Band gap renormalization in diamond using one-shot method
Task
Calculating the zero-point renormalization of the band gap in cubic diamond carbon.
Input
POSCAR
C1 [FCC,FCC,cF8] (STD_PRIM doi:10.1016
1.00000000000000
0.00000000 7.13397200 7.13397200
7.13397200 0.00000000 7.13397200
7.13397200 7.13397200 0.00000000
C
128
Direct
0.00000000 0.00000000 0.00000000
0.25000000 0.00000000 0.00000000
0.50000000 0.00000000 0.00000000
0.75000000 0.00000000 0.00000000
0.00000000 0.25000000 0.00000000
0.25000000 0.25000000 0.00000000
0.50000000 0.25000000 0.00000000
0.75000000 0.25000000 0.00000000
0.00000000 0.50000000 0.00000000
0.25000000 0.50000000 0.00000000
0.50000000 0.50000000 0.00000000
0.75000000 0.50000000 0.00000000
0.00000000 0.75000000 0.00000000
0.25000000 0.75000000 0.00000000
0.50000000 0.75000000 0.00000000
0.75000000 0.75000000 0.00000000
0.00000000 0.00000000 0.25000000
0.25000000 0.00000000 0.25000000
0.50000000 0.00000000 0.25000000
0.75000000 0.00000000 0.25000000
0.00000000 0.25000000 0.25000000
0.25000000 0.25000000 0.25000000
0.50000000 0.25000000 0.25000000
0.75000000 0.25000000 0.25000000
0.00000000 0.50000000 0.25000000
0.25000000 0.50000000 0.25000000
0.50000000 0.50000000 0.25000000
0.75000000 0.50000000 0.25000000
0.00000000 0.75000000 0.25000000
0.25000000 0.75000000 0.25000000
0.50000000 0.75000000 0.25000000
0.75000000 0.75000000 0.25000000
0.00000000 0.00000000 0.50000000
0.25000000 0.00000000 0.50000000
0.50000000 0.00000000 0.50000000
0.75000000 0.00000000 0.50000000
0.00000000 0.25000000 0.50000000
0.25000000 0.25000000 0.50000000
0.50000000 0.25000000 0.50000000
0.75000000 0.25000000 0.50000000
0.00000000 0.50000000 0.50000000
0.25000000 0.50000000 0.50000000
0.50000000 0.50000000 0.50000000
0.75000000 0.50000000 0.50000000
0.00000000 0.75000000 0.50000000
0.25000000 0.75000000 0.50000000
0.50000000 0.75000000 0.50000000
0.75000000 0.75000000 0.50000000
0.00000000 0.00000000 0.75000000
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0.50000000 0.50000000 0.75000000
0.75000000 0.50000000 0.75000000
0.00000000 0.75000000 0.75000000
0.25000000 0.75000000 0.75000000
0.50000000 0.75000000 0.75000000
0.75000000 0.75000000 0.75000000
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0.18750000 0.18750000 0.43750000
0.43750000 0.18750000 0.43750000
0.68750000 0.18750000 0.43750000
0.93750000 0.18750000 0.43750000
0.18750000 0.43750000 0.43750000
0.43750000 0.43750000 0.43750000
0.68750000 0.43750000 0.43750000
0.93750000 0.43750000 0.43750000
0.18750000 0.68750000 0.43750000
0.43750000 0.68750000 0.43750000
0.68750000 0.68750000 0.43750000
0.93750000 0.68750000 0.43750000
0.18750000 0.93750000 0.43750000
0.43750000 0.93750000 0.43750000
0.68750000 0.93750000 0.43750000
0.93750000 0.93750000 0.43750000
0.18750000 0.18750000 0.68750000
0.43750000 0.18750000 0.68750000
0.68750000 0.18750000 0.68750000
0.93750000 0.18750000 0.68750000
0.18750000 0.43750000 0.68750000
0.43750000 0.43750000 0.68750000
0.68750000 0.43750000 0.68750000
0.93750000 0.43750000 0.68750000
0.18750000 0.68750000 0.68750000
0.43750000 0.68750000 0.68750000
0.68750000 0.68750000 0.68750000
0.93750000 0.68750000 0.68750000
0.18750000 0.93750000 0.68750000
0.43750000 0.93750000 0.68750000
0.68750000 0.93750000 0.68750000
0.93750000 0.93750000 0.68750000
0.18750000 0.18750000 0.93750000
0.43750000 0.18750000 0.93750000
0.68750000 0.18750000 0.93750000
0.93750000 0.18750000 0.93750000
0.18750000 0.43750000 0.93750000
0.43750000 0.43750000 0.93750000
0.68750000 0.43750000 0.93750000
0.93750000 0.43750000 0.93750000
0.18750000 0.68750000 0.93750000
0.43750000 0.68750000 0.93750000
0.68750000 0.68750000 0.93750000
0.93750000 0.68750000 0.93750000
0.18750000 0.93750000 0.93750000
0.43750000 0.93750000 0.93750000
0.68750000 0.93750000 0.93750000
0.93750000 0.93750000 0.93750000
KPOINTS
K-Points 0 Gamma 1 1 1 0 0 0
INCAR
general: System = cd-C PREC = Accurate ALGO = FAST ISMEAR = 0 SIGMA = 0.1; IBRION = 6 PHON_LMC = .TRUE. PHON_NSTRUCT = 0 PHON_NTLIST = 1 PHON_TLIST = 0.0
- The tags with "PHON_" control the electron phonon options. PHON_LMC enables electron phonon calculations using Monte Carlo sampling. By selecting PHON_NSTRUCT=0 a one-shot configuration is obtained. The PHON_NTLIST selects the number of temperatures for which the structure with the one shot calculation is obtained. This requires also the list of temperatures PHON_TLIST which have exact that number of elements.
- IBRION=6 is selected to obtain the eigenvectors and eigenvalues of the dynamical matrix at the Gamma point.
Calculation
This example will use a one-shot method, where only a single structure comprising the electron-phonon interactions is required for a given temperature.
The calculation consists of the following steps:
- Obtain new "distorted" POSCAR file which contains the electron-phonon interactions. At zero temperature that file is called POSCAR.T=0..
- Execute simple DFT calculation for the new structure to obtain the band gap.
- Optional: execute DFT calculation for the original POSCAR file to obtain the band gap of the structure without electron-phonon interactions using the same calculational parameters as in the previous step. Since the phonon calculation from the first step contains the band structure, this step can be skipped if the calculational parameters are the same in that step as for the second step.