Musa E. Mohamed, Abdelhafeez M.A. Mohammed, Experimental and Computational Vibration Study of Amino Acids, ILCPA Volume 15, International Letters of Chemistry, Physics and Astronomy (Volume 15)
https://www.scipress.com/ILCPA.15.1
Abstract:
    Vibrational studies of amino acids experimentally and theoretically have been performed. The Semi-empirical methods optimization by PM6 and RM1 on the l- and d-amino acids (alanine, phenylalanine, aspartic and glutamic acid), showed no difference in energy between l-and d-isomers. The vibrational frequencies were calculated by semi-emprical methods (PM6 and RM1) and<i> Ab Initio</i> methods (B3LYP/6-31+G(d) and were scaled down by factors of 0.925 (RM1), 1.09 (PM6) and 0.89 (B3LYP/6-31+G(d)). The calculated and experimental vibrational frequencies have shown good general agreement.
Keywords:
    <i>Ab Initio</i> Methods (B3LYP/6-31+G(d), Amino Acids, Semi-Empirical Methods (PM6 and RM1), Vibrational Studies