Electride Formation in Ba–P System and the Unexpected Structure Transition of Electrides under Pressure

Abstract

It is believed that the anionic electrons localized in the crystallographic subnanometer space (void, channel, and interlayer) can stabilize electrides and affect their electronic and magnetic properties. However, the influence of anionic electrons on the stability and properties of electrides is not clear yet. In the present work, ab initio evolutionary structure searches, combined with the first-principles calculations, were employed to predict the stable structures of the Ba–P system under external pressures of 0–20 GPa. Among these predicted compounds, Ba5P3 and Ba8P5 were identified as 1D and 0D electrides, respectively. Our calculations proved that anionic electrons dominate the magnetic and electronic properties of Ba–P electrides. Moreover, it is revealed that anionic electrons have two effects on the stability of electrides: the stabilizing effect caused by the attraction of anionic electrons and the surrounding cations in both 0D and 1D electrides and the destabilizing effect caused by the repulsion between anionic electrons in 1D electrides. Upon the applied external pressure, both effects can be weakened in Ba5P3, while only the former effect was weakened in Ba8P5. Therefore, the 1D electride Ba5P3 becomes thermodynamically stable over the 0D electride Ba8P5 with increasing pressure, which is opposite with the previous concept that the low-dimensional electrides are usually more stable than the high-dimensional ones. The finding of this study may shed light on the design and synthesis of new electrides with different dimensions with the assistance of an external pressure.