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Scientific Report regarding the CECAM Workshop: “Tackling complexity of the nano/bio interface – computational and experimental approaches”

Organizers:   Thomas Frauenheim (University of Bremen)

Qiang Cui (University of Wisconsin, Madison, USA)

Bob Hamers, University of Wisconsin, Madison, USA)

Joel Pedersen, University of Wisconsin, Madison, USA)

Location:       University of Bremen, Germany,

12th June until 16th June 2017

  1. Summary

The workshop “Tackling Complexity of the Nano/Bio Interface – Computational and Experimental Approaches” was held at the University of Bremen, Germany from June 12th to 16th 2017. In total, 72 participants from Belgium, Brazil, Finland, Ireland, Luxemburg, The Netherlands, Portugal, Slovenia, Spain, Sweden, Switzerland, Russia, France, Germany, UK and US attended the workshop.

The programme consisted of 28 invited lectures, one poster session presenting 27 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 27 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 had to stay 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 QM/MM-techniques, nanoparticle synthesis, environmental and health risk management, nanomedicine, etc. attended 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, cecam-mm1p.de and the University Bremen is gratefully acknowledged. 

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

Various sessions were related to the topics (a) nano-bio interfaces and interactions (b) nanoparticle synthesis, (c) nanoparticle-membrane interaction (d) computational analysis of solid/liquid interfaces, (e) multi-scale computational methods, and (f) experimantal characterization of interface properties. These topics are interrelated leading to stimulating discussions between researchers from different fields.

On the technological side, nanotechnology has already led to numerous applications in the areas of batteries, electronics, water desalination, drug/gene delivery, and diagnostics and energy production. Considering these trends, there is little doubt that the impact of nanotechnology will only increase in the future.

Given the tremendous impact of nanotechnology, it is also important to consider the sustainability of nanotechnologies, particularly the potential for nanomaterials to elicit detrimental biological outcomes. The small size and often reactive nature of nanomaterials raise concern about their potential environmental, health and safety (EHS) impacts. This has been realized, for example, from the very beginning of the National Nano Initiative in the US, which encouraged programs that systematically analyze EHS issues of nanotechnology. However, the interactions between nanomaterials and biological systems are complex and involve physical, chemical and biological processes that span broad length and spatial scales. These facets were presented and discussed during the workshop. To properly address the EHS issues of nanotechnology, it is essential to understand the mechanistic details of nanomaterials/biological system interactions; i.e., it is essential to establish causality, rather than correlations, in how nanomaterials impact biological outcomes. Only with this level of understanding can we design the next generation of nanomaterials that are functional yet with minimal deleterious EHS impacts.

The workshop was kicked off with two broad overview talks by the directors of two national centers supported by the US National Science Foundation, A. E. Nel from the UCLA Center of Predictive Nanotoxicology and R. J. Hamers from the UW-Madison Center for Sustainable Nanotechnology. The two talks highlighted complementary strategies to tackle EHS concerns of nanomaterials. The UCLA led center focused on mechanism-based in vitro assays and in silico predictive tools for expedited screening of the hazard potential of broad classes of chemical substances and engineered nanomaterials. The CSN effort led by UW-Madison focused on understanding the molecular transformations of nanomaterials (e.g., metal oxides used for energy storage) under simulated environmental conditions, as well as understanding the potential for these materials to induce toxicity in single-celled and multi-cellular organisms. Nanomaterials can also be introduced into cells in a site-selective manner to enable their participation in desired cell metabolic functions, forming a basis for new tools for biomedicine and biotechnology. Striking examples were given by T. Rajh from the Argonne National lab where photoinduced charge separation in TiO2 was employed to create reactive oxygen species and induce apoptosis in tumor cells.

Synthesis and characterization of nanomaterials for specific properties are essential to both application and mechanistic analyses. Cathy Murphy from UIUC described the synthesis and surface chemistry of gold nanoparticles, and a series of biophysical measurements that quantify the composition and even orientation of biomolecules on the nanoparticle surface; the talk also highlighted opportunities for theory and computations for better understanding several key mechanistic issues concerning the biological exposure to these nanomaterials. Since nanoparticles potentially can perturb cellular redox processes, which in turn may lead to the formation of damaging reactive oxygen species, characterizing the “flat band potential” is essential to describe the electrochemical behaviour of nanoparticles in aqueous biological environments. Lutz Madler described a novel approach based on porous electrode and electrochemical impedance spectroscopy.

Since lipid membranes form a natural barrier between cells and the environment, understanding the interactions between nanomaterials and lipid membranes represents a major topic of the workshop and was covered by two sessions. The studies involved diverse experimental analyses of model membrane systems of increasing complexity (J. Pedersen of UW-Madison), polymeric materials (W. H. Briscoe from Bristol) and interaction of high aspect ratio materials with cells (R. Hurt from Brown). The observations and analyses highlighted the complexity of such interactions and the roles of membrane phase behaviors and mechanical properties. To help tease out physical factors that dictate nanoparticle/membrane interactions, computational studies are highly valuable, as demonstrated by several talks. Electrostatic interactions between charged ligands of nanoparticles and lipids were shown to be important by both atomistic (I. Vattulainen from Helsinki) and coarse-grained (G. Rossi of Genoa) molecular dynamics simulations. More subtle effects were also seen on the lipid phase behavior (L. Monticelli from Lyon and Z. Cournia from Academy of Athens): for example, polypropylene disfavors lipid phase separation, polystyrene stabilizes it, and polyethylene modifies the topology of the phase boundaries and causes cholesterol depletion from the liquid ordered phase. Therefore, different hydrophobic ligands also have major effects on the properties of lipid membranes, which in turn modulate the assembly behavior of nanoparticles on membrane (shown by both Z. Cournia and F. Stellacci) calling for further investigations on model systems and cell membranes. These studies may also shed lights on other problems that implicate assembly of materials, such as biominerialization, as discussed by L. Ciacchi from Bremen.

The complexity of the nano-bio interface calls for the development of novel computational methodologies across different scales. These start with electronic structure methods at the DFT level, which have been well established for molecules but involve significant complications when applied to reactions at solid/liquid interfaces, as discussed by J. Bennett (U. Iowa), A. Gross (Ulm) and M. Sprik (Cambridge) using different examples of metal oxides and surface reactions. To expand the length and time scales of computations of solid/liquid interface, robust hybrid QM/MM models and classical force fields need to be developed, as discussed by Q. Cui (UW-Madison), H. Heinz (U. Corolada) and U. Kleinekathoefer (Jaobs). To further enhance the scale accessible to computations, coarse-grained models that faithfully describe not only structural and energetics properties but also dynamic characteristics are required; initial efforts along this line have been discussed by R. Hernandez (Johns Hopkins). Given the importance of electrostatic interactions to nano-bio interfaces, methods that are able to predict charge of functionalized nanoparticles are required; different strategies were presented by Q. Cui and G. Groenhof (Jyväskylä), and methods for describing other relevant properties such as hydrogen-bonding network of complex proteins (A. Bondar) and charge transport (T. Kubar) were also discussed. Finally, to ensure reproducibility and to minimize technical errors of simulations for complex systems, W. Im discussed recent advances in the popular Web-based tool CHARMM-GUI, which was initially developed for biomolecular simulations but recently extended to treat complex materials and nano-bio interfaces. Ultimately, it is essential to integrate these computational advances with experimental studies to tackle the mechanism of processes at the nano-bio interface; such integration was already demonstrated in several presentations, such as the analysis of metal oxide dissolution (R.J. Hamers and J. Bennet) and peptide/silica interactions (C. C. Perry and H. Heinz).

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

The foremost objective of the proposed workshop was to bring together leading and active researchers who work on nano-bio interactions in both experiment and theory and to discuss about the environmental implications and risks of nanotechnology. Aiming for a focused meeting with 70-80 participants we have stimulated exchange, awareness of challenges, approaches and achievements in the respective fields. Moreover, we emphasize to strengthen the links between experimental and computational groups in this fast-developing field and to interconnect current multi-scale classical and first-principles descriptions.

The workshop became a forum to discuss the particular potential of nanomaterials, to learn about nano-bio interactions and to control the environmental implications of nanotechnology. We have been able to achieve the following key objectives:

  1. On the experimental side, we have invited leading researchers in the area of nanoparticle synthesis and characterization, including those who develop and apply cutting-edge non-linear spectroscopies (e.g., sum frequency and second harmonic scattering) and imaging techniques (e.g., super resolution fluorescence imaging) that provide molecular level information at complex soli-liquid interfaces. Other invite speakers reported about the impact of nanoparticles on both model (e.g., supported lipid bilayers) and actual biological systems. Although the primary focus of the workshop was to understand mechanisms at a molecular level, the program included a number of researchers who characterize the impact of nanoparticles at the whole organism levels (e.g., gene transcription, protein expression, small molecule secretion) to help put the molecular level investigations into proper context.
  2. On the theory/computation side, we have invited researchers who develop techniques that bridge scales from electronic through atomistic to coarse-grained levels. Although many techniques at these three scales have been well developed, how to integrate information at these scales in a robust and smooth fashion is not trivial, and has been discussed widely. Most importantly, we have encouraged discussions between experimentalists and theorists to identify the pressing challenges and opportunities for better understanding processes at the nano/bio interface. We hope we could stimulate new collaborations between two or more research groups that will help answer key mechanistic questions that will impact the design of the next generation of nanomaterials. In the organization of our workshop, we have tried to balance researchers at different stages of their career and from different geographic regions (Europe, the US and Asia).
  1. Infrastructure requirements to make advances in the field

As discussed above, the advancement of theories and computational techniques to describe and understand nano-bio 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 involved with the environment, 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.

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

Progress in the field of nano-bio interactions and interfaces, is fundamental to many European nanotechnology industries connected to high-tech materials design and device applications. Examples are

  • Nanomaterials for energy conversion and environmental waste management
  • Photo-catalytic processes in energy storage and pollutant degradation
  • Hybrid nano/bio-systems for medical applications
  • Nanomedicine and cancer treatment using nanomaterials

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 metaloxide nanoparticles and 2D nanomaterials. 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.

 

July 12th 2017

The Organizers

CECAM_DFG2017RepBioNano

 

Scientific report on “HoW exciting! Workshop on excitations in solids Humboldt-Universität zu Berlin”, Berlin, Germany August 3 – 11, 2016

 

The third Berlin edition of the “HoW exciting! Workshop on excitations in solids” was a very successful event. It took place in the Campus Adlershof of the Humboldt-Universität zu Berlin. The subject of the workshop, namely excitations in solids, is extremely up-to-date, attracting the attention of a vast interdisciplinary community. Technological applications based on excitations in solids are closely interconnected with the fundamental physical mechanisms ruling them. A deep understanding of such basic properties is therefore essential and makes the role of theory crucial in this respect. Assessing the state of the art of the theoretical approaches to address excited-state properties of materials and establishing their link with the most recent experimental observations were the main goals of this workshop, which can be considered successfully achieved.

The even was organized in two main blocks:

  • An international conference, with 17 invited speakers, 12 contributed talks, and a poster session with about 20 contributions. The conference took place on August 3 – 6, 2016. A complete list of the keynote speakers can be found here.
  • hands-on tutorial with members of the exciting developers’ team guiding and supervising the participants to discover the great potential of this code. The tutorial was held between August 7 to August 11, 2016.

The conference included 8 topical sessions:

  • Quasiparticles and Beyond
  • Transport and Spin
  • Spectroscopy
  • Theoretical Methods for Excitations
  • Excitations in 2D Materials
  • Electron-Phonon Coupling
  • Excitations in Photovoltaic Materials
  • Core-Level Excitations

Different aspects of the complex landscape of excitations in solids could be addressed and discussed, from both an experimental and a theoretical perspective. Specifically, the fundamental physical mechanisms ruling the response of materials to an external perturbation were the subject of the sessions Quasiparticles and Beyond, Transport and Spin, Spectroscopy, and Core-Level Excitations. Basic concepts introduced in the keynote lectures were supported by state-of-the-art study cases. In the session Theoretical Methods for Excitations advanced methods for a theoretical description of complex excitation processes in materials were presented, while in the session Electron-Phonon Coupling, the relevant aspect concerning the coupling of different types of excitations was discussed exhaustively. The possibility of tailoring bulk crystals into low-dimensional systems and nanostructures has enormously increased the possibilities to tune the energy range and the intensity of their excitations in view of specific application, as discussed in the session Excitations in 2D Materials. This aspect becomes particularly important in the field of photovoltaics, as discussed extensively in the session Excitations in Photovoltaic Materials.

Electronic-structure-theory methods had a prominent relevance in the workshop. The outstanding power of density-functional theory (DFT) to assess and predict crystal structures and ground-state properties of almost any material emerged in the majority of lectures and contributions. Besides the successes, also the limits of this approach were extensively discussed and analyzed. The treatment of excited-states properties is one of the most apparent failures of DFT. Electronic correlations, van der Waals interactions, electron-hole pairs, and out-of-equilibrium phenomena indeed require theoretical treatments that go beyond a mean-field approach. The increasing complexity coming naturally with advanced methods such as time-dependent DFT, dynamical mean-field theory and many-body perturbation theory was extensively addressed during the workshop. A crucial aspect that was extensively addressed in this scientific event is the interconnection between theory and experiment in describing complex excited-state phenomena occurring in solids. Advances in theoretical and computational condensed-matter physics need to be reflected in the novel experimental techniques, in order to give rise to new scientific breakthroughs. This issue emerged naturally during the scientific contributions and the discussions among speakers and participants with such a diversified background, and was carefully considered from both the theoretical and an experimental perspective. These exchanges greatly enriched the workshop as a whole and represented an added value for the participants, which will possibly be reflected in their future research work.

These topics well reflected the state of the art of theoretical and computational approaches to describe excitation processes in solids. This was further complemented by an extended overview about the most recent advances in the experimental techniques to probe and detect complex phenomena on different time and energy scales. At the same time the workshop provided an excellent opportunity to discuss future perspectives in the field of excitations in solids, to go beyond the current status quo in terms of methodologies and applications. The presence of prominent scientists, representing different fields in both theoretical and experimental condensed-matter physics, spontaneously triggered fruitful exchanges also in view of future collaborations.

The hands-on tutorial based on the exciting code reflected all the aspects discussed in the conferences. Participants had the opportunity to put their knowledge into practice with the help of the tutorials of the code. A new release of exciting, named carbon, was published for the workshop.

The audience was very diverse, making the event very lively and stimulating. Among the approximately 70 participants, almost 30 nations were represented. While, on the one hand, this is an indication of the international relevance of the topics addressed in the workshop, on the other hand, such a diversity contributed to large extent also to the lively cultural and scientific exchange that took place during the workshop. One fifth of the oral contributions (including invited lectures) was given by women, who represented 25% of the all participants. This proportion is unfortunately in line with the average under-representation of the female gender in physics and in the other related disciplines.

The social program effectively complemented the scientific one, by promoting further exchange among the organizers, the invited speakers, and the participants. Coffee breaks and meals organized in loco helped socialization and thereby promoted scientific discussions, which contributed essentially to the success of the workshop. For the invited speakers, a social dinner was organized in the relaxing atmosphere of an urban garden downtown Berlin. This was an excellent opportunity to tighten existing scientific connections and foster new collaborations. For the younger participants a Korean Burger evening was organized in parallel.

On the last evening of the hands-on tutorial, as a farewell party, a barbecue took place on beach at the Müggelsee, the largest lake of the Berlin area.

The workshop received a very positive feedback from invited lecturers and attendees. On the last day participants were asked to fill in a questionnaire, answering questions about the scientific merit of the event and its organization. A very positive evaluation was given to the program as well as to the quality of the posters and oral contributions, with a particularly positive emphasis on the merit of the keynote lectures. Lecture slides and tutorial talks are publicly available within the exciting webpage.

 

 

 

 

 

14th ETSF Young Researchers’ Meeting (Tarragona)

In 2017, the ETSF Young Researchers’ Meeting made its way to Tarragona, Spain for the first time. Sunny weather, great food, a beautiful old city and the kind hosts at the Catalan Institute for Chemical Research (ICIQ) provided a fantastic setting for a week of science that will stay in our memory.

The Young Researchers’ Meeting (YRM) of the European Theoretical Spectroscopy Facility (ETSF) is a workshop organised by young researchers for young researchers. Every year, postdocs, PhD students and Master students gather from all over Europe to discuss problems and recent advances in theoretical and computational methods for the study of the electronic and optical properties of materials. The YRM is where you can present your work in progress, float new ideas, and learn from others at your own level – both scientifically and personally. Talks at the YRM are 25 minutes, which gives you enough time to introduce your topic, what you did and, crucially, how you did it. Each session starts with an introductory keynote that provides an overview of the field, introduces the theoretical framework and points out open questions. Continue reading 14th ETSF Young Researchers’ Meeting (Tarragona)

SCIENTIFIC REPORT ON THE “18TH INTERNATIONAL WORKSHOP ON COMPUTATIONAL PHYSICS AND MATERIALS SCIENCE: TOTAL ENERGY AND FORCE METHODS”

18th Total Energy Workshop, ICTP, Trieste (Italy), 12-14 January 2017

Group picture from the 18th Total Energy International Workshop, ICTP, Trieste, January 2017

The “Total Energy” Workshop is held traditionally in Trieste every two years, since 1987. It is devoted to recent advances in computational condensed matter physics and materials science, based on realistic calculations of the electronic structure of complex systems. It has become one of the most popular regular events of the international ab-initio electronic-structure community. The 2017 edition confirmed this tradition, with a large number of participants, lively discussions and, furthermore, with an impressive number of contributed posters. Overview, speakers list, program with the relevant material (Conference Book, abstracts, list of attendees, …) are available on the web page: http://indico.ictp.it/event/7948/overview

Report

The Workshop involved 225 attendees, including Directors, Scientific Committee members, speakers, and selected participants.

Following the tradition of the previous meetings of the series, the Workshop has been structured in thematic sessions with oral presentations by invitation only. The aim was to gather speakers presenting current topics of research of broad interest as well as future research directions for the electronic structure community. The chairpersons introduced each session with a short overview (about 5 min) to set the subject and point out open problems.  The introductions were very useful, especially for those people working on other subjects. In addition, large space was devoted to discussion. This format has been greatly appreciated and contributed to create, most noteworthy, a lively atmosphere.

Selected contributions from participants have been solicited as posters. The large number of selected posters (140) has been a testament of the enthusiastic and active participation of the attendees. Consequently, two large poster sessions have been organized.

In Honor of Walter Kohn

The Workshop included one special Lecture and one entire session in honor of Walter Kohn, Continue reading SCIENTIFIC REPORT ON THE “18TH INTERNATIONAL WORKSHOP ON COMPUTATIONAL PHYSICS AND MATERIALS SCIENCE: TOTAL ENERGY AND FORCE METHODS”

Questaal Hands-On Course

Daresbury Laboratory was pleased to welcome 40 scientists to the “Questaal Hands-On Course” which took place over four days between May 16th and 19th.  The Questaal software suite features the first all-electron GW code and the first implementation of the quasiparticle-self-consistent GW method, which is significantly more accurate and reliable than conventional density-functional methods.  The focus of the course was to introduce these advanced methods to researchers already familiar with electronic structure calculations and to teach them the practical details needed to perform such calculations for materials and systems relevant to their individual research areas.

Read the full workshop report here.

Scientific Report on the “2017 MARVEL/Psi-k/MaX tutorial on high-throughput computations: general methods and applications using AiiDA”

EPFL, Lausanne, Switzerland, 29-31 May 2017

Group picture from the AiiDA tutorial, EPFL May 2017

High-throughput computing (HTC) is emerging as an effective methodology in computational materials science for the discovery of novel materials and the optimisation of selected properties. Its adoption is spreading rapidly at the point that HTC is becoming an essential tool for computational materials scientists.

The aim of the tutorial was to introduce young researchers and more experienced practitioners to HTC, with hands-on tutorials based on the open-source high-throughput platform AiiDA (http://www.aiida.net), complemented by four invited keynote talks to overview the diverse application fields of HTC.

We report here a summary of what has happened.

Continue reading Scientific Report on the “2017 MARVEL/Psi-k/MaX tutorial on high-throughput computations: general methods and applications using AiiDA”

Advanced computing of excited state properties in solids and nanostructures with Yambo – CECAM HQ 24-28 April 2017

Organisers Grüning Myrta, Hogan Conor, Marini Andrea, Molina-Sánchez Alejandro, Varsano  Daniele

Short report

The goal of this school, co-funded by CECAM and University of Luxembourg,  was to provide the participants with the theoretical and computational tools to study the excited properties of advanced materials and nanostructures. In the morning, the students followed lectures on the fundamentals of linear response and many-body perturbation theory together with more technical lectures on the implementation of the theory into first-principles approaches.  During the afternoon sessions (and the Friday morning Continue reading Advanced computing of excited state properties in solids and nanostructures with Yambo – CECAM HQ 24-28 April 2017

Scientific Report on the workshop: “MARVEL/MaX/Psi-k Tutorial on high-throughput computations: general methods and applications using AiiDA”

EPFL, Lausanne, Switzerland, 22-24 June 2016

Group picture from the AiiDA tutorial, EPFL June 2016

High-throughput computing (HTC) is emerging as an effective methodology in computational materials science for the discovery of novel materials. Its adoption is spreading rapidly at the point that HTC is becoming an essential tool for computational materials scientists.

The aim of the tutorial was to introduce young researchers to HTC, with hands-on tutorials based on the open-source high-throughput platform AiiDA (http://www.aiida.net), complemented by three invited highlight talks to underscore the diverse application fields of HTC.

We report here a summary of what has happened.

Continue reading Scientific Report on the workshop: “MARVEL/MaX/Psi-k Tutorial on high-throughput computations: general methods and applications using AiiDA”

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

Organizers:

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

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

The Benasque Center for Science

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

INTRODUCTION
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.
Continue reading 7th School & Workshop on Time Dependent Density Functional Theory: Prospects and Applications