H

Mixed-anion compounds, which contain multiple anionic species in a single phase, such as oxyfluorides and oxyhydrides, have been gathering growing attention as a new platform of materials science [1]. While it is an attracting idea to employ the anionic degrees of freedom for tuning the cation environment, much less is known about mixed-anion compounds than oxides. In particular, understanding and controlling the stable configuration of multiple anions in crystal is one of the most challenging issues. For example, hydrogen atoms are aligned along one direction in some oxyhydrides such as SrVO₂H [2-3], but are randomly distributed in some oxyhydrides such as SrCrO₂H [4]. In this study, we investigate the stable hydrogen configuration in SrVO₂H by performing first-principles calculation of the total energy for several hundreds of possible crystal structures with different hydrogen configurations. In this talk, we will discuss what determines the stability of the hydrogen configuration in this material. References: [1] H. Kageyama et al., Nat. Commun. 9, 772 (2018). [2] F. D. Romero et al., Angew. Chem. Int. Ed. 53, 7556 (2014). [3] J. Bang et al., JACS 136, 7221 (2014). [4] C. Tassel et al., Angew. Chem. Int. Ed. 53, 10377 (2014).