Wrong(?) results in DYNMAT with IBRION = 8: Significant difference between IBRION = 6 and IBRION = 8

Problems running VASP: crashes, internal errors, "wrong" results.


Moderators: Global Moderator, Moderator

Post Reply
Message
Author
forsdan
Sr. Member
Sr. Member
Posts: 339
Joined: Mon Apr 24, 2006 9:07 am
License Nr.: 173
Location: Gothenburg, Sweden

Wrong(?) results in DYNMAT with IBRION = 8: Significant difference between IBRION = 6 and IBRION = 8

#1 Post by forsdan » Thu Jan 21, 2010 7:56 pm

EDIT: This issue has been resolved. The output in the DYNMAT is scaled by a parameter STEP. For IBRION = 5,6 then STEP = POTIM, while for IBRION = 7,8 then STEP = 1. The frequency difference between IBRION = 6 and IBRION = 8 also goes away if the accuracy is increased for the IBRION = 6 case.


Dear admin and vasp-users,

I'm performing calculations to determine the vibrational frequencies of bulk bcc Fe. I set up a cell with 128 atoms and use IBRION = 8. VASP correctly identifies that only one degree of freedom needs to be evaluated, in this case the x-coordinate for the 1st atom. The obtained frequencies look reasonable and if I evaluate the phonon DOS I get something that resembles experimental results.

The problem I'm having is that if I look at the DYNMAT file the entry for the x-coordinate is extremely large and the displacement is indicated to be 1.00. Since the POTIM tag doesn't affect anything when using DFPT (I've checked to be absolutely sure) I must have missed something.

I've performed calculations using IBRION = 6 and POTIM = 0.005 in order to compare. A direct comparison between the two DYNMAT files would be dependent of the POTIM value for the IBRION = 6 case, but it seems to show that IBRION = 8 gives very large values in the DYNMAT file. I also found a large difference between the frequencies with almost 0.2 THz per degree of freedom, which is not good. I expected to see a reasonable agreement between the DFPT results and the IBRION = 6 results when POTIM tends to be small. So I'm starting to question if I can trust the results for IBRION = 8.

Do anyone has a suggestion to what might be going on here? Can I improve the IBRION = 8 calculations in some way?

I have verified that the geometry is correct and that I'm using the same POTCAR, KPOINTS and POSCAR for both runs. All calculations were performed with VASP 5.2.2.


Best regards,
/Dan Fors


DYNMAT (IBRION = 8):
===============

1 128 1
55.847
1 1 1.0000 0.0000 0.0000
-11.948513 0.000000 0.000000
-0.020332 0.000000 0.000841
0.020933 0.000000 0.000000
-0.020332 0.000000 -0.000841
-0.020332 0.000841 0.000000
-0.061039 0.000123 0.000123
...


DYNMAT (IBRION = 6):
===============
1 128 1
55.847
1 1 0.0050 0.0000 0.0000
-0.056924 0.000000 0.000000
-0.000259 0.000000 -0.000004
0.000504 0.000000 0.000000
-0.000259 0.000000 0.000004
-0.000259 -0.000004 0.000000
-0.000211 -0.000001 -0.000001
-0.000089 0.000000 0.000000
...


INCAR (IBRION = 8):
==============

SYSTEM = Fe128


ENCUT = 700 eV
ENAUG = 700 eV

EDIFF = 1E-8
EDIFFG = 1E-5

LREAL = A
PREC = Accurate
ADDGRID = .TRUE.

ISMEAR = 1
SIGMA = 0.1

IBRION = 8

MAGMOM = 128*4
ISPIN = 2
LORBIT = 12
NEDOS = 1000
ALGO = Fast



INCAR (IBRION = 6):
=============

SYSTEM = Fe128


ENCUT = 700 eV
ENAUG = 700 eV

EDIFF = 1E-8
EDIFFG = 1E-5

LREAL = A
PREC = Accurate
ADDGRID = .TRUE.

ISMEAR = 1
SIGMA = 0.1

IBRION = 6
POTIM = 0.005

MAGMOM = 128*4
ISPIN = 2
LORBIT = 12
NEDOS = 1000
ALGO = Fast

KPOINTS
======

Monk
0
Monk
4 4 4
0 0 0


POSCAR:
======

bcc:
2.83310000000000
4.0065391828051933 0.0000000000000000 0.0000000000000000
0.0000000000000000 4.0065391828051933 0.0000000000000000
0.0000000000000000 0.0000000000000000 4.0065391828051933
Fe
128
Direct
0.0000000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 0.2500000000000000
0.0000000000000000 0.0000000000000000 0.5000000000000000
0.0000000000000000 0.0000000000000000 0.7500000000000000
0.0000000000000000 0.2500000000000000 0.0000000000000000
0.0000000000000000 0.2500000000000000 0.2500000000000000
0.0000000000000000 0.2500000000000000 0.5000000000000000
0.0000000000000000 0.2500000000000000 0.7500000000000000
0.0000000000000000 0.5000000000000000 0.0000000000000000
0.0000000000000000 0.5000000000000000 0.2500000000000000
0.0000000000000000 0.5000000000000000 0.5000000000000000
0.0000000000000000 0.5000000000000000 0.7500000000000000
0.0000000000000000 0.7500000000000000 0.0000000000000000
0.0000000000000000 0.7500000000000000 0.2500000000000000
0.0000000000000000 0.7500000000000000 0.5000000000000000
0.0000000000000000 0.7500000000000000 0.7500000000000000
0.2500000000000000 0.0000000000000000 0.0000000000000000
0.2500000000000000 0.0000000000000000 0.2500000000000000
0.2500000000000000 0.0000000000000000 0.5000000000000000
0.2500000000000000 0.0000000000000000 0.7500000000000000
0.2500000000000000 0.2500000000000000 0.0000000000000000
0.2500000000000000 0.2500000000000000 0.2500000000000000
0.2500000000000000 0.2500000000000000 0.5000000000000000
0.2500000000000000 0.2500000000000000 0.7500000000000000
0.2500000000000000 0.5000000000000000 0.0000000000000000
0.2500000000000000 0.5000000000000000 0.2500000000000000
0.2500000000000000 0.5000000000000000 0.5000000000000000
0.2500000000000000 0.5000000000000000 0.7500000000000000
0.2500000000000000 0.7500000000000000 0.0000000000000000
0.2500000000000000 0.7500000000000000 0.2500000000000000
0.2500000000000000 0.7500000000000000 0.5000000000000000
0.2500000000000000 0.7500000000000000 0.7500000000000000
0.5000000000000000 0.0000000000000000 0.0000000000000000
0.5000000000000000 0.0000000000000000 0.2500000000000000
0.5000000000000000 0.0000000000000000 0.5000000000000000
0.5000000000000000 0.0000000000000000 0.7500000000000000
0.5000000000000000 0.2500000000000000 0.0000000000000000
0.5000000000000000 0.2500000000000000 0.2500000000000000
0.5000000000000000 0.2500000000000000 0.5000000000000000
0.5000000000000000 0.2500000000000000 0.7500000000000000
0.5000000000000000 0.5000000000000000 0.0000000000000000
0.5000000000000000 0.5000000000000000 0.2500000000000000
0.5000000000000000 0.5000000000000000 0.5000000000000000
0.5000000000000000 0.5000000000000000 0.7500000000000000
0.5000000000000000 0.7500000000000000 0.0000000000000000
0.5000000000000000 0.7500000000000000 0.2500000000000000
0.5000000000000000 0.7500000000000000 0.5000000000000000
0.5000000000000000 0.7500000000000000 0.7500000000000000
0.7500000000000000 0.0000000000000000 0.0000000000000000
0.7500000000000000 0.0000000000000000 0.2500000000000000
0.7500000000000000 0.0000000000000000 0.5000000000000000
0.7500000000000000 0.0000000000000000 0.7500000000000000
0.7500000000000000 0.2500000000000000 0.0000000000000000
0.7500000000000000 0.2500000000000000 0.2500000000000000
0.7500000000000000 0.2500000000000000 0.5000000000000000
0.7500000000000000 0.2500000000000000 0.7500000000000000
0.7500000000000000 0.5000000000000000 0.0000000000000000
0.7500000000000000 0.5000000000000000 0.2500000000000000
0.7500000000000000 0.5000000000000000 0.5000000000000000
0.7500000000000000 0.5000000000000000 0.7500000000000000
0.7500000000000000 0.7500000000000000 0.0000000000000000
0.7500000000000000 0.7500000000000000 0.2500000000000000
0.7500000000000000 0.7500000000000000 0.5000000000000000
0.7500000000000000 0.7500000000000000 0.7500000000000000
0.1250000000000000 0.1250000000000000 0.3750000000000000
0.1250000000000000 0.1250000000000000 0.6250000000000000
0.1250000000000000 0.1250000000000000 0.8750000000000000
0.1250000000000000 0.3750000000000000 0.1250000000000000
0.1250000000000000 0.3750000000000000 0.3750000000000000
0.1250000000000000 0.3750000000000000 0.6250000000000000
0.1250000000000000 0.3750000000000000 0.8750000000000000
0.1250000000000000 0.6250000000000000 0.1250000000000000
0.1250000000000000 0.6250000000000000 0.3750000000000000
0.1250000000000000 0.6250000000000000 0.6250000000000000
0.1250000000000000 0.6250000000000000 0.8750000000000000
0.1250000000000000 0.8750000000000000 0.1250000000000000
0.1250000000000000 0.8750000000000000 0.3750000000000000
0.1250000000000000 0.8750000000000000 0.6250000000000000
0.1250000000000000 0.8750000000000000 0.8750000000000000
0.3750000000000000 0.1250000000000000 0.1250000000000000
0.3750000000000000 0.1250000000000000 0.3750000000000000
0.3750000000000000 0.1250000000000000 0.6250000000000000
0.3750000000000000 0.1250000000000000 0.8750000000000000
0.3750000000000000 0.3750000000000000 0.1250000000000000
0.3750000000000000 0.3750000000000000 0.3750000000000000
0.3750000000000000 0.3750000000000000 0.6250000000000000
0.3750000000000000 0.3750000000000000 0.8750000000000000
0.3750000000000000 0.6250000000000000 0.1250000000000000
0.3750000000000000 0.6250000000000000 0.3750000000000000
0.3750000000000000 0.6250000000000000 0.6250000000000000
0.3750000000000000 0.6250000000000000 0.8750000000000000
0.3750000000000000 0.8750000000000000 0.1250000000000000
0.3750000000000000 0.8750000000000000 0.3750000000000000
0.3750000000000000 0.8750000000000000 0.6250000000000000
0.3750000000000000 0.8750000000000000 0.8750000000000000
0.6250000000000000 0.1250000000000000 0.1250000000000000
0.6250000000000000 0.1250000000000000 0.3750000000000000
0.6250000000000000 0.1250000000000000 0.6250000000000000
0.6250000000000000 0.1250000000000000 0.8750000000000000
0.6250000000000000 0.3750000000000000 0.1250000000000000
0.6250000000000000 0.3750000000000000 0.3750000000000000
0.6250000000000000 0.3750000000000000 0.6250000000000000
0.6250000000000000 0.3750000000000000 0.8750000000000000
0.6250000000000000 0.6250000000000000 0.1250000000000000
0.6250000000000000 0.6250000000000000 0.3750000000000000
0.6250000000000000 0.6250000000000000 0.6250000000000000
0.6250000000000000 0.6250000000000000 0.8750000000000000
0.6250000000000000 0.8750000000000000 0.1250000000000000
0.6250000000000000 0.8750000000000000 0.3750000000000000
0.6250000000000000 0.8750000000000000 0.6250000000000000
0.6250000000000000 0.8750000000000000 0.8750000000000000
0.8750000000000000 0.1250000000000000 0.1250000000000000
0.8750000000000000 0.1250000000000000 0.3750000000000000
0.8750000000000000 0.1250000000000000 0.6250000000000000
0.8750000000000000 0.1250000000000000 0.8750000000000000
0.8750000000000000 0.3750000000000000 0.1250000000000000
0.8750000000000000 0.3750000000000000 0.3750000000000000
0.8750000000000000 0.3750000000000000 0.6250000000000000
0.8750000000000000 0.3750000000000000 0.8750000000000000
0.8750000000000000 0.6250000000000000 0.1250000000000000
0.8750000000000000 0.6250000000000000 0.3750000000000000
0.8750000000000000 0.6250000000000000 0.6250000000000000
0.8750000000000000 0.6250000000000000 0.8750000000000000
0.8750000000000000 0.8750000000000000 0.1250000000000000
0.8750000000000000 0.8750000000000000 0.3750000000000000
0.8750000000000000 0.8750000000000000 0.6250000000000000
0.8750000000000000 0.8750000000000000 0.8750000000000000
0.1250000000000000 0.1250000000000000 0.1250000000000000





<span class='smallblacktext'>[ Edited ]</span>
Last edited by forsdan on Thu Jan 21, 2010 7:56 pm, edited 1 time in total.

jsfilhol
Newbie
Newbie
Posts: 13
Joined: Mon Nov 13, 2006 3:30 pm

Wrong(?) results in DYNMAT with IBRION = 8: Significant difference between IBRION = 6 and IBRION = 8

#2 Post by jsfilhol » Tue Jan 26, 2010 3:49 pm

Hello,
I have been doing some comparison between the IBRION = 5-6-(7 not tested yet)-8 and all vibrations are inconsistent for the three methods !!!!! It is quite frightening at that point.
I have tested it on a polymer (C H and N atoms nothing fancy) in a triclinic cell at gamma point with

INCAR
PREC = Normal
GGA =PS
ALGO = FAST
EDIFF = 1e-7
ISPIN=1
NELM = 60
ENCUT = 750
LREAL= A
ISIF=3
Ionic relaxation
EDIFFG = -5e-3
NSW = 550
IBRION = 5 (6 and 8)
POTIM =0.01
LPLANE = .TRUE.
LSCALU = .FALSE.
NSIM = 4
DOS related values
ISMEAR = 0 ; SIGMA=0.05


----------------------------------------------------
IBRION =5 extract of OUTCAR
49 f = 68.823435 THz 432.430393 2PiTHz 2295.702601 cm-1 284.630949 meV
50 f = 68.764645 THz 432.061007 2PiTHz 2293.741586 cm-1 284.387814 meV
51 f = 65.489736 THz 411.484150 2PiTHz 2184.502402 cm-1 270.843876 meV
52 f = 65.473768 THz 411.383814 2PiTHz 2183.969736 cm-1 270.777834 meV
53 f = 48.509155 THz 304.792011 2PiTHz 1618.091196 cm-1 200.617812 meV
54 f = 48.479099 THz 304.603165 2PiTHz 1617.088641 cm-1 200.493511 meV
55 f = 48.348256 THz 303.781053 2PiTHz 1612.724187 cm-1 199.952387 meV
56 f = 48.333537 THz 303.688571 2PiTHz 1612.233211 cm-1 199.891514 meV
57 f = 48.052772 THz 301.924470 2PiTHz 1602.867888 cm-1 198.730362 meV
58 f = 48.030621 THz 301.785294 2PiTHz 1602.129026 cm-1 198.638754 meV
----------------------------------------------------
IBRION =6 extract of OUTCAR
49 f = 68.923065 THz 433.056387 2PiTHz 2299.025900 cm-1 285.042986 meV
50 f = 68.865741 THz 432.696212 2PiTHz 2297.113786 cm-1 284.805914 meV
51 f = 65.805941 THz 413.470919 2PiTHz 2195.049836 cm-1 272.151592 meV
52 f = 65.800068 THz 413.434022 2PiTHz 2194.853953 cm-1 272.127306 meV
53 f = 52.355775 THz 328.961038 2PiTHz 1746.400627 cm-1 216.526160 meV
54 f = 52.348511 THz 328.915396 2PiTHz 1746.158323 cm-1 216.496118 meV
55 f = 48.508840 THz 304.790033 2PiTHz 1618.080696 cm-1 200.616510 meV
56 f = 48.478853 THz 304.601617 2PiTHz 1617.080427 cm-1 200.492492 meV
57 f = 48.291499 THz 303.424439 2PiTHz 1610.830979 cm-1 199.717659 meV
58 f = 48.287123 THz 303.396944 2PiTHz 1610.685013 cm-1 199.699562 meV
----------------------------------------------------
IBRION =8 extracted from OUTCAR
49 f = 69.471154 THz 436.500136 2PiTHz 2317.308202 cm-1 287.309703 meV
50 f = 69.417908 THz 436.165577 2PiTHz 2315.532083 cm-1 287.089492 meV
51 f = 66.262504 THz 416.339592 2PiTHz 2210.279156 cm-1 274.039788 meV
52 f = 66.252048 THz 416.273895 2PiTHz 2209.930381 cm-1 273.996545 meV
53 f = 51.967422 THz 326.520942 2PiTHz 1733.446553 cm-1 214.920058 meV
54 f = 51.933800 THz 326.309687 2PiTHz 1732.325036 cm-1 214.781008 meV
55 f = 48.833059 THz 306.827156 2PiTHz 1628.895452 cm-1 201.957369 meV
56 f = 48.804781 THz 306.649485 2PiTHz 1627.952222 cm-1 201.840424 meV
57 f = 48.406730 THz 304.148455 2PiTHz 1614.674663 cm-1 200.194216 meV


IBRION = 6 gives an insertion of two C=C frequency in to the C-C(triple) zone compared to IBRION=5
IBRION=8 shift of at least 100 cm-1 some frquencies

Is there some kind of bug in the symmetry ???
HAs someone an idea to solve this problem ??

Best regards

JS
Last edited by jsfilhol on Tue Jan 26, 2010 3:49 pm, edited 1 time in total.

jsfilhol
Newbie
Newbie
Posts: 13
Joined: Mon Nov 13, 2006 3:30 pm

Wrong(?) results in DYNMAT with IBRION = 8: Significant difference between IBRION = 6 and IBRION = 8

#3 Post by jsfilhol » Fri Jan 29, 2010 5:48 pm

Here is the IBRION=7 to complete the study
49 f = 70.239111 THz 441.325350 2PiTHz 2342.924476 cm-1 290.485717 meV
50 f = 70.201660 THz 441.090036 2PiTHz 2341.675235 cm-1 290.330831 meV
51 f = 67.049577 THz 421.284918 2PiTHz 2236.533084 cm-1 277.294861 meV
52 f = 67.035701 THz 421.197733 2PiTHz 2236.070232 cm-1 277.237475 meV
53 f = 50.250615 THz 315.733928 2PiTHz 1676.180052 cm-1 207.819915 meV
54 f = 50.226389 THz 315.581707 2PiTHz 1675.371935 cm-1 207.719721 meV
55 f = 50.198013 THz 315.403418 2PiTHz 1674.425429 cm-1 207.602369 meV
56 f = 50.166849 THz 315.207608 2PiTHz 1673.385905 cm-1 207.473485 meV
57 f = 49.933133 THz 313.739129 2PiTHz 1665.589989 cm-1 206.506914 meV

The symmetry and no symmetry should gibe the same results ( or at least close enought) so I would agree that something looks bogus for non cubic cell
also
the difference between ibrion 5-6 is 130 cm-1
but the difference 5-7 is still 60 cm-1

I do not have much experience with vibration from response but I would have expected it to be much closer to the finite displacement ?
Last edited by jsfilhol on Fri Jan 29, 2010 5:48 pm, edited 1 time in total.

forsdan
Sr. Member
Sr. Member
Posts: 339
Joined: Mon Apr 24, 2006 9:07 am
License Nr.: 173
Location: Gothenburg, Sweden

Wrong(?) results in DYNMAT with IBRION = 8: Significant difference between IBRION = 6 and IBRION = 8

#4 Post by forsdan » Fri Jan 29, 2010 6:41 pm

@jsfilhol

No offense, but I think the symmetry issuses for noncubic cells should be separated from the issue that DFPT results seem to differ from the finite difference results.

The issue I raised in the thread was that I am concerned about the magnitudes in the DYNMAT file when using DFPT. Therefore I doubt my calculations and I guess the INCAR file is lacking a crucial parameter. I have no concern with symmetry issues since IBRION = 7 gives the same result as IBRION = 8, while IBRION = 5 gives the same as IBRION = 6.

So the two issues, even though they are connected to the accuracy of the frequency calculations, must have two separate origins. User widom started a thread a couple of days ago

http://cms.mpi.univie.ac.at/vasp-forum/ ... php?3.6669

where the symmetry issues for noncubic cells were raised. Therefore I suggest we split the issues and treat them in different threads. This will also be more consistent with the thread topics.

Best regards,
/Dan


<span class='smallblacktext'>[ Edited Fri Jan 29 2010, 07:46PM ]</span>
Last edited by forsdan on Fri Jan 29, 2010 6:41 pm, edited 1 time in total.

boris
Full Member
Full Member
Posts: 106
Joined: Wed Jan 16, 2008 1:27 pm
License Nr.: 567
Location: France

Wrong(?) results in DYNMAT with IBRION = 8: Significant difference between IBRION = 6 and IBRION = 8

#5 Post by boris » Fri Feb 19, 2010 12:20 pm

Dear Dan

First, thank you for this topic which has clarified most of my questions on linear response.

Second, I performed calculations on silver using both finite differences and DFPT and I also observed that there is a large displacement in the DYNMAT file of the DFPT run:
1 4 1
107.868
1 1 1.0000 0.0000 0.0000
-4.447133 0.000000 0.000000
2.318145 0.000000 0.000000
-0.189157 0.000000 0.000000
2.318145 0.000000 0.000000

Of course, resulting phonon frequencies are largely different in both cases.

I think that in order to determine whether IBRION=8 works, we should try to compare the value of the second derivative of the total energy in both calculations. They should be similar if the calculation precision is high enough.

Problem is, I don't know where to find them...

Regards
Last edited by boris on Fri Feb 19, 2010 12:20 pm, edited 1 time in total.

Post Reply