Differences

This shows you the differences between two versions of the page.

--- band_structure [2009/11/25 22:18]
jelen
+++ band_structure [2014/10/20 12:42]
@@ Line 1: / Line 1: @@
-===== The band structure =====
-to calculate the band structure for given lattice parameter we need to achieve SCF solution.
-Therefore we run a standard bulk calculation as described in previous [[bulk optimization|chapter]]. Let's calculate the band structure
-for the lattice parameter ''alat = 5.5 Å'', than the **''fireball.in''** file contains:
-  &OPTION
-  basisfile = Si.bas
-  lvsfile = Si.lvs
-  kptpreference = Si.kpts
-  nstepf = 1
-  rescal = 5.5
-  &END
-where **''Si.bas''**, **''Si.lvs''** and **''Si.kpts''** files are identical as those used in previous [[bulk optimization|chapter]].
-Once we obtain the SCF solution, we determine the Fermi level from output file
-  mac135> grep "Fermi Level" $output_file | tail -1
-   Fermi Level =   -4.33045968490834
-In next step, we run the ''FIREBALL'' code again, but now with fixed charges (**''ifixcharge = 1''**) and with a new set of k-points in desired high-symmetry directions in the first Brillouin zone. Remember we need having **''CHARGES''** file in a working directory for a restart. In this particular case,we have chosen a direction ''L-Γ-X-Γ'' stored in a **''lgxg.kpts''** file (see also fig. 1).
-{{:si-bulk:fcc_brillouin.png?400|Brillouin zone FCC}}
-In addition, we have to write out a list of eigenvalues at each k-point switching on **''iwrteigen''** variable. Our input file **''fireball.in''** has following form now:
-  &OPTION
-  basisfile = Si.bas
-  lvsfile = Si.lvs
-  kptpreference = lgxg.kpts
-  nstepf = 1
-  ifixcharge = 1
-  rescal = 5.5
-  &END
-  &OUTPUT
-  iwrteigen = 1
-  &END
-After the run, we obtain a file **''ek.dat''** appears in a working directory. This file contains at each line set of eigenvalues for given k-points ordered in ascending form. The Fermi level can
-Now we have all information to plot the band structure of the Si bulk.
-  mac135> gnuplot
-  gnuplot> set xrange [0:300]
-  gnuplot> set yrange [-17:0]
-  gnuplot> set xlabel "k-points"
-  gnuplot> set ylabel "Energy [eV]"
-  gnuplot> set nokey
-  gnuplot> set multiplot
-  multiplot> plot "ek.dat" using 1:2 with lines
-  multiplot> plot "ek.dat" using 1:3 with lines
-  multiplot> plot "ek.dat" using 1:4 with lines
-  multiplot> plot "ek.dat" using 1:5 with lines
-  multiplot> plot "ek.dat" using 1:6 with lines
-  multiplot> plot "ek.dat" using 1:7 with lines
-{{:si-bulk:si-bulk.png|Si-bulk Band Structure}}
-===== DOS =====

Nanosurf Lab

User Tools

Site Tools

Differences

Page Tools