[CPMD-list] Torsion constraints
Erik Santiso
eesantis at unity.ncsu.edu
Tue Apr 27 00:16:11 CEST 2004
Good! At least I know I wasn't defining the constraints wrong :)
I've been able to get it to work by setting the torsion angle to some
value close to zero but not zero (say 0.01). Sometimes it still jumps and
shows a huge value of GNMAX, but at the end it converges. Guess I'll have
to check the numbers again when the new version comes out.
Thanks for your help!
Erik.
-------------------------------------
Vir prudens non contra ventum mingit.
>
> Dear Erik,
>
> There's indeed a bug in the CPMD version 3.7.*, and it's exactly the
> phase of the angle (-1 degree becomes 359 or vice versa). It should be
> fixed in the new version (out any day now...!! I hope). Sorry for the
> inconvenience.
>
> GNMAX is the largest simple component of ionic forces, however
> what's printed with the coordinates are the forces without/before the
> applying the constraints, that's why GNMAX is huge even though the forces
> in the output seem to be small.
>
> Greetings,
>
> apsi
>
> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
> Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
> Tel +41 1 635 44 97 / Fax +41 1 635 68 38 / GSM +41 79 719 09 35
> Anschrift: Physikalisch Chemisches Institut (PCI), Universität Zürich
> (UniZh)
> Indirizzo: Winterthurerstraße 190, CH-8057 Zürich
> Address: Schweiz / Svizzera / Suisse / Svizra / Switzerland
>
> On Sun, 18 Apr 2004, Erik Santiso wrote:
>
>> Hi,
>>
>> I've been doing some geometry optimizations with torsion constraints,
>> and
>> for most cases thinks seem to work well. However, if I set a torsion
>> angle
>> to be 0 degrees (or 360), the geometry optimization starts doing funny
>> things. Here's an example. The constraint in this case is that the
>> torsion
>> between atoms 7, 8, 9, 10 should be 0.0:
>>
>> ATOM COORDINATES GRADIENTS (-FORCES)
>> 1 H 0.6369 11.2421 7.3588 0.132E-03 -0.197E-04 0.250E-03
>> 2 H 2.7954 13.9975 7.3282 -0.144E-03 0.423E-04 -0.288E-03
>> 3 H -3.0319 13.9637 7.3442 0.110E-03 0.155E-04 -0.891E-04
>> 4 H -3.0301 18.4817 7.3516 -0.723E-04 0.549E-04 0.348E-03
>> 5 H 0.6320 21.2032 7.3462 0.238E-04 -0.108E-03 -0.193E-03
>> 6 H 2.7974 18.4518 7.3616 -0.199E-04 -0.110E-03 0.265E-03
>> 7 C 0.8615 13.2867 7.3435 0.171E-03 -0.140E-03 0.750E-03
>> 8 C -1.1573 14.8298 7.3389 -0.341E-03 0.187E-03 -0.477E-03
>> 9 C -1.1552 17.6146 7.3452 0.332E-03 -0.267E-03 0.557E-03
>> 10 C 0.8619 19.1595 7.3501 -0.956E-05 0.325E-03 0.346E-03
>> ****************************************************************
>> *** TOTAL STEP NR. 166 GEOMETRY STEP NR. 24 ***
>> *** GNMAX= 1.696295E-02 [8.02E-03] ETOT= -26.304652 ***
>> *** GNORM= 4.848471E-03 DETOT= -1.048E-05 ***
>> *** CNSTR= 1.745681E-02 TCPU= 31.09 ***
>> ****************************************************************
>> 1 2.674E-04 4.708E-05 -26.304543 1.082E-04 4.04
>> 2 1.048E-04 1.539E-05 -26.304644 -1.002E-04 4.07
>> 3 5.823E-05 8.073E-06 -26.304651 -7.269E-06 4.05
>> 4 5.257E-05 4.483E-06 -26.304654 -3.038E-06 4.10
>> 5 2.776E-05 2.903E-06 -26.304654 -6.502E-07 4.10
>> 6 1.711E-05 1.621E-06 -26.304655 -4.005E-07 4.90
>> 7 1.186E-05 6.911E-07 -26.304655 -2.197E-07 4.78
>> 8 6.332E-06 3.436E-07 -26.304655 -6.332E-09 4.85
>>
>> RESTART INFORMATION WRITTEN ON FILE ./RESTART.1
>>
>> ATOM COORDINATES GRADIENTS (-FORCES)
>> 1 H 0.6355 11.2413 7.3588 0.526E-04 -0.877E-04 0.409E-03
>> 2 H 2.7954 13.9970 7.3292 -0.168E-03 0.962E-04 -0.229E-04
>> 3 H -3.0314 13.9634 7.3479 0.132E-03 -0.633E-05 -0.574E-04
>> 4 H -3.0297 18.4816 7.3509 -0.160E-03 0.100E-03 0.300E-03
>> 5 H 0.6309 21.2036 7.3458 0.320E-04 -0.158E-03 -0.187E-03
>> 6 H 2.7984 18.4542 7.3634 0.473E-04 -0.805E-04 0.287E-03
>> 7 C 0.8617 13.2859 7.3373 0.252E-03 -0.145E-03 0.562E-04
>> 8 C -1.1569 14.8295 7.3402 -0.414E-03 0.118E-03 -0.197E-03
>> 9 C -1.1545 17.6146 7.3461 0.506E-03 -0.255E-03 0.583E-03
>> 10 C 0.8621 19.1602 7.3504 -0.729E-04 0.368E-03 0.278E-03
>> ****************************************************************
>> *** TOTAL STEP NR. 174 GEOMETRY STEP NR. 25 ***
>> *** GNMAX= 3.285935E+01 [6.14E-03] ETOT= -26.304655 ***
>> *** GNORM= 9.384478E+00 DETOT= -3.556E-06 ***
>> *** CNSTR= 3.285993E+01 TCPU= 34.97 ***
>> ****************************************************************
>> 1 2.379E-04 4.148E-05 -26.304568 8.690E-05 4.05
>> 2 9.553E-05 1.362E-05 -26.304642 -7.339E-05 4.02
>> 3 5.412E-05 7.187E-06 -26.304650 -8.253E-06 4.04
>> 4 4.862E-05 3.975E-06 -26.304651 -1.259E-06 4.21
>> 5 2.584E-05 2.507E-06 -26.304652 -7.716E-07 4.10
>> 6 1.562E-05 1.417E-06 -26.304652 -3.099E-07 4.83
>> 7 1.029E-05 5.705E-07 -26.304652 -7.033E-08 4.83
>> 8 5.174E-06 2.462E-07 -26.304652 -3.037E-08 4.79
>>
>> RESTART INFORMATION WRITTEN ON FILE ./RESTART.1
>>
>> ATOM COORDINATES GRADIENTS (-FORCES)
>> 1 H 0.6367 11.2421 7.3587 0.158E-03 0.159E-04 0.284E-03
>> 2 H 2.7959 13.9965 7.3279 -0.479E-04 0.339E-04 -0.247E-03
>> 3 H -3.0317 13.9639 7.3445 0.308E-04 0.242E-04 -0.100E-03
>> 4 H -3.0299 18.4821 7.3517 0.805E-04 0.338E-04 0.350E-03
>> 5 H 0.6315 21.2030 7.3463 0.164E-04 -0.373E-04 -0.187E-03
>> 6 H 2.7977 18.4529 7.3624 -0.468E-05 -0.183E-04 0.273E-03
>> 7 C 0.8614 13.2866 7.3426 -0.168E-03 -0.316E-04 0.715E-03
>> 8 C -1.1568 14.8297 7.3389 0.467E-04 0.347E-04 -0.483E-03
>> 9 C -1.1557 17.6147 7.3453 0.256E-04 -0.184E-03 0.562E-03
>> 10 C 0.8618 19.1591 7.3502 0.529E-04 0.812E-04 0.308E-03
>> ****************************************************************
>> *** TOTAL STEP NR. 182 GEOMETRY STEP NR. 26 ***
>> *** GNMAX= 1.532222E-02 [5.30E-03] ETOT= -26.304652 ***
>> *** GNORM= 4.377040E-03 DETOT= 2.814E-06 ***
>> *** CNSTR= 1.581241E-02 TCPU= 34.95 ***
>> ****************************************************************
>> 1 8.455E-06 2.055E-06 -26.304652 2.594E-07 4.12
>> 2 6.064E-06 6.952E-07 -26.304652 -2.099E-07 4.85
>>
>> RESTART INFORMATION WRITTEN ON FILE ./RESTART.1
>>
>> In the middle step (25), it appears that the constraint has a difference
>> of 32.8, but the torsion angle is actually much smaller (the coordinates
>> of the 4 atoms are pretty much equal to those in the other two steps).
>> Any
>> idea what is causing this? One thing that comes to mind is the
>> discontinuity of the torsion angle at 0 (360), could this be the cause
>> (and if it is, is there any way around it?).
>>
>> I also have another question. What are exactly the quantities in the
>> GNMAX
>> line of the output at each geometry step? Before I thought it was the
>> maximum nuclear gradient, but in this case it is clearly not.
>>
>> Thanks a lot!
>>
>> Erik.
>>
>> -------------------------------------
>> Vir prudens non contra ventum mingit.
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