[CP2K-user] [CP2K:13946] Re: gas phase calculations

Marcella Iannuzzi marci... at gmail.com
Tue Sep 22 13:00:34 UTC 2020

Dear Pierre, 

from the timings in the output you should be able to determine where the 
calculation is spending most of the time and compare to the condensed 
matter calculation. Most probably OMP is not the most efficient in this 
case to parallelise. Have you tried with 8 tasks instead. 

On Tuesday, September 22, 2020 at 1:53:36 PM UTC+2 pier... at gmail.com 

> Hi Marcella,
> I am trying to run the calculation on my workstation with just OMP (8 
> threads). This usually works for condensed phase with a two hundred atoms 
> so I thought it would be fine for just 75 atoms. Anyway, I reduced the 
> cutoffs and it seems to be helping a lot but it is still slow and require a 
> lot of memory. Please find as attached document the input file I am using.
> Regards,
> Pierre
> On 22/09/2020 11:06, Marcella Iannuzzi wrote:
> Dear Pierre,  
> Without additional information, like input, output, scaling with the 
> number of processors ..., 
> it is not possible fo provide any help.
> Regards
> Marcella
> On Monday, September 21, 2020 at 1:09:03 PM UTC+2 pier... at gmail.com 
> wrote:
>> Dear CP2K users, 
>> I would like to know how to perform a gas phase calculation with CP2K. I 
>> tried to follow some of the examples available in the tutorials but they 
>> lead to very slow and heavy calculations for a system with only 75 atoms.
>> I used wavelet for the Poisson solver, I set periodic none for both the 
>> solver and the cell. The cell is cubic with a size of 26.250 A. I am using 
>> DFT (PBE) with OT. Should the number of grid be changed compared to a 
>> condensed phase? What about the cutoffs?
>> Alternatively, I tried the periodic approach with a larger cell so that 
>> the molecule "does not interact" with its periodic image .Yet again, the 
>> calculation is extremely demanding in terms of memory which makes the OS 
>> kill the job.
>> Is there a solution to these problems?
>> Regards,
>> Pierre
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> -- 
> Dr Pierre Cazade, PhD
> AD3-023, Bernal Institute,
> University of Limerick,
> Plassey Park Road,
> Castletroy, co. Limerick,
> Ireland
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