An error with ab initio md with vasp

[lanjh]

I have performed some AIMD simulation with vasp recently, but found that several initial structures always converge to very unreasonable structures. The detailed systems I modeled include one metal ion (UO22+ and Eu3+) and more 30 water or other sovent such as CH2Cl2, but after 1000 steps I observed terrible results. For examle, one NO3- ion lost one N atom, or CH2Cl2 lost ether one H or one Cl.

Actually, the UO22+ U=O bond stretched to 2.06 eV after 1000 steps, which is much larger than the qm results. Could anyone gives some instructions about this situation? thanks

one Gamma point is used, as well as PBE GGA method. The following is the parameters.

PREC = Normal
ENCUT = 400.000
EDIFF = 1.0e-04
EDIFFG = -0.02

IBRION = 0
NSW = 2000
POTIM = 1.0
SMASS = 1
TEBEG = 298.0
TEEND = 298.0

ISIF = 2
ISYM = 0
NELMIN=8
ALGO = 48
ISPIN = 2
LWAVE = .FALSE.
LCHARG = .FALSE.
ISMEAR = -1
SIGMA = 0.05
LREAL= Auto
NGX=64
NGY=64
NGZ=64

NUPDOWN=0
NELECT=424

APACO=10
NPACO=200
NBLOCK = 1
KBLOCK = 20

[support_vasp]

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