[CP2K:8589] imaginary frequencies of water dimer even with tight convergence parameters

[Luis Ruiz Pestana]

Hi Ali,

Thanks for the response! I am using 400 Ry because I needed it to be the
same cutoff that I used in some other AIMD simulations in the
condensed phase. Regardless, I have tried the suggested changes and I still
get imaginary frequencies. I am quite surprised that cp2k is having a hard
time with such simple small systems, am I missing something?

Best,
Luis

On Wed, Jan 25, 2017 at 9:35 AM, Ali KACHMAR <ali.kac... at gmail.com>
wrote:

> Dear Luis,
>
> 1. a cutoff of 400 Ry is a bit low for geometry optimization + vibrational
> frequency calculations on water systems. Please run your geometry
> optimization with tight convergence and a cutoff=550 Ry, Relcutoff=70 Ry
>
> 2. Starting from the optimized geometry, please run your vibrational
> analysis calculation using a DX=0.01, and add to the GEO_OPT section
>
>   &GEO_OPT
>     TYPE MINIMIZATION
>     OPTIMIZER CG
>   &END GEO_OPT
>
>
> All the best,
> Ali
>
>
> On Tue, Jan 24, 2017 at 6:00 PM, <lar... at lbl.gov> wrote:
>
>> I am trying to compute the vibrational frequencies of small water
>> clusters, and I am having trouble getting rid of imaginary frequencies,
>> even for the water dimer, using very tight convergence parameters during
>> the geometry optimization.I have also tried to run the simulations with
>> periodic boundary conditions, different values of the displacement, etc.,
>> but I still get a few imaginary frequencies. I have run out of ideas to try
>> so any advice will be greatly appreciated. I have attached here the input
>> files of the calculations.
>>
>> Thanks for your time!
>> Luis
>>
>> --
>> 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 cp2k+uns... at googlegroups.com.
>> To post to this group, send email to cp... at googlegroups.com.
>> Visit this group at https://groups.google.com/group/cp2k.
>> For more options, visit https://groups.google.com/d/optout.
>>
>
> --
> You received this message because you are subscribed to a topic in the
> Google Groups "cp2k" group.
> To unsubscribe from this topic, visit https://groups.google.com/d/
> topic/cp2k/F42_Nn9BqYg/unsubscribe.
> To unsubscribe from this group and all its topics, send an email to
> cp2k+uns... at googlegroups.com.
> To post to this group, send email to cp... at googlegroups.com.
> Visit this group at https://groups.google.com/group/cp2k.
> For more options, visit https://groups.google.com/d/optout.
>



-- 
Luis A. Ruiz Pestana, PhD
Postdoctoral Fellow
University of California, Berkeley
Lawrence Berkeley National Laboratory
Berkeley, CA 94720
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20170126/ae9df631/attachment.htm>