Total E not conserved in a MD run (smass=-3)

Message

phtobias · #1 Post by **phtobias** » Tue Apr 18, 2006 3:05 am

Dear all,

I am simulating the motion of a reactive molecule on TiO2 surfaces and are puzzled by the gradual drift in TOTAL energy in a smass=-3 (mirco canonical emsemble) run. I have tried two values of POTIM, 1 and 0.3, which gave the drift of 1.8 and 1.3 eV (out of 431 eV) respectively.

I also observed the drift appeared, when a bond is about to break at which time the (Total) K.E. droped to ~1.0 EV from the initial 1.7 eV.

In the POSCAR, I set the velocity of all atoms to zeros, except the reactive molecule.

I would appreciate greatly any comments and suggestions.

yi-ren

This is the INCAR:
-----------------------
ISMEAR = -1
SIGMA = 0.1
GGA = 91
LREAL = A
NELM = 100
encut = 700

IBRION = 0
NSW = 200

smass = -3
potim = 0.3

prec = low
nelmin = 4
ialgo = 48

phtobias · #2 Post by **phtobias** » Fri May 12, 2006 1:08 am

May I ask if this kind of energy drift is normal in a MD run? I would appreciate greatly any comment. --yi-ren

forsdan · #3 Post by **forsdan** » Fri May 12, 2006 5:55 am

I don't know if this will help you, but there is a discussion about the energy drift in the FAQ.

http://cms.mpi.univie.ac.at/vasp/vasp/node265.html

Best regards

Dan Fors

phtobias · #4 Post by **phtobias** » Sat May 13, 2006 7:37 am

Dear Dan,

Thank you very much for the link. I will try those recommanded parameters to see how they affect the energy drift.

yi-ren