1
Introduction
VASP is a complex package for performing ab-initio quantum-mechanical molecular dynamics (MD) simulations using pseu-
dopotentials or the projector-augmented wave method and a plane wave basis set. The approach implemented in VASP
is based on the (finite-temperature) local-density approximation with the free energy as variational quantity and an exact
evaluation of the instantaneous electronic ground state at each MD time step. VASP uses efficient matrix diagonalisation
schemes and an efficient Pulay/Broyden charge density mixing. These techniques avoid all problems possibly occurring in
the original Car-Parrinello method, which is based on the simultaneous integration of electronic and ionic equations of mo-
tion. The interaction between ions and electrons is described by ultra-soft Vanderbilt pseudopotentials (US-PP) or by the
projector-augmented wave (PAW) method. US-PP (and the PAW method) allow for a considerable reduction of the number
of plane-waves per atom for transition metals and first row elements. Forces and the full stress tensor can be calculated with
VASP and used to relax atoms into their instantaneous ground-state.
The VASP guide is written for experienced user, although even beginners might find it useful to read. The book is mainly
a reference guide and explains most files and control flags implemented in the code. The book also tries to give an impression,
how VASP works. However, a more complete description of the underlying algorithms can be found elsewhere. The guide
continues to grow as new features are added to the code. It is therefore always possible that the version you hold in your
hands is outdated. Therefore, users might find it useful to check the online version of the VASP guide from time to time, to
learn about new features added to the code.
Here is a short summary of some highlights of the VASP code:
• VASP uses the PAW method or ultra-soft pseudopotentials. Therefore the size of the basis-set can be kept very small
even for transition metals and first row elements like C and O. Generally not more than 100 plane waves (PW) per atom
are required to describe bulk materials, in most cases even 50 PW per atom will be sufficient for a reliable description.
• In any plane wave program, the execution time scales like N
3
for some parts of the code, where N is the number of
valence electrons in the system. In the VASP, the pre-factors for the cubic parts are almost negligible leading to an
efficient scaling with respect to system size. This is possible by evaluating the non local contributions to the potentials
in real space and by keeping the number of orthogonalisations small. For systems with roughly 2000 electronic bands,
the N
3
part becomes comparable to other parts. Hence we expect VASP to be useful for systems with up to 4000 valence
electrons.
• VASP uses a rather “traditional” and “old fashioned” self-consistency cycle to calculate the electronic ground-state. The
combination of this scheme with efficient numerical methods leads to an efficient, robust and fast scheme for evaluating
the self-consistent solution of the Kohn-Sham functional. The implemented iterative matrix diagonalisation schemes
(RMM-DISS, and blocked Davidson) are probably among the fastest schemes currently available.
• VASP includes a full featured symmetry code which determines the symmetry of arbitrary configurations automatically.
• The symmetry code is also used to set up the Monkhorst Pack special points allowing an efficient calculation of bulk
materials, symmetric clusters. The integration of the band-structure energy over the Brillouin zone is performed with
smearing or tetrahedron methods. For the tetrahedron method, Bl
¨
ochl’s corrections, which remove the quadratic error
of the linear tetrahedron method, can be used resulting in a fast convergence speed with respect to the number of special
points.
• VASP runs equally well on super-scalar processors, vector computers and parallel computers. Presently support for the
following platforms is offered:
– Pentium Duo, Intel(R) Core(TM)2, Intel(R), i-7(TM).
– Athlon64(TM) and Opteron(TM) based PC’s under LINUX.
– Presently, only the Intel(R) Fortran compilers are supported.
– MPI bases parallelization, with excellent scaling on multicore machines (Nehalem(TM), Opteron(TM), Intel
Core(TM)2 Quad core, INTEL i-7(TM)).
(for a performance profile of these machines have a look at the Section 3.8).
In addition, makefiles for the following platforms are supplied. Since we do not have access to most of these machines,
support for these platforms is usually not available (the value in brackets indicates whether is likely that VASP runs
without problems: ++ no problems excellent performance; + usually no problems; 0 presently unknown; - unlikely):
– IBM-SP2, SP3, SP4, Blue Gene (++)
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