We mediate efficient utilization of our leading national supercomputing infrastructure in order to increase the competitiveness and innovation of Czech science and industry. IT4Innovations primarily provides computational resources to researchers and academics from the Czech Republic as part of the Open Access Grant Competition. Within this competition in the years 2013-2020, 902 projects with a total of 1,027 billion core hours have been supported so far with the overall demand for the computational resources exceeding 1,404 billion core hours in this period (a core hour = one processor core per hour).
Computational resources allocated within the Open Access Grant Competitions in 2020 by scientific disciplines [%]
Computational resources allocated within the Open Access Grant Competitions in 2020 by institutions [%]
selected projects from 22nd open access grant competition
Photoexcited electrons in the complex structures of carbon dots
Call: 22nd Open Access Grant Competition; OPEN-22-11 multiyear
Researcher: Michal Otyepka
Institution: Palacky University Olomouc
Field: Material Sciences, 3 000 000 core hours
Carbon dots have only recently been discovered, yet today they represent one of the most intensively studied nanomaterials. Indeed, their excellent photoluminescence properties predestine them for a variety of applications ranging from LED light sources to biological imaging and medical diagnostics to chemical catalysis. This is also due to the fact that they are easy and cheap to prepare as well as they are stable and non-toxic. However, carbon dots are very reluctant to reveal their secrets, which makes it difficult to design them rationally and to optimise their properties in a targeted manner. Computer simulations are among the useful tools of the modern chemist, as they allow to answer questions that are very complicated for experiments. Simulations have been used for several years to understand the behaviour of carbon dots by the group led by Michal Otyepka. Thanks to the computational resources they have gained on IT4I computers, they will be able to study the mechanism by which a carbon dot absorbs light radiation, how the absorbed energy propagates through the dot structure, and how and why it is emitted. The scientists anticipate that if they understand this mechanism, it will allow them to target the design of carbon dots and expand their applications.
Accelerating particles to relativistic energies has become one of the most studied branches of physics over the past century. Conventional accelerators are nowadays very expensive to build, mainly because of their large size. Plasma accelerators can solve this problem. Using them, a wave with a strong electric field is excited in the plasma (ionised gas) by very intense laser pulses. Electrons are trapped and accelerated. On the plasma wave they behave like a surfer on a wave in the water. This technology allows for an acceleration length 1000 times smaller than conventional accelerators and therefore accelerators can be much more compact. Electrons emit intense X-ray flashes as they move through the plasma wave. Using sophisticated computer simulations, we are able to design experiments that help improve the quality of X-ray beams. This allows us to move plasma accelerators closer to practical applications such as studying the dynamics of processes occurring on femtosecond scales, such as chemical reactions and phase transitions as well as improving medical imaging techniques.
Computational modelling of fast ion orbits in tokamak plasmas
Call: 22nd Open Access Grant Competition; OPEN-22-34
Researcher: Fabien Jaulmes
Institution: Institute of plasma physics, Czech Academy of Science
Field: Physics, 1 000 000 core hours
Nuclear fusion technology might enable us to generate energy without releasing large amounts of greenhouse gases into the atmosphere or leaving behind us long lived radioactive waste. The tokamak concept involves the use of magnetic fields to confine plasma hot enough to sustain fusion within itself. Today, as a part of international project under the title ITER, a new tokamak is built in southern France. If successful, the device would be the first one of its kind to produce net energy.
Future fusion power plants will rely on self-heating by fast 3.5 Mev Helium particles generated by the fusion reactions. They will also rely on additional heating by neutral beam for current drive and stability optimization. The study of the physics of the fast ions in current-day devices is paving the way for optimum operation and design of future power plants.
Thanks to detailed computational modelling  based on the equation of motion and collisional cross sections, we can improve our understanding of the physics of the fast particle and describe the distribution of heating in the tokamak and the losses of the energetic particles: there is concern that fast ions could cause damage to plasma-facing components.
COMPASS Upgrade will be a large magnetic field (5 T) tokamak that will allow the scientific investigation of various physics issues related to the operation of the future ITER. In particular, an 80 keV Neutral Beam Injection (NBI) system is planned to heat up the plasma with 4 MW of external power. The study and modelling of NBI-born particle behavior might influence the future design of the experiment. In the COMPASS Upgrade experiments, a great opportunity will arise to study the interaction of the fast ions with the edge plasma.
An illustration of the improvement of the understanding of the edge physics enabled by the computational modelling is given in the figure below. We show the impact of the plasma density and temperatures profiles in the edge (Scrape-Off Layer or SOL) region on the losses of the fast ions originating from the NBI for various orientation of the beam (tangency radius or Rtan).
Figure from : Left: kinetic profiles used to mimic the absence (green) or existence (red) of an SOL density shoulder in COMPASS Upgrade (scenario modelling F or #13450). Right: assessment of NBI losses for a total of 1 MW of injected power: the shoulder (red curves) reduces the Charge-exchange (CX) losses for all injection geometries but increases slightly the ion losses at perpendicular injection (Rtan < 30 cm). Overall, the density shoulder will be beneficial for the NBI performances.
 F. Jaulmes et al 2021 Nucl. Fusion 61 046012
Magnetostriction is a physical phenomenon in which the process of magnetization induces a change in the shape or dimension of a magnetic material. Magnetostrictive materials are widely used in many technological applications like sensors (torque sensors, motion and position sensors, force and stress sensors) and actuators (sonar transducers, linear motors, rotational motors, and hybrid magnetostrictive/piezoelectric devices) where a high magnetostriction is required. Recently, we developed the program MAELAS [(version 1.0) P. Nieves et al., Computer Physics Communications 264 (2021) 107964, (version 2.0) P. Nieves et al., Computer Physics Communications (2021) 108197] to calculate magnetostrictive coefficients in an automated way. Presently, we are using MAELAS in IT4Innovations supercomputers to search for novel magnetic materials with high magnetostriction.
Thermal properties of Cerium Titanides
Call: 22nd Open Access Grant Competition; OPEN-22-18
Researcher: Andrzej Kadzielawa
Institution: IT4Innovations, VŠB-TUO
Field: Material Sciences, 3 457 000 core hours
Our industry is still based on steam. In coal, gas, and nuclear power plants, the water produces electricity, the fuel used to heat it up. The reader, an astute person obviously, already sees significant problems: (i) carbon emissions; (ii) safety. Whilst emitting almost no CO2, nuclear energy has regrettably become loathsome after the Chornobyl and Fukushima incidents. Although the design of reactors based on fission (splitting atom nuclei into two or more particles, releasing excess energy) was significantly improved, there is another way. A clean way: Thermonuclear Fusion Reactors. The idea is simple: to reproduce the same process that a star does to produce energy. Fusion of two Hydrogen (H) atoms into Helium (He), c.f. .
In other words, we heat our steam engine with a small, artificial sun. Some of these devices are already operating (one in Prague ), yet there are still many engineering problems to solve. One of them is siphoning the radiating heat of plasma (temperature ~200 000 000 ℃, confined in the strong magnetic field) to water, i.e., a wall. While there is no possibility of an ecological catastrophe, the device itself can be damaged in an accident. Thus, the material for the reactor wall must withstand the so-called fail-safe scenarios.Trivializing, we have to consider the bombardment of our material with ions, atoms, and molecules of hydrogen (and its isotopes). Horse sense tells us that the wall should be hard, the classical physics, that the atoms it is built from should be heavy. These points provide a starting point: Tungsten (W) - a heavy yet stable and inexpensive element with high hardness. Unfortunately, while the performance in a vacuum is excellent, Tungsten is explosively oxidizing when exposed to the air. Therefore, coating the wall is out of the question, as a film might disrupt the heat conductivity can be easily damaged by plasma.
The next logical step is to create an alloy of Tungsten with a small addition of an element that (i) has an oxide that does not allow oxygen molecules to pass (making a make-shift, self-healing coating); (ii) is oxidizing at least as fast as Tungsten. Conveniently, adding ~10 % of Chromium (Cr) does precisely that. The story does not end here, as there is a new problem - W-Cr alloys slowly but steadily diffuse into a mixture of two: W- and Cr-rich grains. Our work is to find a third stabilizing element (X) of the W-Cr-X alloy slowing (or ideally stoping) the diffusion.
The first step of computational modelling is to reproduce the problem. The approach we chose is to describe an alloy as a quantum-mechanical system of electrons and ions, then use the outcome to build a statistical model. First, we create our building blocks using the Density Functional Theory (DFT [3,4]) by calculating the electronic behaviour on the lattice of Tungsten and Chromium atoms. The outcome charge distribution (Fig. 1) allows us to understand the electric and heat conductivities change with composition and the impact of lattice shape on vibrations of the ions in the lattice. We first use the IT4Innovations clusters to generate the Special Quasirandom Structures  (Fig. 2): the distributions of atoms in a finite cell, reproducing the alloy randomness in the best possible way. Then, the bulk of calculations occurs: we obtain each cell model's electronic and dynamic behaviour using the Vienna Ab initio Simulation Package (VASP ) by minimizing its energy (E). Then, having a representative set of states (a part of the statistical ensemble - set of all possible realizations), we can incorporate temperature (T). Intuitively it is not a big deal, but in reality, the temperature is anything but ostensible. In physics, it is a single parameter that describes the kinetics of the elements in a model (e.g., the average kinetic energy of gas particles). While it is rather inconvenient in understanding, it is useful to treat temperature as an intensive variable (non depending on the number of particles) coupled with extensive entropy (S) - the measure of disorder in the system. What is and how to describe, calculate, and understand entropy is a topic on a separate article (or a book); let us assume now that we can calculate it for each of the states calculated using VASP. Here, minimizing the so-called Free energy (F = E - S×T), we find the optimal state of each composition of elements in each temperature.
Completing the procedure described in the paragraph above for different X in W-Cr-X gives us information on the stability and properties of these alloys and whether it makes sense to synthesize them in a lab. Following this approach, we recently published promising results on Tungsten - Chromium - Hafnium (Hf) systems .
This project is a part of a GAČR standard grant No. 20-18392S Tailoring thermal stability of W-Cr based alloys for fusion applications.
 wikipedia.org, Fusion power, https://en.wikipedia.org/wiki/Fusion_power
, accessed 1 November 2021.
 COMPASS, Institute of Plasma Physics of the Czech Academy of Sciences, Prague, http://www.ipp.cas.cz/vedecka_struktura_ufp/tokamak/COMPASS
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