How to do a DOS calculation for collinear and non collinear magnetic structures

 We take the example of Nickel 

 

Collinear calculation

POSCAR

fcc:                             
 -10.93    
 0.5 0.5 0.0
 0.0 0.5 0.5
 0.5 0.0 0.5
   1  
Cartesian
0 0 0

  INCAR

SYSTEM  = Ni fcc bulk 
ISTART  = 0
ISPIN   = 2
MAGMOM  = 1.0
ISMEAR  = -5
VOSKOWN = 1
LORBIT  = 11

• Spin-polarized calculation with initial magnetic moment of 1 µB.
• Interpolation scheme of Vosko, Wilk and Nusair is used (see VOSKOWN=1).
• lm-decomposed DOSCAR is created.
• Tetrahedron method with Blöchl's corrections used for k-mesh integration
  

   

KPOINTS

k-points
0
Gamma
 11 11 11
  0  0  0

 

POTCAR

Download the pseudopotential file from this link 4_1_Ni.tgz

/Ni_col> vasp_std

• The output for the magnetic moments in the OSZICAR should look like the following:

       N        E
DAV:   1     0.139935173959E+02    0.13994E+02   -0.35801E+03  2338   0.828E+02
DAV:   2    -0.623612680591E+01   -0.20230E+02   -0.19281E+02  2282   0.123E+02
DAV:   3    -0.643764005251E+01   -0.20151E+00   -0.19906E+00  2536   0.140E+01
DAV:   4    -0.643786482872E+01   -0.22478E-03   -0.22442E-03  2344   0.459E-01
DAV:   5    -0.643786514671E+01   -0.31798E-06   -0.31687E-06  1832   0.173E-02    0.793E+00
...
DAV:   9    -0.545953126374E+01    0.48409E-02   -0.96206E-03  2946   0.839E-01    0.847E-02
DAV:  10    -0.545946513577E+01    0.66128E-04   -0.77007E-05  1364   0.126E-01
   1 F= -.54594651E+01 E0= -.54594651E+01  d E =0.000000E+00  mag=     0.5781

 

• The l decomposed parts of the magnetic moment are written in the OUTCAR file:
  

 magnetization (x)

# of ion     s       p       p       tot
----------------------------------------
  1       -0.007  -0.026   0.625   0.591

 

 Plotting DOS

To get a nice plotting we will another script called  plotDOS.py from the  package:       MatSciScripts

To use the script we need to install the Pymatgen library. To install this library check the following link:

How to download and install the Pymatgen library

 

Now we need to create a tools directory inside the root directory

> cd $VASPROOT
/vasp.5.4.1> mkdir tools

and copy the script plotDOS.py inside this created directory

> cp path/MatSciScripts/plotDOS.py $VASPROOT/tools/plotDOS.py

 

 At the end we need to add the path of tools directory to the path of vasp code as follows:

VASPROOT=/home/algerien1970/abinitio/vasp.5.4.1
export PATH=$PATH:$VASPROOT
export VASPBIN=$VASPROOT/bin 
export VASPTOOLS=$VASPROOT/tools

 

Plotting total DOS

plotDOS.py total -show

 

• The example output for the spin up and down DOS shows an exchange splitting of approximately 0.5 eV.
  

 Proper initialization of magnetic moments is very important:

• Too small initial magnetic moments will/may lead to nonmagnetic solution (by starting with an initial moment of 0.0 we arrive only to a magnetic of 0.002).
• Badly initialized calculations take longer to converge.
• Coexistence of low- and high spin solution

 

Non collinear calculation

• For a noncollinear calculation replace ISPIN=2 and MAGMOM=1.0 in the INCAR file by the following:
  

LNONCOLLINEAR = .TRUE.
MAGMOM        = 0.0 0.0 1.0

 

INCAR

SYSTEM  = Ni fcc bulk 
ISTART  = 0
LNONCOLLINEAR = .TRUE.
MAGMOM        = 0.0 0.0 1.0
ISMEAR  = -5
VOSKOWN = 1
LORBIT  = 11

/Ni_ncol> vasp_ncl

 

• The last three lines of the OSZICAR file using this parameter should look like the following:
  

DAV:   9    -0.546480633680E+01    0.41628E-02   -0.49402E-04  7532   0.330E-01    0.695E-02
DAV:  10    -0.546475032360E+01    0.56013E-04   -0.52286E-05  4328   0.446E-02
   1 F= -.54647503E+01 E0= -.54647503E+01  d E =0.000000E+00  mag= 0.0000   0.0000   0.5792

 

• By using MAGMOM = 1.0 0.0 0.0 we get the following output:
  

DAV:   9    -0.546481348871E+01    0.41496E-02   -0.50294E-04  7548   0.330E-01    0.692E-02
DAV:  10    -0.546474438319E+01    0.69106E-04   -0.51451E-05  4288   0.432E-02
   1 F= -.54647444E+01 E0= -.54647444E+01  d E =0.000000E+00  mag= 0.5792   0.0000   0.0000  

 

• Analogously if we set MAGMOM = 0.0 1.0 0.0 we get the following output:
  

DAV:   9    -0.546481179459E+01    0.41515E-02   -0.50430E-04  7552   0.330E-01    0.692E-02
DAV:  10    -0.546474640011E+01    0.65394E-04   -0.51658E-05  4292   0.434E-02
   1 F= -.54647464E+01 E0= -.54647464E+01  d E =0.000000E+00  mag= 0.0000   0.5792   0.0000

 

Plotting total DOS

plotDOS.py total -show