[Pw_forum] relaxation of doped system

[Giuseppe Mattioli]

Dear Yao-Hong

it is difficult to say much without seeing any detail of your calculation (version of the code, method, functional, pseudopotentials, ...)

> My question is should I do the vc-relax again after doping?

Yes, you should do it. And sometimes you should also check the stress tensor to verify that doping does not tend to alter too much the lattice 
parameter. It is not strictly mandatory, but sometimes you find interesting physics/chemistry (isoelectronic N in GaAs, H in InN only to provide a 
couple of examples).

> After relaxation, I built a 1*2*2 supercell (32 atoms),
> then I changed one Sn atom into Cu and do the vc-relax again,

This is > 6% doping. Are you sure that it is correct for your system?

> The program have been working for 3 days but it seems that it won't be done

What is it doing? Where is it running? Are you using LDA/GGA or EXX?

HTH
Giuseppe

On Sunday, May 01, 2016 01:00:58 PM n16031320 wrote:
> Dear users and developers:
> 
> I'm studying SnSe doped with Cu, first I do the vc-relax for SnSe of unitcell. 
> 
> After relaxation, I built a 1*2*2 supercell (32 atoms),
> 
> then I changed one Sn atom into Cu and do the vc-relax again,
> 
> My question is should I do the vc-relax again after doping? 
> 
> The program have been working for 3 days but it seems that it won't be done... 
> 
> Thank you in advance !
> 
> Regards
> 
>  
> Yao-Hong Huang

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   Giuseppe Mattioli                            
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