How to prepare inputs
Geometry
Crystal Structures
| Material | Lattice | Stacking | Exp. Param. | Brillouin Zone | Band Structure | Gap | Eg [eV] |
|---|---|---|---|---|---|---|---|
| 3C SiC | Zincblende | ABC | ioffe.ru | FCC (cubic) | PL97 HF74 | Γ - X | 2.36 (300K) |
| 4H SiC | Moissanite-4H | ABAC | ioffe.ru | Hexagonal | PL97 | Γ - M | 3.23 (300K) |
| 6H SiC | Moissanite-6H | ABCACB | ioffe.ru | Hexagonal | PL97 | Γ - M-L | 3.00 (300K) |
Hyperfine parameters
Vasp manual on hyperfine calculations. Derive NGYROMAG parameters from Magnetogyric ratio (MR) of webelements.com.
NGYROMAG = MR[Mhz T-1 rad] / 2*PI
| Isotope | MR | NGYROMAG |
|---|---|---|
| 31 P | 108.394 | 17.2514 |
| 29 Si | -53.190 | -8.4655 |
| 14 N | 19.338 | 3.0777 |
| 15 N | -27.126 | -4.3172 |
| 13 C | 67.283 | 10.7084 |
| 69 Ga | 64.389 | 10.2477 |
| 71 Ga | 81.812 | 13.0207 |
Generating Supercells
You can generate supercells from primitive cells by the wsgen package:
git://github.com/hornos/wsgen.git cd wsgen/src make
Copy src/wsgen and scgen to $HOME/bin . Edit the config file for the input generator. The scale variable sets multipliers for the lattice vectors and shift sets a shift for each sub-lattice (eg.: center sub-lattices for cubic or hexagonal place).
VASP
./scgen -p vasp -d -i <INPUT> -m "<LIST>"
where <INPUT> it the primitive CONTCAR and "<LIST>" is a space separated list of species for merge order of sub-lattices (eg.: "Si C").
You can make transformation on the merged geometry by creating a transform file merge.tf. Eg.: center the final geometry on the 1st Si atom (VMD atom index is used):
@center 1 Si
The final geometry is in merge.transform.POSCAR . Please be aware that the generated geometry is not VASP-normalized and not all atom is in the primitive cell of the supercell.
Brillouin Zone
K-points
| Lattice | X | L | M |
|---|---|---|---|
| FCC (cubic) | 0.500 0.500 0.000 | 0.500 0.500 0.500 | |
| Hexagonal | 0.000 0.500 0.500 | 0.000 0.500 0.000 |