VASPの使い方（英語）

# 初めに

VASPの簡単な使い方を英語でまとめたものになります。
もうほとんど使うことはないと思うのでここに供養しておきます。
（2020年3月26日）

# How to Use VASP

## Structural optimization

### Input files

#### POSCAR

```POSCAR
Si
1.0
3.000000 3.000000 0.000000
0.000000 3.000000 3.000000
3.000000 0.000000 3.000000
Si
2
direct
0.000000 0.000000 0.000000
0.250000 0.250000 0.250000
```

|Line|Explanation|
|:-----|:-----|
|1|job name (arbitrary)|
|2|Fixed (recommended)|
|3-5|Primitive translation vectors|
|6|Atomic species|
|7|Number of atoms for each element|
|8|Fixed (recommended)|
|9-10|Atom positions for each atom (Cartesian coordinates representation)|

You can see the structure by a visualization software, VESTA.

#### KPOINTS

```KPOINTS
Auto
0
Gamma
5 5 5
0 0 0
```

|Line|Explanation|
|:-----|:-----|
|1||
|2||
|3||
|4||
|5||

#### INCAR

```INCAR
IBRION = 2
NSW    = 300
ISIF   = 3
ENCUT  = 400
```

|Line|Explanation|
|:-----|:-----|
|1|Structual optimization<br>IBRION = -1 : No optimization<br>IBRION = 2 : Structural optimization with CG method|
|2|Maximum number of structural opt.|
|3|Option for structural optimization (Default is 2)|
|4|cutoff energy [eV]|

Option for structural optimization (ISIF)

|ISIF|calculate force|calculate stress tensor|relax ions|change cell shape|change cell volume|
|-----|-----|-----|-----|-----|-----|
|0|yes|no|yes|no|no|
|1|yes|trace only|yes|no|no|
|2|yes|yes|yes|no|no|
|3|yes|yes|yes|yes|yes|
|4|yes|yes|yes|yes|no|
|5|yes|yes|no|yes|no|
|6|yes|yes|no|yes|yes|
|7|yes|yes|no|no|yes|

#### POTCAR

```shell
cat ~~~/VASP/PP/Si/POTCAR > POTCAR
```

### Output files

#### OUTCAR

You can see the total energy in the unit of eV.

```OUTCAR
FREE ENERGIE OF THE ION-ELECTRON SYSTEM (eV)
---------------------------------------------------
free  energy   TOTEN  =        -10.787124 eV

energy  without entropy=       -10.787690  energy(sigma->0) =       -10.787313
```

#### CONTCAR

You can see the structure by a visualization software, VESTA.

<div style="page-break-before:always"></div>

## Band structure calculation

### Run SCF calculation

#### POSCAR

#### INCAR

#### KPOINTS

```KPOINTS
Auto
0
Gamma
5  5  5
0  0  0
```

### KPOINTS generation for band structure calculations

#### syml

```syml
6
40 20 30 30 40
G  0.000  0.000  0.000
X  0.500  0.000  0.500
W  0.500  0.250  0.750
K  0.375  0.375  0.375
G  0.000  0.000  0.000
L  0.500  0.500  0.500
    2.735494611  2.735494611  0.000000000     0.182782301  0.182782301 -0.182782301
    0.000000000  2.735494611  2.735494611    -0.182782301  0.182782301  0.182782301
    2.735494611  0.000000000  2.735494611     0.182782301 -0.182782301  0.182782301
-10.0  5.0
5.7993
```

|Line|Explanation|
|:-----|:-----|
|1|Total number of high symmetric k-points|
|2|Number of grid points between symmetric k-points|
|3-8|Symmetric k-points|
|9-11|Direct & reciprocal vector<br>Copy and paste from OUTCAR|
|12|Energy range|
|13|Fermi energy<br>Copy and paste from OUTCAR|

#### Terminal

```
> gfortran kpt-gen-vasp.f90
> ./a.out
> less KPOINTS
```

### DFT calculation

#### INCAR

```INCAR
IBRION = -1
NSW    = 0
EXCUT  = 400
ICHARG = 11
``` 

|Line|Explanation|
|:-----|:-----|
|4|electron density is fixed|

#### Terminal

```
> gfortran eig2gp-vasp-largeband.f90
> ./a.out
> gnuplot band.gp
```