[Wien] error : ifft too small in xcpot3

[Mojtaba Zareii]

Dear Wien2k users
I wanted to study the electronic structure of LaNi5H7 compound. I used
the experimental lattice constants and Wyckoff positions as start
point. To get the optimized lattice parameters, I set Rmt equal to
2.35, 1.8 and 0.9 (in a.u.) for La, Ni and H atoms, respectively. The
RmtKmat value of 4.5 was also chosen by energy convergence criterion.
Gmax was set to 18.
I run the optimization program by option [1], i.e. “VARY VOLUME with
CONSTANT RATIO A: B: C”
With volume variations of +9, +6, +3, 0, -3, -6, -9 %.
The optimization program run successfully for volume variations of +3,
0, -3, -6, -9 %, but it was stopped , in the first itineration of +6%
volume, with the following error:
Error in LAPW0
 'SETFF1' - ifft too small in xcpot3
 'SETFF1' - 2*(KKK+1) LARGER THAN IFFT PARAMETERS IN XCPOT3
 'SETFF1' - KKK=  30 -15   0
 'SETFF1' - IIx=  30 -15   0
 'SETFF1' - IFFT=  60  60  96

As suggested in UG, one should increase IFFT factor for system
containing H atoms. So I find “case.ino” file as follows:
------------------------ case. In0 -----------
TOT   13    (5...CA-LDA, 13...PBE-GGA, 11...WC-GGA)
NR2V      IFFT      (R2V)
  60  60  96    1.00  1    min IFFT-parameters, enhancement factor, iprint
---------------------------------------
It seems that IFFT was automatically set equal to 1 by program.
Now, I don’t know how to edit “case.in0” file and choose a proper IFFT factor?
Should I also change IFFTx,y,z ? What are the proper values for them?


Thank you
S.M.Zareii