[Wien] Difference with case.in0_std and case.in0_st?

[Peter Blaha]

in0_st confirms to the "old" default input for lapw0.

We found that for GGA (and in particular meta-GGA or hybrid-DFT calculations,
the default FFT-mesh for the xc-potential/energy in the interstitial may in
some cases not be of highest accuracy. (This was known for long time and
a possible cure was to increase GMAX in case.in2, which, however, also increases
the cpu-time for the coulomb-potential.

the new in0_std format allows to specify the FFT mesh explicitly (and fix it
for different volumes/c_a ratios) as well as enhance it with a single number
(which is 2.0 by default).

When you want to save time I'd recommend to reduce the multiplication factor
from 2 to 1 and memory/cpu-time will be reduced.

PS: The default WIEN2k-inputs are generally at the "save side", i.e. I'd say
for 70% of the cases they are too large, for 20% of the cases they are ok and for
maybe 10% of the cases one should improve them.
This philosophy leads of course to an impression that WIEN2k is "slow", but accurate.

I myself reduce the default parameters in 90% of my cases (sometimes drastically),
but of course I always check the results later on for convergence.

Johan Eriksson schrieb:
> Dear Wien community,
> What is the difference and consequence, when using the .in0_std file 
> created by dstart compared to the standard case.in0_st as input for lapw0?
> Is convergence faster with in0_std? Is it converging to some faulty 
> density without it?
> Running lapw0 is generally much slower and more memory consuming with 
> in0_std, so how would you rank these alternatives:
> 
> A. not use in0_std at all, but use in0_st
> B. use in0_std always
> C. use in0_st in the early cycles, and then switch to in0_std
> 
> 
> 
> /Johan Eriksson
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien

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                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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