[Pw_forum] About the mean square displacement in CP output

[Bertrand SITAMTZE]

Dear Sandro,

Thanks very much,
May be I should search for another method to compute the diffusion coefficient.


Best regards.

****************************

Bertrand SITAMTZE YOUMBI

Laboratory of Material Sciences

Department of Physics

University of Yaounde I-Cameroon

************************************

--- En date de : Sam 1.5.10, Sandro Scandolo <scandolo at ictp.it> a écrit :

De: Sandro Scandolo <scandolo at ictp.it>
Objet: Re: [Pw_forum] About the mean square displacement in CP output
À: "PWSCF Forum" <pw_forum at pwscf.org>
Date: Samedi 1 mai 2010, 12h33





  
  
Dear Bernard,



if it converges to a finite value, your system is a solid (a crystal or
a glass), not a fluid, so it makes no sense to compute the diffusion
coefficient with MD, as the time scale for diffusion in solids are
dictated by defect diffusion, which takes place on a much longer time
scale than a MD simulation. 



NB: The MSD is also printed out (together with the temperature of each
species) in the standard output of cp.x, every iprint. 



Regards

Sandro 



On 30/04/2010 17:28, Bertrand SITAMTZE wrote:

  
    
      
        Dear Sandro,

        

Thanks very much for giving tangible responses to my questions.

My aim was to compute the diffusion coefficient using the linear
dependence of the MDS(t).  Now that it converge to a finite value, how
should I proceed?

        

Your help is of great interest for me.

Thanks once again

        

****************************

Bertrand SITAMTZE YOUMBI

Laboratory of Material Sciences

Department of Physics

University of Yaounde I-Cameroon

************************************

        
      
    
  
  

  
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Sandro Scandolo, ICTP | http://www.ictp.it/~scandolo

 

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