about Max_force convergence , help me.

[Jj Ll]

when i take a  task about  cell and geo optimize,  

the default value is  MAX_FORCE is   4.50000000E-04,



but   with a long long time opt,  my structure  can't meet the Convergence 
criterium.


  anyone  konw how to  dealing with it?

can i increasing it ?

is there any paper talking  about this? 


thanks  a lot.




*something from the output:*


 OPTIMIZATION STEP:   9575
 --------------------------

 DISTRIBUTION OF THE NEIGHBOR LISTS
              Total number of particle pairs:                              
20542
              Total number of matrix elements:                             
20542
              Average number of particle pairs:                             
1712
              Maximum number of particle pairs:                             
1775
              Average number of matrix element:                             
1712
              Maximum number of matrix elements:                            
1775

 Number of electrons:                                                       
1792
 Number of occupied 
orbitals:                                                896
 Number of molecular 
orbitals:                                               896

 Number of orbital functions:                                               
1408
 Number of independent orbital functions:                                   
1408

  Parameters for the always stable predictor-corrector (ASPC) method:

  ASPC order: 3

  B(1) =   3.000000
  B(2) =  -3.428571
  B(3) =   1.928571
  B(4) =  -0.571429
  B(5) =   0.071429

 Extrapolation method: ASPC


 SCF WAVEFUNCTION OPTIMIZATION

  ----------------------------------- OT 
---------------------------------------

  Allowing for rotations:  F
  Optimizing orbital energies:  F
  Minimizer      : CG                  : conjugate gradient
  Preconditioner : FULL_ALL            : diagonalization, state selective
  Precond_solver : DEFAULT
  Line search    : 2PNT                : 2 energies, one gradient
  stepsize       :    0.15000000
  energy_gap     :    0.20000000

  eps_taylor     :   0.10000E-15
  max_taylor     :             4

  mixed_precision    : F

  ----------------------------------- OT 
---------------------------------------

  Step     Update method      Time    Convergence         Total energy    
Change
  
------------------------------------------------------------------------------
     1 OT CG       0.15E+00    3.0     0.00003133      -884.3152090742 
-8.84E+02
     2 OT LS       0.13E+00    0.3                     -884.3152837966
     3 OT CG       0.13E+00    1.3     0.00001002      -884.3152867640 
-7.77E-05
     4 OT LS       0.10E+00    0.4                     -884.3152926677
     5 OT CG       0.10E+00    1.4     0.00000280      -884.3152930860 
-6.32E-06

  *** SCF run converged in     5 steps ***


  Core Hamiltonian energy:                                   
-926.02883202152839
  Repulsive potential energy:                                  
36.85512369648072
  Electronic energy:                                            
3.40659059074630
  Dispersion energy:                                            
1.45182464828800

  Total energy:                                              
-884.31529308601330

 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.):             
-884.315293703488464


 STRESS TENSOR [GPa]

            X               Y               Z
  X      -0.20218774     -0.00014323      0.21301866
  Y      -0.00014323     -0.01707579     -0.00040963
  Z       0.21301866     -0.00040963      0.05463897

  1/3 Trace(stress tensor):  -5.48748551E-02

  Det(stress tensor)      :   9.63547122E-04


 EIGENVECTORS AND EIGENVALUES OF THE STRESS TENSOR

         -0.32250506     -0.01707672      0.17495722

          0.87071071      0.00131261      0.49179380
         -0.00025127      0.99999749     -0.00222416
         -0.49179549      0.00181303      0.87070886

 --------  Informations at step =  9575 ------------
  Optimization Method        =                 BFGS
  Total Energy               =      -884.3152937035
  Real energy change         =         0.0003074503
  Predicted change in energy =        -0.0000004083
  Scaling factor             =         0.0000000000
  Step size                  =         0.0006388253
  Trust radius               =         0.1000000000
  Decrease in energy         =                   NO
  Used time                  =                8.364

  Convergence check :
  Max. step size             =         0.0001684277
  Conv. limit for step size  =         0.0030000000
  Convergence in step size   =                  YES
  RMS step size              =         0.0000283733
  Conv. limit for RMS step   =         0.0015000000
  Convergence in RMS step    =                  YES
  Max. gradient              =         0.0007125337
  Conv. limit for gradients  =         0.0005000000
  Conv. for gradients        =                   NO
  RMS gradient               =         0.0001207326
  Conv. limit for RMS grad.  =         0.0003000000
  Conv. in RMS gradients     =                  YES
 ---------------------------------------------------

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