[CP2K-user] [CP2K:12777] Negative frequencies in vibrational analysis

[sumit agrawal]

Hi Lucas Lodeiro,
Thanks for your response. Actually I want to do vibrational analysis in the 
matrix such as Ar and N2. So basically I want to make a cubic cell of the 
Ar or N2 and i want to put my molecule of interest inside this cube. So can 
you tell me what is the exact procedure to do such kind of calculations? 
Should I have to make a cubic cell first then optimized first and after 
optimization of this cubic cell I have to put my molecule of interest 
inside this and again I have to optimize this system? or simply should I 
make a system of interest and optimize this. 

And one more inquiry I want that my interest in systems has less than 100 
atoms so should I have to apply PBC of such kind of systems?

Thanks, Sumit

On Thursday, January 16, 2020 at 7:31:13 AM UTC-8, Lucas Lodeiro wrote:
>
> Hi Sumit,
> If a vibrational mode presents a "negative" frequency (really it is an 
> imaginary frequency, due to the hessian element is the negative one), it is 
> because your system is not at minimmum stationary point (it could be in a 
> 1° order saddle point). To fix it you must to do a geometry optimization 
> first, to reach a stationary point, then a vibrational analysis will have 
> useful information.
> It is important to note that a vibrational analysis with Harmonic 
> approximation does not have sense if you do not found a stationary point on 
> the Potential Energy Surface.
>
> Regards - Lucas Lodeiro
>
> El mar., 14 ene. 2020 a las 9:23, sumit agrawal (<sum... at gmail.com 
> <javascript:>>) escribió:
>
>> When I am trying to do to vibrational analysis, there are some modes that 
>> have negative frequencies. How can I solve this issue? 
>>
>> -- 
>> You received this message because you are subscribed to the Google Groups 
>> "cp2k" group.
>> To unsubscribe from this group and stop receiving emails from it, send an 
>> email to c... at googlegroups.com <javascript:>.
>> To view this discussion on the web visit 
>> https://groups.google.com/d/msgid/cp2k/90400cfa-ea6a-4785-b78d-cf66f2de5c4d%40googlegroups.com 
>> <https://groups.google.com/d/msgid/cp2k/90400cfa-ea6a-4785-b78d-cf66f2de5c4d%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20200117/9e80141d/attachment.htm>