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ODDONLYGW and EVENONLYGW and NKRED:
reducing the grid for the response functions
ODDONLYGW= .TRUE.  .FALSE.
EVENONLYGW= .TRUE.  .FALSE.
ODDONLYGW allows to avoid the inclusion of the
point in the evaluation of response functions.
The independent particle polarizability
is given by:

(6.80) 
If the point is included in the summation over
, convergence
is very slow for some materials (e.g. GaAs).
To deal with this problem the flag ODDONLYGW has been included.
In the automatic mode, the grid is given by (see Sec. 5.5.3):
If the three integers sum to an odd value, the point is included in
the previous summation in the GW routine (ODDONLYGW=.TRUE.).
Note that other routines (linear optical properties) presently do not recognize this flag.
EVENONLYGW=.TRUE. is only of limited use and restricts the summation to
points with
being even (point and from there on ever second kpoint included).
Accelerations are also possible by evaluating the response function
itself at a restricted number of points (see also Sec. 6.73.1).
Note that the GW loop, involves a sum over
, and a second one over the momentum transfer vector
(the index in the response function). To
some extend both can be varied independently. The former one by
using ODDONLYGW, and the latter one
using the HartreeFock related flags NKRED, NKREDX, NKREDY, NKREDZ and EVENONLY, ODDONLY.
As explained in Sec. 6.71.9 the index can be restricted to the values

(6.81) 
The integer grid reduction factors are either set separately through
=NKREDX, =NKREDY, and =NKREDZ, or simultaneously
through
=NKRED.
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N.B. Requests for support are to be addressed to: vasp.materialphysik@univie.ac.at