Structural exploration of holmium fluoride selenide (HoFSe): theory and experiment

Rare-earth metal (RE), and in particular holmium (Ho) based materials have received considerable attention due to their scientific and industrial applications. While rare-earth metal fluorides and rare-earth metal selenides have been studied for a long time for various applications, as well as their very interesting electronic properties, optical properties, and superconductivity, Holmium selenides and holmium fluoride selenides have only been recently investigated. An exhaustive study of the holmium fluoride selenide (HoFSe) was performed using a multidisciplinary approach, providing fundamental research in this chemical system. Three polymorphs of HoFSe were synthesized through high-temperature experiments and characterized using single-crystal X-ray diffractometry (SCXRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. Energy landscape exploration and crystal structure prediction (CSP) were performed using global optimization (GO) and data mining (DM) based searches, followed by local optimization using density functional theory (DFT), resulting in alternative crystal structures at non-equilibrium conditions as a function of pressure and temperature. We believe this study provides a unique perspective and complete picture of the structural features of HoFSe which will enable future investigations of properties and applications.