Two imaginary frequencies in the transition state in NEB

foucault3 · Post by **foucault3** » Mon Oct 14, 2024 7:55 pm

Hello,
I ran a vibrational frequency calculation for the transition state structure obtained from the NEB calculation dimer. I find that there are two large imaginary frequencies. I am not sure what contributes to this unexpected result. I tried changing different flags (e.g POTIM), but I was not able to get rid of the second imaginary frequency. Any suggestion on how to fix the problem is appreciated. Thank you.

1 f = 34.616099 THz 217.499365 2PiTHz 1154.668774 cm-1 143.160618 meV
2 f = 32.913453 THz 206.801322 2PiTHz 1097.874605 cm-1 136.119041 meV
3 f = 31.624827 THz 198.704651 2PiTHz 1054.890696 cm-1 130.789718 meV
4 f = 30.502092 THz 191.650295 2PiTHz 1017.440263 cm-1 126.146459 meV
5 f = 13.852408 THz 87.037249 2PiTHz 462.066605 cm-1 57.288932 meV
6 f = 12.130810 THz 76.220125 2PiTHz 404.640254 cm-1 50.168975 meV
7 f = 7.175303 THz 45.083761 2PiTHz 239.342361 cm-1 29.674657 meV
8 f = 6.336087 THz 39.810807 2PiTHz 211.349102 cm-1 26.203937 meV
9 f = 5.091282 THz 31.989466 2PiTHz 169.826877 cm-1 21.055840 meV
10 f = 5.018189 THz 31.530211 2PiTHz 167.388764 cm-1 20.753552 meV
11 f = 4.324435 THz 27.171226 2PiTHz 144.247623 cm-1 17.884418 meV
12 f = 4.238026 THz 26.628302 2PiTHz 141.365326 cm-1 17.527059 meV
13 f = 3.905560 THz 24.539354 2PiTHz 130.275443 cm-1 16.152089 meV
14 f = 3.557582 THz 22.352949 2PiTHz 118.668174 cm-1 14.712972 meV
15 f = 3.407740 THz 21.411462 2PiTHz 113.669970 cm-1 14.093274 meV
16 f = 3.125111 THz 19.635653 2PiTHz 104.242488 cm-1 12.924415 meV
17 f = 2.982482 THz 18.739489 2PiTHz 99.484903 cm-1 12.334550 meV
18 f = 1.637520 THz 10.288840 2PiTHz 54.621780 cm-1 6.772235 meV
19 f = 1.592645 THz 10.006886 2PiTHz 53.124931 cm-1 6.586649 meV
20 f/i= 36.870124 THz 231.661820 2PiTHz 1229.854948 cm-1 152.482511 meV
21 f/i= 50.493946 THz 317.262820 2PiTHz 1684.296742 cm-1 208.826087 meV

Here is the INCAR file I used:

SYSTEM = Zr-NH2
NWRITE = 1
ISTART = 0

ENCUT = 400.0 eV
PREC = HIGH
EDIFF = 1E-08
EDFIFFG = -3E-04

LCORR = T
ISIF = 2

ISMEAR = 0
SIGMA = 0.1

IALGO = 38
LDIAG = T
LREAL = F

NBANDS = 206
LDIPOL = T
IDIPOL = 3
LWAVE = F
NSW=100
POTIM = 0.001
IBRION=5
NFREE=2
NELM = 200