C) from first principles study*

Gd₂C is one of the famous electrides. We investigate the electronic properties of few-layer Gd₂C that is one of the two-dimensional (2d) electrides. We focus on anionic electrons at the interstitial space. In this study, we employ the Vienna Ab Initio Simulation Package (VASP). The wave functions were expanded using a plane-wave basis set. We presented the electronic properties of the monolayer to the pentalayer of Gd₂C. Moreover, we study the effect of interstitial anionic electrons and surface, compared with bulk state Gd₂C. We also calculate the work functions of the few-layer Gd₂C structures to investigate the layer dependence. The monolayer and the pentalayer have the work functions of 3.426 and 3.350 eV, respectively. Interestingly, the Gd₂C has a lower work function than Y₂C. This tendency of the work function seems to be related to the localization of the electrons in the interstitial space. In other words, the anionic electron density in the interstitial space of Gd₂C is more delocalized than in the case of Y₂C. Finally, we study the response of Gd₂C to the external electric field.