Noticing that ismear = -5 for graphene DOS is better than ismear=0 Noticing that ismear =0 or -5 does not matter for BS for graphene.

https://www.materialscloud.org/learn/sections/VNL7RL/a-gentle-introduction-to-dft-calculations-april-2020

Band structure calculations using VASP and vaspkit

IMPORTANT: VALUES OF PREC, ACCURACY and ENCUT must be the same for SCF and DOS calculation! NOTE: do not need the same KPOINTS file (can actually increase number in DOS calculation step)

Step 1. Optimize Structures using VASP

create a folder named opt

create an INCAR file

### Relaxation 
 # ENCUT = 500
 SIGMA = 0.010000
 # PREC = Accurate
 IBRION = 2
 ISMEAR = 0
 NSW = 1000
 # IVDW = 12                             
 # LREAL = Auto
 EDIFF = 1.0e-7
 EDIFFG = -0.01

create a KPOINTS file (example)

K-Spacing Value to Generate K-Mesh: 0.030
0
Monkhorst-Pack
  15  15   1
0.0  0.0  0.0

generate POTCAR and POSCAR

note: increase kpoints untill energy convergence note: N N 1 for graphene note: N M ? for mos2 ?

Step 2. Convert POSCAR to standardized primitive cell

In the opt folder containing the CONTCAR

cp POSCAR POSCAR.opt
rm POSCAR 
cp CONTCAR POSCAR

open vaspkit and select option 602

rm POSCAR

you should have no POSCAR file, but instead two files: POSCAR.opt and PRIMCELL.vasp

an additional file that is generated SYMMETRY

Step 3. Calculate CHGCAR file by performing a single-point self-consistent calculation

Create a new folder called scf and copy the PRIMCELL.vasp file into that folder as POSCAR using: also copy POTCAR and batch.sh files from opt folder to scf folder

Create KPATH.in file using VASPKIT option 302 and copy/save it as KPOINTS file,

it will look like this (this can be double checked and visualized in Link: seeK-path:

K-Path Generated by VASPKIT.
   20
Line-Mode
Reciprocal
   0.0000000000   0.0000000000   0.0000000000     GAMMA          
   0.5000000000   0.0000000000   0.0000000000     X              
 
   0.5000000000   0.0000000000   0.0000000000     X              
   0.5000000000   0.5000000000   0.0000000000     S              
 
   0.5000000000   0.5000000000   0.0000000000     S              
   0.0000000000   0.5000000000   0.0000000000     Y              
 
   0.0000000000   0.5000000000   0.0000000000     Y              
   0.0000000000   0.0000000000   0.0000000000     GAMMA    

that is :

cp ../opt/PRIMCELL.vasp POSCAR
cp ../opt/POTCAR .
cp ../opt/batch.sh .
cp KPATH.in KPOINTS

Create INCAR

Global Parameters
NCORE  =  4
ISTART =  1            #(Read existing wavefunction, if there)
ISPIN  =  1            #(Non-Spin polarised DFT)
LREAL  = .FALSE.       #(Projection operators: automatic)
ENCUT  =  500        #(Cut-off energy for plane wave basis set, in eV)
PREC   =  Accurate   #(Precision level: Normal or Accurate, set Accurate when perform structure lattice relaxation calculation)
LWAVE  = .TRUE.        #(Write WAVECAR or not)
LCHARG = .TRUE.        #(Write CHGCAR or not)
ADDGRID= .TRUE.        #(Increase grid, helps GGA convergence)
IVDW = 12 
# LVTOT  = .TRUE.      #(Write total electrostatic potential into LOCPOT or not)
# LVHAR  = .TRUE.      #(Write ionic + Hartree electrostatic potential into LOCPOT or not)
# NELECT =             #(No. of electrons: charged cells, be careful)
# LPLANE = .TRUE.      #(Real space distribution, supercells)
# NWRITE = 2           #(Medium-level output)
# KPAR   = 2           #(Divides k-grid into separate groups)
# NGXF    = 300        #(FFT grid mesh density for nice charge/potential plots)
# NGYF    = 300        #(FFT grid mesh density for nice charge/potential plots)
# NGZF    = 300        #(FFT grid mesh density for nice charge/potential plots)
 
Static Calculation
ISMEAR =  0            #(gaussian smearing method)
SIGMA  =  0.05         #(please check the width of the smearing)
LORBIT =  11           #(PAW radii for projected DOS)
NEDOS  =  2001         #(DOSCAR points)
NELM   =  60           #(Max electronic SCF steps)
EDIFF  =  1E-08        #(SCF energy convergence, in eV)

Step 4. Calculate DOS

NOTE: make sure that PRECISION and ENCUT are the same in the INCAR file Copy CHGCAR file from previous step to new folder called dos Copy WAVECAR file from scf folder to dos folder

cp ../scf/POTCAR .
cp ../scf/POSCAR .
cp ../scf/batch.sh .
cp ../scf/CHGCAR .
cp ../scf/WAVECAR .

Create INCAR

 ISTART = 2
 PREC = Accurate
 LREAL = Auto
 ENCUT = 500
 EDIFF = 1.0e-7
 IVDW = 12    
 ISMEAR = 0
 SIGMA = 0.010000
 ICHARG = 11

Step 4. Generate DOS plots

note: must not be done using terminus, use the default terminal and have -X11 forwarding turned on.

in dos folder, run vaspkit 211 to get the band structure. a band.png figure will result. Additional files including , , `` are also generated.

BAND.dat and BAND_RECORMATTED.dat can be used in ORIGIN. in BAND_RECORMATTED.dat , the first column is the length of the K-path in units of 1/Angstrom, the following columns are the energy of each bands.

in KLABELS, contains the positions of high symmetry points on band structure figures