关键词: 从头计算法, 振动谱, 吡啶甲酸, 谐性力场

The harmonic vibrational force field and the vibrational spectrum of γ-picolinic acid have been calculated by the ab initio gradient program TEXAS using a STO-4-21G basis set. The directly computed theoretical harmonic force field was scaled with a set of scaling factors transferred from related molecules to obtain a prediction of fundamental frequencies. The mean deviation between prediction and experimental IR spectrum of γ-picolinic acid in solid phase was 20cm^-^1(23cm^-^1 for in-plane modes, 11cm^-^1 for out-of-plane ones). The vibrational spectra of two isotopic derivatives of γ-picolinic acid (-C^1^6O~2D, -C^1^8O~2H) have been predicted with the SQM force field resulting from the transferred scaling factors. The calculated isotopic shifts are in good agreement with experimental data. A few scaling factors of in-plane modes were optimized to fit theoretical predicted frequencies to the experimental spectrum, reducing the mean deviation of in-plane modes to 15cm^-^1, and the total one to 14cm^-^1. The deviations and the assignments of some fundamentals were discussed.

Key words: AB INITIO CALCULATION, VIBRATIONAL SPECTRA, PYRIDINECARBOXYLIC ACID