High temperature crystal structure prediction from ab initio molecular dynamics with SLUSCHI

Most properties of crystalline materials are closely associated with their structures. The theoretical prediction of crystal structures at finite temperatures is a formidable task, but significant progress has been made recently. In this work we employ the open source SLUSCHI (Solid and Liquid in Ultra Small Coexistence with Hovering Interfaces) package interfaced with the first-principles VASP code for prediction of high temperature structures from ab initio molecular dynamics. The approach is tested by prediction of the stable and metastable phases for tungsten (W) and titanium (Ti) and by analysis of high temperature and high pressure phases of Y ₂O ₃. The high temperature phase of Y ₂O ₃ is stable for 100 K below the melting temperature (2712 K). It is proposed to possess either cubic or hexagonal symmetry but has never been experimentally refined due to the low quality of high temperature diffraction data. The prediction with SLUSCHI indicated that Y ₂O ₃ crystallizes from the melt in hexagonal structure, with the P6 ₃/mmc space group. The refinement of Y ₂O ₃ high temperature synchrotron diffraction data using predicted coordinates produces realistic atomic displacement parameters, corroborating fast oxygen diffusion evident from computations. These findings demonstrate the efficacy of our computational method in predicting material behavior across a wide range of conditions, supporting the development of new ultra-high temperature materials.