[Pw_forum] calculating equilibrium lattice constant

[Giovanni Cantele]

On Oct 26, 2009, at 2:53 PM, mohnish pandey wrote:

> I am beginner of quantum espresso. I am trying to calculate the  
> lattice constant for zinc oxide graphitic and wurtzitic structure .  
> I am using a script for that. But I have to see each and every file  
> to check the energy and to decide which one is minimum. Can you guys  
> please help me to get a shortcut for this I mean after running a  
> loop I get a minimum energy file instead of doing it manually and  
> then deciding which lattice parammeters fits to minimum energy..
>
> Thanks in advance.
> Mohnish Pandey



- to extract the final energy of a scf loop just add, at the end of  
each step of your script loop
grep ^!  fileout | tail -1 | awk '{print $5}'
or, if you want to store it into a variable etot
etot=$(grep ^!  fileout | tail -1 | awk '{print $5}')

(the "tail -1" is maybe reduntant if you're using version >= 4.0)

- to find the minimum, you can make parabolic fits of etot vs  
lattice_parameter or, maybe better, use and equation of state. Fort  
the latter,
a simple utility is available within the QE package, read the header  
of pwtools/ev.f90 (useful for cubic / hexagonal systems).

Giovanni



--

Dr. Giovanni Cantele
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario di Monte S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
Phone: +39 081 676910
Fax:   +39 081 676346
E-mail: giovanni.cantele at cnr.it
               giovanni.cantele at na.infn.it
Web: http://people.na.infn.it/~cantele
Research Group: http://www.nanomat.unina.it
Skype contact: giocan74

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