[CP2K:2248] convergence & cutoff madness

Toon Verstraelen toon.ver... at UGent.be
Mon Sep 7 12:11:55 CEST 2009


Hi,

Below a similar table with the DZVP-GTH basis instead of the SZV-GTH basis.

Number of failed SCF	 7
cutoff [Ry]   energy [kjmol]   time [s]   steps   time per step [s]"
    100.0         755266.00      875.24     250        3.50
    110.0           1849.77      159.59      42        3.80
    120.0           1849.20      129.75      35        3.71
    130.0            986.17      210.71      54        3.90
    140.0            823.57      489.46     114        4.29
    150.0            762.08      130.94      30        4.36
    160.0            604.84      521.14     113        4.61
    170.0            294.25      176.77      37        4.78
    180.0            319.16     1270.09     250        5.08
    190.0            323.22     1198.53     250        4.79
    200.0             87.76     1330.97     250        5.32
    210.0             87.63     1330.64     250        5.32
    220.0             83.83     1375.40     250        5.50
    230.0             90.91      630.85     104        6.07
    240.0             74.54      552.09      87        6.35
    250.0             41.28      207.62      30        6.92
    260.0             39.96     1330.75     250        5.32
    270.0             24.73      598.13      89        6.72
    280.0             16.34      237.48      29        8.19
    290.0              5.94      285.42      31        9.21
    300.0              4.92      303.03      34        8.91
    310.0              7.34      628.55      86        7.31
    320.0              0.00      453.03      57        7.95
    330.0              1.91      250.62      26        9.64
    340.0              4.26      287.63      27       10.65
    350.0              5.16      239.20      23       10.40
    360.0              5.30      341.52      35        9.76
    370.0              8.57      303.73      26       11.68
    380.0              8.52      286.88      24       11.95
    390.0             12.97      262.10      24       10.92
    400.0             12.20      289.96      26       11.15

It is a bit strange that the timings improve and convergence is
obtained with less steps compared to the smaller basis.

We also did similar tests with the PBE functional. All those
computations ran smoothly without any convergence issue.


Citeren Toon Verstraelen <Toon.Ver... at UGent.be>:

>
> Dear CP2K users,
>
> I'm running a few basic tests to get a better understanding of the
> relation between SCF convergence and the plane wave cutoff. The table
> below summarizes a series of trivial energy calculations with different
> cutoffs. The input files are attached.
>
> The system in the input is MIL-53-Al, a well-known metal-organic
> framework. To keep things simple, I've used a very minimal basis
> (SZV-GTH). The largest basis set exponent is 8.3744350009, which
> corresponds to a cutoff of 330 Rydberg. (if not mistaken). The
> functional is blyp.
>
> There are two weird things in this table:
>
> 1) The lowest energy is not obtained with the highest cutoff. It gets
> worse above 320.
>
> 2) For some high cutoff's there is no SCF convergence. For the low
> range, up to 150, this is normal. I would not expect this for a cutoff
> of 330.
>
> Does somebody know what is going on? The input files are rather simple,
> but maybe I've put in something pernicious? With larger basis sets,
> there are more cases where the SCF convergence fails. It becomes
> practically useless, even when a decent initial guess with a smaller
> basis set is constructed.
>
>
> Number of failed SCF	 10
> cutoff [Ry]   energy [kjmol]   time [s]   #iters   time per iter [s]"
>     100.0         370146.36      841.59     250        3.37
>     110.0           4309.36     1023.83     250        4.10
>     120.0           4311.87     1053.45     250        4.21
>     130.0           1159.84     1099.50     250        4.40
>     140.0            939.17     1166.17     250        4.66
>     150.0           2549.48     1206.51     250        4.83
>     160.0            804.26      227.56      42        5.42
>     170.0            354.60      159.26      29        5.49
>     180.0            412.98      177.18      29        6.11
>     190.0            685.96     1455.42     250        5.82
>     200.0             79.06      199.92      32        6.25
>     210.0             79.17      262.35      40        6.56
>     220.0             78.54      201.22      28        7.19
>     230.0             86.04      218.52      28        7.80
>     240.0             63.43      261.85      35        7.48
>     250.0             33.38     2067.27     250        8.27
>     260.0             34.90     2237.25     250        8.95
>     270.0             22.10      225.49      28        8.05
>     280.0             14.48      458.72      52        8.82
>     290.0              5.22      322.73      32       10.09
>     300.0              4.17      251.49      28        8.98
>     310.0              6.07      319.30      32        9.98
>     320.0              0.00      296.63      29       10.23
>     330.0              2.18     2370.99     250        9.48
>     340.0              4.32      351.99      28       12.57
>     350.0              4.38      398.81      32       12.46
>     360.0              4.37      332.36      25       13.29
>     370.0              8.01      496.19      39       12.72
>     380.0              8.10      368.99      29       12.72
>     390.0             13.16      402.97      29       13.90
>     400.0             12.49      410.13      29       14.14
>
>
> cheers,
>
> Toon
>
>
> >
>






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