Ionic contributions to the frequency dependent dielectric function of NaCl

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Revision as of 10:51, 17 July 2019 by Bokdam (talk | contribs)

Task

Calculation of the ionic contruibutions to the frequency dependent dielectric function of NaCl. Please have a look at the example on calculation of the static and frequency dependent dielectric properties of SiC first. The same procedures dor the electronic contributions apply to this example.

Input

POSCAR

NaCl FCC                               
  5.55596202    
    0.5000000000000000    0.5000000000000000    0.0000000000000000
    0.0000000000000000    0.5000000000000000    0.5000000000000000
    0.5000000000000000    0.0000000000000000    0.5000000000000000
  Na   Cl
    1     1
Direct
 0.0000000000000000  0.0000000000000000  0.0000000000000000
 0.5000000000000000  0.5000000000000000  0.5000000000000000

INCAR

  • INCAR file for the static calculation:
PREC = High
ISMEAR = 0 ; ISIGMA = 0.01
EDIFF = 1.E-8
GGA = PS
  • INCAR electronic contributions to the frequency dependent dielectric function (see other tutorials for more advanced options):
PREC = High
ISMEAR = 0 ; ISIGMA = 0.01
EDIFF = 1.E-8
GGA = PS
ALGO = Exact
LOPTICS = .TRUE.
  • INCAR ionic contributions to the frequency dependent dielectric function:
PREC = High
ISMEAR = 0 ; ISIGMA = 0.01
EDIFF = 1.E-8
GGA = PS
EDIFF = 1.E-8
#The ionic dielectric function can be calculated in two ways:################
#1# DFPT (faster), but does not allow for METAGGA use. ######################
IBRION = 8; LEPSILON=.TRUE.
#2# Finite differences (slower). ############################################
#IBRION = 6; LPEAD=.TRUE; LCALCEPS=.TRUE.
#NFREE = 2 ; POTIM = 0.015
#In both 1 and 2 the calculated dielectric function is in vasprun.xml #######


Calculation

Download all necessary files and run doall.sh. An Awk script ("extract_diel_vasprun") is used to extract the dielectric function from the vasprun.xml file and write it into a easy to plot two-column format. If everything goes well you will obtain two files ("diel.electron.dat" and "diel.ion.dat"). The two dielectric functions have been plotted in the following figure.

Download

NaCl_dielectric.tgz

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