[Wien] GMAX = 15 causes xcpot3 error in LAPW0

[Thomas Claesson]

Dear Wien users and developers!

My question concerns the parameter GMAX. I have seen a comment on the
mailing list about the importance of not using a too small value of GMAX
in order to avoid discontinuities in the charge density at the sphere
boundary. With an RKmax value of 7.0 I increased GMAX to from 12 to 15,
which resulted in the following error in LAPW0:

 'SETFF1' - ifft too small in xcpot3
 'SETFF1' - 2*(KKK+1) LARGER THAN IFFT PARAMETERS IN XCPOT3
 'SETFF1' - KKK=   0   0  16
 'SETFF1' - IIx=   0   0  16
 'SETFF1' - IFFT=  32  32  32

So I would like to know, why can't I use use GMAX > 14 in my case? I have
tried to increase RKmax to 8.0 but that had no effect on the problem with
GMAX. Are the possible  values of RKmax and Gmax related to each other? If
so, how can I determine which RKmax value to use for a specific choice of
GMAX?

Any comments are welcome! Thanks in advance for your replies.

Best regards, Thomas Claesson