VASP

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

First derivatives
    Forces and stress tensor for DFT, Hartree-Fock, and hybrid functionals

Dynamics and relaxation
    Born-Oppenheimer molecular dynamics
    Relaxation using conjugate gradient, Quasi-Newton or damped molecular dynamics
    Nudged elastic band methods (transition states search)
    Climbing dimer method (transition state search)

Magnetism
    Collinear and non-collinear
    Spin-orbit coupling
    Constrained magnetic moments approach

Linear response to electric fields
    Static dielectric properties
    Born effective charge tensors
    Piezoelectric tensors (including ionic contributions)

Linear response to ionic displacements
    Phonons
    Elastic constants (including ionic contributions)
    Internal strain tensors

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

Green's function methods
    GW quasiparticles
    ACFDT total energies in the RPA
 
Many-body perturbation theory
    2nd-order Møller-Plesset perturbation theory