[Pw_forum] INPUT file for average.x

[Stefano Baroni]

On Apr 26, 2010, at 8:41 AM, Gabriele Sclauzero wrote:

> 
> 
> wulilixiangguo at sina.com wrote:
>> I read below and have a question about macroscopic averages. If my 
>> system have a surface between two materials which have different lattice 
>> constant. 
> 
> Do you mean an interface? (I would say a "surface" only if one of the two "materials" is 
> vacuum, but maybe I'm pedantic...)
> 
> How to set the awin?
> 
> Not sure of this, but I think that it is not a good idea to use macroscopic averages when 
> there is a change in the periodicity. For instance, in a recent paper by Singh-Miller and 
> Marzari (PRB, 2010) it has been reported that the technique is not well suited for slab 
> geometries when you account for the relaxation of the distances between layers.
> 
> 
> How to macroscopic it twice?
> 
> Maybe I don't understand this point.
> 
> You could run the program twice, with two different window sizes, in order to match the 
> two different lattice spacings, but then I don't know if there is a way to give a 
> meaningful interpretation to the data at the interface.

What you propose, Gabriele, is perfectly legitimate and has been done indeed af few times in the good ol' times when macroscopic averages had been invented. I do not remember by heart the reference, but somebody may want to try a bibliographic search with "resta" and "baroni" as authors and select the title(s) that may suggest the investigation of lattice mismatched interfaces.

SB

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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