| 8:33:40 PM PST - Tue, Feb 26th 2019 |
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The OPTTOL in GAMESS is set to 1.0D-10 for DFTB, and also to 1.0D-11, and the related RHF
frequency analysis is
1 22.790 A 4.789345 0.040791
2 0.084 A 6.890251 0.000000
3 0.023 A 6.885812 0.000000
4 0.034 A 6.890374 0.000000
5 37.846 A 3.929379 0.036886
6 172.729 A 2.086567 0.022109
7 363.748 A 3.410336 0.077421
8 434.011 A 1.023444 0.000317
9 615.593 A 1.038901 0.723858
10 751.224 A 4.094947 0.087465
11 979.847 A 1.089670 0.094492
12 1038.404 A 1.197033 0.161830
13 1134.356 A 1.978351 0.117989
14 1237.757 A 1.203437 0.002447
15 1264.022 A 1.567909 0.140356
16 1456.219 A 1.189515 0.011190
17 1530.772 A 1.269786 1.076701
18 1617.789 A 1.219209 0.186595
19 1662.150 A 1.039877 0.219738
20 1669.327 A 1.045953 0.090570
21 1686.310 A 1.098514 0.141698
22 2126.253 A 1.037980 1.311076
23 2985.475 A 1.057992 0.829015
24 3016.134 A 1.106556 0.438324
25 3073.863 A 1.036438 0.693348
26 3132.885 A 1.099075 0.716761
27 3145.120 A 1.101099 0.797947
No imaginary frequency existing in GAMESS.
According to an article published in JACS in 1995, the ab initio vibrational analysis of the minimum of D-H exchange of CD4 and Zeolite cluster had 5 imaginary frequencies -200.414, -127.723, -56.788, -22.541, -12,698cms-1, which was explained as a spurious consequence of the Cs symmetry of the cluster. The transition state also has 3 imaginary frequencies -1423.384, -155.086 and -42.834 cms-1.
I think the optimized geometry at this level makes this intrisinc and only a very good first guess may eliminate it, thus the warnings from GAMESS perhaps can be ignored with an low enough OPTTOL.
Special, sincere thanks should be given to Dr. Schmidt for his clarification of the technical meaning of this warning in GAMESS and instructions for me to beigin with GAMESS, especially geometry optimization, etc., and long time lucid explanations as well as useful advices on my ceaseless questions; and all those on this forum and NWCHEM Github to teach me to compile NWCHEM.
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