All posts by Damian Jones

Member of the STFC Scientific Computing Department. Based at STFC Daresbury Laboratory, Warrington, UK.

Progresses in NonEquilibrium Green’s Functions VII

With the advent of nanoscale physics and ultrafast lasers it is now possible to directly probe real-time the correlated motion of electrons and nuclei in excited quantum states. In addition, the intensity and profile of the laser field can be tuned to control and manipulate the opto-electronic properties of a wide range of molecules and materials. All these progresses have opened new fields of research like, e.g., molecular transport, nanoelectronics, atto-physics/chemistry, nonequilibrium phase transitions, ultracold atomic gases, optimal control theory, etc.

Experiments are usually carried on large molecules, biological systems and nanostructures whose peculiar dynamical properties are inevitably linked to their atomistic structure. Thus, an ab-initio, time-dependent and quantum-mechanical approach is required for reliable calculations. The aim of this workshop was to gather together many of the most prominent theoretical and experimental scientists to advance our fundamental understanding of matter under extreme nonequilibrium conditions. Particular emphasis was given to many-body methods like Nonequilibrium Green’s Functions Theory (NEGF) and how to combine NEGF with ab initio methods like Density Functional Theory.

Read the full report.

Ab Initio Spin Modelling Workshop

CECAM-HQ-EPFL, Lausanne, Switzerland, 26-28 November 2018

Organizers: Jerome Jackson and Martin Lüders, STFC Daresbury Laboratory, UK

http://www.cecam.org/workshop-0-1549.html

32 speakers and participants took part in the Psi-k, CCP-magnetism and CECAM financed Workshop on the subject of Ab Initio Spin Modelling, which was held at CECAM-HQ, Lausanne, between 26—28 November 2018. The format of the event was designed to foster discussion between groups working on diverse problems in the ab initio treatment of magnetism in solids. Talks of approximately one hour by the invited speakers were interspaced with much lively and enjoyable discussion. The long talks were intended to allow detailed, in depth presentations and this was indeed the outcome. The speakers represented work in quite different methods with electronic structure (e.g., from fully relativistic KKR to perturbation theory based on pseudopotentials/plane waves) – this seemed, if anything, to motivate and promote questions and active involvement by all the participants. Productive discussion also took place during the poster sessions where the quality of the poster presentations was extremely high.

Read the full report here.

CAMD Summer School 2018

The Psi-k sponsored “CAMD Summer School 2018 Electronic Structure Theory and Materials Design” took place in the week August 12-17, 2018 at Strandhotel Marienlyst in Helsingør, Denmark. Thanks to the more than 100 external attentive summer school students and the 15 very helpful invited lecturers, the school was the nice success that we had hoped for. The school taught PhD students from all over the world the basic and more advanced concepts in modern electronic structure theory including ground state density functional theory (DFT), many-body methods materials informatics and machine learning. Emphasis was put on the methodology applied “on-top” of ab-initio calculations which is essential for the computational design of new functional materials.

Read the full report here.

Report on the Psi-k/CECAM Research Conference “Ab initio Spin-Orbitronics”

September 25, 2017 – September 29, 2017
Hotel Promenade, Montesilvano, Pescara (Italy)

Organizers:
Silvia Picozzi (Consiglio Nazionale delle Ricerche CNR-SPIN, Italy)
Stefan Blügel (Forschungszentrum Jülich, Germany)
Ingrid Mertig (Martin Luther University Halle, Germany)

The main purpose of this Psi-k/CECAM research conference (with about 110 participants) has been to highlight the very recent theoretical and computational developments related to the interplay of spin-orbit interaction with electronic structure, magnetism, transport as well as its link to strongly correlated materials and ultrafast currents in diverse materials. We have focused on discussing spin-orbit coupling (SOC) as a means of engendering fundamentally novel physical phenomena in exotic systems. The Conference therefore spanned several research dimensions, ranging from Materials (in the form of bulk compounds, surfaces and interfaces, thin films and heterostructures) to Functionalities (associated with topology, spin-momentum locking, valley degrees of freedom, skyrmions, coupling to electric currents by Berry phases, etc.) to method developments (in terms of dynamical processes in out-of-equilibrium quantum matter, Berry phase physics, etc). A brainstorm about concepts and ideas in a little understood phenomenon, such as orbital magnetization, was carried out under the guidance of Prof. Ivo Souza. While the main focus was on ab initio simulations, a few leading scientists in experiments were invited (Prof. Stuart Parkin, Prof. Claudia Felser, etc) and a strong interface to many-body physics treated on the basis of realistic model Hamiltonians was included.

Read the full report here.

Modern Approaches to Coupling Scales in Materials Simulation

Hotel Jäger von Fall, Lenggries, Bavaria, Germany
Organizers: Harald Oberhofer, Johannes Margraf
Webpage: http://macsims.ch.tum.de

Multi-scale simulation approaches rely on a hierarchy of increasingly accurate and highly resolved methods to capture the different time- and length-scales relevant to a process of
interest. Traditionally, this might involve coupling classical molecular dynamics with electronic structure calculations (QM/MM), or embedding a quantum mechanical system in a point charge
or continuum environment. In this context, the models comprising the individual layers of the multi-scale hierarchy are often unrelated. For instance, the empirical potential and DFT method in a QM/MM simulation are independently defined at the beginning of the simulation. Enormous advances in electronic structure algorithms and hardware now allow first principles calculations to be carried out on a truly massive scale. This leads to a novel perspective of multi-scale models: electronic structure data can be generated with high enough quality and quantity to allow the application of coarse graining and machine learning techniques. Instead of defining
separate physical models at different scales, the electronic structure method directly informs the next layer of the multi-scale hierarchy. The goal of this workshop was to bridge the gap between
traditional, layered multi-scale techniques and the more direct coarse graining and machine learning approaches to the simulation of extended systems, thereby bringing together researchers working on QM/MM or other embedding techniques with those who apply coarse graining and interpolation to electronic structure data in different contexts (e.g. potential energy surfaces, electronic properties, charge transport, rate constants in catalysis) and with different methods (neural networks, Gaussian process regression, kernel ridge regression, splining, etc).

Read the full report here.

CECAM/Marvel/Psi-k School on Path Integral Quantum Mechanics: From the Basics to the Latest Developments

Organisers: Michele Ceriotti, Tom Markland, Jeremy Richardson and Mariana Rossi

Dates: 25 -29 June, 2018

We convened a School on Path Integral Quantum Mechanics at the CECAM headquarters in Lausanne, Switzerland. The school gathered together 17 speakers (11 invited and 6 contributed) and 46 participants affiliated with 15 different countries. We
received a total of 85 applications to attend the school and unfortunately could not accept more participants due to space constraints in the lecture room. This amount of applications, only two years after we had the last school on the same topic, underlines
the growth of the community performing research on the theory and practice of Path Integral (PI) techniques for the atomic-scale modelling of the quantum behavior of materials and molecules.

As in the last school, we explicitly asked the speakers to prepare pedagogic talks aimed at introducing the participants to the methods and simulation techniques to treat imaginary and real time path integrals, for both adiabatic and non-adiabatic dynamics.
Invited and contributed speakers were encouraged to give lectures that explained the methods in great detail, so that the students could benefit the most from the school, even if this was their first contact with path integral methods.

Read the full report here.

Alessandro De Vita

Dear friends,

Many of you will have heard by now the tragic news that our dearest friend and colleague Alessandro De Vita passed away on Tuesday afternoon. Sandro was killed in a motorbike accident while going to the airport. Commuting between Trieste and London, two most beloved cities for him, was part of his life – a life that he lived so fully.

We have received an outpouring of grief in the last two days that is a testament to how much loved he was, and how strong was his impact in the life of the people that met him – his sharp intelligence, his infinite knowledge, his surprising imagination, his unbridled talk, his mischievous and deeply generous spirit all stood out. And most of all, his passions in life – the friends, the science, the music, the poetry.

Psi-k and CECAM, to which Sandro gave so much, will think of public ways to celebrate him, and any suggestion would be most welcome. If you wanted to dedicate some of your thoughts to him, he would have had a few suggestions himself. Light a candle, somewhere. Say a prayer. Listen to Glenn Gould play the 25th Goldberg variation – he always said that it contained all the sorrow of the world.

We are all with you, Sandro – with Christine, with your family, with your friends.

Atque in perpetuum, frater, ave atque vale.

Psi-k and CECAM

https://www.cecam.org/devita.html

8th School and Workshop on Time-Dependent Density-Functional Theory: Prospects and Applications

August 20th-31st, 2018
Benasque Center for Science “Pedro Pascual”, Benasque, Spain

http://www.benasque.org/2018tddft/

Organizers: Angel Rubio, Eberhard K. U. Gross, Miguel A. L. Marques, Neepa Maitra, Alberto Castro

There are many alternative schemes to approach the time-dependent, out-of-equilibrium, many-electron problem. Time-dependent density-functional theory (TDDFT) has a significant “market share” due to the same reasons that make conventional ground state density-functional theory (DFT) a successful scheme: the fairly good predictive power at a moderate computational cost. As a consequence, its use has quickly grown, and its reliability for many purposes has been sanctioned by many applications and benchmarks over the years. As the computational resources increase, however, various alternatives such as advanced post-Hartree Fock multi-configuration schemes or many-body perturbation theory techniques can be applied to larger systems, and may provide more precise results. Newer and more intriguing possibilities, such as the direct solution of the many-electron Schrödinger equation with quantum computers, and the use of machine learning techniques for the prediction of many properties, appear also in the horizon. It is therefore necessary to review the capabilities and perspectives of TDDFT. This is the main goal of the Workshop, and of the School that we organized immediately before the Workshop.

This School+Workshop event is in fact a new iteration of a series dedicated to TDDFT, that started in 2004. It takes place every two years, a periodicity that we feel that is adequate to follow the advances in the topic. However, it always takes place in Europe, and there was a strong demand for a similar event taking place in the US, due to the difficulties in the travel, specially for students and young researchers. Fortunately, the demand was met in the last year by a similar event (a school on TDDFT followed by a workshop on first principles approaches to the electronic excited states problem) that took place in Telluride, Colorado. Part of the organizers of this event were also present in Benasque, and the goal is to periodically repeat the US event, also every two years if possible. It should be noted, also, that a similar event is being planned in Asia (Tsukuba, Japan), by Prof. K. Yabana.

You can read the full workshop report here.