Stability and electronic structure of the Co–P compounds from first-principle calculations

First-principle calculations based on density functional theory (DFT) were performed to investigate the structural stability and electronic properties of Co–P compounds such as Co2P(I) (orthorhombic), Co2P(II) (hexagonal), CoP, CoP2 and CoP3. The cohesive energies of Co–P compounds are all negative, which indicates that they are thermodynamically stable. Furthermore, the stability of Co–P compounds decreases with the increase of P element. By analyzing the electronic structures of Co–P compounds, we have found that Co2P(I) (orthorhombic), Co2P(II) (hexagonal) and CoP show metallic character, while CoP2 and CoP3 show semiconductor character. The bonding behaviour between Co atom and P atom in Co–P compounds is a combination of covalent and ionic nature.

Research highlights▶ The stability of Co–P compounds will decrease with the increase of P element content, and CoP3 has the worst structural stability. ▶ Co2P(I), Co2P(II) and CoP exhibit metallic character while CoP2 and CoP3 show semiconductor character. And the increase of P content could impair the electronic conductivity of Co–P compounds. ▶ It can be concluded that the bond between Co atom and P atom is a mixture of covalent and ionic components.