[CP2K-user] MD calculation of NPT_F ensemble including baro- and thermostats at various T

Marcella Iannuzzi marci... at gmail.com
Mon Nov 16 11:40:20 UTC 2020

Dear Lukas, 

Did you  first  equilibrate the system at room temperature?  
Why did you choose the Langevin thermostat? How does the cell fluctuate? 
Which is the energy of the barostat? The stress tensor?
Is the total energy conserved? 
Without more information it is hard to guess what the problem might be. 
If you have an initially equilibrated sample (stress tensor around zero, 
conserved total energy, etc. ), try annealing it progressively to higher 

The model looks quite small and it will be anyway difficult to get a 
disordered structure due to the strong spatial correlations. 

Kind regards

On Monday, November 16, 2020 at 12:03:49 PM UTC+1 Lukas C wrote:

> Hi everyone!
> I am trying to see signs of melting for a given SiO2 bulk. In order to 
> achieve this, I ran MD calculations for a NPT_F (constant pressure and 
> temperature, flexible cell) ensemble which is connected to a thermal bath 
> (adaptive langevin thermostat) and to a barostat which are utilized to keep 
> T and p at constant values for each simulation respectively. The 
> temperature was set to T=600K,900K,1200K,1500K,1800K,2100K and 3000K. 
> However, i am experiencing multiple problems.
> 1. The calculations abort after 20 steps (every time) with the error:
>  *******************************************************************************
>  *   
> ___                                                                       *
>  *  /   
> \                                                                      *
>  * 
> [ABORT]                                                                     
> *
>  *  \___/                  invalid value for enumeration:   
> 104                *
>  *    
> |                                                                        *
>  *  
> O/|                                                                        *
>  * /| 
> |                                                                        *
>  * / \                                     
> input/input_enumeration_types.F:188 *
>  *******************************************************************************
> 2. by comparing the output files, i found out that the simulation seems to 
> trigger the same reactions (altough the temperature is very different). 
> cp2k did recognice the temperature (thus, the kinetic energy is changed) 
> but the curves that represent the change of kinetic energy resemble each 
> other perfectly. to my understanding, this means that exactly the same 
> reactions were triggered, which should not be the case for different 
> temperatures. Each simulation was started with a .wfn file as an initial 
> guess, which was taken from an single-point ENERGY calculation that was 
> conducted beforehand. Thus the potential energy is the same for each 
> simulation at t=0. The plot is attached together with the input file. I 
> already tried to use various optimizers, preconditioners and so on. am i 
> doing something seriously wrong? Thank you, your help is appreciated!
> Regards,
> Lukas
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