Interrelation of Work Function and Surface Stability: The Case of BaAl4

The relationship between the work function (Φ) and the surface stability of compounds is, to our knowledge, unknown but very important for applications such as organic light-emitting diodes. This relation is studied using first-principles calculations on various surfaces of BaAl 4 . The most stable surface [Ba-terminated (001)] has the lowest Φ (1.95 eV), which is lower than that of any elemental metal including Ba. Adding barium to this surface neither increases its stability nor lowers its work function. BaAl 4 is also strongly bound. These results run counter to the common perception that stability and a low Φ are incompatible. Furthermore, a large anisotropy and a stable low-work-function surface are predicted for intermetallic compounds with polar surfaces.