It seems only HF Hessian analysis using GAMESS with the default solver setup can be compared with the experimental data in peak numbers and positions in the THz region.
For example, in the case of alanine, the RHF semi-numerical and analytical methods with 6-311G++(2d,2p) of the geometry obtained by mp2 optimization with the almost same basis set, having a warning meaning the analysis is not very rigorous because of the geometry obtained by optimization is not a true stationary point. The analytical method gives
MODE FREQ(CM**-1) ... IR INTENS.
1 0.015 A 0.000000
2 0.008 A 0.000000
3 0.016 A 0.000000
4 61.236 A 0.032632
5 79.238 A 0.013808
which can be compared with the data of D or L alanine in Terahertz absorption spectra of L-,D-,and DL-alanine and their application to determination of enantiomeric composition, in peak numbers and positions, but the mp2 semi-numerical
Hessian analysis with the same basis set and geometry, with no such warning, renders
MODE FREQ(CM**-1) ... IR INTENS.
1 2.723 A 0.057955
2 2.307 A 0.101703
3 1.393 A 0.010289
4 0.149 A 0.000367
5 0.340 A 0.001699
6 2.174 A 0.005833
7 56.927 A 0.082500
The b3lyp analysis with the default analytical hessian input setup gives
MODE FREQ(CM**-1) ... IR INTENS.
1 64.741 A 0.012959
2 38.942 A 0.034262
3 0.098 A 0.000032
4 0.007 A 0.000000
5 0.021 A 0.000000
6 4.677 A 0.072961
7 71.778 A 0.191482
|