[Wien] RKMAX

[Stefaan Cottenier]

> Hi, What is the criteria for choosing RKMAX? I changed RKMAX then the
> total energy and Fermi energy also changed.  As I increase RKMAX, the
> total energy becomes smaller and Fermi energy become larger.
> RKMAX    Total energy            Fermi energy
> *7              -41000.012971        0.53253
> 8              -41000.07176987     0.54963
> 9              -41000.08216064     0.5621


The total energy will keep decreasing with increasing basis set size 
(cfr. variational principle). And so will the Fermi energy, due to the 
way the energy reference is defined in wien2k (see Sec. 6.2 of 
http://www.wien2k.at/reg_user/textbooks/DFT_and_LAPW-2_cottenier.pdf).

For studying convergence, you should not monitor the energy at a given 
volume, but rather the energy difference between two volumes (or other 
observable properties).

Stefaan