Incorrect vibration mode after ci-neb convergency

Vasp transition state theory tools

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lgxyz
Posts: 51
Joined: Tue Sep 07, 2010 1:52 pm

Incorrect vibration mode after ci-neb convergency

Post by lgxyz »

hi,
recently, one TS I calculated is well convergent after ci-neb calculation. These images are:
0 0.015991 -159.536108 0.000000
1 0.022558 -159.527371 0.008737
2 0.043312 -159.466460 0.069648
3 0.046132 -159.250819 0.285289
4 0.045178 -159.200728 0.335380
5 0.028051 -159.262260 0.273848
6 0.040377 -159.950231 -0.414123
7 0.009477 -160.059744 -0.523636
8 0.012619 -160.101961 -0.565853
9 0.010891 -160.116247 -0.580139

After that I do frequency calculation (IBRION=5), I got two small imaginary frequency, -39.597248 cm-1 and -13.737954 cm-1; the worse is that both vibration mode of the two imaginary frequency is not consistent with the reaction coordinate. Please give some suggestions.
Thank you very much. The INCAR I used is:

SYSTEM = name
ISTART = 0
ICHARG = 2

ENCUT = 400 eV
NELM = 100
NELMIN = 8
EDIFF = 1.0E-8
ALGO = F
AMIX = 0.2
BMIX = 0.0001

NSW = 400
IBRION = 5
POTIM = 0.001
EDIFFG = -0.05
ISIF = 2

ISMEAR = 1
SIGMA = 0.2

GGA = 91
VOSKOWN = 1
PREC = Accurate
ADDGRID = .TRUE.
LREAL = .FALSE.

#IDIPOL = 3
ISYM = 0
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