timestep in MD simulation

tao liu liut... at gmail.com
Mon Jan 4 07:46:44 CET 2016


Dear All,

I am running a NVT MD simulation on MgSiO3 (250 atoms) at high pressure and 
temperature by cp2k2.7 on ARCHER. The problem is relating to TIMESTEP.

Because it is a high pressure and temperature simulation, so I try 
different TIMESTEP  = 0.5 fs, 0.75 fs,  1.0 fs, 1.5 fs, 2.0 fs to run MD 
simulation.
0.5 fs, 1.5 fs, and 2.0 fs works well.
But 0.75 fs, and 1 fs don't work, crash at thousand steps because reaching 
the max SCF cycles. Even though I restart it, it will crash in a few of 
steps.   
Could anyone tell me if I got anything wrong? I prefer to use 1 fs, but 
doesn't work. Thanks.

I pasted input file and bottom of .ener .stress and output file here. 

Regards,
Tao


*'input file'*
<https://en.wikipedia.org/wiki/Car%E2%80%93Parrinello_molecular_dynamics#cite_note-3>&GLOBAL                                                                                                                           

  PROJECT 
pv-lad                                                                                                                  

  RUN_TYPE 
md                                                                                                                     

  PRINT_LEVEL 
low                                                                                                                 

&END 
GLOBAL                                                                                                                       


&MOTION                                                                                                  

  
&PRINT                                                                                                 

    
&STRESS                                                                                              

    &END 
STRESS                                                                                          

    
&velocities                                                                                          

    &end 
velocities                                                                                      

  &END 
PRINT                                                                                             


  &MD
    ENSEMBLE NVT
    STEPS 5000   
    TIMESTEP 1   
    TEMPERATURE 4000.0
    &THERMOSTAT       
      &NOSE           
        LENGTH 3      
        YOSHIDA 3     
        TIMECON 10.0  
        MTS 2         
      &END NOSE       
    &END              
  &END MD             

&END MOTION

&FORCE_EVAL                                                                                             

  METHOD 
Quickstep                                                                                      

  STRESS_TENSOR 
analytical                                                                              

  
&DFT                                                                                                  

    BASIS_SET_FILE_NAME 
BASIS_MOLOPT                                                                    

    POTENTIAL_FILE_NAME 
POTENTIAL                                                                       

    
&MGRID                                                                                              

      CUTOFF 
500                                                                                        

      REL_CUTOFF 
40                                                                                     

    &END 
MGRID                                                                                          


    &PRINT
      &DFT_CONTROL_PARAMETERS
      &END DFT_CONTROL_PARAMETERS
    &END PRINT                   

    &QS
      ls_scf
      EPS_DEFAULT 1.0E-10
      EXTRAPOLATION use_prev_p
      MAP_CONSISTENT          
    &END QS                   

    &LS_SCF
      PURIFICATION_METHOD TRS4
      MU         0.15         
      MAX_SCF    200          
      S_PRECONDITIONER ATOMIC 
    &END                      

    &SCF
      &OT ON
      MIXED_PRECISION .TRUE. 
      &END OT                
      EPS_SCF 1.0E-5         
      MAX_SCF 200            
      SCF_GUESS atomic       
       &OUTER_SCF            
          EPS_SCF 1.0E-7     
          MAX_SCF 500        
       &END                  
    &END SCF                 

    &XC
      &XC_FUNCTIONAL LDA
      &END XC_FUNCTIONAL
    &END XC             
  &END DFT              
  &PRINT                
    &STRESS_TENSOR      
      NDIGITS 4         
    &END STRESS_TENSOR  
  &END PRINT            
  &SUBSYS               
    &CELL               
      ABC  26.0369999999999990 9.1050000000000004 6.2900000000000000
MULTIPLE_UNIT_CELL   1 1 1                                          

       SYMMETRY ORTHORHOMBIC                                        
    &END CELL                                                       
    &COORD                                                          
 Mg      0.0835357257057528 0.2080505102144339 
0.7695373512802808                                                                                      

 Mg      0.4168690590390862 0.2080505102144339 
0.7695373512802808                                                                                      

...
...
...
...
...


    SCALED T
    &END COORD
    &TOPOLOGY
     MULTIPLE_UNIT_CELL   1 1 1

    &END TOPOLOGY


    &KIND Mg
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PADE-q10
    &END KIND
    &KIND Si
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PADE-q4
    &END KIND
    &KIND O
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PADE-q6
    &END KIND

    &PRINT
      &CELL
      &END CELL
      &KINDS
        BASIS_SET
        POTENTIAL
      &END KINDS
    &END PRINT
  &END SUBSYS
&END FORCE_EVAL


*'*.ener'*
     52241        99241.000000         4.411213874      3885.493746208     
-5533.754419320     -5511.857390810        25.345344531
     52242        99242.000000         4.342485222      3824.956044365     
-5533.605897687     -5511.856215770        18.092279346
     52243        99243.000000         4.276184769      3766.557154129     
-5533.468202487     -5511.855599935        13.521783815
     52244        99244.000000         4.219259478      3716.416111920     
-5533.347713891     -5511.855260868        20.452569381
     52245        99245.000000         4.174711953      3677.177676762     
-5533.244993727     -5511.854024077        13.410673904
     52246        99246.000000         4.157625727      3662.127754916     
-5533.174592854     -5511.853076546        18.038370990
     52247        99247.000000         4.175426934      3677.807447113     
-5533.137836015     -5511.847932992        13.264672622
     52248        99248.000000                 NaN                 
NaN                156032.896882306                 NaN                 
575.632388886

*'*.stress'*
   52241   99241.000  1393467.1901913243    -4049.0319591435    
16542.2251158790    -4049.0319591435  1342881.5952529698     
6198.4426952424    16542.2251158790     6198.4426952424  1366629.9398137301
   52242   99242.000  1397547.5508231323    -4579.9413527279    
13810.5798040272    -4579.9413527279  1347383.1869124325     
4835.2659481228    13810.5798040272     4835.2659481228  1367257.9328355824
   52243   99243.000  1402562.0095211340    -2469.8827275863    
11326.0268584547    -2469.8827275863  1355053.6419066861     
2967.7081481965    11326.0268584547     2967.7081481965  1368330.4512780211
   52244   99244.000  1408171.8438126745      888.5049041032     
7965.5485159208      888.5049041032  1364397.2652421803      
822.2322445308     7965.5485159208      822.2322445308  1372140.1351925349
   52245   99245.000  1409730.5634058635     5552.5388752075     
4525.6394441786     5552.5388752075  1370727.1093890155    
-1862.2415766141     4525.6394441786    -1862.2415766141  1376614.3797829675
   52246   99246.000  1412460.3088731237     9057.5282769796      
628.5805615638     9057.5282769796  1378499.6190023583    
-4538.0776370565      628.5805615638    -4538.0776370565  1383519.0328408128
   52247   99247.000  1411091.8367309219    13731.7124595861    
-2346.7333744248    13731.7124595861  1387502.2123396317    
-7483.0678576032    -2346.7333744248    -7483.0678576032  1382544.9170446743
   52248   99248.000                 NaN                 
NaN                 NaN                 NaN                 
NaN                 NaN                 NaN                 
NaN                 NaN

*'.out'*

 SCF   198    158962.937507772      1965.560497129    2.771007

*********************************************************
 Using MIXING_FRACTION=0.450 to mix KS matrix:  iscf=199 
 KS_nw=0.450*KS + 0.550*KS_old                           
*********************************************************
     Lanczos converged:                  F               
     change in mixed matrix:     141.05387               
     HOMO upper bound:           104.64941               
     LUMO lower bound:          -177.33021               
     Predicts a gap ?                    F               
     Est. extremal eigenvalues    -69.03105    87.29441  converged:  F
     TRS4 it   1 1.00000000   0.897E+02       0.047     4763.272   0.100E-05
     TRS4 it   2 1.00000000   0.857E+02       0.052     4321.115   0.100E-05
     TRS4 it   3 1.00000000   0.635E+02       0.094     4126.422   0.100E-05
     TRS4 it   4 1.00000000   0.439E+02       0.087     4013.760   0.100E-05
     TRS4 it   5 0.96654122   0.289E+02       0.090     3488.278   0.100E-05
     TRS4 it   6 0.95568580   0.191E+02       0.078     3775.442   0.100E-05
     TRS4 it   7 0.95672906   0.125E+02       0.082     3520.711   0.100E-05
     TRS4 it   8 0.96273637   0.816E+01       0.081     3564.536   0.100E-05
     TRS4 it   9 0.98135529   0.537E+01       0.078     3735.249   0.100E-05
     TRS4 it  10 0.98941451   0.355E+01       0.080     3692.521   0.100E-05
     TRS4 it  11 0.99104224   0.234E+01       0.076     3897.213   0.100E-05
     TRS4 it  12 0.99253780   0.154E+01       0.077     3886.772   0.100E-05
     TRS4 it  13 0.99272503   0.102E+01       0.078     3853.237   0.100E-05
     TRS4 it  14 0.99881619   0.707E+00       0.078     3893.548   0.100E-05
     TRS4 it  15 0.99760219   0.494E+00       0.078     3867.742   0.100E-05
     TRS4 it  16 0.99128755   0.319E+00       0.079     3805.687   0.100E-05
     TRS4 it  17 0.98412362   0.194E+00       0.082     3627.809   0.100E-05
     TRS4 it  18 0.95759578   0.119E+00       0.078     3733.491   0.100E-05
     TRS4 it  19 0.96372829   0.735E-01       0.077     3804.604   0.100E-05
     TRS4 it  20 0.98971046   0.351E-01       0.080     3743.113   0.100E-05
     TRS4 it  21 0.99122111   0.764E-02       0.078     3818.051   0.100E-05
     TRS4 it  22 0.99122111   0.275E-03       0.079     3795.518   0.100E-05
     Final TRS4 iteration   22 0.99122111   0.275E-03
     Chemical potential (mu):     -37.10018
     Lanczos converged:                  F
     Lanczos converged:                  F
     HOMO/LUMO/gap    -37.15175   -36.90884     0.24291

 SCF   199    157261.886998689     -1701.050509083    2.799975

*********************************************************
 Using MIXING_FRACTION=0.450 to mix KS matrix:  iscf=200
 KS_nw=0.450*KS + 0.550*KS_old
*********************************************************
     Lanczos converged:                  F
     change in mixed matrix:     139.91979
     HOMO upper bound:           102.76805
     LUMO lower bound:          -176.82863
     Predicts a gap ?                    F
     Est. extremal eigenvalues    -68.87729    85.63565  converged:  F
     TRS4 it   1 1.00000000   0.905E+02       0.047     4789.695   0.100E-05
     TRS4 it   2 1.00000000   0.860E+02       0.048     4640.079   0.100E-05
     TRS4 it   3 1.00000000   0.629E+02       0.093     4197.692   0.100E-05
     TRS4 it   4 0.99871352   0.431E+02       0.084     4141.198   0.100E-05
     TRS4 it   5 0.96728110   0.284E+02       0.084     3755.189   0.100E-05
     TRS4 it   6 0.95162355   0.186E+02       0.079     3730.035   0.100E-05
     TRS4 it   7 0.95464254   0.121E+02       0.077     3690.826   0.100E-05
     TRS4 it   8 0.95691490   0.785E+01       0.077     3676.631   0.100E-05
     TRS4 it   9 0.96656933   0.508E+01       0.077     3733.906   0.100E-05
     TRS4 it  10 0.98102775   0.329E+01       0.080     3647.389   0.100E-05
     TRS4 it  11 0.98165356   0.215E+01       0.084     3493.869   0.100E-05
     TRS4 it  12 0.98033688   0.142E+01       0.078     3737.030   0.100E-05
     TRS4 it  13 0.98043352   0.922E+00       0.082     3590.334   0.100E-05
     TRS4 it  14 0.98047952   0.557E+00       0.078     3774.055   0.100E-05
     TRS4 it  15 0.98190189   0.302E+00       0.079     3753.784   0.100E-05
     TRS4 it  16 0.99003522   0.149E+00       0.080     3713.618   0.100E-05
     TRS4 it  17 0.99753877   0.652E-01       0.078     3861.570   0.100E-05
     TRS4 it  18 0.99875278   0.190E-01       0.083     3665.070   0.100E-05
     TRS4 it  19 0.99753877   0.147E-02       0.080     3805.444   0.100E-05
     TRS4 it  20 0.98989026   0.193E-04       0.080     3729.016   0.100E-05
     Final TRS4 iteration   20 0.98989026   0.193E-04
     Chemical potential (mu):     -36.52358
     Lanczos converged:                  F
     Lanczos converged:                  F
     HOMO/LUMO/gap    -36.71009   -36.28310     0.42699

 SCF   200    156032.896882306     -1228.990116383    2.659866


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