How to prepare inputs

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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
13 C 67.283 10.7084
14 N 19.338 3.0777
15 N -27.126 -4.3172
17 O -36.264 -5.772
19 F 251.662 40.052
29 Si -53.190 -8.4655
31 P 108.394 17.2514
69 Ga 64.389 10.2477
71 Ga 81.812 13.0207
73 Ge -9.3603 -1.4897

Core levels calculation

VASP manual: http://cms.mpi.univie.ac.at/vasp/vasp/ICORELEVEL_tag_core_level_shifts.html

Two main methods

1. Initial state approximation

  ICORELEVEL = 1

2. Final state approximation

 ICORELEVEL = 2
 CLNT = ns   # ns: species number
 CLN = N      #  N: main quantum numer of excited core electron
 CLL = L        #  L:      l     quantum number of excited core electron
 CLZ = Z       #  Z: excited electron count (1 or 0.5)*
                       According Slater-Janak transition state approach (PRB 63 (2001) 205419; PRB 18 (1978) 7165)
                                E(n_c - 1)-E(n_c) = \int_0^1 \epsilon (n) dn \approx \epsilon (1/2)

Example: calculate C1s core level

 ICORELEVEL = 2
 CLNT = 1      # The first species is Carbon
 CLN = 1        #  1s core level, N=1
 CLL = 0         #  1s core level, l=0
 CLZ = 0.5      #  1/2

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 W K A H N P
FCC (cubic) 1/2, 1/2, 0 1/2, 1/2, 1/2 1/4, 1/2, 3/4 3/8, 3/8, 3/4
Hexagonal 0, 1/2, 1/2 0, 1/2, 0 1/3, 1/3, 0 0, 0, 1/2
BCC -1/2, 1/2, 1/2 0, 0, 1/2 1/4, 1/4, 1/4

Band Structure Calculation