1. Practice #2: Solid
Yong-Hyun Kim
NST551

2. VASP
VASP ?
The Vienna Ab initio Simulation Package (VASP) is a computer program for atomic scale materials modelling, e.g. electronic structure calculations and quantum-mechanical molecular dynamics, from first principles.
POSCAR
: Initial atomic position
Input
run.sh
: parallel computing
KPOINTS
: K-point sampling parameters
POTCAR
: Pseudo potential, ex-co. Energy
INCAR
: Input parameters for calculation
Output
OUTCAR
: Overall calculation results (total energy, force..)
CONTCAR
: Atomic position
WAVECAR
: Wavefunctions
EIGENVALUE
: Eigenvalues
CHGCAR
: Charge densities
. . .
DOSCAR
: DOS

3. Input- INCAR http://cms.mpi.univie.ac.at/vasp/vasp/vasp.html
System =graphene
ISTART=0
ICHARG=2
GGA_COMPAT=.FALSE.
ISPIN = 1
SYMPREC=1E-2
ENCUT=400
prec=Normal
NELMIN=4
EDIFF=1E-5
EDIFFG=-0.02
LREAL= .FALSE.
ISMEAR = 0 ; SIGMA=0.05
NSW = ; ISIF=2 ; IBRION=2
POTIM=0.1
NPAR=8
NSIM=4
LPLANE=.TRUE.
ALGO=fast
KBLOCK=1
NBLOCK=1
LWAVE=.FALSE.
LCHARG=.FALSE.
LVTOT=.FALSE.
System’s name
Whether to read the file WAVECAR or not. (0-new 1-cont. 2-samecut)
How to construct the 'initial' charge density. (1-file 2-atom)
Refer to the manual. (.FALSE. is recommended)
1- non spin polarized calculations, 2- spin polarized calculations.
How accurate the positions in the POSCAR file must be for symmetry.
Energy cutoff in eV.
Refer to the manual. (Normal is recommended)
The minimum number of electronic SC steps.
Stopping-criterion for electronic update.
Stopping-criterion for ionic update.
.FALSE.- projection done in reciprocal space, .TRUE.- projection done in real space.
Partial occupancies. (0-Gaussain, -1-Fermi); The width of the smearing in eV.
The maximum number of ionic steps.; Degrees of freedoms allowed to change.(2-cell shape and volume fixed); How the ions are updated and moved.(2-the conjugate gradient algorithm)
Time-step for ion-motion (fs)
Do not modify this line
Refer to the manual. (4 is recommended)
Refer to the manual. (.TRUE. is recommended)
The electronic minimization algorithm. (fast is recommended)
Refer to the manual. (1 is recommended)
Create waverfunctions (WAVECAR) file.
Create charge densities (CHG/CHGCAR) files.
Create total local potential (LOCPOT) files.

4. Input- POSCAR You can see the structure you made
graphene 2
Direct
System’s name
Lattice constant and unit cell coordinate
- a1 (x y z)
- a2 (x y z)
- a3 (x y z)
Number of atoms per unit cell.
Atomic position inside unit cell.
(Direct-ratio, Cartesian-absolute coordinate(x,y,z))
You can see the structure you made
Make a ‘input’ text file in the same directory with POSCAR.
Command ‘poscar.x’, and then ‘poscar.xyz’ file is made.
Command ‘xmakemol –f poscar.xyz’ to run program xmakemol.
- input file - 1
C 2
3 3 2
Number of atom type
Atom symbol; Number of atom per unit cell
Size of cell

5. Input- KPOINTS Output- total energy
graphene
gamma
0 0 0
System’s name
Refer to the manual. (0 is recommended)
Refer to the manual. (gamma is recommended)
How many k-points are sampled each reciprocal axis. (b1,b2,b3)
Output- total energy
You have to check the total energy after calculation is finished.
Command ‘grep "free energy" OUTCAR | tail -1’

6. Cufoff - Energy
400eV
300eV
graphene
Si-diamond

7. Kpoints - Energy 20 8
graphene
Si-diamond

8. Birch–Murnaghan EOS - eos.in - - Instruction -
1. To get the equilibrium volume, you need the Birch-Murnaghan fitting.
2. To use Birch-Murnaghan fitting, you have to run the program eos.x.
3. To run the program eos.x, you need the input file eos.in.
- eos.in -
- Instruction -
- PARAM.out -
4. After enter the eos.x, following files are generated.
Equilibrium volume
(Bohr3)
Bulk modulus

9. Volume- Energy 4.663 bohr 2.468 Å 10.337 bohr 5.470 Å graphene
Si-diamond

10. Practice #2
Find 3 converge parameters (cutoff, k-point, lattice constant) and compare the lattice constants with experimental values for graphene and Si-diamond solids (~ 10/16)