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From: Yang Ming <phyym@nu...>  20130901 09:32:21
Attachments:
text/plain
image001.gif

From: Atsushi Togo <atz.togo@gm...>  20130901 12:30:33

Hi, Without watching your band structure, it is difficult to guess what your problem is. Togo On Sun, Sep 1, 2013 at 6:32 PM, Yang Ming <phyym@...> wrote: > Dear All, > > > > I am new in Phonopy. I was just using Phonopy to calculate phonon dispersion > of graphene for testing, but the results are incorrect (negative frequencies > were found). Could anyone there help to check my inputs below? > > > > > > Basically, I followed the Phonopy tutorial for VASP step by step: > > > > 1. Generate a 6×6×1 supercell from below bulk by using the commad: > phonopy –d –dim="6 6 1". > > > > C > > 1.00000000000000 > > 2.1304215583187101 1.2299994601826900 0.0000000000000000 > > 0.0000000000000000 2.4599989203653800 0.0000000000000000 > > 0.0000000000000000 0.0000000000000000 12.0000000000000000 > > 2 > > Direct > > 0.0000000000000000 0.0000000000000000 0.5000000000000000 > > 0.6666666699999979 0.3333333300000021 0.5000000000000000 > > > > 2. Calculate the force using the generated structure POSCAR001 and > standard VASP setting: > > > > ENCUT = 400 > > ISMEAR = 0; SIGMA = 0.01 > > PREC = A > > > > EDIFF = 1.0E8 > > NELM = 400 > > > > IDIPOL = 3 > > > > LWAVE = .F. > > LCHARG = .F. > > LREAL = .F. > > NPAR = 2 > > NELMDL = 5 > > LPLANE = .T. > > > > The KPOINTS for VASP calculation were set to 3×3×1. > > > > 3. Create the FORCE_SETS by using: phonopy –f disp001/vasprun.xml > > 4. > > 5. Phonon band structure was calculated by using the band.conf like > below: > > > > ATOM_NAME = C > > DIM = 6 6 1 > > BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 > > 6. Plot the band structure by using: phonopy –p band.conf > > > > After all these steps, I found some negative frequencies and the values of > the related frequencies are not consistent with those of previous results > also. I doulechecked the calculation processes, but don’t know the problem. > > > > Thank you a lot for your time, and any comments are appreciated. > > > > Best regards, > > Yang Ming > > ****** > > Computational CondensedMatter Physics Lab > > Department of Physics > > National University of Singapore > > Singapore 117542 > > Email: phyym@...; ming_young@... > > Tel: +65 6516 4335 (office) > > > > >  > Learn the latestVisual Studio 2012, SharePoint 2013, SQL 2012, more! > Discover the easy way to master current and previous Microsoft technologies > and advance your career. Get an incredible 1,500+ hours of stepbystep > tutorial videos with LearnDevNow. Subscribe today and save! > http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk > _______________________________________________ > Phonopyusers mailing list > Phonopyusers@... > https://lists.sourceforge.net/lists/listinfo/phonopyusers >  Atsushi Togo http://atztogo.github.com/ atz.togo@... 
From: Atsushi Togo <atz.togo@gm...>  20130901 13:43:49
Attachments:
bandgraphenesmall.jpg

Hi, Your band structure is really broken. I doubt your setting of ISMEAR = 0; SIGMA = 0.01, and few kpoints though I don't know how much it affect to phonons. So I recommend you to check carefully about VASP setting, e.g. by drawing electronic band structure. If you don't know well about electronic structure calculations, you may ask it to your colleagues. Togo On Sun, Sep 1, 2013 at 10:21 PM, Yang Ming <phyym@...> wrote: > Dear Dr. Togo, > > Thanks a lot for the prompt reply. > > Please find the attached data and calculated eigenvalue. > > Thanks. > > Best regards, > Yang Ming > ****** > Computational CondensedMatter Physics Lab > Department of Physics > National University of Singapore > Singapore 117542 > Email: phyym@...; ming_young@... > Tel: +65 6516 4335 (office) > > Original Message > From: Atsushi Togo [mailto:atz.togo@...] > Sent: Sunday, 1 September, 2013 8:30 PM > To: Yang Ming > Cc: phonopyusers@... > Subject: Re: [Phonopyusers] Phonon dispersion of graphene > > Hi, > > Without watching your band structure, it is difficult to guess what your problem is. > > Togo > > On Sun, Sep 1, 2013 at 6:32 PM, Yang Ming <phyym@...> wrote: >> Dear All, >> >> >> >> I am new in Phonopy. I was just using Phonopy to calculate phonon >> dispersion of graphene for testing, but the results are incorrect >> (negative frequencies were found). Could anyone there help to check my inputs below? >> >> >> >> >> >> Basically, I followed the Phonopy tutorial for VASP step by step: >> >> >> >> 1. Generate a 6×6×1 supercell from below bulk by using the commad: >> phonopy d dim="6 6 1". >> >> >> >> C >> >> 1.00000000000000 >> >> 2.1304215583187101 1.2299994601826900 0.0000000000000000 >> >> 0.0000000000000000 2.4599989203653800 0.0000000000000000 >> >> 0.0000000000000000 0.0000000000000000 12.0000000000000000 >> >> 2 >> >> Direct >> >> 0.0000000000000000 0.0000000000000000 0.5000000000000000 >> >> 0.6666666699999979 0.3333333300000021 0.5000000000000000 >> >> >> >> 2. Calculate the force using the generated structure POSCAR001 and >> standard VASP setting: >> >> >> >> ENCUT = 400 >> >> ISMEAR = 0; SIGMA = 0.01 >> >> PREC = A >> >> >> >> EDIFF = 1.0E8 >> >> NELM = 400 >> >> >> >> IDIPOL = 3 >> >> >> >> LWAVE = .F. >> >> LCHARG = .F. >> >> LREAL = .F. >> >> NPAR = 2 >> >> NELMDL = 5 >> >> LPLANE = .T. >> >> >> >> The KPOINTS for VASP calculation were set to 3×3×1. >> >> >> >> 3. Create the FORCE_SETS by using: phonopy f disp001/vasprun.xml >> >> 4. >> >> 5. Phonon band structure was calculated by using the band.conf like >> below: >> >> >> >> ATOM_NAME = C >> >> DIM = 6 6 1 >> >> BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 >> >> 6. Plot the band structure by using: phonopy p band.conf >> >> >> >> After all these steps, I found some negative frequencies and the >> values of the related frequencies are not consistent with those of >> previous results also. I doulechecked the calculation processes, but don't know the problem. >> >> >> >> Thank you a lot for your time, and any comments are appreciated. >> >> >> >> Best regards, >> >> Yang Ming >> >> ****** >> >> Computational CondensedMatter Physics Lab >> >> Department of Physics >> >> National University of Singapore >> >> Singapore 117542 >> >> Email: phyym@...; ming_young@... >> >> Tel: +65 6516 4335 (office) >> >> >> >> >>  >>  Learn the latestVisual Studio 2012, SharePoint 2013, SQL >> 2012, more! >> Discover the easy way to master current and previous Microsoft >> technologies and advance your career. Get an incredible 1,500+ hours >> of stepbystep tutorial videos with LearnDevNow. Subscribe today and save! >> http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.c >> lktrk _______________________________________________ >> Phonopyusers mailing list >> Phonopyusers@... >> https://lists.sourceforge.net/lists/listinfo/phonopyusers >> > > > >  > Atsushi Togo > http://atztogo.github.com/ > atz.togo@...  Atsushi Togo http://atztogo.github.com/ atz.togo@... 
From: Yang Ming <phyym@nu...>  20130903 03:03:06
Attachments:
band strucutre of graphene.opj

Dear Prof. Togo, Thank you so much for the kind reply. I just checked the KPOINTS and the INCAR setting, which are correct for the electronic structure (see the band structure attached). Actually, I also increased denser kpoint meshes (18×18×1), and also changed the INCAR setting (ENCUT =500, ISMEAR=5, EDIFF=1.0E8, and ADDGRID = .True) , but still got negative frequencies. Let me show you my calculation processes again below, and please help me to check the problems and let me know if the settings are incorrect: 1. Generate a 6×6×1 supercell from below bulk by using the commad: phonopy d dim="6 6 1". 2. Calculate the force using the generated structure POSCAR001 and standard VASP setting. 3. Create the FORCE_SETS by using: phonopy f disp001/vasprun.xml 4 Phonon band structure was calculated by using the band.conf like below: ATOM_NAME = C DIM = 6 6 1 BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 5. Plot the band structure by using: phonopy p band.conf Thanks a lot. Best regards, Yang Ming ****** Computational CondensedMatter Physics Lab Department of Physics National University of Singapore Singapore 117542 Email: phyym@...; ming_young@... Tel: +65 6516 4335 (office) Original Message From: Yang Ming Sent: Sunday, 1 September, 2013 9:22 PM To: 'Atsushi Togo' Subject: RE: [Phonopyusers] Phonon dispersion of graphene Dear Dr. Togo, Thanks a lot for the prompt reply. Please find the attached data and calculated eigenvalue. Thanks. Best regards, Yang Ming ****** Computational CondensedMatter Physics Lab Department of Physics National University of Singapore Singapore 117542 Email: phyym@...; ming_young@... Tel: +65 6516 4335 (office) Original Message From: Atsushi Togo [mailto:atz.togo@...] Sent: Sunday, 1 September, 2013 8:30 PM To: Yang Ming Cc: phonopyusers@... Subject: Re: [Phonopyusers] Phonon dispersion of graphene Hi, Without watching your band structure, it is difficult to guess what your problem is. Togo On Sun, Sep 1, 2013 at 6:32 PM, Yang Ming <phyym@...> wrote: > Dear All, > > > > I am new in Phonopy. I was just using Phonopy to calculate phonon > dispersion of graphene for testing, but the results are incorrect > (negative frequencies were found). Could anyone there help to check my inputs below? > > > > > > Basically, I followed the Phonopy tutorial for VASP step by step: > > > > 1. Generate a 6×6×1 supercell from below bulk by using the commad: > phonopy d dim="6 6 1". > > > > C > > 1.00000000000000 > > 2.1304215583187101 1.2299994601826900 0.0000000000000000 > > 0.0000000000000000 2.4599989203653800 0.0000000000000000 > > 0.0000000000000000 0.0000000000000000 12.0000000000000000 > > 2 > > Direct > > 0.0000000000000000 0.0000000000000000 0.5000000000000000 > > 0.6666666699999979 0.3333333300000021 0.5000000000000000 > > > > 2. Calculate the force using the generated structure POSCAR001 and > standard VASP setting: > > > > ENCUT = 400 > > ISMEAR = 0; SIGMA = 0.01 > > PREC = A > > > > EDIFF = 1.0E8 > > NELM = 400 > > > > IDIPOL = 3 > > > > LWAVE = .F. > > LCHARG = .F. > > LREAL = .F. > > NPAR = 2 > > NELMDL = 5 > > LPLANE = .T. > > > > The KPOINTS for VASP calculation were set to 3×3×1. > > > > 3. Create the FORCE_SETS by using: phonopy f disp001/vasprun.xml > > 4. > > 5. Phonon band structure was calculated by using the band.conf like > below: > > > > ATOM_NAME = C > > DIM = 6 6 1 > > BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 > > 6. Plot the band structure by using: phonopy p band.conf > > > > After all these steps, I found some negative frequencies and the > values of the related frequencies are not consistent with those of > previous results also. I doulechecked the calculation processes, but don't know the problem. > > > > Thank you a lot for your time, and any comments are appreciated. > > > > Best regards, > > Yang Ming > > ****** > > Computational CondensedMatter Physics Lab > > Department of Physics > > National University of Singapore > > Singapore 117542 > > Email: phyym@...; ming_young@... > > Tel: +65 6516 4335 (office) > > > > >  >  Learn the latestVisual Studio 2012, SharePoint 2013, SQL > 2012, more! > Discover the easy way to master current and previous Microsoft > technologies and advance your career. Get an incredible 1,500+ hours > of stepbystep tutorial videos with LearnDevNow. Subscribe today and save! > http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.c > lktrk _______________________________________________ > Phonopyusers mailing list > Phonopyusers@... > https://lists.sourceforge.net/lists/listinfo/phonopyusers >  Atsushi Togo http://atztogo.github.com/ atz.togo@... 
From: Atsushi Togo <atz.togo@gm...>  20130903 05:04:57

Hi, Now I think your problem is not in phonopy but VASP. From vasp web site, For the calculation of the total energy in bulk materials we recommend the tetrahedron method with Blöchl corrections (ISMEAR=5). This method also gives a smooth nice electronic density of states (DOS). The only drawback is that the methods is not variational with respect to the partial occupancies, therefore the calculated forces might be wrong by a few percent for metals. For the calculation of phonon frequencies based on forces we recommend the method of MethfesselPaxton (ISMEAR>0). For semiconductors and insulators the forces are always correct, because partial occupancies do not vary! So you can read VASP manual carefully before asking VASP questions to the phonopy mailing list or you can ask them at the VASP forum. Togo On Tue, Sep 3, 2013 at 12:02 PM, Yang Ming <phyym@...> wrote: > Dear Prof. Togo, > > Thank you so much for the kind reply. > > I just checked the KPOINTS and the INCAR setting, which are correct for the electronic structure (see the band structure attached). > > Actually, I also increased denser kpoint meshes (18×18×1), and also changed the INCAR setting (ENCUT =500, ISMEAR=5, EDIFF=1.0E8, and ADDGRID = .True) , but still got negative frequencies. > > Let me show you my calculation processes again below, and please help me to check the problems and let me know if the settings are incorrect: > > 1. Generate a 6×6×1 supercell from below bulk by using the commad: phonopy d dim="6 6 1". > > 2. Calculate the force using the generated structure POSCAR001 and standard VASP setting. > > 3. Create the FORCE_SETS by using: phonopy f disp001/vasprun.xml > > 4 Phonon band structure was calculated by using the band.conf like below: > > ATOM_NAME = C > DIM = 6 6 1 > BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 > > 5. Plot the band structure by using: phonopy p band.conf > > > Thanks a lot. > Best regards, > Yang Ming > ****** > Computational CondensedMatter Physics Lab > Department of Physics > National University of Singapore > Singapore 117542 > Email: phyym@...; ming_young@... > Tel: +65 6516 4335 (office) > > > Original Message > From: Yang Ming > Sent: Sunday, 1 September, 2013 9:22 PM > To: 'Atsushi Togo' > Subject: RE: [Phonopyusers] Phonon dispersion of graphene > > Dear Dr. Togo, > > Thanks a lot for the prompt reply. > > Please find the attached data and calculated eigenvalue. > > Thanks. > > Best regards, > Yang Ming > ****** > Computational CondensedMatter Physics Lab Department of Physics National University of Singapore Singapore 117542 > Email: phyym@...; ming_young@... > Tel: +65 6516 4335 (office) > > Original Message > From: Atsushi Togo [mailto:atz.togo@...] > Sent: Sunday, 1 September, 2013 8:30 PM > To: Yang Ming > Cc: phonopyusers@... > Subject: Re: [Phonopyusers] Phonon dispersion of graphene > > Hi, > > Without watching your band structure, it is difficult to guess what your problem is. > > Togo > > On Sun, Sep 1, 2013 at 6:32 PM, Yang Ming <phyym@...> wrote: >> Dear All, >> >> >> >> I am new in Phonopy. I was just using Phonopy to calculate phonon >> dispersion of graphene for testing, but the results are incorrect >> (negative frequencies were found). Could anyone there help to check my inputs below? >> >> >> >> >> >> Basically, I followed the Phonopy tutorial for VASP step by step: >> >> >> >> 1. Generate a 6×6×1 supercell from below bulk by using the commad: >> phonopy d dim="6 6 1". >> >> >> >> C >> >> 1.00000000000000 >> >> 2.1304215583187101 1.2299994601826900 0.0000000000000000 >> >> 0.0000000000000000 2.4599989203653800 0.0000000000000000 >> >> 0.0000000000000000 0.0000000000000000 12.0000000000000000 >> >> 2 >> >> Direct >> >> 0.0000000000000000 0.0000000000000000 0.5000000000000000 >> >> 0.6666666699999979 0.3333333300000021 0.5000000000000000 >> >> >> >> 2. Calculate the force using the generated structure POSCAR001 and >> standard VASP setting: >> >> >> >> ENCUT = 400 >> >> ISMEAR = 0; SIGMA = 0.01 >> >> PREC = A >> >> >> >> EDIFF = 1.0E8 >> >> NELM = 400 >> >> >> >> IDIPOL = 3 >> >> >> >> LWAVE = .F. >> >> LCHARG = .F. >> >> LREAL = .F. >> >> NPAR = 2 >> >> NELMDL = 5 >> >> LPLANE = .T. >> >> >> >> The KPOINTS for VASP calculation were set to 3×3×1. >> >> >> >> 3. Create the FORCE_SETS by using: phonopy f disp001/vasprun.xml >> >> 4. >> >> 5. Phonon band structure was calculated by using the band.conf like >> below: >> >> >> >> ATOM_NAME = C >> >> DIM = 6 6 1 >> >> BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 >> >> 6. Plot the band structure by using: phonopy p band.conf >> >> >> >> After all these steps, I found some negative frequencies and the >> values of the related frequencies are not consistent with those of >> previous results also. I doulechecked the calculation processes, but don't know the problem. >> >> >> >> Thank you a lot for your time, and any comments are appreciated. >> >> >> >> Best regards, >> >> Yang Ming >> >> ****** >> >> Computational CondensedMatter Physics Lab >> >> Department of Physics >> >> National University of Singapore >> >> Singapore 117542 >> >> Email: phyym@...; ming_young@... >> >> Tel: +65 6516 4335 (office) >> >> >> >> >>  >>  Learn the latestVisual Studio 2012, SharePoint 2013, SQL >> 2012, more! >> Discover the easy way to master current and previous Microsoft >> technologies and advance your career. Get an incredible 1,500+ hours >> of stepbystep tutorial videos with LearnDevNow. Subscribe today and save! >> http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.c >> lktrk _______________________________________________ >> Phonopyusers mailing list >> Phonopyusers@... >> https://lists.sourceforge.net/lists/listinfo/phonopyusers >> > > > >  > Atsushi Togo > http://atztogo.github.com/ > atz.togo@...  Atsushi Togo http://atztogo.github.com/ atz.togo@... 
From: Atsushi Togo <atz.togo@gm...>  20130903 07:26:24
Attachments:
graphene.jpg

And just as an example, I attach a graphene band structure that I calculated just now. As we can see, the acoustic modes are very soft, in this case the structure optimization is better to be done by the supercell though I didn't in this calculation. Then, I don't (can't) describe all about my VASP settings (please don't ask me about VASP), but some are shown as follows: For the structure optimization of theunit cell, INCAR: PREC = Accurate IBRION = 2 NSW = 20 NELMIN = 5 ISIF = 3 ENCUT = 500 EDIFF = 1.000000e08 EDIFFG = 1.000000e08 ISMEAR = 1 SIGMA = 2.000000e01 IALGO = 38 LREAL = .FALSE. ADDGRID = .TRUE. LWAVE = .FALSE. LCHARG = .FALSE. KPOINTS: Automatic mesh 0 Monkhorstpack 12 12 1 0.500 0.500 0.000 For force calculations of supercells, INCAR: PREC = Accurate IBRION = 1 NELMIN = 5 ENCUT = 500 EDIFF = 1.000000e08 ISMEAR = 1 SIGMA = 2.000000e01 IALGO = 38 LREAL = .FALSE. ADDGRID = .TRUE. LWAVE = .FALSE. LCHARG = .FALSE. NPAR = 4 KPOINTS: Automatic mesh 0 Monkhorstpack 2 2 1 0.500 0.500 0.000 phonopy: % phonopy dim="6 6 1" band="0 1/2 0 0 0 0 1/3 2/3 0 0 1/2 0" p c POSCARunitcell Togo On Tue, Sep 3, 2013 at 2:04 PM, Atsushi Togo <atz.togo@...> wrote: > Hi, > > Now I think your problem is not in phonopy but VASP. From vasp web site, > > For the calculation of the total energy in bulk materials we recommend > the tetrahedron method with Blöchl corrections (ISMEAR=5). This > method also gives a smooth nice electronic density of states (DOS). > The only drawback is that the methods is not variational with respect > to the partial occupancies, therefore the calculated forces might be > wrong by a few percent for metals. For the calculation of phonon > frequencies based on forces we recommend the method of > MethfesselPaxton (ISMEAR>0). For semiconductors and insulators the > forces are always correct, because partial occupancies do not vary! > > So you can read VASP manual carefully before asking VASP questions to > the phonopy mailing list or you can ask them at the VASP forum. > > Togo > > On Tue, Sep 3, 2013 at 12:02 PM, Yang Ming <phyym@...> wrote: >> Dear Prof. Togo, >> >> Thank you so much for the kind reply. >> >> I just checked the KPOINTS and the INCAR setting, which are correct for the electronic structure (see the band structure attached). >> >> Actually, I also increased denser kpoint meshes (18×18×1), and also changed the INCAR setting (ENCUT =500, ISMEAR=5, EDIFF=1.0E8, and ADDGRID = .True) , but still got negative frequencies. >> >> Let me show you my calculation processes again below, and please help me to check the problems and let me know if the settings are incorrect: >> >> 1. Generate a 6×6×1 supercell from below bulk by using the commad: phonopy d dim="6 6 1". >> >> 2. Calculate the force using the generated structure POSCAR001 and standard VASP setting. >> >> 3. Create the FORCE_SETS by using: phonopy f disp001/vasprun.xml >> >> 4 Phonon band structure was calculated by using the band.conf like below: >> >> ATOM_NAME = C >> DIM = 6 6 1 >> BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 >> >> 5. Plot the band structure by using: phonopy p band.conf >> >> >> Thanks a lot. >> Best regards, >> Yang Ming >> ****** >> Computational CondensedMatter Physics Lab >> Department of Physics >> National University of Singapore >> Singapore 117542 >> Email: phyym@...; ming_young@... >> Tel: +65 6516 4335 (office) >> >> >> Original Message >> From: Yang Ming >> Sent: Sunday, 1 September, 2013 9:22 PM >> To: 'Atsushi Togo' >> Subject: RE: [Phonopyusers] Phonon dispersion of graphene >> >> Dear Dr. Togo, >> >> Thanks a lot for the prompt reply. >> >> Please find the attached data and calculated eigenvalue. >> >> Thanks. >> >> Best regards, >> Yang Ming >> ****** >> Computational CondensedMatter Physics Lab Department of Physics National University of Singapore Singapore 117542 >> Email: phyym@...; ming_young@... >> Tel: +65 6516 4335 (office) >> >> Original Message >> From: Atsushi Togo [mailto:atz.togo@...] >> Sent: Sunday, 1 September, 2013 8:30 PM >> To: Yang Ming >> Cc: phonopyusers@... >> Subject: Re: [Phonopyusers] Phonon dispersion of graphene >> >> Hi, >> >> Without watching your band structure, it is difficult to guess what your problem is. >> >> Togo >> >> On Sun, Sep 1, 2013 at 6:32 PM, Yang Ming <phyym@...> wrote: >>> Dear All, >>> >>> >>> >>> I am new in Phonopy. I was just using Phonopy to calculate phonon >>> dispersion of graphene for testing, but the results are incorrect >>> (negative frequencies were found). Could anyone there help to check my inputs below? >>> >>> >>> >>> >>> >>> Basically, I followed the Phonopy tutorial for VASP step by step: >>> >>> >>> >>> 1. Generate a 6×6×1 supercell from below bulk by using the commad: >>> phonopy d dim="6 6 1". >>> >>> >>> >>> C >>> >>> 1.00000000000000 >>> >>> 2.1304215583187101 1.2299994601826900 0.0000000000000000 >>> >>> 0.0000000000000000 2.4599989203653800 0.0000000000000000 >>> >>> 0.0000000000000000 0.0000000000000000 12.0000000000000000 >>> >>> 2 >>> >>> Direct >>> >>> 0.0000000000000000 0.0000000000000000 0.5000000000000000 >>> >>> 0.6666666699999979 0.3333333300000021 0.5000000000000000 >>> >>> >>> >>> 2. Calculate the force using the generated structure POSCAR001 and >>> standard VASP setting: >>> >>> >>> >>> ENCUT = 400 >>> >>> ISMEAR = 0; SIGMA = 0.01 >>> >>> PREC = A >>> >>> >>> >>> EDIFF = 1.0E8 >>> >>> NELM = 400 >>> >>> >>> >>> IDIPOL = 3 >>> >>> >>> >>> LWAVE = .F. >>> >>> LCHARG = .F. >>> >>> LREAL = .F. >>> >>> NPAR = 2 >>> >>> NELMDL = 5 >>> >>> LPLANE = .T. >>> >>> >>> >>> The KPOINTS for VASP calculation were set to 3×3×1. >>> >>> >>> >>> 3. Create the FORCE_SETS by using: phonopy f disp001/vasprun.xml >>> >>> 4. >>> >>> 5. Phonon band structure was calculated by using the band.conf like >>> below: >>> >>> >>> >>> ATOM_NAME = C >>> >>> DIM = 6 6 1 >>> >>> BAND = 0.0 0.5 0.0 0.0 0.0 0.0 0.3333 0.6667 0.0 0.0 0.5 0.0 >>> >>> 6. Plot the band structure by using: phonopy p band.conf >>> >>> >>> >>> After all these steps, I found some negative frequencies and the >>> values of the related frequencies are not consistent with those of >>> previous results also. I doulechecked the calculation processes, but don't know the problem. >>> >>> >>> >>> Thank you a lot for your time, and any comments are appreciated. >>> >>> >>> >>> Best regards, >>> >>> Yang Ming >>> >>> ****** >>> >>> Computational CondensedMatter Physics Lab >>> >>> Department of Physics >>> >>> National University of Singapore >>> >>> Singapore 117542 >>> >>> Email: phyym@...; ming_young@... >>> >>> Tel: +65 6516 4335 (office) >>> >>> >>> >>> >>>  >>>  Learn the latestVisual Studio 2012, SharePoint 2013, SQL >>> 2012, more! >>> Discover the easy way to master current and previous Microsoft >>> technologies and advance your career. Get an incredible 1,500+ hours >>> of stepbystep tutorial videos with LearnDevNow. Subscribe today and save! >>> http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.c >>> lktrk _______________________________________________ >>> Phonopyusers mailing list >>> Phonopyusers@... >>> https://lists.sourceforge.net/lists/listinfo/phonopyusers >>> >> >> >> >>  >> Atsushi Togo >> http://atztogo.github.com/ >> atz.togo@... > > > >  > Atsushi Togo > http://atztogo.github.com/ > atz.togo@...  Atsushi Togo http://atztogo.github.com/ atz.togo@... 