[CPMD-list] Torsion constraints
Erik Santiso
eesantis at unity.ncsu.edu
Sun Apr 18 23:20:24 CEST 2004
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.
More information about the CPMD-list
mailing list