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Restrictions in VASP.4.X and restrictions due to parallelization
In most respects
VASP.4.X should behave like VASP.3.2. However in VASP.4.4, IALGO=48 was redesigned
to work more reliable in problematic cases. Therefore the iteration
history might not be directly comparable. VASP.4.X also subtracts
the atomic energies in each iteration, VASP.3.2 does not. Once again
this means that the energies written in each electronic step are
The parallel version (i.e. if VASP is compiled with the MPI flag)
has some further restriction, some
of them might be removed in the future:
Here is a list of features not supported by VASP.4.4 running
on a parallel machine:
- VASP.4.4 (VASP.4.5 does not posses this restriction):
The most severe restriction is that it is not possible
to change the cutoff or the cell size/shape on restart from existing WAVECAR
file. This means that if the cell size/shape and or the cutoff
has been changed the WAVECAR should be removed before starting the
next calculation (actually VASP will realize if the cutoff or
the cell shape have been changed and will proceed automatically
as if the WAVECAR file does not exist).
The reason for this restriction is that the re-padding (i.e. the
redistribution of the plane wave coefficients on changing the
cutoff sphere) would require a sophisticated
redistribution of data and the required communication routines
are not implemented at present.
As a matter of fact, it is of course possible to restart with
an existing WAVECAR file even if the number of nodes has changed.
The only point that requires attention is that changing the NPAR
parameter might also effect the number of bands (NBANDS).
WAVECAR files can only be read if the numbers of bands is strictly the same
on the file and for the present run. In some cases, it might be
required to set the number of bands explicitly in the INCAR file
by specifying the NBANDS parameter.
- Symmetry is fully supported by the parallel version,
BUT we have used a brute force method to implement it.
The charge density is first merged from all nodes, then
symmetrized locally and finally the result is redistributed onto the nodes.
This means that the symmetrization of the charge density will
be very slow, this can have serious impact on the total
In VASP.4.4.3 (and newer version) this problem can be reduced
by specifying ISYM=2 instead of ISYM=1. In this case only
the soft charge density and the augmentation occupancies are
symmetrized, which results in precisely the same result as
ISYM=1 but requires less memory. ISYM=2 is the default for
the PAW method.
- Partial local DOS is only supported with parallelization
over plane wave coefficients but not with parallelization over
bands. The reason is that some files (like PROCAR) have a rather
complicated band-by-band layout, and it would be complicated
to mimic this layout with a data distribution over bands.
N.B. Requests for support are to be addressed to: email@example.com