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

Sen asen at iitk.ac.in
Sat Jun 9 11:21:11 CEST 2007


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






More information about the users mailing list