What is 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.
VASP computes an approximate solution to the many-body Schrödinger equation, either within density functional theory (DFT), solving the Kohn-Sham equations, or within the Hartree-Fock (HF) approximation, solving the Roothaan equations. Hybrid functionals that mix the Hartree-Fock approach with density functional theory are implemented as well. Furthermore, Green’s functions methods (GW quasiparticles, and ACFDT-RPA) and many-body perturbation theory (2nd-order Møller-Plesset) are available in VASP.
In VASP, central quantities, like the one-electron orbitals, the electronic charge density, and the local potential are expressed in plane wave basis sets. The interactions between the electrons and ions are described using norm-conserving or ultrasoft pseudopotentials, or the projector-augmented-wave method.
To determine the electronic groundstate, VASP makes use of efficient iterative matrix diagonalisation techniques, like the residual minimisation method with direct inversion of the iterative subspace (RMM-DIIS) or blocked Davidson algorithms. These are coupled to highly efficient Broyden and Pulay density mixing schemes to speed up the self-consistency cycle.
And what can VASP do?
The following is a (by no means complete) list of VASP features:
Functionals
- LDA, GGAs, metaGGAs
- Hartree-Fock, Hartree-Fock/DFT hybrids
Structure relaxation
- Relaxation using conjugate gradient, Quasi-Newton or damped molecular dynamics
- Nudged elastic band methods (transition states search)
- Climbing dimer method (transition state search)
Molecular dynamics
- Born-Oppenheimer molecular dynamics
- Interface pinning
- Slow-growth approach
- On-the-fly machine learning force fields
Magnetism
- Collinear and non-collinear
- Spin-orbit coupling
- Constrained magnetic moments approach
Green's function methods
- GW quasiparticles
- ACFDT total energies in the RPA
Many-body perturbation theory
- 2nd-order Møller-Plesset perturbation theory
First derivatives
- Forces and stress tensor for DFT, Hartree-Fock, and hybrid functionals
Linear response to ionic displacements
- Phonons
- Elastic constants (including ionic contributions)
- Internal strain tensors
Linear response to electric fields
- Static dielectric properties
- Born effective charge tensors
- Piezoelectric tensors (including ionic contributions)
Optical properties
- Frequency dependent dielectric tensors in the independent particle approximation
- Frequency dependent tensors in the RPA and TD-DFT
- Cassida’s equation for TD-DFT and TD-Hartree-Fock
Berry phases
- Macroscopic polarization
- Finite electric fields
