The arrangement of atoms in a solid, its crystal structure, is of key importance for its chemical and physical properties. This includes type of atoms are present, their relative positioning, are they fixed or can some become mobile as temperature is increased? In particular, for novel compounds not earlier studied, or to classes of materials where current insight is limited, it is desirable to gain insight in composition - structure - property relations. This is a fundamental basis in the search for better materials for technologies. The current proposal addresses such issues for a less studied class of materials, hydride oxide, that may find applications in electrochemistry (batteries for instance) or in fuel cells for energy conversion. The main objective is to learn how the two different types of anions, hydride and oxide anions, are distributed and move in the solid compound.