MgO optimum mixing
Overview > bandgap of Si using different DFT+HF methods > MgO optimum mixing > fcc Ni DOS with hybrid functional > Si bandstructure > List of tutorials
Task
Find optimum HSE mixing parameter for MgO.
Input
POSCAR
MgO -18.79350000000000000000 0.5 0.5 0.0 0.0 0.5 0.5 0.5 0.0 0.5 1 1 cart 0.00 0.00 0.00 0.50 0.0 0.0
INCAR
############################################## ## Optimum HSE mixing parameter (AEXX) for MgO ## Expt gap = 7.8 eV ## fit gap wrt. 0<AEXX<1 ## Compute the bandgap using different value of AEXX ## in the range (0,1) and find the value which leads ## to the best agreement with the experimental gap. ## hint: the gap grows lineraly with AEXX ## Better preconverge with PBE first! ############################################## ## Selects the HSE06 hybrid functional #LHFCALC = .TRUE. ; HFSCREEN = 0.2 ; AEXX=0.25 #ALGO = D ; TIME = 0.4 ## Leave this in ISMEAR = 0 SIGMA = 0.01 GGA = PE
KPOINTS
k-points 0 Gamma 4 4 4 0 0 0
Calculation
- script to extract G-eigenvalues and calculate the bandgap
grep " 4 " OUTCAR | head -8 | \
awk 'BEGIN{i=1}{a[i]=$2 ; i=2} END{for (j=1;j<i;j++) print j,a[j]}' > vband.dat
grep " 5 " OUTCAR | head -8 | \
awk 'BEGIN{i=1}{a[i]=$2 ; i=2} END{for (j=1;j<i;j++) print j,a[j]}' > cband.dat
The bandgap is obainted by substracting the eigenvalues written in cband.dat (conduction band minimum at Gamma) and vband.dat (valence band maximum at Gamma)