Editing Loop.s

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This is an example loop for finding the lattice constant of an FCC primitive cell (a rhomboeder: see the figure below for elements appearing in FCC lattice). 

[[Image:CrystalStructures.png|frame|none|alt=Crystal Structures|Crystal Structures of The Elements (for usual form at room temeperature).]]

The loop creates a series of <TT>POSCAR</TT> files with primitive cell size length specified in the <TT>seq</TT> command (3.1 to 4.0 &#197; with steps of 0.1 &#197;, i.e. 10 runs).

This cell size parameter, cell volume from <TT>OUTCAR</TT> and energy form <TT>OSZICAR</TT> are extracted into the output files.

Evaluation using a proper EOS method (preferentially the ''[http://en.wikipedia.org/wiki/Murnaghan_Equation Murnaghan equation]'' or ''Birch-Murnaghan equation'') should follow.

'''Important'''
Do not use quadratic regression (second order polynom)! - it's not an equation of state (EOS)!! Some tools for the non-linear fitting of Murnaghan Equation are listed online here: [http://courses.cit.cornell.edu/das248/equation_of_state.html Online Resources for Calculating the Equation of State])

'''Note'''
In the <TT>INCAR</TT> file, please take care that you set up a rigid calculation - <TT>NSW=1</TT> - and that the electronic density is properly converged - <TT>NELMIN=10</TT>. The <TT>KPOINTS</TT> should define a very dense ''k''-point grid (such as 10x10x10 or more).

The script <TT>loop.s</TT> itself:

 #!/bin/bash
 #$ -N Cu-lattice
 #$ -pe c8m24_ompi 8
 #$ -cwd
 #$ -o vasp-ompi.out
 #$ -e vasp-ompi.err
 #$ -S /bin/bash
  
 . /etc/profile.d/modules.sh
 
 module load vasp/5.2
 export OMP_NUM_THREADS=1
 
 for L in `seq -f %3.1f 3.2 0.1 4.0`
 do
 cat >POSCAR <<!
 Copper bulk - Cu1
   $L
     0.500000000000000   0.500000000000000   0.000000000000000
     0.000000000000000   0.500000000000000   0.500000000000000
     0.500000000000000   0.000000000000000   0.500000000000000
   1 
 Selective dynamics
 Direct
     0.000000000000000   0.000000000000000   0.000000000000000   T   T   T
 !
 
 echo "a= $L"
 mpirun -np $NSLOTS vasp
 
 V=`grep "volume " OUTCAR | tail -1 | awk '{print $5}'`
 E=`tail -1 OSZICAR | awk '{print $5}'`
 
 printf "%3.1f %6.2f %13.7f\n" $L $V $E >> SUMMARY-LVE.log
 printf "%3.1f %13.7f\n" $L $E >> SUMMARY-LE.log
 printf "%6.2f %13.7f\n" $V $E >> SUMMARY-VE.log
 cp OSZICAR OSZICAR-$L
 cp  OUTCAR  OUTCAR-$L
 done
 
 rm -f CHG* WAVE*

--[[User:Dkarhanek|Dkarhanek]] 13:53, 15 December 2010 (CET)