Dear SIESTA Users,
I have encounter a problem in performing constant volume MD calculations. I
started the MD at low temperature and try to raise the temperature to 500K in
500 time steps using the Anneal option. The MD progress normally for the first
200 steps but then suddenly the atomic forces changes dramatically (in none time
step) leading to non-converged SCF and of course unreasonable temperature. I
also have tried NOSE dynamics and different time steps and also change the mass
of the Nose thermstat but to no avail.
The following is an abridged output of the MDE file ...
200 169.87 -23255.21081 -23252.31257 1536.800 17.379
201 170.88 -23255.20528 -23252.28986 1536.800 17.414
202 172.07 -23255.20332 -23252.26748 1536.800 17.441
203 173.45 -23255.20452 -23252.24509 1536.800 17.451
204 175.01 -23255.20882 -23252.22291 1536.800 17.478
205 176.70 -23255.21547 -23252.20072 1536.800 17.488
206 178.49 -23255.22409 -23252.17868 1536.800 17.534
207 180.36 -23255.23397 -23252.15676 1536.800 17.560
208 182.24 -23255.24428 -23252.13502 1536.800 17.597
209 184.09 -23255.25429 -23252.11338 1536.800 17.650
210 185.89 -23255.26351 -23252.09186 1536.800 17.642
211 187.61 -23255.27136 -23252.07049 1536.800 17.667
212 176240.45 -23036.46700 -20029.51243 1536.800 -21626.198
213 702356.30 -23135.40998 -11152.04565 1536.800 2207.655
214 697099.78 -23096.23435 -11202.55494 1536.800 8468.843
215 690174.22 -23000.15007 -11224.63224 1536.800 8519.062
216 684813.06 -22890.65629 -11206.60878 1536.800 8603.375
217 732449.58 -22559.70731 -10062.90163 1536.800 8827.300
218 816250.59 -22813.80843 -8887.21840 1536.800 9097.997
219 828687.19 -22893.10419 -8754.32514 1536.800 10050.024
220 827549.27 -22827.52277 -8708.15855 1536.800 10245.348
221 826980.05 -22820.38365 -8710.73128 1536.800 10188.770
The following is the control parametrs for the MD step ..
MD.TypeOfRun Anneal
MD.AnnealOption Temperature
MD.TauRelax 500.0 fs
MD.ConstantVolume .true.
MD.InitialTimeStep 1
MD.FinalTimeStep 1000
MD.LengthTimsStep 0.8 fs
MD.InitialTemperature 1.0 K
MD.TargetTemperature 500.0 K
I wonder if any parameters I can use to eliminate the sudden change in the
forces ... etc.
Thank you.
John
Dr. John S. Tse
Professor
Canada Research Chair (Tier I)
Department of Physics and Engineering Physics
University of Saskatchewan
116 Science Place
Saskatoon, SK S7N 5E2
Canada
(Tel) +1 306 966 6410
(Fax) +1 306 966 6400
