[Pw_forum] pseudopotential for studying high-pressure elements

[Paolo Giannozzi]

On Saturday 10 September 2005 02:41, Nichols A. Romero wrote:

> Will the PP give meaning results once the atomic seperation is less
> than r_c. In general, I would think not

so would I. If the sum of the r_c is of the same order of the
interatomic distance, the error might be minor, but if it is
definitely larger, I wouldn't trust too much the results

> So the next question is that for a fixed r_c what PP will be softess: 
> TM, RRKJ, Ultrasoft-PP, etc.? 

Ultrasoft are ultra, and not just soft, because they allow larger r_c,
not because their pseudization produces intrinsically softer PPs.
I know people working in high-pressure physics that do not trust
ultrasoft PPs for this reason. I have heard that RRKJ pseudization 
is very effective in producing soft PPs, but it occasionally fails; TM
always work

Paolo

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Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
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