Interface to VASP

General remarks

One can use the official Vasp 5.4.4 patch 1 version with a few modifications:

there is a bug in fileio.F around line 1710 where the code tries print out something like “reading the density matrix from Gamma”, but this should be done only by the master node. Adding a IF (IO%IU0>=0) THEN ... ENDIF around it fixes this
in the current version of the dft_tools interface the file LOCPROJ should contain the fermi energy in the header. Therefore one should replace the following line in locproj.F:

WRITE(99,'(4I6,"  # of spin, # of k-points, # of bands, # of proj" )') NS,NK,NB,NF

by

WRITE(99,'(4I6,F12.7,"  # of spin, # of k-points, # of bands, # of proj, Efermi" )') W%WDES%NCDIJ,NK,NB,NF,EFERMI

and add the variable EFERMI accordingly in the function call.

Vasp gets sometimes stuck and does not write the OSZICAR file correctly due to a stuck buffer. Adding a flush to the buffer to have a correctly written OSZICAR to extract the DFT energy helps, by adding in electron.F around line 580 after

CALL STOP_TIMING("G",IO%IU6,"DOS")

two lines:

flush(17)
print *, ' '

this one is essential for the current version of the DMFT code. Vasp spends a very long time in the function LPRJ_LDApU and this function is not needed! It is used for some basic checks and a manual LDA+U implementation. Removing the call to this function in electron.F in line 644 speeds up the calculation by up to 30%! If this is not done, Vasp will create a GAMMA file each iteration which needs to be removed manually to not overwrite the DMFT GAMMA file!
make sure that mixing in VASP stays turned on. Don’t set IMIX or the DFT steps won’t converge!

LOCPROJ bug for individual projections:

Example use of LOCPROJ for t2g manifold of SrVO3 (the order of the orbitals seems to be mixed up… this example leads to x^2 -y^2, z^2, yz… ) In the current version there is some mix up in the mapping between selected orbitals in the INCAR and actual selected in the LOCPROJ. This is what the software does (left side is INCAR, right side is resulting in the LOCPROJ)

xy -> x2-y2
yz -> z2
xz -> yz
x2-y2 -> xz
z2 -> xy

LOCPROJ = 2 : dxz : Pr 1
LOCPROJ = 2 : dx2-y2 : Pr 1
LOCPROJ = 2 : dz2 : Pr 1

However, if the complete d manifold is chosen, the usual VASP order (xy, yz, z2, xz, x2-y2) is obtained in the LOCPROJ. This is done as shown below

LOCPROJ = 2 : d : Pr 1

convergence of projectors with Vasp

for a good convergence of the projectors it is important to convergence the wavefunctions to high accuracy. Otherwise this often leads to off-diagonal elements in the the local Green’s function. To check convergence pay attention to the rms and rms© values in the Vasp output. The former specifies the convergence of the KS wavefunction and the latter is difference of the input and out charge density. Note, this does not necessarily coincide with good convergence of the total energy in DFT! Here an example of two calculations for the same system, both converged down to EDIFF= 1E-10 and Vasp stopped. First run:

       N       E                     dE             d eps       ncg     rms          rms(c)
...
DAV:  25    -0.394708006287E+02   -0.65893E-09   -0.11730E-10 134994   0.197E-06  0.992E-05
...

second run with different smearing:

...
DAV:  31    -0.394760088659E+02    0.39472E-09    0.35516E-13 132366   0.110E-10  0.245E-10
...

The total energy is lower as well. But more importantly the second calculation produces well converged projectors preserving symmetries way better, with less off-diagonal elements in Gloc, making it way easier for the solver. Always pay attention to rms.

Enabling CSC calculations with Wannier90 projectors

You basically only need to add two things to have W90 run in Vasp’s CSC mode, all in electron.F:

the line USE mlwf at the top of the SUBROUTINE ELMIN together with all the other USE ... statements.
right below where you removed the call to LPRJ_LDApU (see above, around line 650), there is the line CALL LPRJ_DEALLOC_COVL. Just add the following block right below, inside the same “if” as the CALL LPRJ_DEALLOC_COVL:

IF (WANNIER90()) THEN
   CALL KPAR_SYNC_ALL(WDES,W)
   CALL MLWF_WANNIER90(WDES,W,P,CQIJ,T_INFO,LATT_CUR,INFO,IO)
ENDIF

Then, the only problem you’ll have is the order of compilation in the .objects file. It has to change because now electron.F references mlwf. For that move the entries twoelectron4o.o and mlwf.o (in this order) up right behind linear_optics.o. Then, move the lines from electron.o to stm.o behind the new position of mlwf.o.

Remarks:

W90-CSC requires Wannier90 v3, in v2 the tag write_u_matrices does not work correctly. Until now, linking W90 v3 to Vasp with the DVASP2WANNIER90v2 has worked without any problems even though it is not officially supported
symmetries in Vasp should remain turned on, otherwise the determination of rotation matrices in dft_tools’ wannier converter will most likely fail

Speeding up by not writing projectors at every step

This is very important for CSC calculations with W90 but also speeds up the PLO-based ones.

Writing the Wannier projectors is a time consuming step (and to a lesser extent, the PLO projectors) and basically needs only to be done in the DFT iteration right before a DMFT iteration. Therefore, solid_dmft writes the file vasp.suppress_projs that tells Vasp when not to compute/write the projectors. This requires two small changes in electron.F in the Vasp source code:

adding the definition of a logical variable where all other variables are defined for SUBROUTINE ELMIN, e.g. around line 150, by inserting LOGICAL :: LSUPPRESS_PROJS_EXISTS
go to the place where you removed the call to LPRJ_LDApU (see above, around line 650). This is inside a IF (MOD(INFO%ICHARG,10)==5) THEN ... ENDIF block. This whole block has to be disabled when the file vasp.suppress_projs exists. So, right under this block’s “IF”, add the lines

INQUIRE(FILE='vasp.suppress_projs',&
        EXIST=LSUPPRESS_PROJS_EXISTS)

IF (.NOT. LSUPPRESS_PROJS_EXISTS) THEN

and right before this block’s “ENDIF”, add another ENDIF.