VASP is a complex package for performing
ab-initio quantum-mechanical molecular
dynamics (MD) simulations using pseudopotentials 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 motion.
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hands is outdated.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.
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
- In any plane wave program, the execution time
scales like for some parts of the code, where 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 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,
The integration of the band-structure energy over the Brillouin zone
is performed with smearing or tetrahedron methods.
For the tetrahedron method, Blöchl'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:
(for a performance profile of these machines have a look at the Section 3.8).
- 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)).
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):
For these platforms makefiles are distributed, but we can not offer help,
if the compilations fails
or if the executable crashes during execution.
- IBM-SP2, SP3, SP4, Blue Gene (++)
- SGI Power Challenge, Origin 2000, Origin 200 (+)
- Cray T3D and T3E (+)
- Cray vector machines (+)
- NEC vector machines (+)
- Fujitsu vector machines (0)
- HP (PA-RISC), and other models (0)
N.B. Requests for support are to be addressed to: firstname.lastname@example.org