VASP Tutorial @ UGent

Danny Vanpoucke

11-01-2010

VASP Tutorial @ Ugent

OUTLINE

D.E.P.Vanpoucke

• Goal of this tutorial

• What is VASP

• Lock and load: time to start working1. Basics: Self Consistent Calculation

2. Relaxing a structure3. DOS

4. Bands5. Partial Charge Density � STM

• It’s all true ... For certain values of true

1. K-point convergence2. Kinetic energy cutoff convergence

3. Volume-scans, external pressure, Birch Murnaghan Equation of state

• Additional information

VASP Tutorial @ Ugent

Goal of this Tutorial

D.E.P.Vanpoucke

� Provide some basic knowledge, to setup standard (minimal) VASP

calculations.

�This tutorial will allow you to use the VASP program as a black-box

device. (Assume the program works, and those who wrote it had a clue

of what they were doing ;-) )

�For detailed information on the inner workings of the program itself

(and the theory behind it) I refer to the literature, online sources,

textbooks and the source-code itself.

� Give enough background knowledge to allow further self-education

on more specific details and specialized calculations.

� Give some hints with regard to possible pitfalls of the VASP-program.

VASP Tutorial @ Ugent

What is VASP?

D.E.P.Vanpoucke

VASP is a package for performing ab-initio quantum-mechanical molecular

dynamics (MD) using pseudo-potentials and a plane wave basis set. Both

LDA and GGA potentials/functionals are available. This code can be used to

obtain electronic and structural properties of small atomic systems (roughly

up to 100-200 atoms).

1) Periodic boundary conditions

Good for bulk materials ( = not so good for isolated systems i.e. molecules)

Ideal for Plane wave basis-sets

VASP Tutorial @ Ugent

What is VASP?

D.E.P.Vanpoucke

VASP is a package for performing ab-initio quantum-mechanical molecular

dynamics (MD) using pseudo-potentials and a plane wave basis set. Both

LDA and GGA potentials/functionals are available. This code can be used to

obtain electronic and structural properties of small atomic systems (roughly

up to 100-200 atoms).

1) Periodic boundary conditions

Good for bulk materials ( = not so good for isolated systems i.e. molecules)

Ideal for Plane wave basis-sets

2) Pseudo-potentials

To make life easier with the plane waves

Different flavors: LDA, GGA, hybrid (> v5)

VASP Tutorial @ Ugent

What is VASP?

D.E.P.Vanpoucke

VASP is a package for performing ab-initio quantum-mechanical molecular

dynamics (MD) using pseudo-potentials and a plane wave basis set. Both

LDA and GGA potentials/functionals are available. This code can be used to

obtain electronic and structural properties of small atomic systems (roughly

up to 100-200 atoms).

1) Periodic boundary conditions

Good for bulk materials ( = not so good for isolated systems i.e. molecules)

Ideal for Plane wave basis-sets

2) Pseudo-potentials

To make life easier with the plane waves

Different flavors: LDA, GGA, hybrid (> v5)

3) Small systems

Periodic Boundary conditions allow you to simulateBulk.

100 atoms are already large systems. Relaxation on 32 cores can take a week (real time!).

VASP Tutorial @ Ugent

Lock and Load

D.E.P.Vanpoucke

• Did you bring your own problem(atic system)?� 2 – 5 atoms� structure data

* coordinates in real/direct space* lattice parameter* lattice-vectors

If not:example system 1

Ge-bulk* 2-atoms, diamond lattice• Lattice parameter= 5.6575A• a1=(0.5; 0.5; 0.0)• a2=(0.0; 0.5; 0.5)• a3=(0.5; 0;0; 0.5)•�@1 (0.00, 0.00, 0.00) Ge•�@2 (0.25, 0.25, 0.25) Ge

example system 2C0-molecule

• 2-atoms , molecule• bond length: 1.128A

VASP Tutorial @ Ugent

Basics: Self Consistent Calculation I

D.E.P.Vanpoucke

VASP always needs minimum 4 files:

1) INCAR : contains all the settings of the program parametersyou wish to use. (energy cutoff, parallelism, smearing,...)

2) KPOINTS : all the information with regard to your k-point set.

3) POSCAR : all the information with regard to the actual geometry of your system.

4) POTCAR : the information regarding the potentials/functionals used� this one you get from a database

Let’s finally get started:�Make a folder with the name of your system. Inside this folder make a new folder

named: SelfConsistent.

VASP Tutorial @ Ugent

Basics: SC Calculation II �POTCAR-file

D.E.P.Vanpoucke

VASP provides potential files for all chemical elements. Each of these files is called POTCAR, and VASP only recognizes a file named POTCAR as potential file.

# electrons: 4 valence electrons for

this Ge potential, there also exists a

Ge potential including the d-

electrons in the valence shell� 14e-

This is a PAW potential for Ge

Type of exchange-functional:

CA=Ceperley-Alder � LDA

What if you have multiple/different kinds of atoms in your system?

e.g. CO molecule> cat POTCAR_C POTCAR_O >> POTCAR

Ge-Bulk CO-molecule

VASP Tutorial @ Ugent

Basics: SC Calculation III �POSCAR-file

D.E.P.Vanpoucke

Comment-tag

Scale factor

3 lattice vectors

Type and #atoms

Type coordinates: Direct or Cartesian

Positions of the atoms

Comments

Important: The order of the atom positions in the POSCAR file needs to be the

same as in the POTCAR file!