Theory and Simulation Group

Group Leader: Pablo Ordejón

Main Research Lines

  • Development of theoretical methods, numerical algorithms and simulation tools

  • Codes: SIESTA and TRANSIESTA

  • First-principles simulations at the nanoscale

  • Novel physical properties in 2D materials

In 2017 we have continued to focus our efforts on work related to the MaX Centre (www.max-centre.eu), one of the eight European Centres of Excellence in HPC Applications supported by the EU under its 2105 H2020 e-infrastructure funding programme.

MaX supports developers and end users of advanced applications for materials simulations, design and discovery, and works at the frontiers of current and future high performance computing (HPC) technologies. It brings together leading developers and users of materials applications, together with top experts in HPC. It is based on the collaboration of 13 teams, including five research groups, like the ICN2 Theory and Simulation Group, which will focus on enhancing the capabilities of the SIESTA package and develop new methodologies for industrial applications of simulation tools in materials science.

We have continued improving the modularity and efficiency of the SIESTA and TRANSIESTA codes. We participated in the organisation of a “SIESTA School” at the Barcelona Supercomputing Center, under the umbrella of MaX activities. Most of the new functionalities developed for SIESTA have been related to the spin-orbit implementation (including a constrained-DFT approach to compute exchange couplings in magnetic materials) and the parallelisation of the Density Functional Perturbation Theory within the code.

The group has continued its participation in NFFAEurope (www.nffa.eu), a project funded under the H2020-INFRAIA-2014-2015 call “Integrating and opening existing national and regional research infrastructures of European interest”. The NFFA (Nanoscience Foundries and Fine Analysis) is a platform for interdisciplinary research at the nanoscale, in which our group participates as an “installation” offering computational support for experimental user projects. This year we have received our first approved application, to be executed in 2018.

In 2017 we hosted two international PhD students who came to learn about the techniques developed in the group: Ms. Şentürk, from the Middle East Technical University (Turkey), who spent two months working on novel magnetic 2D materials, and Mr. Bahmani, from the Bremen Center for Computational Materials Science, who spent three months learning about SIESTA and spin-orbit effects in transition metal dichalcogenides.

On the science side of things, in 2017 we made progress in the two research lines we started to develop last year:

Thermal transport at the nanoscale: Taking advantage of the expertise of visiting Prof. Colombo on thermal transport at the nanoscale, and coordinated with other theoretical and experimental collaborators, the group has moved forward in this exciting topic, developing new tools and methodologies. In particular, we are exploring the thermal transport properties of 2D materials, which have revealed unusual behaviours (as compared to bulk systems), leading to unexpected intriguing features with significant potential for various front-edge and emerging nanotechnologies (e.g. heat management in nanodevices, thermoelectric energy conversion or the manipulation of lattice heat to engineer phononic devices). The implementation of the Approach to Equilibrium Molecular Dynamics (AEMD) into the SIESTA package will allow other researchers to investigate thermal properties at the nanoscale, from first principles. Within the MaX Centre, and in the context of an industrial collaboration, we have also focused on techniques to study thermal properties in nanofluids, with potential impact on energy storage. Some exciting results have been applied to understand new in-house experiments (a collaboration between the Novel Energy-Oriented Materials, and the Phononic and Photonic Nanostructures groups and ourselves) on the thermal properties of graphene-dispersed nanofluids.

Magnetic properties at the nanoscale, with new developments in SIESTA that make the study of systems with strong spin-orbit effects (including topological insulators) possible, as well as the study of magnetic anisotropies in thin films and other nanostructured materials. We have used the working versions in our study of layered graphene-based magnetic nanostructures (published in Nature Communications), frustated magnetic materials, and topological insulators. These materials are very promising in the development of spin-based applications, which are of great interest at the ICN2 as a whole.

In existing research lines, we have made strong progress in:

Understanding the properties of 2D materials: In 2017 we have been working on grain boundaries in 2D materials, and 1D polar discontinuities; graphene-based devices for DNA sequencing; insights into the superconducting transition from STM experiments; and novel charge density wave instabilities.

Understanding nanostructured oxides: In collaboration with experimental colleagues in Argentina, we studied the mechanisms contributing to oxygen reduction reactions in manganites (La(1-x)SrxMnO3), identifying an increased oxygen vacancy concentration close to the surfaces that causes significant ionic conduction and enables the use of these nanostructured materials in solid oxide fuel cells in the “intermediate” temperature range. In addition to this collaboration, and motivated by the MaX Centre, we have established a new research collaboration with industry to advance oxygen diffusion in materials for sensor applications, which will run over the coming years.

Group Leader

Pablo Ordejón

CSIC Research Professor

Prof. Ordejón earned his degree in physics (1987) and PhD in science (1992) at the Universidad Autónoma de Madrid. He worked as a postdoctoral researcher at the University of Illinois at Urbana-Champaign (USA) from 1992 to 1995, and as assistant professor at the Universidad de Oviedo from 1995 to 1999. In 1999, he obtained a research staff position at the Institut de Ciència de Materials de Barcelona of the Consejo Superior de Investigaciones Científicas (CSIC). In 2007 he moved to the former CIN2 (now ICN2) as the leader of the Theory and Simulation Group, where he is currently a CSIC Research Professor. Since July 2012 he has served as director of the ICN2.

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