SIESTA is both a method and its computer program implementation, to
perform efficient electronic structure calculations and ab initio
molecular dynamics simulations of molecules and solids. SIESTA's
efficiency stems from the use of a basis set of strictly-localized
atomic orbitals. A very important feature of the code is
that its accuracy and cost can be tuned in a wide range, from quick
exploratory calculations to highly accurate simulations matching the
quality of other approaches, such as plane-wave methods.
The possibility of treating large systems with some first-principles
electronic-structure methods has opened up new opportunities in many
disciplines. The SIESTA program is open source and has become quite
popular, being increasingly used by researchers in
geosciences, biology, and engineering (apart from those in its natural
habitat of materials physics and chemistry). Currently there are
several thousand users all over the world, and the paper describing
(J. Phys. Cond. Matt. 14,
2745 (2002)) has received more than 8000 citations so far.
SIESTA's main characteristics are:
It uses the standard Kohn-Sham self-consistent density functional
method in the local density (LDA-LSD) or generalized gradient (GGA)
approximations. Recent versions implement a functional capable of
describing van der Waals interactions.
It employs norm-conserving pseudopotentials in their fully
nonlocal (Kleinman-Bylander) form.
It uses atomic orbitals with finite support as a basis set,
allowing unlimited multiple-zeta and angular momenta, polarization and
off-site orbitals. Finite-support basis sets are the key for
calculating the Hamiltonian and overlap matrices in O(N) operations.
Projects the electron wavefunctions and density onto a real-space
grid in order to calculate the Hartree and exchange-correlation
potentials and their matrix elements.
SIESTA can be compiled for serial or parallel execution (under MPI),
and can provide (the list is continuously expanding):
COOP and COHP curves for
chemical bonding analysis.
Starting from version 3.0, SIESTA includes the TranSIESTA module,
which provides the ability to model open-boundary systems where
ballistic electron transport is taking place. Using TranSIESTA one can
compute electronic transport properties, such as the zero-bias
conductance and the I-V characteristic, of a nanoscale system in
contact with two electrodes at different electrochemical potentials.