[Pw_forum] 回覆： Re: [Pw_forum] How to calculate the relaxation calculation by setting one of the atomic coordinate fixed???

[Lawrence Lee]

Hi Eyvaz.,

I've tried this method (doing relaxation while holding some atoms fixed) long ago when I started learning using PWSCF. But the problem was that the number of iterations needed in this case is much much more than if I set all atoms free!! I have this problem in my mind since then. Do any one know why?

Thank you!

Lawrence

Eyvaz Isaev <eyvaz_isaev at yahoo.com> 說： Hi Prithwish,

You can do it easily. From INPUT_PW:
    X  x y z   {if_pos(1) if_pos(2) if_pos(3)}
  where :
    X         Character: label of the atom as specified in ATOMIC_SPECIES
    x, y, z   Real: atomic positions
    if_pos:   Integer, optional ( default = 1 ): component i of the force for
              this atom is multiplied by if_pos(i), which must be either 0 or 1.
              Used to keep selected atoms and/or selected components  fixed in
              meta-dynamics, neb, smd, MD dynamics or structural optimization
              run.
I.e. like this where Al atom is supposed to be relaxed, but As atom not.

Al 0.5 0.5 0.5 1 1 1
...........................
As  0 0 .5   0 0 0

Bests,
Eyvaz.
P.S. By the way there is no need to duplicate your message.

----- Original Message ----
From: Prithwish Nandi <pnspeaks at sify.com>
To: pw_forum at pwscf.org
Sent: Thursday, April 5, 2007 1:38:55 PM
Subject: [Pw_forum] How to calculate the relaxation calculation by setting one of the atomic coordinate fixed???


  Hi, 
     I want to do a relaxation calculation of a 32
  atom
cell by keeping one atom at a fixed position and other 31 atoms to be
relaxed.Is it possible to do the problem by setting X-iforce,Y-iforce
and Z-iforce equals to 1 for 31 atoms and by not setting for the atom I
want to be fixed ? Or, there is some other procedures for doing the job?
Please help.


  Prithwish Nandi
  Research Scholar
  IGCAR,
Kalpakkam, India
   
  

  
 Now book your  Railway Tickets by cash at Sify Iway. For more details contact  our Customer Care 

 Complete Coverage of the ICC World Cup '07! Log on to www.sify.com/khel for latest updates, expert columns, schedule, desktop scorecard, photo galleries and more! 

 For the Expert view of the ICC World Cup log on to www.sify.com/khel. Read exclusive interviews with Sachin, Ganguly, Yuvraj, Sreesanth, Expert Columns by Gavaskar, Web chat with Dhoni and more! 
 




  
---------------------------------
Sucker-punch spam with award-winning protection.
 Try the free Yahoo! Mail Beta.

 _______________________________________
 YM - 離線訊息
 就算你沒有上網，你的朋友仍可以留下訊息給你，當你上網時就能立即看到，任何說話都冇走失。
 http://messenger.yahoo.com.hk
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20070409/8289948a/attachment.html>