Practice #2: Solid Yong-Hyun Kim NST551.

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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 Practice #2 Find 2 converge parameters (cutoff, k-point) for graphene and Si-diamond solids.