[Pw_forum] utilization of different Ultrasoft pseudopotentials

[Marcel Mohr]

On Fri, 27 Mar 2009, saqib.javaid at ipcms.u-strasbg.fr wrote:

>
> Dear PWSCF users,
> I have question regarding utilization of different type of Ultrasoft
> pseudopotentials. Is it correct to use different type of ultrasoft PS ( like
> rrkjus and Vanderbilt) for different atoms in a given system??? (e.g. one can
> use rrkjus PS of Cobalt and Vanderbilt PS of Mn with same XC functionals in a
> given system)

There is a similar question from beginning of this month, and the answer I 
remember is yes, as long as they use the same XC functional (as you 
stated)

However I got a question arising from this, too.

Why are rrkj pseudos sometimes called ultrasoft?
  In the book by Richard 
Martin the terms "ultra-soft" and "norm-conserving" are opposites, so only 
Vanderbuilt pseudos or (PAW) are "ultrasoft".
However Troullier-Martins and rrkj are norm-conserving and thus I 
conclude "not" ultrasoft ?!

I would greatly acknowledge any comment.

Cheers
Marcel