[gmx-users] normal mode analysis for high frequency vibrations

[Hao Ren]

Hi all,

I am trying to do vibrational analysis for some high frequency modes in 
peptides (using force field method), such as the N-H stretching, C=O 
stretching, N-H bending, etc.

However, I got some unreasonable large frequencies, 6,000-250,000 
wavenumbers, which are obviously not correct.

Does anyone has experience on this issue? I just wanna know whether 
force filed can predict such kind of vibrations with frequencies usually 
in the range 1,000~3,000 wavenumbers.

I appreciate any help and suggestions,
Best Regards,
Hao