[ase-users] Efficiency of vibrational frequency using VASP as the calculator
陳佑任
b00504051 at ntu.edu.tw
Mon Jun 5 05:11:19 CEST 2017
Dear ASE users,
I am using ASE’s vibrations package and VASP as a calculator to calculate the vibrational frequencies for a benzene molecule on a graphene nanoribbon. The calculated frequencies are in good agreement with the values computed with the normal mode analysis implemented in VASP itself. However, the total CPU time is much longer when using ASE (almost 3 times as long as directly using VASP). The reason is that the SCF calculations in the VASP-native normal mode analysis require fewer SCF cycles than the single points calculations when ASE calls VASP (<10 vs about 20), even if we read in the WAVECAR file (the stored wavefunction) of the previous calculations. So, seemingly the initial guess for the wavefunction of each perturbed geometry is not good enough. We have tried two approaches, 1) always reading the WAVECAR saved for the unperturbed equilibrium geometry and 2) reading in the WAVECAR from the previous geometry step. Both approaches do not differ too much in the CPU time. Does anybody know how which settings I have to set so the computation time for the normal mode analysis with ASE can be reduced to the computation time of the normal mode analysis as implemented in VASP? Below are my settings:
-----------------------------------
INCAR from VASP:
ISMEAR = -1
SIGMA = 0.01
EDIFF = 1.d-6
EDIFFG = -0.01
ISPIN = 2
ALGO = fast
NSW = 600
ISIF = 0
IBRION = 5
LREAL = .F.
IALGO = 38
NELM = 60
ENCUT = 500
ISYM = 0
NPAR = 4
ISTART = 1
IDIPOL = 3
LDIPOL = T
GGA = MK
PARAM1 = 0.1234
PARAM2 = 1.0000
LUSE_VDW = .TRUE.
AGGAC = 0.0000
-----------------------------------
INCAR generated from ASE:
ENCUT = 500.000000
PARAM2 = 1.000000
AGGAC = 0.000000
PARAM1 = 0.123400
SIGMA = 0.010000
POTIM = 0.015000
EDIFF = 1.00e-06
EDIFFG = -1.00e-02
SYSTEM = graphene
GGA = MK
ALGO = fast
ISYM = 0
ISPIN = 2
ISMEAR = -1
ISTART = 1
IALGO = 38
NELM = 60
NSW = 1
IBRION = -1
NPAR = 4
IDIPOL = 3
ISIF = 0
LUSE_VDW = .TRUE.
LDIPOL = .TRUE.
LREAL = .FALSE.
-----------------------------------
VASP’s one of the SCF steps:
N E dE d eps ncg rms rms(c)
DAV: 1 -0.781201282540E+03 0.45811E-03 -0.75927E-02 4148 0.365E-01 0.929E-02
RMM: 2 -0.781201302856E+03 -0.20316E-04 -0.75765E-04 3552 0.346E-02 0.556E-02
RMM: 3 -0.781201306607E+03 -0.37512E-05 -0.11168E-04 3467 0.122E-02 0.838E-03
RMM: 4 -0.781201305914E+03 0.69345E-06 -0.58417E-06 2832 0.291E-03
2 F= -.78120131E+03 E0= -.78120113E+03 d E =-.353918E-03 mag= 2.5054
-----------------------------------
ASE’s one of the SCF steps:
N E dE d eps ncg rms rms(c)
DAV: 1 -0.781205901599E+03 -0.78121E+03 -0.34936E-01 3944 0.790E-01 0.441E-01
RMM: 2 -0.781202464766E+03 0.34368E-02 -0.87841E-03 3849 0.121E-01 0.252E-01
RMM: 3 -0.781200989068E+03 0.14757E-02 -0.43555E-03 4124 0.666E-02 0.494E-02
RMM: 4 -0.781200905776E+03 0.83293E-04 -0.14996E-04 4230 0.150E-02 0.225E-02
RMM: 5 -0.781200879684E+03 0.26091E-04 -0.41327E-05 3953 0.778E-03 0.907E-03
RMM: 6 -0.781200886517E+03 -0.68326E-05 -0.71667E-06 3586 0.368E-03 0.489E-03
RMM: 7 -0.781200904313E+03 -0.17796E-04 -0.53720E-06 3272 0.273E-03 0.230E-03
RMM: 8 -0.781200927253E+03 -0.22940E-04 -0.28785E-06 3218 0.179E-03 0.149E-03
RMM: 9 -0.781200963183E+03 -0.35930E-04 -0.49109E-06 3057 0.214E-03 0.827E-04
RMM: 10 -0.781200986671E+03 -0.23488E-04 -0.27405E-06 3064 0.154E-03 0.595E-04
RMM: 11 -0.781201007939E+03 -0.21268E-04 -0.24989E-06 2888 0.143E-03 0.347E-04
RMM: 12 -0.781201019595E+03 -0.11657E-04 -0.15067E-06 2791 0.116E-03 0.226E-04
RMM: 13 -0.781201025267E+03 -0.56721E-05 -0.66097E-07 2534 0.834E-04 0.139E-04
RMM: 14 -0.781201028437E+03 -0.31692E-05 -0.32406E-07 2352 0.677E-04 0.860E-05
RMM: 15 -0.781201029598E+03 -0.11619E-05 -0.10339E-07 2381 0.466E-04 0.627E-05
RMM: 16 -0.781201030812E+03 -0.12132E-05 -0.10772E-07 2194 0.519E-04 0.344E-05
RMM: 17 -0.781201031253E+03 -0.44139E-06 -0.45790E-08 2116 0.374E-04
2 F= -.78120103E+03 E0= -.78120085E+03 d E =-.353970E-03 mag= 2.5054
-----------------------------------
Yu-Ren Chen
Institute of Atomic and Molecular Sciences, Academia Sinica
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