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Dear All,
a question about NSW in IBRION=8 calculation.

Should I setup NSW=number of ions?
I mean I did NSW=1 and I got the 3 displacement (x,y,z) only for 1 ion, thus I wonder if I have to choose NSW=32 for my 32 atom supercell of graphene in order to calculate the frequencies of my system.

Thanks in advance,
Best.

Giacomo

Below My INCAR

SYSTEM = C_Graphene_like

# xc
ISTART = 1
GGA=PE

#electronic relaxation
PREC= High

ENCUT=500.0
ENAUG=605.0

#SIGMA = 0.05 eV of Temperature smearing
ISMEAR = -5
SIGMA = 0.005


#electronic RELAXATION
NELMIN = 4
NELM = 200

ISIF = 3
ISPIN=2

LORBIT = 11

ALGO=Fast
ICHARG=0
IBRION= 8
LREAL=.FALSE. !needed for good convergence

NFREE=2
POTIM=0.015
EDIFF = 1.E-8

#Ionic Relaxation (coarse for structural opt only)
NSW= 1

ANY IDEA?

Thanks and Merry Xmas,

Giacomo

Is it my INCAR safe?

Hi Giacomo,

IBRIOUN = 7 or 8 calculates analytical derivatives, so you may omit NFREE, POTIM and NSW.

Cheers,

alex

Thanks Alex!

Let me ask you one thing more. Even if my system is constituted by 32 atoms, should I wait for such vasp.log file where it seems there are only three displacements? Does it depend by The fact that IBRION=8 uses analytical derivatives ?
Thanks a lot,
Giacomo

FFT: planning ...( 1 )
reading WAVECAR
the WAVECAR file was read sucessfully
initial charge from wavefunction
entering main loop
N E dE d eps ncg rms rms(c)
DAV: 1 -0.173329520421E+03 -0.17333E+03 -0.91480E-11 10736 0.256E-04 0.454E-06
RMM: 2 -0.173329520421E+03 -0.51386E-09 -0.69042E-10 6754 0.354E-04 0.220E-06
RMM: 3 -0.173329520421E+03 0.79581E-10 -0.53843E-10 6663 0.251E-04 0.252E-06
RMM: 4 -0.173329520421E+03 0.12233E-09 -0.43684E-10 6548 0.218E-04
1 F= -.17332952E+03 E0= -.17332952E+03 d E =0.000000E+00 mag= 0.0000
Linear response reoptimize wavefunctions to high precision
DAV: 1 -0.173329520420E+03 0.74533E-09 0.37999E-10 10072 0.207E-04
DAV: 2 -0.173329520420E+03 -0.86402E-11 0.44986E-10 9168 0.181E-04
Linear response DOF= 3
Linear response progress:
Degree of freedom: 1/ 3
N E dE d eps ncg rms rms(c)
RMM: 1 -0.287018621122E-01 0.40630E-01 -0.25147E-01 11982 0.151E+01
RMM: 2 -0.437991253726E-01 -0.15097E-01 -0.90657E-03 22190 0.833E-01 0.299E-01
RMM: 3 -0.414564304497E-01 0.23427E-02 -0.46209E-03 19614 0.537E-01 0.146E-01
RMM: 4 -0.409554145879E-01 0.50102E-03 -0.80727E-04 19114 0.240E-01 0.763E-02
RMM: 5 -0.408490596537E-01 0.10635E-03 -0.36256E-04 20988 0.984E-02 0.397E-02
RMM: 6 -0.408210718129E-01 0.27988E-04 -0.11999E-04 21620 0.571E-02 0.188E-02
RMM: 7 -0.408168511824E-01 0.42206E-05 -0.36158E-05 21674 0.317E-02 0.860E-03
RMM: 8 -0.408164210824E-01 0.43010E-06 -0.14801E-05 23256 0.146E-02 0.412E-03
RMM: 9 -0.408158985015E-01 0.52258E-06 -0.21810E-06 22476 0.731E-03 0.185E-03
RMM: 10 -0.408161126522E-01 -0.21415E-06 -0.22261E-06 23056 0.392E-03 0.973E-04
RMM: 11 -0.408161537572E-01 -0.41105E-07 -0.73473E-07 21922 0.214E-03 0.350E-04
RMM: 12 -0.408161319240E-01 0.21833E-07 -0.77718E-07 23791 0.111E-03 0.189E-04
RMM: 13 -0.408161434599E-01 -0.11536E-07 -0.26148E-07 25479 0.601E-04 0.117E-04
RMM: 14 -0.408161293054E-01 0.14155E-07 -0.18244E-07 22846 0.451E-04 0.467E-05
RMM: 15 -0.408160944239E-01 0.34881E-07 -0.41324E-08 25865 0.341E-04 0.220E-05
RMM: 16 -0.408161027778E-01 -0.83538E-08 -0.58286E-08 24598 0.315E-04 0.161E-05
force on displaced ion 1 direction 1 : -13.138 0.288 0.000
Linear response progress:
Degree of freedom: 2/ 3
N E dE d eps ncg rms rms(c)
RMM: 1 -0.288127661640E-01 0.12003E-01 -0.24839E-01 11994 0.150E+01
RMM: 2 -0.441372378639E-01 -0.15324E-01 -0.10778E-02 21742 0.837E-01 0.301E-01
RMM: 3 -0.415944417254E-01 0.25428E-02 -0.48655E-03 19770 0.539E-01 0.146E-01
RMM: 4 -0.410963359286E-01 0.49811E-03 -0.92339E-04 18948 0.239E-01 0.766E-02
RMM: 5 -0.409853161363E-01 0.11102E-03 -0.47931E-04 21244 0.101E-01 0.402E-02
RMM: 6 -0.409508415506E-01 0.34475E-04 -0.11101E-04 21234 0.575E-02 0.191E-02
RMM: 7 -0.409451543223E-01 0.56872E-05 -0.11060E-05 21820 0.328E-02 0.880E-03
RMM: 8 -0.409468615685E-01 -0.17072E-05 -0.77795E-06 23116 0.143E-02 0.478E-03
RMM: 9 -0.409466866198E-01 0.17495E-06 -0.59683E-07 22474 0.782E-03 0.190E-03
RMM: 10 -0.409468978719E-01 -0.21125E-06 -0.11970E-06 22332 0.399E-03 0.905E-04
RMM: 11 -0.409467987801E-01 0.99092E-07 0.73545E-07 22336 0.227E-03 0.354E-04
RMM: 12 -0.409468806964E-01 -0.81916E-07 -0.14577E-07 23240 0.118E-03 0.206E-04
RMM: 13 -0.409468971471E-01 -0.16451E-07 -0.16643E-09 25154 0.674E-04 0.122E-04
RMM: 14 -0.409469235040E-01 -0.26357E-07 -0.19085E-08 22042 0.495E-04 0.505E-05
RMM: 15 -0.409469095396E-01 0.13964E-07 -0.12091E-07 25914 0.347E-04 0.250E-05
RMM: 16 -0.409468920525E-01 0.17487E-07 0.39470E-08 24020 0.327E-04 0.187E-05
RMM: 17 -0.409468993656E-01 -0.73131E-08 0.99548E-09 26763 0.269E-04 0.108E-05
force on displaced ion 1 direction 2 : 0.207 -13.416 0.000
Linear response progress:
Degree of freedom: 3/ 3
N E dE d eps ncg rms rms(c)
RMM: 1 -0.226435860904E-01 0.18303E-01 -0.43073E-01 13466 0.142E+01
RMM: 2 -0.300502081822E-01 -0.74066E-02 -0.27540E-03 19576 0.446E-01 0.168E-01
RMM: 3 -0.296678317629E-01 0.38238E-03 -0.47350E-04 19171 0.164E-01 0.900E-02
RMM: 4 -0.295124710152E-01 0.15536E-03 -0.27675E-04 20810 0.726E-02 0.188E-02
RMM: 5 -0.295134291115E-01 -0.95810E-06 -0.27331E-05 20879 0.351E-02 0.396E-03
RMM: 6 -0.295100715597E-01 0.33576E-05 -0.65731E-06 22259 0.154E-02 0.141E-03
RMM: 7 -0.295178029139E-01 -0.77314E-05 -0.42377E-05 23524 0.214E-02 0.468E-04
RMM: 8 -0.295225531375E-01 -0.47502E-05 -0.49682E-05 23814 0.241E-02 0.309E-04
RMM: 9 -0.295326248347E-01 -0.10072E-04 -0.35742E-05 23946 0.204E-02 0.176E-04
RMM: 10 -0.295333515273E-01 -0.72669E-06 -0.14264E-05 23774 0.135E-02 0.955E-05
RMM: 11 -0.295338447388E-01 -0.49321E-06 -0.15713E-05 23650 0.139E-02 0.709E-05
RMM: 12 -0.295350652494E-01 -0.12205E-05 -0.16230E-05 23703 0.134E-02 0.432E-05
force on displaced ion 1 direction 3 : 0.000 0.000 -2.022
Linear response finished
writing wavefunctions

Check the number of modes (with _m_). You need to find 3N (N number of atoms) modes for this kind of calculation.
Maybe symmetry brings the calculation to a fast end?!

Cheers,

alex