[Pw_forum] structural relaxation for a M-M-M system

Xunlei Ding ding at sissa.it
Sat Jun 9 15:32:59 CEST 2007


Dear Sen,

 What the directions of the forces, mostly in XY plane or in Z direction?
 Are you using slab model? Where you get the number celldm(1) = 16.0?

Please give more information.

Yours sincerely,
Ding
 
Sen wrote:

>Dear all,
>         After a lot of trials, I am, however, not yet successful in
>optimizing a metal-molecule-metal system as the forces are coming
>like this:
>.........
>     Total force =     0.095460     Total SCF correction =     0.000604
>     Total force =     0.082488     Total SCF correction =     0.000306
>     Total force =     0.046922     Total SCF correction =     0.000911
>     Total force =     0.056506     Total SCF correction =     0.000344
>     Total force =     0.054621     Total SCF correction =     0.000626
>     Total force =     0.065249     Total SCF correction =     0.000466
>     Total force =     0.083905     Total SCF correction =     0.000689
>     Total force =     0.079088     Total SCF correction =     0.000242
>     Total force =     0.062822     Total SCF correction =     0.000331
>     Total force =     0.042837     Total SCF correction =     0.000466
>     Total force =     0.043863     Total SCF correction =     0.000608
>     Total force =     0.060127     Total SCF correction =     0.000548
>     Total force =     0.056791     Total SCF correction =     0.000600
>     Total force =     0.055846     Total SCF correction =     0.000490
>     Total force =     0.048528     Total SCF correction =     0.000801
>     Total force =     0.035071     Total SCF correction =     0.000413
>     Total force =     0.032172     Total SCF correction =     0.000433
>     Total force =     0.039041     Total SCF correction =     0.000416
>     Total force =     0.044582     Total SCF correction =     0.000545
>     Total force =     0.046444     Total SCF correction =     0.000524
>     Total force =     0.054854     Total SCF correction =     0.000818
>     Total force =     0.063710     Total SCF correction =     0.000484
>     Total force =     0.062717     Total SCF correction =     0.000626
>     Total force =     0.065163     Total SCF correction =     0.000812
>     Total force =     0.075249     Total SCF correction =     0.001036
>     Total force =     0.088846     Total SCF correction =     0.000643
>     Total force =     0.105373     Total SCF correction =     0.000338
>     Total force =     0.120634     Total SCF correction =     0.000572
>     Total force =     0.126982     Total SCF correction =     0.000283
>     Total force =     0.113945     Total SCF correction =     0.000450
>     Total force =     0.108384     Total SCF correction =     0.000297
>     Total force =     0.099096     Total SCF correction =     0.000580
>     Total force =     0.077881     Total SCF correction =     0.000668
>     Total force =     0.095374     Total SCF correction =     0.000452
>
> while the stress is the following:
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.70
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.72
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>35.27
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>35.66
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>35.07
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>33.99
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.67
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>31.43
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>31.16
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>31.69
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.41
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>33.54
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>33.84
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.53
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.35
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.06
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>33.97
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.12
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.65
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.86
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.38
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>33.60
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.83
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.23
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.38
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.16
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.24
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.34
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.88
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>34.00
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>33.58
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>33.10
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>32.30
>          total   stress  (Ry/bohr**3)                   (kbar)     P=  
>31.50
>
>I start my calculations with the following input file:
>&CONTROL
>  calculation = "relax",
>  tstress = .TRUE.,
>  tprnfor = .TRUE.,
>  dt= 20,
>  outdir       = "/work1/tmp",
>  prefix       = "6r_md",
>  pseudo_dir   = "/work1/pwscf/newwork1/pseudo",
>/
>&SYSTEM
>  nosym = .TRUE.,
>  ibrav = 6,
>  celldm(1) = 16.0,
>  celldm(3) = 6.7,
>  nat       = 108,
>  ntyp      = 4,
>  ecutwfc = 25.0,
>  ecutrho  =  200.0 ,
>  occupations = "smearing",
>  degauss     = 0.01,
>  smearing    = "gauss",
>/
>&ELECTRONS
>  conv_thr    = 1.e-7,
>  mixing_beta = 0.1,
>/
>&IONS
>  ion_dynamics = "damp",
>  pot_extrapolation = "second_order",
>  wfc_extrapolation = "second_order",
>ATOMIC_SPECIES
>Au 1.00  Au.pbe-van_ak.UPF
>S  1.00  S.pbe-van_ak.UPF
>C  1.00  C.pbe-van_ak.UPF
>H  1.00  H.pbe-van_ak.UPF
>ATOMIC_POSITIONS {bohr}
>Au       0.000000000  -4.965200000   0.000000000 0 0 0
>Au      -4.319724000  -2.482600000   0.000000000 0 0 0
>Au      -4.319724000   2.482600000   0.000000000 0 0 0
>.................
>Au      -2.774561616   0.031062380  28.596765964 1 1 1
>Au       0.041848351  -0.082778583  32.636501628 1 1 1
>Au      -0.028301935   1.263362498  37.301572656 1 1 1
>.................
>C        0.003014820  -0.792207427  45.903314488 1 1 1
>H       -1.656592433  -2.071574048  45.925688702 1 1 1
>H        1.659769150  -2.074993963  45.925343414 1 1 1
>.................
>Au       0.002439106   5.120271920  81.897457381 1 1 1
>Au      -4.361967945   2.134818447  81.462315449 1 1 1
>Au      -5.204105949  -3.027358489  81.522909929 1 1 1
>.................
>Au      -4.319724000   2.482600000  98.968460000 0 0 0
>Au      -4.319724000  -2.482600000  98.968460000 0 0 0
>Au       0.000000000  -4.965200000  98.968460000 0 0 0
>K_POINTS {Gamma}
>
>I tried with vc-relax as well but could not improve it much. In another
>system, I came across the following forces:
>     Total force =     0.506859     Total SCF correction =     0.000423
>     Total force =     0.501602     Total SCF correction =     0.000666
>     Total force =     0.504022     Total SCF correction =     0.000468
>     Total force =     0.515807     Total SCF correction =     0.000445
>     Total force =     0.531093     Total SCF correction =     0.000497
>     Total force =     0.546169     Total SCF correction =     0.000294
>     Total force =     0.565997     Total SCF correction =     0.000298
>     Total force =     0.594369     Total SCF correction =     0.000437
>     Total force =     0.628540     Total SCF correction =     0.000323
>     Total force =     0.652224     Total SCF correction =     0.000388
>     Total force =     0.636638     Total SCF correction =     0.000299
>     Total force =     0.558604     Total SCF correction =     0.000572
>     Total force =     0.441045     Total SCF correction =     0.000310
>     Total force =     0.331614     Total SCF correction =     0.000424
>     Total force =     0.230756     Total SCF correction =     0.000319
>     Total force =     0.188110     Total SCF correction =     0.000422
>     Total force =     0.160244     Total SCF correction =     0.000236
>     Total force =     0.145254     Total SCF correction =     0.000270
>     Total force =     0.139637     Total SCF correction =     0.000262
>     Total force =     0.125084     Total SCF correction =     0.000424
>     Total force =     0.150679     Total SCF correction =     0.000854
>     Total force =     0.167059     Total SCF correction =     0.000294
>     Total force =     0.172462     Total SCF correction =     0.000478
>     Total force =     0.179529     Total SCF correction =     0.000434
>     Total force =     0.187906     Total SCF correction =     0.000499
>     Total force =     0.191868     Total SCF correction =     0.000428
>     Total force =     0.188061     Total SCF correction =     0.000504
>     Total force =     0.175147     Total SCF correction =     0.000272
>     Total force =     0.159927     Total SCF correction =     0.000273
>     Total force =     0.161611     Total SCF correction =     0.000373
>     Total force =     0.208462     Total SCF correction =     0.000460
>     Total force =     0.280821     Total SCF correction =     0.000192
>     Total force =     0.353126     Total SCF correction =     0.000699
>     Total force =     0.420761     Total SCF correction =     0.000602
>     Total force =     0.486584     Total SCF correction =     0.000230
>     Total force =     0.550967     Total SCF correction =     0.000360
>     Total force =     0.606887     Total SCF correction =     0.000672
>     Total force =     0.640920     Total SCF correction =     0.000602
>     Total force =     0.632764     Total SCF correction =     0.000467
>     Total force =     0.559615     Total SCF correction =     0.000506
>     Total force =     0.526823     Total SCF correction =     0.000464
>     Total force =     0.503575     Total SCF correction =     0.000432
>.........
>Could you please suggest me as to how I could get the "Total force"
>something like 0.001 or of that sort?
>Best regards,
>Sen
>
>
>
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