[CPMD-list] Slow convergence with surface calculations

[Shiwu Gao]

Hi,

I was trying to optimize the wavefunction of a Ag(110) 
surface with CPMD. The convergence is extemely slow. At some
stage, the calculation can not gets better, the typical output 
looks this, 
----------------------------------------------------------------------
 586  1.826E-03   1.439E-04   -3211.132742    6.223E-03     27.70
 ODIIS| Insufficient progress; reset!
 587  3.384E-04   3.336E-05   -3211.138854   -6.112E-03     26.41
 588  3.097E-03   2.982E-04   -3211.130273    8.581E-03     26.11
 589  7.925E-04   6.519E-05   -3211.138705   -8.432E-03     26.96
 590  3.273E-04   1.751E-05   -3211.139188   -4.824E-04     26.77
 591  3.376E-04   1.319E-05   -3211.139248   -5.974E-05     26.92
 592  3.427E-04   9.324E-06   -3211.139297   -4.982E-05     27.05
 593  3.372E-04   7.054E-06   -3211.139344   -4.654E-05     26.85
 594  3.388E-04   1.027E-05   -3211.139451   -1.070E-04     26.97
 595  1.293E-03   1.008E-04   -3211.135294    4.157E-03     27.09
 596  3.386E-04   7.014E-06   -3211.139096   -3.802E-03     26.46
 597  3.395E-04   6.826E-06   -3211.139109   -1.347E-05     27.85
 598  3.350E-04   1.909E-05   -3211.138445    6.640E-04     27.78
 599  3.353E-04   2.010E-05   -3211.138577   -1.318E-04     26.41
 ODIIS| Insufficient progress; reset!
 600  8.653E-04   9.429E-05   -3211.135636    2.941E-03     26.42
 601  1.010E-02   1.010E-03   -3211.046595    8.904E-02     26.14
 602  1.548E-03   1.165E-04   -3211.134862   -8.827E-02     26.24
 603  4.091E-04   3.887E-05   -3211.136805   -1.943E-03     26.94
 604  4.192E-04   3.997E-05   -3211.136854   -4.923E-05     26.38
 605  3.237E-04   1.982E-05   -3211.137049   -1.949E-04     26.23
-----------------------------------------------------------------------

When running the same cell with FP-LAPW method. The calculation
converges
within 15-20 iterations, although each iteration with FLAPW takes
more than 20 time longer time than an electronic step in CPMD. 
I understand that slow convergence is not a unfamiliar problem with CPMD
in a surface calculation. My questions is: Is there any tricks one can 
play in CPMD to accelerate the convergences? Or we should turn to 
other methods for a surface calculation? 

Thanks for any hint/help,

Shiwu


--------------------------------------------------------------------------
My input file for a Ag(110) surface is as follows

# O2 on Ag(110) 5x3x5--12 slab
&CPMD
    OPTIMIZE WAVEFUNCTION
    ODIIS 
    60
    STRUCTURE BONDS ANGLES DIHEDRAS 
    SPLINE QFUNCTIONS POINTS 
    6000
    BIG MEMORY  
&END
&SYSTEM
   SYMMETRY
   8 
   SURFACE  
   TESR 
   4 
   CELL ABSOLUTE DEGREE 
   27.299375 23.164300 32.759236 90.000000 90.000000 90.000000           
   CUTOFF
   25.
   POISSON SOLVER MORTENSEN 
&END
&ATOMS
*ag_ps.uspp          BINARY    NEWF 
  LMAX=D
   75    
         0.00000000     0.00000000    16.37961800
         5.45987500     0.00000000    16.37961800
        21.83950000     0.00000000    16.37961800
...................
       10.91975000     7.72143326    10.91974522
       21.83950000    15.44286674    21.83949078
        5.45987500     7.72143326    10.91974522

&END
&DFT
  FUNCTIONAL PBE 
&END
&PROP
  PROJECT WAVEFUNCTION
&END