Category Archives: reports

Scientific Report regarding the CECAM Workshop: “Computational insight into photo-induced processes at interfaces”


Thomas Frauenheim (University of Bremen, Germany)

Oleg Prezhdo (University of Southern California, L. A., US)

Sheng Meng (Institute of Physics, CAS Beijing, China)

Johannes Lischner (Imperial College London, UK)


Location:       University of Bremen, Germany,

10th until 14th of October 2016


1. Summary

There is enormous interest in understanding and controlling photo-induced charge transfer and chemical reactions for energy storage. These can be due either to water splitting and carbon dioxide reduction or by electro-hole pair separation at hybrid chromophore- or hybrid polymer-solid interfaces in photovoltaic devices, stimulating an increasing number of experimental and theoretical studies. Computational atomistic studies of experimental realistic setups require models that include an inorganic semiconductor nanostructure, acting as a catalyst and organic molecules in solvents. In photovoltaic applications, e.g. one has to consider multi-component systems, involving several chromophores tuned to absorb different wavelengths of light, an acceptor that removes an electron from the chromophores and creates separated electron-hole pairs, as well as electron and hole conducting media. Such models already may involve hundreds to thousands of atoms, extending far beyond the limits of any ab initio calculations. Furthermore, the non-equilibrium processes involved in the photo-induced charge separation and transport require explicit time domain modelling. Relevant processes occur on ultrafast time-scales and in most cases cannot be described by rate expressions. Charge separation, Auger-type energy exchange between electrons and holes, generation of additional charges by Auger mechanisms, energy losses to heat due to charge-phonon interactions, charge and energy transfer, and electron-hole recombination occur in parallel and competition requiring significant efforts in method development and clarification of multiple conceptual problems.

As major scientific objectives of the proposed workshop we have achieved:

  • Bringing together researchers from quantum chemistry and computational solid state physics working on photo-catalysis and photovoltaics. We were able to highlight recent progress and discuss challenges and opportunities in the materials aspect of tailor-made nanostructures and hybrid interfaces for highly efficient energy applications.
  • We have fostered the exchange of methodological expertise and new developments between scientists working on different aspects of metal oxide photo-catalysis.
  • We discussed possibilities for optimizing the materials properties and device design. The interdisciplinary character of the workshop helped finding solutions for overcoming current limitations.
  • The workshop stimulated new worldwide interdisciplinary collaborations on computational photo-catalysis and photovoltaics for the mutual benefit of theoretical, experimental and applied researchers.

The program consisted of 30 invited talks of 40 minutes (35+5) each and one poster session presenting 39 posters. In addition, many social events (reception and conference dinner) to allow for informal exchange were held. The invited talks were given by well-established scientists from the different theoretical communities, which acted as platform for interesting cross-/interdisciplinary discussions. The invited talks were followed by a poster session where the younger participants could show their scientific work and exchange of ideas with a broad knowledge in computational chemistry, solid state physics and computational materials science. The organization was very compact with the scientists accommodated in the same hotel fostering exchange and discussion between the participants also outside the meeting room.

Financial support from the DFG, Psi-k Network, Fonds der Chemischen Industrie im Verband der Chemischen Industrie e.V., and the German CECAM node multi-scale modelling from first principles, and the University Bremen is gratefull acknowledged.


2. Scientific content, main outcome of key presentations, selected discussions

Currently, theoretical studies of light-induced processes at interfaces usually fall in one of two broad categories: i) modelling of the atomic structure and ground state electronic properties of complex interfaces and ii) simulation of light-matter interactions and electronic excited states in relatively simple systems. For example, several talks at the conference addressed the atomic surface structure of photocatalysts, such as titanium dioxide, and discussed the complex interaction of these surfaces with adsorbed atoms and molecules. Other talks addressed excited states of such photocatalysts with high-level methods, such as many-body perturbation theory. For a full understanding of photocatalysis and other light-induced processes at interfaces, it is necessary to combine these two aspects. We therefore expect and hope that in the near future more studies will attempt to bridge and connect these categories, i.e. simulate the interaction of light with matter at realistically complex systems.

For the light-matter interaction, there has been an increasing number of studies using the real-time formalism. These studies give important insights into the kinetics of light-induced processes at interfaces. However, the increased numerical effort of these simulations usually necessitates the use of approximate theories, such as time-dependent density-functional theory with its well-known limitations. Conversely, higher-level methods, such as quantum chemical wavefunction approaches or the Bethe-Salpeter equation, can only be applied with a linear-response framework. We expect that the next 2-3 years will see the transfer of high-level methods from the frequency-domain to the real-time domain. This would open up the description of exciton dynamics in heterogeneous systems which are highly relevant to photocatalysis and photovoltaics.


3. Assessment of the results and impact on future direction of the field

A major obstacle to the accurate description of light-induced processes at interfaces is the intrinsic interdisciplinarity of the subject. The study of such processes requires knowledge of physics, chemistry, materials science and even biology. Therefore, advancing our understanding of photocatalysis and photovoltaics necessitates a joint effort from experts in different fields. To enable such collaborations, it is of crucial importance to organize interdisciplinary workshops like ours to act as platforms for exchanging ideas and for bringing together researchers from different subject areas who work on different aspects of the same topic. In the future, we will try to continue organizing workshop to achieve this goal.

The workshop became a forum to discuss about possible solutions of improving the quality of hybrid interfaces for studying electron dynamics and charge transfer reactions and correlating experiment and theory on a highly predictive level. We have been able to achieve the following key objectives:

  1. In the discussions we have identified the major problems in our current understanding of novel photoactive materials with a focus on lateral and multi-layer stacking effects (moiré structures, novel electronic states), transport (heat and charge carrier), contacts, quantum confinement, and doping. To this end we brought together experiment and different theory communities seeking for predictive power and general understanding of electronic properties of novel photoactive materials. Invited overview talks by highly recognised experimentalists from different parts of the field (transport and STM of organic and inorganic layered materials, topological insulators, biological sensors, supercapacitors, solar cells, and lithium ion batteries) and related computational talks have contributed to the general understanding.
  2. We have summarised the major achievements from communities working on different time-dependent approaches to study the coupled electron-ion dynamics in organic and hybrid materials, and have identified common problems. The workshop has stimulated knowledge exchange across the boundaries of formerly rather separate communities.
  3. In the discussions the main advantages and shortcomings of currently available theoretical techniques to model and understand the electronic, electrical and charge transfer properties of novel photoactive materials have been specified. The techniques considered and discussed comprise (but not be limited to): density functional theory (LDA, GGA, LDA+U, etc), TD-DFT, GW and BSE quasi-particle methods, quantum transport techniques (Landauer Büttiker, Kubo formula), multi-scale approaches, quantum lattice models, many-body theory and quantum optics.
  4. During the period of the workshop possible solutions in optimizing the quality and properties of novel photoactive materials and fabricating new devices have been outlined. The mutual exchange between researchers from both experiments and computational materials science helped a lot to better understand current problems in synthesis and application of photoactive materials in photocatalysis and photovoltaics, and determined the priority target of questions to be addressed by state-of-the-art first-principle methods.


4. Infrastructure requirements to make advances in the field

As discussed above, the advancement of theories of light-induced processes at interfaces requires the development of novel theories and codes which can i) capture the inherent complexity of realistic interfaces and ii) contain sufficiently accurate description of physico-chemical processes, including photon-electron interactions, electron-hole coupling, electron-phonon coupling, etc. The development of such theories and the resulting computer software will benefit the broad community of theoretical researchers, but also have important impacts on experimental studies and industry. However, to achieve this, a continued investment is required, as method and code development usually occur on a longer time scale compared to the study of applications. This also requires the training of masters and PhD students not only in physics, materials science or biology, but also in computer programming (including parallelization of software) and use of high-performance computing resources.


5. Impact to address the need of industry in driving economic growth

Progress in the field of many body physics, time-dependent electron dynamics and wave function based correlated quantum chemistry is fundamental to many European industries connected to high-tech materials design and device applications. Examples are

  • Advanced hybrid photovoltaics
  • Photo-catalytic processes in energy storage and pollutant degradation
  • Hybrid nano/bio-systems for medical applications
  • Single-defect-based quantum optical and spintronic devices

Such directions can be strengthened by focused research projects for the development of new materials and devices in key enabling technologies. The field of nanodevices is currently opening to new materials, especially 2D. The EU flagship on graphene and 2D materials is indeed expected with the aid of computational predictions to produce several new outcomes. However, technological innovation is not limited to these materials.


November 25th 2016

The Organizers


7th School & Workshop on Time Dependent Density Functional Theory: Prospects and Applications

The Benasque Center for Science

Alberto Castro
Neepa Maitra
Fernando Nogueira
Angel Rubio
E. K. U. Gross

Time-dependent density-functional theory (TDDFT) is but one of the numerous methods used to model the electronic structure in atoms, molecules, and extended systems. Its use is growing fast, as its reliability for many purposes has been sanctioned by many successful applications over the years. The calculation of excitation energies of many varieties of molecules, and the optical absorption spectrum of many solids can be cited as examples. However, in other circumstances TDDFT has to be substituted by more accurate, yet more expensive techniques: advanced correlated post-Hartree Fock techniques, or many-body perturbation theory techniques such as any of the approximations to the solution of Hedin’s equations. Yet TDDFT, as ground-state DFT, could in principle be exact, providing inexpensive solutions to all electronic structure problemas. How can one approach this goal was the starting question for this workshop – and, in fact, it has been the motivation behind the full series of the Benasque Workshop (and School) on TDDFT, since 2004.
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Scientific Report regarding the CECAM Workshop: “Tailor-made 2D-materials and functional devices”


Thomas Heine, University of Leipzig (Germany)

Yandong Ma, Jacobs University Bremen (Germany)

Tim Wehling, University of Bremen (Germany)

Young-Hee Lee (Institute for Basic Science, Suwon (Korea)

Thomas Frauenheim, University of Bremen (Germany)



University of Bremen, Germany, 27th June until 1st of July 2016


I. Summary

The workshop “Tailor-made 2D-materials and functional devices” was held at the University of Bremen, Germany from June 27th to 1st 2016. In total, 76 participants from Belgium, Brazil, Finland, Ireland, Luxemburg, The Netherlands, Portugal, Slovenia, Spain, Sweden, Switzerland, Denmark, France, Germany, UK and US attended the workshop.

The programme consisted of 30 invited lectures, one poster session presenting 37 posters and many events (reception / conference dinner) to allow for informal exchange. The lectures were scheduled to last 40 min, including 5-10 min discussion time. In addition to this extended time for discussion, the chairpersons were instructed to introduce the subject of the session and to actively participate in the discussion. This “Gordon-conference-style” was essential to guarantee a vivid discussion. The organizers ensured that well-established scientists acted as invited speakers and chairpersons.

Concerning the poster session, we accepted only 37 posters to allow for an intense exchange of ideas at each single poster. Here, we encouraged in particular the young scientists to ask questions. The participation of PhD students was supported by partly covering local accommodation costs.

Due to the compact organization and accommodation in one hotel only all participants stayed together for the whole time of the conference, which additionally enforced the scientific discussion which was mandatory since scientists from various separated fields, i.e. advanced quantum chemistry, many-body perturbation theory, DFT and beyond, scanning probe techniques, optical spectroscopy, ARPES, etc. were attending the meeting to merge ideas and formulate a common goal for future directions and collaborations of theory groups with experimental groups.

Financial support from the DFG, Psi-k Network, and the German CECAM node multi-scale modelling from first principles, and the University Bremen is gratefully acknowledged.

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17th Workshop on Dynamical Phenomena at Surfaces

Report on the WDPS-17 workshop held in Milan, Italy, from Sept. 19th to 21st, 2016.

WDPS logo

The Workshops on Dynamical Phenomena at Surfaces (WDPS) are an active biennial series of scientific workshops that deal with dynamical aspects of surface behaviour. A special characteristic of the series is the emphasis on bringing theory and experiment together in an intimate setting, a feature that was initiated by in the first meeting of the series. The present workshop combined an exceptional setting with a programme that balanced experimental and theoretical talks, as before; however, the scientific context was expanded significantly in 2016. In the first meeting of the series, in 1983, the topic focussed exclusively on surface phonons and indeed the emphasis within that topic was a single experimental technique, namely inelastic helium atom scattering. Both the experimental technique and the tools for theoretical analysis were under active development at the time and that emphasis was reflected in the title of the first workshop, SURPHON.

The Milano workshop touched on neither topic though there were contributions on more recent developments in molecular beam scattering. The overall impression was one of a greatly expanded scientific activity within a thriving community. Topics varied from understanding bio-systems and nano-friction to macro-molecules, self-assembly and the diffusion dynamics of complex systems, all from an atomistic perspective. The dramatic evolution of scientific breadth displayed in the present meeting is a reflection of the vigour that exists in the community today. Everyone looks forward to the next meeting in the series, which was advertised as to be held in Orlando, USA, in 2018.

WDPS-17 group photo

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Psi-K Quantum-ESPRESSO School on Ab-Initio Thermal Transport


Ab-initio prediction of thermal properties for condensed matter has been a blossoming field in the last few years, thank to its numerous applications mainly in thermoelectric materials and heat dissipation technologies. This methodology however does require to master a certain amount of expertise, both technical and theoretical, in order to be executed rigorously and efficiently. In this school, we wanted to provide an in-depth view of the theoretical framework, without neglecting the importance of applying the theory on some practical examples.

The school has been composed of theory sessions and hands-on tutorials suitable for anybody with graduate-level knowledge of condensed matter physics. As we planned to release all the software with an open-source license just after the end of the school, it was extremely useful for us to collect some feedback from this first batch of users.
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Hermes 2016. Multiscale modelling and science communication

Hermes 2016
Hermes 2016 – demanding workshop had drained all the seriousness from the participants and organisers.


Erich Wimmer’s key note talk kick started a summer school on multi-scale materials modelling and science communication. Erich shared an exciting story of his personal journey and work in the field of computational materials science – with experience in academia, industry and even running a company (a co-founder at Materials Design).

A human element shone throughout the talk, emphasising  the importance of collaboration and the relationships between colleagues for making the numerous advances in the field possible, and importantly making the process fun and rewarding.

Following the Q&A session informal discussions continued over the dinner in the beautiful dining halls of the Cumberland Lodge. The evening ended with an informal ice-breaking game of treasure hunt, allowing the participants to relax, explore the great Windsor Park and the lodge itself while getting to know each other. Demanding several days awaited – a series of master classes each focusing on time/length scale beyond the familiar grounds for most of the participants; a series of work shops on engaging presentations, communication through infographics and a technical session on data visualization using Mathematica leading to group projects and individual presentations. Continue reading Hermes 2016. Multiscale modelling and science communication

College on Multiscale Computational Modeling of Materials for Energy Application

From the 4th to the 15th July, over 90 scientists from 30 countries have gathered at the Abdus Salam ICTP in Trieste, Italy, to attend the College on Multiscale Computational Modeling of Materials for Energy Applications. This college had the goal to put together experts in multiscale modeling from the atomistic scale up to the macroscopic continuum. The idea is that multiscale modeling is necessary because of mutual interdependence of processes taking place at very different length and time scales. Therefore, only a multiscale approach is able to provide insight into the effect of microscopic processes on the actual device performance and stability, and to provide understanding and guidance relevant to process and device optimization, also in an industrial context.

The college consisted of theoretical lectures on the computational methods, hands-on sessions to get practically acquainted with techniques and codes, seminars on current materials challenges in the energy sector held by leading experts from academia and industry, and seminars on career development.

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13th ETSF Young Researchers’ Meering (London)


For 13 years now ETSF has encouraged young researchers to take part in the ETSF Young Researchers’ Meeting (YRM). This event which is organised by young researchers for young researchers made its way to London for the first time, as always the high standard of talks encouraged much debate and discussion among the attendees while enjoying all that London has to offer (for a brief moment we had some sun too!!!).

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Probing Potential-Energy Surfaces (PPES IV)


The potential energy surface (PES) is a central quantity in the modelling of materials properties. Ab initio total energy methods like density-functional theory are increasingly used to probe the PES in order to determine not only the equilibrium configurations of particular systems, but also potential energy barriers for certain processes and/or attempt frequencies. The goal of the workshop was to discuss current issues and perspectives in the underlying theoretical concepts and methods, as well as corresponding applications in the fields of heterogeneous catalysis, crystal growth, or biophysics.

After successful meetings in 1994, 1999, and 2005, the workshop stayed within the interdisciplinary tradition of the PPES series and brought together scientists with different backgrounds, e.g. in condensed matter physics, materials science, computational physics, chemistry, and industry. Experts of the field of total-energy calculations, scientists who develop or enhance methods, and those who apply the information gained by these techniques had the possibility to exchange ideas and experiences.

A special focus of the PPES-IV workshop was on big-data-driven materials science, e.g. the Materials Encyclopedia and the development of Big-Data Analytics tools for materials science of the NOMAD Center of Excellence.

pic2PPES Continue reading Probing Potential-Energy Surfaces (PPES IV)

EUSpec Winter School on core-level spectroscopies – Fundamentals and applications of ab-initio methods in spectroscopy


The idea that a two-week school should be held in Slovenia first emerged during the first Whole Action Meeting (WAM 2014) of COST Action EUSpec in Louvain-la-Neuve, Belgium. In compliance with the naming of other action meetings, the school was nicknamed as “EWinS”, standing for “EUSpec Winter School”. The preparations for the school started in spring 2015 and in autumn they became rather intense with many skype calls between the local organizers and Hubert Ebert (action chair), Didier Sébilleau (co-chair), Amélie Juhin as well as other members of the school international committee. The ideas on the table were many and the uncertainties on practical aspects were even more. Let us introduce the context. “EWinS” is the first two-week school organized within the framework of EUSpec. “Being the first” is already a source of concerns. “Being the first” in a small town of 6600 inhabitants in the middle of west Slovenia becomes an epic quest. Fortunately, with the help of volunteers, long and difficult budget plans, creative accommodation and transportation plans, on Monday the 1st of February all trainees were attending the first lecture given by Maria N. Piancastelli. After the coffee break Lucia Reining explained the basis of electronic excitations under a theoretical point of view.


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