Temp control problem, OT convergence problem, Langevin dynamics SGCPMD

[Alex]

Hi,

While I too have questions about the annealing procedure in CP2K, if you 
have a small system, Nose-Hoover thermostatics is a generally bad idea 
regardless of its time constant. 
Try CSVR or adaptive Langevin. For the initial relaxation, try to go with a 
very tight temperature control (a time constant of a few femtoseconds for 
CSVR, for example).

Best,

Alex

On Wednesday, November 5, 2014 2:50:30 AM UTC-7, Bouzid Assil wrote:
>
> Dear CP2k users,
>
> I am using cp2k to perform MD simulations based on the second generation 
> Car-Parrinello MD (Kühne scheme). I have started by a small binary 
> chalcogenide system that I have already generated using the standard CPMD. 
> As a first step I want to relax my system at 0K using the ANNEALING 
> procedure, this is supposed to reduce the forces acting between the "atoms" 
> at each MD step by a given factor (say 0.9). To control the situation I 
> have used at first gamma_D = 0.0000. My problem is that after more than 
> 30ps the temperature stabilize around 1000K and won't go down. I have also 
> tried an NVT run at 300K using the NOSE HOOVER thermostat but no way, the 
> thermostat is not able to control the temperature (I have tried different 
> TIMECON values, always the same behaviour!).
> When analysing the output files, there is a common strange thing between 
> all these runs (and also an other run on water molecules), when performing 
> the SCF WAVEFUNCTION OPTIMIZATION typically the convergence is reached 
> after  2 iterations of the outer SCF loop BUT after the first ~10 MD steps 
> the convergence is not reached at all and only 2 OT steps are performed! is 
> this normal (for sure no!) but why it happens then?!
>
> * here is an example of output: *
>
>    ----------------------------------- OT 
> ---------------------------------------
>
>   Allowing for rotations:  F
>   Optimizing orbital energies:  F
>   Minimizer      : DIIS                : direct inversion
>                                          in the iterative subspace
>                             using      : -   7 DIIS vectors
>                                          - safer DIIS on
>   Preconditioner : FULL_KINETIC        : cholesky inversion of T + eS
>   Precond_solver : DEFAULT
>   stepsize       :    0.08750000
>   energy_gap     :    0.00200000
>
>   eps_taylor     :   0.10000E-15
>   max_taylor     :             4
>
>   mixed_precision    : F
>
>   ----------------------------------- OT 
> ---------------------------------------
>
>   Step     Update method      Time    Convergence         Total energy    
> Change
>   
> ------------------------------------------------------------------------------
>      1 OT DIIS     0.87E-01    2.1     0.00000982      -906.5667899239 
> -9.07E+02
>      2 OT DIIS     0.87E-01    2.5     0.00000932      -906.5667939977 
> -4.07E-06
>
>   *** SCF run NOT converged ***
>
>
>   Electronic density on regular grids:       -640.0000000000       
> -0.0000000000
>   Core density on regular grids:              639.9999999985       
> -0.0000000015
>   Total charge density on r-space grids:       -0.0000000015
>   Total charge density g-space grids:          -0.0000000015
>
>   Overlap energy of the core charge distribution:               
> 0.00000056633200
>   Self energy of the core charge distribution:              
> -1927.34045098667070
>   Core Hamiltonian energy:                                    
> 434.65748894621680
>   Hartree energy:                                             
> 790.75025229030484
>   Exchange-correlation energy:                               
> -204.63408481387373
>
>   Total energy:                                              
> -906.56679399769098
>
>  ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):             
> -906.566801465010712
>
>
>
>  *******************************************************************************
>  ENSEMBLE TYPE                =                                         
> LANGEVIN
>  STEP NUMBER                  =                                            
> 34788
>  TIME [fs]                    =                                     
> 34788.000000
>  CONSERVED QUANTITY [hartree] =                              
> -0.906018037069E+03
>
>                                               INSTANTANEOUS             
> AVERAGES
>  CPU TIME [s]                 =                        
> 9.85                 9.56
>  ENERGY DRIFT PER ATOM [K]    =         -0.352815792553E+06  
> -0.346958228435E+06
>  POTENTIAL ENERGY[hartree]    =         -0.906566801465E+03  
> -0.906008788692E+03
>  KINETIC ENERGY [hartree]     =          0.548764395757E+00   
> 0.221663346691E+01
>  TEMPERATURE [K]              =                     970.789             
> 3921.326
>
>  *******************************************************************************
>
>
>
> *Here is a part of my input file:*
>
>
> &MOTION
>   &MD
>     ENSEMBLE  LANGEVIN     
>     STEPS 15000
>     ANNEALING 0.8
>     TIMESTEP 1.0
>     &LANGEVIN
>       GAMMA       0.0001   
>       NOISY_GAMMA 0.000
>     &END LANGEVIN
>   &END MD
>   &PRINT
>     &RESTART
>       &EACH
>         MD 1
>       &END EACH
>       BACKUP_COPIES 3
>     &END RESTART
>   &END PRINT
> &END MOTION
>
> &FORCE_EVAL
>   METHOD QUICKSTEP
>   &DFT
>     BASIS_SET_FILE_NAME BASIS_MOLOPT
>     POTENTIAL_FILE_NAME GTH_POTENTIALS
>     WFN_RESTART_FILE_NAME meta-RESTART.wfn
>     &MGRID
>       &RS_GRID
>         DISTRIBUTION_TYPE REPLICATED
>       &END RS_GRID
>       CUTOFF 300
>     &END MGRID
>     &PRINT
>       &DFT_CONTROL_PARAMETERS
>       &END DFT_CONTROL_PARAMETERS
>     &END PRINT
>     &QS
>       EPS_DEFAULT 1.0e-12
>       EXTRAPOLATION ASPC     
>       EXTRAPOLATION_ORDER 3  
>       MAP_CONSISTENT TRUE
>     &END QS
>     &SCF
>       EPS_SCF 1.0e-7
>       MAX_SCF 50
>       MAX_SCF_HIST 2         
>       &OT ON
>         MINIMIZER DIIS
>         PRECONDITIONER FULL_KINETIC
>         ENERGY_GAP 0.002
>         STEPSIZE 0.0875     
>       &END OT
>       &OUTER_SCF ON
>         MAX_SCF 100
>         EPS_SCF 1.0e-7
>       &END OUTER_SCF
>
>
>
> Any input on the possible origin of this problem is highly appreciated! 
> Many thanks.
> All the best,
>
> Assil Bouzid
>
>
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