[ase-users] Comparison of Vibrational Frequencies Obtained from VASP and ASE

[陳佑任]

Dear ASE users,

I am using ASE to do a normal mode analysis. However, I have a problem that the frequencies given by ASE is not consistent with the frequencies given by the normal mode analysis implemented in VASP (IBRION = 5) although I think I have used the same settings. The settings are shown below.

--------------------------
POSCAR used by both ASE and VASP:

H O
   1.00000000000000
    10.0000000000000000    0.0000000000000000    0.0000000000000000
     0.0000000000000000   10.0000000000000000    0.0000000000000000
     0.0000000000000000    0.0000000000000000   10.0000000000000000
   H    O
     2     1
Selective dynamics
Cartesian
        5.1707077079      4.0137770615      5.2080185115     T   T   T
        5.0954999575      5.5514905157      5.1493322874     T   T   T
        5.5902191105      4.8193934419      5.5566036301     T   T   T

  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00
  0.00000000E+00  0.00000000E+00  0.00000000E+00


---------------------------------

INCAR generated by ASE:
INCAR created by Atomic Simulation Environment
 ENCUT = 300.000000
 PARAM2 = 1.000000
 AGGAC = 0.000000
 PARAM1 = 0.123400
 SIGMA = 0.010000
 POTIM = 0.015000
 EDIFF = 1.00e-04
 EDIFFG = 5.00e-02
 SYSTEM = H2O
 GGA = MK
 ALGO = fast
 ISYM = 0
 ISPIN = 2
 ISMEAR = -1
 ISTART = 1
 IALGO = 38
 NELM = 60
 NSW = 1
 IBRION = -1
 NPAR = 4
 IDIPOL = 4
 DIPOL = 0.5000 0.5000 0.5000
 LUSE_VDW = .TRUE.
 LDIPOL = .TRUE.
 LREAL = .FALSE.

----------------------------------------

INCAR used for the normal mode analysis implemented in VASP

ISMEAR = -1
SIGMA  = 0.01
EDIFF  = 1.d-4
EDIFFG = -0.05
ISPIN  = 2
ALGO   = fast
NSW    = 600
ISIF   = 0
IBRION = 5
LREAL  = .F.
IALGO  = 38
NELM   = 60
ENCUT  = 300
ISYM   = 0
NPAR   = 4
ISTART = 1
IDIPOL = 4
LDIPOL = T
DIPOL = 0.5 0.5 0.5
POTIM = 0.015
GGA = MK
PARAM1 = 0.1234
PARAM2 = 1.0000
LUSE_VDW = .TRUE.
AGGAC = 0.0000

-------------------------

The results are shown below:

VASP:
1 f  = 3677.961907 cm-1
2 f  = 3587.067891 cm-1
3 f  = 1568.669032 cm-1
4 f  =   265.535571 cm-1
5 f  =   234.019931 cm-1
6 f  =   121.480968 cm-1
7 f/i=       8.023132 cm-1
8 f/i=     19.960428 cm-1
9 f/i=   309.311267 cm-1

ASE:
#   mev      cm-1
0   23.0i    185.3i
1   12.9i    104.3i
2    2.3i     18.8i
3   10.1      81.6
4   27.3     220.5
5   32.2     259.8
6  199.1    1605.8
7  436.9    3523.6
8  457.0    3685.7

As we can see from the results, the difference between the two calculations is not small. Does anyone have an idea where this mismatch may come from, or whether this is within the range of the error of the method?

Yu-Ren Chen

Institute of Atomic and Molecular Sciences, Academia Sinica
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