b'CONDENSED MATTER PHYSICSAND MATERIALS SCIENCEDOE defines the condensed matter physics and materials science core capability as the ability to conduct experimental, theoretical, and computational research to fundamentally understand condensed matter physics and materials sciences that provide a basis for the development of materials that improve the efficiency, economy, environmental acceptability, and safety in energy generation, conversion, transmission, and utilization. INLs condensed matter physics and materials science capability focuses on developing a comprehensive atomic-to-bulk understanding of material behavior in extreme environments. The fundamental interactions and mechanisms discovered through this capability are key computational science parameters for advanced modeling and simulation of nuclear materials.Of the 14 projects in this report that support condensedResearchers study fuelsmatter physics and materials science, this core capabilityfor molten saltreactors.was the primary focus of the five projects in this section. Researchers studied phase stability and high temperature phase transition of yttrium titanium oxides, magnetic orders and spin-orbit coupling effects on defect formation in uranium dioxide, a uranium-zirconium phase diagram correction, electronic correlations and topology in neptunium telluride, and thermal properties of ceramic fuels, Projects highlighted in other areas of this report used this capability to study microstructural evolution in metallic fuel pins, metal hydride moderators in microreactors, nanostructures of uranium based metallic fuels, corrosion mechanisms in chloride molten salts, and other areas relevant to INLs mission.134'