[DFTB-Plus-User] Convergence issues?

Dave Schall schall2 at oakland.edu
Fri Mar 19 16:39:36 CET 2010 

Hello,
I'm trying to do an energy minimization of slab-like planar structure and I
cannot get convergence of steepest descents or cg method. In a separate, but
possibly related issue, I can't get the scc calculation to converge either.
I started with a 1x1 unit cell "slab" of the material, then a 2x2 unit cell
slab. These both converge in around 8 iterations. If I scale up to 3x3 cells
or greater, I do not achieve convergence and the energy oscilates or
actually goes up. Any suggestions for achieving convergence for energy
minimization and / or scc? Ideally I'd like to scale up to a 10x5 unit cell
slab for my calculations.

Attached are the input files for a 2x2 and 3x3 unit cell energy minimization
calculations with scc off.

Thanks in advance for your assistance!

Dave Schall

#2x2 unit cell: Converges just fine.
Geometry = GenFormat {
          32 S
C H
1 1 -2.5319 -0.2582 -4.3855
2 1 -1.2659 0.2584 -3.6545
3 1 -1.2659 -0.2582 -2.1927
4 1 -2.5319 0.2584 -1.4617
5 2 -2.5319 -1.3798 -4.3855
6 2 -1.2659 1.3800 -3.6545
7 2 -1.2659 -1.3798 -2.1927
8 2 -2.5319 1.3800 -1.4617
9 1 0.0001 -0.2582 -4.3855
10 1 1.2661 0.2584 -3.6545
11 1 1.2661 -0.2582 -2.1927
12 1 0.0001 0.2584 -1.4617
13 2 0.0001 -1.3798 -4.3855
14 2 1.2661 1.3800 -3.6545
15 2 1.2661 -1.3798 -2.1927
16 2 0.0001 1.3800 -1.4617
17 1 -2.5319 -0.2582 0.0001
18 1 -1.2659 0.2584 0.7310
19 1 -1.2659 -0.2582 2.1929
20 1 -2.5319 0.2584 2.9238
21 2 -2.5319 -1.3798 0.0001
22 2 -1.2659 1.3800 0.7310
23 2 -1.2659 -1.3798 2.1929
24 2 -2.5319 1.3800 2.9238
25 1 0.0001 -0.2582 0.0001
26 1 1.2661 0.2584 0.7310
27 1 1.2661 -0.2582 2.1929
28 1 0.0001 0.2584 2.9238
29 2 0.0001 -1.3798 0.0001
30 2 1.2661 1.3800 0.7310
31 2 1.2661 -1.3798 2.1929
32 2 0.0001 1.3800 2.9238
0.0 0.0 0.0
5.0640000000000001 0.0 0.0
0.0 20.000000000000000 0.0
0.0 0.0 8.7711518399999999
}
Driver = ConjugateGradient {
  MovedAtoms =  Range  { 1 -1 }
  MaxForceComponent [eV/AA] = 1.0e-2
  MaxSteps = 100
#  StepSize = 0.1
  OutputPrefix = "geo_end"
}
Hamiltonian = DFTB {
  SCC = No
  MaxAngularMomentum = {
    C = "p"
    H = "s"
#  Eigensolver =  Standard{}
  }
  SlaterKosterFiles = Type2FileNames {
    Prefix = "/home/schall2/Research/
splines/slako/pbc-0-2/"
    Separator = "-"
    Suffix = ".skf"
  }
  KPointsAndWeights = SupercellFolding {
    2   0   0
    0   2   0
    0   0   2
    0.5 0.5 0.5
  }
  Eigensolver = Standard{}
}

#3x3 unit cell: Does not converge!
Geometry = GenFormat {
          72 S
C H
1 1 -3.7979 -0.2582 -6.5783
2 1 -2.5319 0.2584 -5.8473
3 1 -2.5319 -0.2582 -4.3855
4 1 -3.7979 0.2584 -3.6545
5 2 -3.7979 -1.3798 -6.5783
6 2 -2.5319 1.3800 -5.8473
7 2 -2.5319 -1.3798 -4.3855
8 2 -3.7979 1.3800 -3.6545
9 1 -1.2659 -0.2582 -6.5783
10 1 0.0001 0.2584 -5.8473
11 1 0.0001 -0.2582 -4.3855
12 1 -1.2659 0.2584 -3.6545
13 2 -1.2659 -1.3798 -6.5783
14 2 0.0001 1.3800 -5.8473
15 2 0.0001 -1.3798 -4.3855
16 2 -1.2659 1.3800 -3.6545
17 1 1.2661 -0.2582 -6.5783
18 1 2.5321 0.2584 -5.8473
19 1 2.5321 -0.2582 -4.3855
20 1 1.2661 0.2584 -3.6545
21 2 1.2661 -1.3798 -6.5783
22 2 2.5321 1.3800 -5.8473
23 2 2.5321 -1.3798 -4.3855
24 2 1.2661 1.3800 -3.6545
25 1 -3.7979 -0.2582 -2.1927
26 1 -2.5319 0.2584 -1.4617
27 1 -2.5319 -0.2582 0.0001
28 1 -3.7979 0.2584 0.7310
29 2 -3.7979 -1.3798 -2.1927
30 2 -2.5319 1.3800 -1.4617
31 2 -2.5319 -1.3798 0.0001
32 2 -3.7979 1.3800 0.7310
33 1 -1.2659 -0.2582 -2.1927
34 1 0.0001 0.2584 -1.4617
35 1 0.0001 -0.2582 0.0001
36 1 -1.2659 0.2584 0.7310
37 2 -1.2659 -1.3798 -2.1927
38 2 0.0001 1.3800 -1.4617
39 2 0.0001 -1.3798 0.0001
40 2 -1.2659 1.3800 0.7310
41 1 1.2661 -0.2582 -2.1927
42 1 2.5321 0.2584 -1.4617
43 1 2.5321 -0.2582 0.0001
44 1 1.2661 0.2584 0.7310
45 2 1.2661 -1.3798 -2.1927
46 2 2.5321 1.3800 -1.4617
47 2 2.5321 -1.3798 0.0001
48 2 1.2661 1.3800 0.7310
49 1 -3.7979 -0.2582 2.1929
50 1 -2.5319 0.2584 2.9238
51 1 -2.5319 -0.2582 4.3857
52 1 -3.7979 0.2584 5.1166
53 2 -3.7979 -1.3798 2.1929
54 2 -2.5319 1.3800 2.9238
55 2 -2.5319 -1.3798 4.3857
56 2 -3.7979 1.3800 5.1166
57 1 -1.2659 -0.2582 2.1929
58 1 0.0001 0.2584 2.9238
59 1 0.0001 -0.2582 4.3857
60 1 -1.2659 0.2584 5.1166
61 2 -1.2659 -1.3798 2.1929
62 2 0.0001 1.3800 2.9238
63 2 0.0001 -1.3798 4.3857
64 2 -1.2659 1.3800 5.1166
65 1 1.2661 -0.2582 2.1929
66 1 2.5321 0.2584 2.9238
67 1 2.5321 -0.2582 4.3857
68 1 1.2661 0.2584 5.1166
69 2 1.2661 -1.3798 2.1929
70 2 2.5321 1.3800 2.9238
71 2 2.5321 -1.3798 4.3857
72 2 1.2661 1.3800 5.1166
0.0 0.0 0.0
7.5960000000000001 0.0 0.0
0.0 20.000000000000000 0.0
0.0 0.0 13.156727759999999
}
Driver = ConjugateGradient {
  MovedAtoms =  Range  { 1 -1 }
  MaxForceComponent [eV/AA] = 1.0e-2
  MaxSteps = 100
#  StepSize = 0.1
  OutputPrefix = "geo_end"
}
Hamiltonian = DFTB {
  SCC = No
  MaxAngularMomentum = {
    C = "p"
    H = "s"
#  Eigensolver =  Standard{}
  }
  SlaterKosterFiles = Type2FileNames {
    Prefix = "/home/schall2/Research/splines/slako/pbc-0-2/"
    Separator = "-"
    Suffix = ".skf"
  }
  KPointsAndWeights = SupercellFolding {
    2   0   0
    0   2   0
    0   0   2
    0.5 0.5 0.5
  }
  Eigensolver = Standard{}
}


-- 
J. David Schall, Assistant Professor
Dept. of Mechanical Engineering, Oakland University
130 DHE, Rochester, MI 48309
248-370-2870
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