Research Projects

2024–2027

Project ID: 24-11388I

Provider: GAČR

Material elastic properties are important for practical application. Nevertheless, for magnetic materials, high complexity emerges because of the coupling of magnetic and elastic properties. The postdoc project of Jakub Šebesta aims at the generalization of the spin-lattice dynamic approach beyond the scope of cubic materials. This model represents a highly efficient scheme to cover magnetoelastic behavior, such as magnetostriction or magnetoacoustic effects. However, the current approach applies only to simple structures. The generalization will allow one to study and explain magnetoelasticity in more complicated compounds and alloys, i.e. providing more useful materials with high application potential. Namely, the generalization of the magnetic terms in spin-lattice dynamic for tetragonal structures is suggested. Further, the derivation of sound wave propagation in lower symmetry is proposed. Finally, the influence of high-order correction in elastic and magnetoelasticity will be considered.

2022–2025

Project ID: 22-35410K

Provider: GACR

Permanent magnets are a key technology for modern society with applications in air conditioning, mobility, and power generation. In state-of-the-art permanent magnets, the atomic-scale defects, like in the grain boundary phase, have the most significant effects on the macroscopic properties (e.g., coercivity). In this project, a quantitative theory of coercivity, in terms of the local atomic structure, the spatial variation of the intrinsic magnetic properties, and the physical micro-structure of the magnet will be studied. To achieve this goal, a unique scheme of simulation procedures will be developed between quantum mechanical calculations, atomic spin dynamics, and micromagnetic continuum simulations. Magnetic properties will, therefore, be newly taken into account on the atomic scale, i.e., with the inclusion of atomic interface defects and grain boundaries. This will avoid the use of former assumptions in the use of magnetic properties from solid phases. This will allow a multi-scale model to be built to determine the magnetic properties of real materials.

2022–2024

Project ID: 22-22322S

Provider: GACR

The recently discovered superconductivity in the nearly magnetic compound UTe2 boosted interest in unconventional superconductors. The results published so far indicate multiple superconducting phases and magnetic ordering induced by applying an external magnetic field and/or hydrostatic pressure. The revealed analogies of the behaviour of UTe2 with the properties of ferromagnetic superconductors URhGe, UCoGe and UGe2 may help develop a unified theory of unconventional superconductivity. The project will bring together experimentalists (Charles University) and theorists (VSB-TUO) to collaborate intensively in a comprehensive investigation of a complex phase diagram of UTe2 and related compounds employing a yet unseen combination of experimental measurements and state-of-the-art theoretical ab initio calculations of thermal expansion, magnetostriction, heat capacity, magnetisation, elastic constants, and electrical transport of unconventional superconductors under multi extreme conditions.

2020–2022

Project ID: 20-18392S

Provider: GAČR

The project dealt with the physical principles that will increase the phase stability region between the immiscibility and melting temperatures using an example of desired alloys with a self-passivation role for fusion reactor vessels. A phase diagram of the W-Cr system was constructed using first-principles methods, and the physical properties (speed of sound, melting temperature, immiscibility region) were determined. Both the phase diagram and these quantities were verified experimentally. Enriching the alloy with transition metals from the sixth period changed the phases’ melting and miscibility. The project’s main idea is to determine the change in these temperatures based on the change in the acoustic branches of the added element’s phonon spectrum (elasticity). Using XRD analysis and RUS measurements of the experimental samples, data was obtained to provide feedback for theoretical modelling to develop an alloy able to withstand a “Loss of Coolant Accident”. Furthermore, a physical model based on the Hubbard Hamiltonian was derived to determine the influence of quantities such as entropy on the behaviour of the immiscibility region.

2019–2021

Project ID: 19-29698L

The project brings together experts in two related fields, numerical analysis and high-performance computing, to jointly develop fast and massively parallel methods for general discretisation of space-time boundary integral equations for the heat equation to enable adaptive mesh refinement in space and time. The developed methods will be based on clustering, which is used for discretisation with a constant time step and a fixed space mesh. To generate adaptive meshes, classical a posteriori estimate methods will be applied. Being memory--intensive, solution of global space-time problems requires the use of computing clusters. However, it also permits space-time parallelisation. An optimised and parallelised code will thus enable full performance utilisation of the existing as well as future supercomputers.