This type of plots are very common in our area of investigation. But to plot it is not so easy, first you have to split total DOS in partial atomic density, and then to compare between different surfaces you have to make a multiplot. This require time and creativity, here we show some tips and tricks to acomplish this task. First we are going to show how to make a DOS and partial DOS, and then a multiplot of DOS's.
Generate the DOS files
The following instructions are only for VASP code. In this example we are using anatase (101).
- After you relax the geometry of your system you have to generate the charge file to get the DOS. To generate the CHGCAR and CHG, make a single point geometry using the next instructions on the INCAR file.
#General System = TiO2 #Title PREC = NORMAL ENCUT = 400 #Oxigen ENCUT ISTART = 0 #New Job ICHARG = 2 #Initial Charge from atoms LWAVE = .FALSE. #Wavecar is not written LCHARG = .TRUE. #Final charge is written ISPIN = 2 #Spin polarized #Electronic Relaxation instructions NELM = 30; NELMIN= 2; NELMDL= 10 EDIFF = 1.0E-05 #Force stop criteria must be strong for DOS LREAL = .TRUE. #Real Space Projection IALGO = 48 #Normal-Blocked Davidson VOSKOWN = 1 #1-VWN for exact correlation #Ionic Relaxation EDIFFG = -1.0E-02 #stopping-criterion for IOM NSW = 0 #number of steps for IOM; 0 for single point IBRION = -1 #ionic relax: 0-MD 1-quasi-New 2-CG -1 single point ISIF = 2 #stress and relaxation 2-relax ionic 3-relax ionic and cell ISMEAR = 0
- In order to have more points on the DOS, you need a larger k-point mesh, in this example we are using a 6x6x1 because it is a surface.
- After you run and generate the CHG and CHGCAR, you must do a DOS calculation. Create a new folder and paste in it: CHGCAR, CHG, INCAR, POSCAR, POTCAR and KPOINTS.
- Change and add the following instructions on the INCAR file. Everything else gets the same.
#General ISTART = 1 #Job continuation ICHARG = 11 #Reads the charge from a file #DOS related values ISMEAR = -5; SIGMA = 0.10 #broadening in eV -4-tet -1-fermi 0-gaus, -5=DOS RWIGS = 1.217 0.820 #Wigner-Seitz radio of atoms involved as apear on POSCAR EMIN = -30.0 #Minimum range energy for DOS carefull must have decimals EMAX = 15.0 #Maximum range energt for DOS carefull must have decimals NEDOS = 800 #Number of DOS sample sites LORBIT = 11 #Instruction to construct the partial DOS NPAR = 1 #DOS calculation does not run in pararell
- Once you run it, VASP will generate the output files such as OUTCAR, PROCAR, DOSCAR among others. To generate the plots with gnuplot you have to split the total DOSCAR file, so please download the utilities created by the university of texas in this direction http://theory.cm.utexas.edu/vtsttools/scripts.html.
- Use the split_dos utility to separate the total DOS into atomic DOS. Be sure you are in the same directory that your vasp output files.
This will generate many DOS files as atoms are in the unit cell. For example if you have 32 atoms on your POSCAR, there will be 32 files labeled as DOSn. The order of the atoms is the same as in the POSCAR, if you put first 10 atoms of iron and then 20 of oxigen, DOS1 will be the projected density of the first iron, and DOS15 will be the projected density of the fifth oxigen.
Ploting Total DOS
You can skip the previus step and download the files here: dos_files.tar.gz
Now to plot the total density of states change the name file DOS0 to DOS0.dat which contains the total sum of states. First column is the energy, second are the spin up states, and the third are the spin down states of the system.
Use the general gnuplot template and modify the data you want to plot, in this case we are plotting all spin up and spin down states.
Also you can download this gnuplot template here: tdos_png.p. It will generate a png image.
plot "DOS0.dat" using 1:2 title "Spin up" with lines ls 5 , \ "DOS0.dat" using 1:3 title "Spin down" with lines ls 10;
Projected Density of State
You can divide the total DOS into the atoms states which contribute. The split_dos script divides the contribution of the total dos per atom, as said it before. For instance if we want to see the contribution of oxigen atoms into the total DOS, we sum all oxygen atoms states and plot it in the same graphic that the total DOS. To sum the atoms states download the next python script:"SORRY THIS PYTHON CODE IS UNDER REVISION, we recomend to use p4v utility".
- Check that the DOSn files has no a comment line, split dos sometimes generates the first line as a comment, delete the line comment.
- Select the atoms that you want to analize, in this case we want to see the contribution of all Ti into the Total DOS. Create a sum.inp file with the atoms, for this unit cell we have 4 Ti and 8 O. So for Ti sum.inp must look like the following.
DOS1 DOS2 DOS3 DOS4
- Sum the projected DOS per atoms with the python script
python sum_dos.py >> ti_dos.dat
- Do the same for the oxygen atoms. Modify the sum.inp file with:
DOS5 DOS6 DOS7 DOS8 DOS9 DOS10 DOS11 DOS12
- Then sum this 8 oxygen atoms.
python sum_dos.py >> o_dos.dat
- Files *.dat contains 7 columns, first is the energy zone, second and third are the s up/down states, the next 2 columns are the p up/down states, and finally the last two are the d up/down states.
- Now we can plot the projected DOS.
# Color line styles set style line 5 lt 1 lw 1.2 pt 1 ps 0.9 lc rgb "black" set style line 10 lt 1 lw 0.9 pt 2 ps 1.1 lc rgb "red" set style line 11 lt 1 lw 0.9 pt 3 ps 1.1 lc rgb "navy" plot "DOS0.dat" using 1:2 title "Total DOS" with lines ls 5 , \ "DOS0.dat" using 1:3 title "" with lines ls 5, \ "ti_dos.dat" using 1:6 title "Ti (d)" with lines ls 10, \ "ti_dos.dat" using 1:7 title "" with lines ls 10, \ "o_dos.dat" using 1:4 title "O (p)" with lines ls 11, \ "o_dos.dat" using 1:5 title "" with lines ls 11;
- Download this template here: proj_dos.p
# Grayscale PDOS set style line 5 lt 1 lw 1.2 pt 1 ps 0.9 lc rgb "gray80" set style line 10 lt 1 lw 1.0 pt 2 ps 1.1 lc rgb "gray50" set style line 11 lt 5 lw 1.4 pt 3 ps 1.1 lc rgb "gray20" plot "DOS0.dat" using 1:2 title "Total DOS" with filledcurve y1=0 ls 5 , \ "DOS0.dat" using 1:3 title "" with filledcurve y1=0 ls 5, \ "ti_dos.dat" using 1:6 title "Ti (d)" with lines ls 10, \ "ti_dos.dat" using 1:7 title "" with lines ls 10, \ "o_dos.dat" using 1:4 title "O (p)" with lines ls 11, \ "o_dos.dat" using 1:5 title "" with lines ls 11;
- Download this template here: gray_pdos.p