Computational atomic-scale modelling of materials for fusion reactors

Project reference: 2102

Mitigating climate change is one of the most important humankind challenges at the time. Since the 19^th century, fossil fuels’ global use has increased and dominated world energy consumption and supply. The rapid rise of global energy consumption and the cumulative global CO₂ emissions from burning fossil fuels play a critical role in climate change. Nuclear fusion is one of the most promising alternatives for generating large-scale sustainable and carbon-free energy. Fusion is the process that takes place in the sun and generates enormous quantities of heat and light.

Since the 1950s, researchers have tried to replicate nuclear fusion on Earth, a historically coined process as “building the sun in a box”. However, as one can imagine, the conditions in a fusion reactor are quite harsh. Hydrogen gas in the reactor is heated at a very high temperature (over 10⁸ °C) until it forms a plasma; controlled by powerful magnets, the atoms fuse and release energy. Unfortunately, due to the extreme complexity and conditions required to achieve a controlled fusion reaction, no design has achieved positive net energy gain.

The development of new materials is key to meeting and overcoming nearly all the world’s challenges. The study of suitable materials with the desirable chemical and physical properties to be used on the reactor walls is one of the challenges that still need to be overcome. In examples like this one, where experimental data are not available or difficult to obtain, computer simulations are critically important. Furthermore, the continual development of increasingly powerful computers makes discoveries in materials science more achievable than ever before. In the present project, we will use classical molecular dynamics simulations to study the fundamental properties of metals at the atomic scale. We will study materials that can be potentially used as protective layers in fusion reactors. The outcomes from this study will be key for the further development of more resistant materials to be used in fusion technologies.

Schematics of a plasma in a tokamak (left), polycrystalline tungsten metal structure simulated with molecular dynamics (right) and MareNostrum-4 supercomputer (background).

Project Mentor: Julio Gutiérrez Moreno

Project Co-mentor: Mervi Johanna Mantsinen

Site Co-ordinator: Maria-Ribera Sancho and Carolina Olmopenate

Participants: Eoin Kearney, Paolo Settembri

Learning Outcomes:
Training and experience in a nuclear fusion research project involving numerical modeling. The student will learn how to simulate materials at the atomic scale and realistic conditions using one of Europe’s largest HPC platforms.

Student Prerequisites (compulsory):
Background in Materials, Physics or Chemistry.

Student Prerequisites (desirable):
Experience on scientific programming.
Familiarity with Linux

Training Materials:
http://fusion.bsc.es/
https://fusionforenergy.europa.eu/
https://lammps.sandia.gov/tutorials.html

Workplan:
The candidate will be part of the BSC Fusion group where she/he will work in close contact with the group members and the supervisor. Regular monitoring (daily / weekly) of the work is planned according to the student’s progress and the tasks available.

Work packages (weekly schedule):

1. Introduction to materials for fusion (W1)
2. Training and introduction to molecular dynamics simulations and visualization tools (W2)
3. Introductory problems with LAMMPS code (W3)
4. Simulation of fusion materials with LAMMPS, post-processing, and results analyses (W4-W7)
5. Report writing (W8)

Final Product Description:
The outcomes from the proposed project are key to improve our understanding of the fundamental properties of metals in fusion reactors and will show the possibility of simulating realistic large-scale metallic systems based on molecular dynamics.

Adapting the Project: Increasing the Difficulty:
The range of materials and structures is quite broad, so that the project can be easily adapted depending on the student’s interests and capabilities. The project will evolve from relatively easy tasks which are already of high interest and that can be completed within a few weeks, e.g. formation of single and multiple vacancies in a single crystal bulk metal, towards surface models or polycrystalline structures, which require larger atomic structures with more complex geometries.

Adapting the Project: Decreasing the Difficulty:
In the unlikely scenario that the analyses of dynamic models (time and temperature dependent) get too complicated for the student or require too much time to converge, we can limit the study to static models, from which we can extract already some valuable information like the equilibrium structure or the mechanical properties of the system. Working with static (frozen) models, we can make use of more complex and accurate interatomic potentials, and define real-scale structural models with a limited computing cost. Still, the study on the evolution of mechanical properties upon vacancy formation is an interesting topic and many structures can be analysed within the period allocated to this internship.

Resources:
The molecular dynamics simulations will be run on LAMMPS, which is an open source code. The student will make use of BSC’s in-house resources like MareNostrum supercomputer.

*Online only in any case

Organisation:
BSC – Barcelona Supercomputing Center