[CPMD-list] problems with MD -- conservation of energy and translational drift
jernej at cmm.ki.si
jernej at cmm.ki.si
Tue Feb 15 09:57:13 CET 2005
Dear CPMD community,
I wonder if somebody can help me with the following two issues regarding CP
molecular dynamics:
1) Conservation of EHAM: when starting CPMD simulation from a previously
minimized structure, EHAM is by no means constant and features a significant
drift. HOWEVER, if I kill the dynamics after a few (say 10) steps and restart
it with the 'RESTART WAVEFUNCTION COORDINATES VELOCITIES NOSE ACCUMULATORS
LATEST' and 'QUENCH BO' options, EHAM does not drift anymore.
This weird feature does not make any sense to me. It appears with either of the
three popular pseudopotentials I've used so far (i.e., Goedecker,
Trouiller-Martins, and Vanderbilt). I've been using the BLYP functional
throughout. Can somebody tell me if I did something wrong in the simulation
setup, or otherwise explain this feature? Is it possible that this problem has
anything to do with the way in which the code was compiled (I had quite a few
problems with this)?
2) Translational drift: even after "solving" the problem with EHAM, as depicted
above, it happens that after running the MD for quite a while, say 20.000 steps
of 5 a.u., the DIS value that was reasonably small (up to 1.) and stable within
the first 20.000 steps, starts increasing considerably -- it reaches a value of
more than 25. after 60.000 steps! Then the whole MD chrases -- it produces
meaningless characters in the output:
RESTART INFORMATION WRITTEN ON FILE ./RESTART.1
60601 0.00699 335.1 -221.25864 -221.23337 -221.22638 26.429
1.91
60602 0.00697 332.8 -221.25838 -221.23335 -221.22638 26.429
2.05
60603 0.00696 330.9 -221.25816 -221.23334 -221.22638 26.429
1.95
60604 0.00694 329.3 -221.25800 -221.23332 -221.22638 26.430
1.95
60605 0.00692 328.1 -221.25786 -221.23330 -221.22638 26.430
1.99
60606 0.00688 327.1 -221.25774 -221.23326 -221.22638 26.431
1.98
60607 0.00684 326.3 -221.25764 -221.23322 -221.22638 26.432
1.95
60608 0.00679 325.7 -221.25757 -221.23317 -221.22638 26.433
1.94
60609 0.00676 325.2 -221.25752 -221.23314 -221.22638 26.434
1.91
60610 0.00675 324.7 -221.25750 -221.23313 -221.22638 26.436
1.97
60611+++++++++ 324.2 -221.25749 -221.23314++++++++++++++ 26.438
1.96
60612??????????????????????????????????????????????????????????? 26.440
1.86
60613???????????????????????????????????????????????????????????????????
1.83
60614???????????????????????????????????????????????????????????????????
1.98
60615???????????????????????????????????????????????????????????????????
1.88
I've checked the center of mass of the system and indeed it features a drift --
therefore there is considerable translation in the simulation, especially after
the DIS value had increased. I'm a bit puzzled about the origin of this drift,
for I've made sure that I started my MD from a previously minimized structure!
Can somebody tell me what is the source of this problem and how to avoid it?
Could the drift have anything to do with the weird conservation of EHAM
depicted in 1) ?
Thanks in advance for your help,
Dr. Jernej Stare
Los Alamos National Laboratory,
Los Alamos, NM, USA
**** Below is the input file that I've been using for my simulations.
&CPMD
MOLECULAR DYNAMICS CP
RESTART WAVEFUNCTION COORDINATES VELOCITIES NOSE ACCUMULATORS LATEST
TIMESTEP
5.
EMASS
600.
NOSE IONS
300 3200
QUENCH BO
MAXSTEP
500000
STORE
50
&END
&DFT
FUNCTIONAL BLYP
&END
&SYSTEM
ANGSTROM
SYMMETRY
TRICLINIC
CELL ABSOLUTE DEGREE
6.1026 3.4867 11.954 90.0 105.79 90.0
CUTOFF
70.0
POINT GROUP
AUTO
&END
&ATOMS
*O_MT_BLYP KLEINMAN-BYLANDER
LMAX=D
12
0.031558 -0.193163 1.727506
-1.470649 0.849709 0.417095
-1.338586 0.463731 3.698642
-0.031558 0.193163 -1.727506
1.470649 -0.849709 -0.417095
1.338586 -0.463731 -3.698642
1.456458 1.936513 7.478956
-0.045749 0.893641 6.168545
0.086314 1.279619 9.450092
1.393342 1.550187 4.023944
2.895549 2.593059 5.334355
2.763486 2.207081 2.052808
*C_MT_BLYP KLEINMAN-BYLANDER
LMAX=D
4
-0.442416 0.205018 0.597921
0.442416 -0.205018 -0.597921
0.982484 1.538332 6.349371
1.867316 1.948368 5.153529
*H_MT_BLYP KLEINMAN-BYLANDER
LMAX=S
12
-0.581475 0.077056 2.563421
-0.770136 0.692807 4.458524
-2.003665 -0.159691 4.034067
0.581475 -0.077056 -2.563421
0.770136 -0.692807 -4.458524
2.003665 0.159691 -4.034067
0.843425 1.666294 8.314871
0.654764 1.050543 10.209974
-0.578765 1.903041 9.785517
2.006375 1.820406 3.188029
2.195036 2.436157 1.292926
3.428565 1.583659 1.717383
&END
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