The purpose of this project is to (i) investigate the impact of impurities and transmutation products on the mechanical and fracture mechanical properties fusion reactor materials, (ii) investigate the impact of phosphine gas exposure on mechanical properties of cemented carbides and (iii) investigate how the isotope variation affect the thermal scattering laws for LiH. The first project is a collaboration with the ICAMS-group (at Ruhr-University, Bochum) in which we aim to use classical and quantum mechanical modelling to probe the effects of transmutation elements on the grain boundary strength of tungsten alloys. Owing to the fact that empirical potentials for tungsten (W) are notoriously difficult to generate, with severely limiting transferability and predictability, our aim is to generate a machine learning potential for W within the atomic cluster expansion (ACE) formalism, which can be expanded to the ternary W-Re-Os and binary W-He systems to enable classical modelling with close to ab initio accuracy. This requires the systematic establishment of a large database comprising DFT data that covers a large range of low to high coordination configurations and accounts for different local bond orders. The potentials will be used (i) to explore the role of precipitation hardening on the brittle to ductile transition of W while in operation and (ii) to model the formation of helium bubbles and their impact on the grain boundary cohesion. The second part of the project we aim to create an ACE potential for the W-C-Co-P system to investigate how the exposure of phosphorus affect the melting temperature for Co and Co wettability on WC. This aims to investigate the prospect of introducing organic alloying elements to reduce the melting temperature to facilitate the sintering of cemented carbides. To this end we will generate an ACE potential and model the phenomenon using molecular dynamics modelling. The parametrization of ACE potentials requires systematic fitting to large DFT databases meticulously designed to cover the full descriptor space. For the current project this poses two challenges. The first is that P has several morphologies with only subtle energy differences, whose relative stability is largely governed by van der Waals (vdW) interaction. The second is that modelling of Co requires spin-polarized modelling. For the final part of the project, we are particularly interested in probing the vibrational properties hydrides (LiH). Because of the difficulty to reproduce experimental hydrogen phonon spectra using conventional force-constant methods, we need to use ab initio molecular dynamics (AIMD) modelling to probe the dynamics of the system. Specifically for LiH, due to the low mass, we most likely have to resort to path integral approaches, which are expected to be numerically costly. For the TSL generation, we have established a collaboration with another research group at Los Alamos and a group at Idaho National Laboratory. We have expanded the group with one PhD student since the last proposal. Thus, we apply for a larger allocation this time.