SIESTA (computer program): Difference between revisions

Revision as of 17:00, 6 February 2018

Revision as of 09:40, 29 March 2018

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[[File:SIESTA logo TM.jpg|center|thumb|SIESTA]]

{{redirect|SIESTA|other uses|Siesta (disambiguation)}}

[[File:SIESTA logo TM.jpg|center|thumb|SIESTA]]

'''SIESTA''' ('''Spanish Initiative for Electronic Simulations with Thousands of Atoms''') is an original 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 strictly localized basis sets and from the implementation of linear-scaling algorithms which can be applied to suitable systems. 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 and all-electron methods.

SIESTA's [[backronym]] is Spanish Initiative for Electronic Simulations with Thousands of Atoms.

Since 13th13 May 2016, with the 4.0 version announcement, SIESTA is released under the terms of the [[GPL]] open-source license. Source packages and access to the development versions can be obtained from the [https://launchpad.net/siesta new development and distribution platform].

== Features ==

SIESTA main characteristics are:

* It uses the standard Kohn-Sham selfconsistent [[Density functional theory|density functiona]]<nowiki/>l method in the [[Local-density approximation|local density]] (LDA-LSD) and generalized gradient (GGA) approximations, as well as in a non local functional that includes [[van der Waals interactions]] (VDW-DF).

* It uses norm-conserving [[Pseudopotential|pseudopotentialspseudopotential]]s in their fully nonlocal (Kleinman-Bylander) form.

* It uses [[Atomicatomic orbital|atomic orbitals]]s as a basis set, allowing unlimited multiple-zeta and angular momenta, polarization and off-site orbitals. The radial shape of every orbital is numerical and any shape can be used and provided by the user, with the only condition that it has to be of finite support, i.e., it has to be strictly zero beyond a user-provided distance from the corresponding nucleus. 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.

* Besides the standard Rayleigh-Ritz eigenstate method, it allows the use of localized linear combinations of the occupied orbitals (valence-bond or Wannier-like functions), making the computer time and memory scale linearly with the number of atoms. Simulations with several hundred atoms are feasible with modest workstations.

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* Vibrations (phonons).

* [[Electronic band structure|Band structure]].

* Ballistic electron transport under non-equilibrium (through TranSIESTA)

== Strengths of SIESTA ==

SIESTA main strengths are:

# '''Flexible code''' in accuracy

# It can tackle '''computationally demanding systems'''  (systems currently out of the reach of plane-wave codes)

# '''High efficient''' parallelization

# '''[http://www.simune.eu Support for a professional use]'''

The use of linear combination of numerical atomic orbitals makes SIESTA a flexible and efficient DFT code. SIESTA is able to produce very fast calculations with small basis sets, allowing computing systems with a thousand of atoms. At the same time, the use of more complete and accurate bases allows to achieve accuracies comparable to those of standard plane waves calculations, still at an advantageous computational cost.

== Implemented Solutions ==

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* [[Spin-orbit coupling]] (SOC) (NEW! In version 4.1)

* Topological insulator, semiconductor structures, and quantum-transport calculations

* NEB (Nudged Elastic Band) (interfacing  with [https://github.com/siesta-project/flos LUA]) (NEW! In version 4.1)

== Solutions under development    ==

* [[GW approximation]]

* Time Dependent DFT ([[TDDFT]])

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== Post-processing tools ==

A number of '''post-processing tools for SIESTA''' have been developed. These programs can be helpful to process SIESTA output, or to supplement the functionality of the program.

== Applications ==

Since its implementation, SIESTA 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) and has been applied to a large variety of systems including surfaces, adsorbates, nanotubes, nanoclusters, biological molecules, amorphous semiconductors, ferroelectric films, low-dimensional metals, etc.<ref>Mashaghi A et al. Hydration strongly affects the molecular and electronic structure of membrane phospholipids J. Chem. Phys. 136, 114709 (2012) [http://scitation.aip.org/content/aip/journal/jcp/136/11/10.1063/1.3694280]</ref><ref>Mashaghi A et al. Interfacial Water Facilitates Energy Transfer by Inducing Extended Vibrations in Membrane Lipids, J. Phys. Chem. B, 2012, 116 (22), pp 6455–6460 [http://pubs.acs.org/doi/abs/10.1021/jp302478a]</ref><ref>Mashaghi A et al. Enhanced Autoionization of Water at Phospholipid Interfaces. J. Phys. Chem. C, 2013, 117 (1), pp 510–514 [http://pubs.acs.org/doi/abs/10.1021/jp3119617]</ref>

== See also ==

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[[Category:Physics software]]

[[Category:Density functional theory software]]

{{science-software-stub}}

{{physics-stub}}

[[Category:Scientific simulation software]]