[Wien] :FCHECK in Wien2k 13.1 vs. 14

[Elias Assmann]

Dear Prof. Marks,
Dear Peter,

Thank you both for your comments.  It took a little while for me to
digest them.  Let me try and answer some of your points.

On 11/30/2015 04:40 PM, Laurence Marks wrote:
> In your case this "disturbed" 14.2 and it is adjusting the greed
> down to try and stabilize. In 13.1 this push is missing, so it starts
> with a small greed and finds what it thinks might be a solution.

Fair enough.  I guess I can see the “push” in the first to :MIX lines

14.2 :MIX  :   PRATT  REG: 1.00E-06  GREED: 0.200
     :MIX  :   PRATT  REG: 1.00E-06  GREED: 0.200  Reduce 0.25  0.20

13.1 :MIX  :   PRATT  REG: 1.00E-06  GREED: 0.025
     :MIX  :   MSR1a  REG: 1.00E-06  GREED: 0.030  Newton 1.00  0.03

But is this really a sufficient explanation for the difference in the
forces?  To reiterate, :FCHECK stays in the hundreds with 14.2
throughout hundreds of iterations and shows no sign of getting better.
In 13.1, it may still be “large” in the segment I posted, but (a) the
difference (an order of magnitude!) to 14.2 seems significant to me, and
(b) it does get better in 13.1.  I let the calculation continue for some
iterations, and it seems to be converging (in :DIS, :ENE, :FCHECK):

:FCHECK:   -0.032439112    -1.135943714    16.929383355
:FCHECK:   -0.028389245    -1.094880711    15.228531069
:FCHECK:   -0.019806079    -1.047241495    15.222784275
:FCHECK:    0.066957613    -0.532750625     6.877936902
:FCHECK:    0.198624197     0.113074627     4.947166063
:FCHECK:    0.290335137     0.709393143     5.480758387
:FCHECK:    0.230186592     0.748489732     8.063734492

Of course, this decrease happens only after the mixer switches off
MSR1a, so maybe it is really a consequence of that.

On 11/30/2015 05:59 PM, Peter Blaha wrote:
> However, you should now check if the final forces with 13.1 are 
> really small (so that it was "justified" that the mixer switched from
> MSR1a to MSR1 and stopped optimizing the positions (you probably need
> a few more normal scf iterations to get a lower :DIS and better 
> converged forces to get a convincing answer) - otherwise 13.1 stopped
> to early and was "stagnating";

It seems to be going that way, but I will certainly do more iterations
and report back then.


Thanks again,

	Elias

-- 
Elias Assmann
Institute of Theoretical and Computational Physics
TU Graz                   ⟨https://itp.tugraz.at/⟩

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