairly good agreement between the observed and calculated wavenumbers. KAP is thermally stable up to 275.0 °C and optically transparent in the visible region.