[Wien] Question about RMT and meaning of optimze.job

[Peter Blaha]

> First,
> when I change the RMT value, calculation results of energy and volume are changed. Does RMT value affect the calculation result?
> Since I have read the literature which says RMT only affects the speed of the calculation, I am so confused now.

The RMT values will of course change the absolute values of the total 
energy, as it also changes your plane wave cutoff Kmax (as defined by 
R*Kmax in case.in1).
However, within REASONABLE changes of RMT the physical meaningful 
results will not change (energy bands, DOS, ....

PS: "Smaller spheres" are always more accurate provided you can converge 
it with enough plane waves (large computational effort, RKMAX=9-10) and 
you have NO CORE-leakage.
PPS: For highly accurate results (like equillibrium volumes with 3 
digits after the comma) I'd for instance not use RMTs above 2.0 (or 
maybe 2.2 for larger, heavier atoms)

> I cannot understand the meaning of the script written in [optimize.job] file.
> 1.
> ---

comments on the side and below ....

>   if (-e case.clmsum &&  ! -z case.clmsum) then      # if this file is exists and is not empty ...
>     x dstart -super                                  # creates  case.clmsum_super, used by clmextrapol
>   endif
>   if (-e case.clmup &&  ! -z case.clmup) then        #   used to detect spin-polarization
>     x dstart -super -up
>     x dstart -super -dn
>   endif
> ---
>
> 2.
> ---
> clmextrapol_lapw

clmextrapol creates a better starting density case.clmsum for the next 
volume by:
calculate the difference between clmsum_super (superposition of atomic 
densities) and case.clmsum (the self-consistent density) for the "old" 
volume. Then add this difference to the superposition of atomic 
densities at the new volume.

>   if (-e case.clmup &&  ! -z case.clmup) then
>       clmextrapol_lapw -up
>       clmextrapol_lapw -dn
>   endif
> ---
> Is there anyone who could help me to understand these script?
>
> Regards
> Taro
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WWW: 
http://info.tuwien.ac.at/theochem/
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