Organisers

• Alberto Garcia (Inst. Ciencia Materiales Barcelona)
• Javier Junquera (Univ. Cantabria)

Supports

 CECAM

 Psi-k

 COST - MolSimu

Description

This is a five-day hands-on tutorial on the use of the Siesta code, aimed at researchers from different disciplines who want to use the code in their research and need, apart from basic practice, a grounding on the capabilities of the method and the approximations used. The main goal is that the students understand the physical and main technical approximations behind the method and can assess its reliability and its usefulness for a particular problem. Apart from the basics of density-functional theory, molecular dynamics simulation and geometry relaxation, which are common to most codes, the specific Siesta topics to be covered are the generation and use of pseudopotentials, the construction of basis sets of strictly localized numerical atomic orbitals, localization issues for linear scaling both in the computation of the matrix elements and in the resolution of the hamiltonian, as well as more technical ones such as the influence of the real-space grid and parallelization. The tutorial will consist of morning lectures followed in the afternoon by a practical "hands-on" session. Some fundamental knowledge of quantum mechanics will be assumed, as well as basic statistical mechanics for the molecular dynamics part. Some solid state physics background will be helpful but not strictly needed. Basic knowledge of UNIX is required.

Scientific Objectives

A first aim of the tutorial is to show the students the thread between fundamental laws of physics and the properties of atomic aggregates, and, in so doing, transmit the difficulty of the problem and the essence of the approximations along that thread. Every student should take away:(i) what can be computed,(ii) how to do it, (iii) how good the results can be, and (iv) how bad they can be if things are not done critically and carefully (even if ab initio).

A second aim of the tutorial is to educate future users of ab-initio methods in general, and of the Siesta method in particular, in the critical use of first-principles methods. We want them to control and assess the main approximations involved (LDA/GGA,pseudopotentials, basis sets, localization for linear scaling) as well as the more technical ones.

Special emphasis will be put on the linear scaling character of the Siesta method.

We will also cover, for the first time, post-processing and visualization tools, which are becoming essential.

References

[1] J. M. Soler, E. Artacho, J. D. Gale, A. Garcia, J. Junquera, P. Ordejon, and D. Sanchez-Portal. The Siesta method for ab initio order-N materials simulations, J. Phys.: Condens. Matter 14 2745-2779 (2002)

[2] D. Sanchez-Portal, P. Ordejon, and E. Canadell. Computing the properties of materials from first principles with Siesta, Principles and applications of density functional theory in inorganic chemistry II: Structure and bonding 113 103-170 (2004)

[3] D. Sanchez-Portal, E. Artacho, P. Ordejon, and J. M. Soler. Density-functional method for very large systems with LCAO basis set, Int. J. Quantum Chem. 65 453-461 (1997)

[4] E. Artacho, D. Sanchez-Portal, P. Ordejon, A. Garcia, and J. M. Soler. Linear-scaling ab-initio calculations for large and complex systems., Phys. Stat. Sol. (b) 215 809-817 (1999)

[5] J. Junquera, O. Paz, D. Sanchez-Portal, and E. Artacho. Numerical atomic orbitals for linear-scaling calculations, Phys. Rev. B 64 235111 (2001)

[6] E. Anglada, J. M. Soler, J. Junquera, and E. Artacho. Systematic generation of finite-range atomic basis sets for linear-scaling calculations, Phys. Rev. B 66 205101 (2002)

[7] P. Ordejon, D. A. Drabold, M. P. Grumbach, and R. M. Martin. Linear system-size scaling methods for electronic-structure calculations, Phys. Rev. B 51 1456-1476 (1995)