[CP2K-user] [CP2K:17185] Re: Problem with 2nd generation CPMD

[Marcella Iannuzzi]

As you may have read in previous works, to run SGCPMD a preliminary study 
is needed to set the proper GAMMA and NOISY_GAMMA parameters, which allow 
for the conservation of energy, for a Gaussian distribution of the error in 
the forces, and for a correct equipartition of the kinetic energy among the 
degrees of freedom. 
Moreover the parameters to tune the convergence of the electronic structure 
at each MD step need also to be properly adjusted to the system. 
This means that a series of preliminary simulations are needed, before the 
production runs are started. 

This said, my suggestions are the following:
- Always start sgcpmd from a well converged wfn obtained along a standard 
BOMD run with diagonalisation and smearing
-  Let the first steps run on many scf iterations if needed, i.e., set 
MAX_SCF large enough
-  But use a relative large eps_scf. The wfn is not going to be optimised 
as in the BOMD, energy convergence  around 10^-5 is desirable
- Use FULL_ALL preconditioner + ASPC
- Use a small time step
- Tune properly GAMMA and NOISY_GAMMA
- Monitor the conservation of energy and the temperature per kind or per 
region : TEMP_KIND

Regards
Marcella

On Thursday, June 16, 2022 at 10:53:53 AM UTC+2 onofr... at gmail.com wrote:

> Hi Sam,
> yes, of course. I set up more standard BOMD with ENSEMBLE NVT and 
> DIAGONALIZATION with smear (look at my input file) and worked fine: it took 
> more or less *30 steps to reach convergence* every AIMD step.
>
> Then, I tried with ENSEMBLE NVT and OT (without smear obviously) and I got 
> (MAX_SCF 200):
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> * *** WARNING in qs_scf.F:598 :: SCF run NOT converged *** *** WARNING in 
> qs_scf.F:598 :: SCF run NOT converged ***  *** SCF run converged in    79 
> steps ***  *** SCF run converged in    72 steps ***  *** SCF run converged 
> in    84 steps ***  *** SCF run converged in    53 steps ***  *** SCF run 
> converged in    49 steps ***  *** SCF run converged in    48 steps ***  *** 
> SCF run converged in    38 steps ***  *** SCF run converged in    40 steps 
> ***  *** SCF run converged in    38 steps ***  *** SCF run converged in   
>  30 steps ***  *** SCF run converged in    23 steps ***  *** SCF run 
> converged in    26 steps ***  *** SCF run converged in    27 steps ***  *** 
> SCF run converged in    26 steps ***  *** SCF run converged in    26 steps 
> ***  *** SCF run converged in    23 steps ***  *** SCF run converged in   
>  16 steps ***  *** SCF run converged in    16 steps ***  *** SCF run 
> converged in    16 steps ***  *** SCF run converged in    18 steps ****
> *   ...*
>
> Though SCF run not converged for the first two AIMD steps, then it worked 
> sometimes fine (SCF run converged in 16 steps, but not always!). Could be a 
> possible solution.
> N.B.: setting MAX_SCF below 200 (i.e., 50) makes SCF run not converged 
> more than two initial AIMD steps.
>
> Anyway, I'm looking for correctly set up SGCPMD as that found in the 
> following works:
> - Lan, Jinggang, Jürg Hutter, and Marcella Iannuzzi. "First-principles 
> simulations of an aqueous CO/Pt (111) interface." *The Journal of 
> Physical Chemistry C* 122.42 (2018): 24068-24076.
> - Musso, Tiziana, et al. "Second generation Car-Parrinello MD: application 
> to the h-BN/Rh (111) nanomesh." *The European Physical Journal B* 91.7 
> (2018): 1-8.
>
> However, I'm struggling with and I kindly need your help.
> Kind regards.
>
> Onofrio
>
> Il giorno giovedì 16 giugno 2022 alle 09:58:41 UTC+2 wave... at gmail.com ha 
> scritto:
>
>> Hi Onofrio
>>
>> Question: have you set this up and run a more standard simulation to work 
>> out the convergence first?
>>
>> If I guess, it's probably Cu as a transition metal with d-orbitals that 
>> is difficult (I am suffering with Au).
>>
>> Kind Regards
>>
>> Sam 
>> On Wednesday, June 15, 2022 at 3:20:20 PM UTC+2 onofr... at gmail.com wrote:
>>
>>> Dear CP2K community,
>>>
>>> I'm new to CP2K and I'm trying to set up a second-generation 
>>> Car-Parrinello (SGCP) MD simulation. I have started with a geometrically 
>>> optimized system of toluene adsorbed on a 3-layer Cu slab (8x6). I would to 
>>> know what sections/keywords in the input file must be used to correctly set 
>>> up a SGCPMD simulation and, possibly, the best settings to improve the 
>>> speed of such simulations since I have not found any related tutorial (but 
>>> only few things in the cp2k google group). 
>>> If I well understood, it has to be turn on the Langevin dynamics section 
>>> in combination with the OT method. For example:
>>>
>>> &FORCE_EVAL
>>>   ...
>>>   &DFT
>>>     ...
>>>     &QS
>>>       METHOD GPW
>>>       EXTRAPOLATION ASPC
>>>       EXTRAPOLATION_ORDER 3
>>>       EPS_DEFAULT 1.0E-10
>>>     &END QS
>>>     ...
>>>     &SCF
>>>     ...
>>>       &OT
>>>         PRECONDITIONER FULL_SINGLE_INVERSE   ! or FULL_KINETIC
>>>         MINIMIZER DIIS
>>>         N_DIIS 7
>>>       &END OT
>>>       &OUTER_SCF
>>>         MAX_SCF 3
>>>         EPS_SCF 1.0E-05
>>>       &END OUTER_SCF    
>>>     ...
>>>     &END SCF
>>>     ...
>>>   &END DFT
>>>   ...
>>> &END FORCE_EVAL
>>>
>>> &MOTION
>>>   &MD
>>>     ENSEMBLE LANGEVIN
>>>     ...
>>>     &LANGEVIN
>>>       GAMMA 0.001
>>>     &END LANGEVIN
>>>     ...
>>>   &END MD
>>>   ...
>>> &END MOTION
>>>
>>> Is it correct? To follow what I just mentioned, I prepared an input file 
>>> (attached below) based on sections/keywords defined just above and I got 
>>> from the output file (attached below) only 
>>>     *"Leaving inner SCF loop after reaching   200 steps" *
>>> (200 steps because I set MAX_SCF 200)
>>> resulting in a very bad convergence. 
>>> As a result, it seems that I have not been running any SGCPMD simulation 
>>> but a simple bad BOMD. Am I missing something?
>>> How can I correctly set up my input file for SGCPMD?
>>>
>>> Any help would be greatly appreciated.
>>> Thanks.
>>>
>>> Onofrio
>>>
>>

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