Structure and stability of α- and β-Ti₂Se. Electron diffraction versus density-functional theory calculations

The α structure as well as the new β modification of Ti₂Se were recently characterized by electron diffraction structural analysis of nanosize crystallites. In this study, both structures are investigated by means of total energy calculations within the non-local density-functional theory in order to validate the experimental results. The calculated parameters for both modifications are in excellent agreement with data determined from electron microscopy. From the calculated equation of states, β-Ti₂Se is predicted to be a high-pressure modification. The present investigation proves by a well established non-crystallographic method that unknown structures, which are not accessible by other standard crystallographic techniques, can be solved and refined with high accuracy using electron diffraction data.