Ionic contributions to the frequency dependent dielectric function of NaCl: Difference between revisions

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  {{TAGBL|GGA}} = PS
  {{TAGBL|GGA}} = PS


*{{TAG|INCAR}} electronic contributions to the frequency dependent dielectric function<ref name=" gajdos:prb:06"/>(see other tutorials for more advanced options):
*{{TAG|INCAR}} electronic contributions to the frequency dependent dielectric function<ref name=" gajdos:prb:06"/>
(see other tutorials for more advanced options: [[Dielectric_properties_of_SiC|Dielectric_properties_of_SiC]] first. The same procedures for the electronic contributions apply to this example.
  {{TAGBL|PREC}} = High
  {{TAGBL|PREC}} = High
  {{TAGBL|ISMEAR}} = 0 ; {{TAGBL|ISIGMA}} = 0.01
  {{TAGBL|ISMEAR}} = 0 ; {{TAGBL|ISIGMA}} = 0.01
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  {{TAGBL|ALGO}} = Exact
  {{TAGBL|ALGO}} = Exact
  {{TAGBL|LOPTICS}} = .TRUE.
  {{TAGBL|LOPTICS}} = .TRUE.
Please have a look at the example on [[Dielectric_properties_of_SiC|calculation of the static and frequency dependent dielectric properties of SiC]] first. The same procedures dor the electronic contributions apply to this example.
 




Line 58: Line 59:
  #{{TAGBL|NFREE}} = 2 ; {{TAGBL|POTIM}} = 0.015
  #{{TAGBL|NFREE}} = 2 ; {{TAGBL|POTIM}} = 0.015
  #In both 1 and 2 the calculated dielectric function is in vasprun.xml #######
  #In both 1 and 2 the calculated dielectric function is in vasprun.xml #######


== Calculation ==
== Calculation ==

Revision as of 11:42, 17 July 2019

Task

Calculation of the ionic contruibutions to the frequency dependent dielectric function of NaCl.


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

KPOINTS

Gamma-centred 11x11x11 Monkhorst-Pack grid
 0 
G
11 11 11
0 0 0

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[1]

(see other tutorials for more advanced options: Dielectric_properties_of_SiC first. The same procedures for the electronic contributions apply to this example.

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 [2]:
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:

The high frequency 'ion-clamped' dielectric constant () was obtained with the LOPTICS calculation. The static field () contribution of the ionic lattice to the dielectric constant ( ) can be calculated by DFPT or by the finite-difference method. In both cases the phonon frequencies and the Born effective charges are calculated. If a phonon mode is 'dipole active', meaning that the dipole moment of all ions involved in the mode changes in size during one period, it will appear in the frequency dependent dielectric function. The total static dielectric constant is then the sum of the two contributions:

Download

NaCl_dielectric.tgz

References

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