[CP2K:8589] imaginary frequencies of water dimer even with tight convergence parameters
MattWa... at gmail.com
Thu Jan 26 14:41:52 UTC 2017
What could be a harder test case than small water clusters?
On Thursday, January 26, 2017 at 2:38:56 PM UTC, Luis Ruiz Pestana wrote:
> 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?
> On Wed, Jan 25, 2017 at 9:35 AM, Ali KACHMAR <ali.k... at gmail.com
>> 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
>> TYPE MINIMIZATION
>> OPTIMIZER CG
>> &END GEO_OPT
>> All the best,
>>> 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!
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> Luis A. Ruiz Pestana, PhD
> Postdoctoral Fellow
> University of California, Berkeley
> Lawrence Berkeley National Laboratory
> Berkeley, CA 94720
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