[CP2K-user] [CP2K:17692] Re: SGCPMD: problem with equilibration?

Alexandra Dávila a.celinda.dl at gmail.com
Thu Sep 15 11:34:39 UTC 2022

Dear Onofrio,

thanks a lot for your fast response! Indeed, I did a NVE simulation with 
Langevin  (as suggested here:https://www.cp2k.org/howto:md). Then I used 
the geometry and wfn for the SGCPMD. 
As you, I use TEMP_TOL, but I set it to the value of 50 for each region. Do 
you think that it makes the difference?

 This are the parameters that I used for the NVE:
     STEPS  6000
     TIMESTEP     5.0E-01
     TEMPERATURE     3.3000000000000006E+02
       GAMMA     1.0000000000000000E-03
       NOISY_GAMMA     0
         LIST  145..546
         TEMPERATURE     3.3000000000000006E+02
         NOISY_GAMMA_REGION     2.1999999999999998E-04
         TEMP_TOL 50
         DO_LANGEVIN F
         LIST  73..144
         TEMPERATURE     3.3000000000000006E+02
         NOISY_GAMMA_REGION     4.9999999999999996E-05
         TEMP_TOL 50
   &END MD
The NOISY_GAMMA is not considered in the simulation. Is there something not 
so good with the set of parameters I used?

[image: NVE_00_TempLANGEVIN.png]

I appreciate a lot your feedback!
Best regards,
El jueves, 15 de septiembre de 2022 a las 12:53:45 UTC+2, 
onofr... at gmail.com escribió:

> Dear Alexandra,
> have you done an equilibration step before starting the SGCPMD run?
> As I can see from your plots it seems that it is not equilibrated yet. I 
> suggest you to make a BOMD run first for better equilibration, then 
> switching to sgcpmd, as follows:
> 1. BOMD as NVE ensemble + TEMP_TOL 100
> 2. switch to SGCPMD using RESTART.wfn of the previous equilibration step 
> as a wfn guess
> It works for me.
> Hope it helps
> Regards
> Onofrio
> Il giorno giovedì 15 settembre 2022 alle 12:04:35 UTC+2 
> a.celi... at gmail.com ha scritto:
>> Dear Cp2k users,
>> I have carried on a second-generation Car-Parrinello (SGCP) MD simulation 
>> for Pt(111)/water interface. Unit cell contains Pt: 6x6x4 (2 frozen 
>> layers), water: 134 molecules.
>> I have performed a similar workflow as Onofrio ("SGCPMD: number of steps 
>> per SCF run increase suddenly after initial 400 MD steps"). But I have 
>> used the NOISY_GAMMA as in the publication *"First-Principles 
>> Simulations of an Aqueous CO/Pt(111) Interface" 
>> doi:10.1021/acs.jpcc.8b05933, *Pt: 5E-05 1/fs and for water 2.2E-04 
>> 1/fs. Temperature is set to 330K. 
>> Unfortunately, in my case along the SGMD the temperature of Pt region 
>> drops to roughly 180 K, the temperature of the hole system is about 328K. I 
>> expected that the temperature of Pt region would be closer to the water 
>> after a equilibration time of 4ps. Does this mean that probably my system 
>> is not well-equilibrated? Is this going to affect the dynamics and energy 
>> of the system? (PS: the density profile seems ok, double peak on oxygen, 
>> well-known for Pt(111))
>> Many thanks in advance!
>> Alexandra
>> PS: I also observed the increase of the SCF steps after a restart!
>> TOP: red dashed line: average temperature of system
>> BOTTOM: temperature for each region
>> [image: SGMD_00MD_Temp.png][image: SGMD_00MD_TempLAN.png]

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