This proposal is for the continuation of the current project: Atomic scale studies of physical-chemical properties of materials for energy applications (NAISS 2024/5-593). Our research with NAISS resources is based on advanced quantum mechanical modelling within the framework of Density Functional Theory (DFT), including method development and benchmarking, to generate large amounts of high-quality data on materials essential to energy production and storage. This project includes the following main research topics: 1. Copper Containment Barrier: A significant effort is underway to model the physical-chemical properties of the copper containment barrier, essential for the Swedish spent nuclear fuel repository's safety assessment. This encompasses chemical reactions (water, sulfide, hydrogenation) of copper surfaces and bulk material; studies of grain boundary structure, impurity distribution, and performance effects of impurity accumulation at defects; and advancing to the study of impurity diffusion within the copper grain boundaries. 2. Accident-Tolerant Fuel: This research models the diffusion of volatile fission products in Uranium Nitride (UN), a Generation IV accident-tolerant fuel. The study analyses the distribution and diffusion of fission products in the UN matrix, accounting for inherent defects. This data is critical for understanding fundamental mechanisms, validating experimental diffusion constants, and informing safety evaluations. 3. Radioactive Iodine Capture: This research focuses on modelling the capture of radioactive iodine using cellulose-based materials to enhance absorption methods, addressing accidental radioactivity releases. Iodine is a highly concerning radioisotope due to health and environmental effects. This work aims to study the atomic-scale mechanisms governing interactions between iodine and the capture materials. The data will improve capture materials and strategies. 4. Magnetism in Uranium Materials: This involves modelling the magnetic properties of uranium carbide and uranium nitride by studying the fundamental phenomena responsible for magnetism in these materials. The study requires using advanced DFT and beyond-DFT methods in non-collinear implementations to scan through various magnetic configurations within both the bulk material and at defect sites. 5. Photocatalysis: Semiconductor catalysts. The surfaces and structural properties of these materials will be studied for harvesting light and driving chemical reactions that can be used to convert water and biomass molecules to solar fuels and hydrogen. These investigations involve accurate studies of structures, energies, and chemical bonding using quantum mechanical modelling primarily at the DFT level. To generate realistic data, these DFT investigations must utilize periodic, large supercells to accurately account for defects and other low-symmetry structural features inherent to the complex materials being studied. The core objective is to study the mechanisms and fundamental physical-chemical properties of these important materials. The resulting data will be employed by us and other scientists who study material performance, validate experimental methods, and further develop systems where these materials operate. The project NAISS 2024/5-593 has generated important data that resulted in several important published reports and manuscripts in preparation (please see the project report). The project was essential for the continuation of two SSM funded projects and one SKB project through 2026.