How to prepare inputs

Geometry

Crystal Structures

• Crystal Lattice 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

• Predefined k-point sets

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

• VASP