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 2018 we have continued to focus our efforts on work related to the MaX Centre, one of the eight European Centres of Excellence in HPC Applications supported by the EU under its 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 was initially based on the collaboration of 13 teams, including five research groups, like the ICN2 Theory and Simulation Group, which focuses on enhancing the capabilities of the SIESTA package and develop new methodologies for industrial applications of simulation tools in materials science. After a first period of three years (2015-2018), the grant has been renewed for the 2018-2021 period, with an increased budget and the incorporation of new groups and codes to the team.

We have continued improving the modularity and efficiency of the SIESTA and its modules (including TranSIESTA for the computation of electronic transport processes in nanodevices). In June 2018 we participated in the organisation of a Hackathon at the Barcelona Supercomputing Center, under the umbrella of MaX activities, for the development of the MaX codes (including SIESTA). 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 implementation and parallelisation of the Density Functional Perturbation Theory for the calculation of the phonon excitations in materials.

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 users’ projects. Up to date, our group has been awarded with eight user’s projects, three of them having been carried out in 2018.

In 2018 we hosted three visiting international PhD students who came to learn about the techniques developed in the group.

On the science side of things, in 2018 we made progress in the following research lines:

Thermal transport in Nanofluids: Our group established a fruitful collaboration with the Novel Energy-Oriented Materials Group (Prof. P. Gomez) and the Phononic and Photonic Nanostructures Group (Prof. Clivia Sotomayor-Torres) to understand their exciting experimental results on the thermal properties of graphene-dispersed nanofluids. This collaboration produced a joint publication in the Nanoscale journal, in which our group was able to determine the effect of the presence of the graphene flakes on the structure of the fluid, demonstrating the formation of layers in the liquid close to the graphene surface.

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. A joint publications with the ICN2 experimental group of Dr. D. Ruiz has been produced in this topic on the spin states of 2D coordination polymers.

Understanding the properties of 2D materials: A major advance has been made in this field during 2018, with several articles being published on the explanation of the existence of Charge Density Waves in 2D transition metal dichalcogenides like TiSe2, TiTe2 and NbSe2. Other work in 2D materials includes spin-proximity effects in graphene/topological insulator heterostructures, and the optical properties of MoS2 under pressure.

Understanding oxygen diffusion in Yttria-stabilized Zirconia: We started a collaboration with an industrial group on the understanding of the microscopic processes related to oxygen transport in materials used for gas sensing for the automotive industry. Our work has studied the mobility of oxygen in these materials by means of atomistic simulations, helping to determine the effect of the interfaces between the material and the metallic electrodes, a key factor of device performance.

Group Leader

Pablo Ordejón

Distinguished Researcher, Group Leader and Director

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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