View source for Input and Output - a short Intro

= Input =

VASP basically needs 4 input files for standard production runs:

== {{FILE|INCAR}} ==
The {{FILE|INCAR}} file holds the input parameters which "steer" the calculation.

*The default values set by VASP itself are a clever choice to do standard calculations.
*These standard settings can be modified to specify:
**What do you want to do? (scf calculation, DOS, dielectric properties ...)
**You can give parameters to fulfill your requirements concerning required precision, requested convergence, calculation time ...


== {{FILE|POSCAR}} ==
The {{FILE|POSCAR}} file contains the information on the structure.
 
*A simple {{FILE|POSCAR}} file may look like this:
 fcc:  Ni
 3.53
 0.5 0.5 0.0
 0.0 0.5 0.5
 0.5 0.0 0.5
 Ni
 1
 Selective Dyn
 Cartesian
 0 0 0  T T T

*The description of each line is given as follows:
**1: Header (comment).
**2: Overall scaling constant.
**3-6: Bravais matrix.
**4: Name(s) of the atom(s).
**5: Number of the atoms (of each atom type).
**6: (optional: selective dynamics).
**7: Specifies which coordinate system is used ("cartesian" or "direct").
**8-x: Positions of the atoms.


== {{FILE|KPOINTS}} ==
The {{FILE|KPOINTS}} file determines the sampling of the 1st Brillouin zone.
 
*A typical {{FILE|KPOINTS}} file:
 Automatic mesh
 0
 G (M)
 4 4 4
 0.  0.  0.

*The description of each line is given as follows:
**1: Header (comment).
**2: Specifies the k mesh generation type. <math>N_{\overrightarrow{k}} = 0</math>: automatic generation scheme.
**3: <math>\Gamma</math>-centered (Monkhorst-Pack) grid.
**4: Number of subdivisions in each direction.
**5: Optional shift of the mesh.


== {{FILE|POTCAR}} ==
The {{FILE|POTCAR}} file contains the relevant information concerning the pseudo potentials that are necessary to run the calculation:

*Data that was required for generating the pseudo potentials.
*Number of valence electrons.
*Atomic mass.
*Energy cut-off.

If the cell contains different atomic species, the corresponding {{FILE|POTCAR}} files have to be concatenated, in the same order as the atomic species are given in the {{FILE|POSCAR}} file.

'''N.B.''': Different XC-types must not be mixed.
 

= Output =

VASP gives several different output files, depending on which task is performed. The most important files that are produced in (almost) every calculation are described in the following: 

== {{FILE|OUTCAR}} ==
The {{FILE|OUTCAR}} file gives detailed output of a VASP run, including:
*A summary of the used input parameters.
*Information about the electronic steps: <math> E_{\mathrm{Fermi}}</math>, KS-eigenvalues.
*Stress tensors.
*Forces on the atoms.
*Local charges and magnetic moments.
*Dielectric properties

The amount of output written onto the {{FILE|OUTCAR}} file can be chosen by modifying the {{TAG|NWRITE}} tag in the {{FILE|INCAR}} file.

== {{FILE|OSZICAR}} and stdout ==
The {{FILE|OSZICAR}} file gives a short summary of the results:
*Chosen SCF algorithm.
*Convergence of the total energy, charge- and spin densities. 
*Free energies.
*Magnetic moments of the cell.

== {{FILE|CONTCAR}} ==
The {{FILE|CONTCAR}} file gives the updated geometry data at the end of a run:
*Lattice parameter.
*Bravais matrix.
*Ionic positions.
*(Optionally velocities).

The format of the {{FILE|CONTCAR}} file is the same as of the {{FILE|POSCAR}} file, hence it can be used directly for continuation runs after having been copied to the {{FILE|POSCAR}} file.

== {{FILE|XDATCAR}} ==
The {{FILE|XDATCAR}} file contains updated ionic positions of each ionic step.

== {{FILE|DOSCAR}} ==
The {{FILE|DOSCAR}} file contains the total and integrated DOS and optionally the local partial DOS.

== {{FILE|CHGCAR}} ==
The {{FILE|CHGCAR}} file contains the charges <math>\rho * V</math>.

== {{FILE|WAVECAR}} ==
The {{FILE|WAVECAR}} file contains the wave function coefficients.
This file can be used to continue from a previous run.

Back to the [[The_VASP_Manual|main page]].

[[Category:Files]]