An interplay of sulfur and phosphorus at the γ-Ni/γ′-Ni3Al interface

• Site preferences of S and P are scarcely affected by one another.
• A favorable duplex doping is to form a substitution–interstice atom pair.
• Cleavage fractures occur in the region between S-doped and P-doped layers.
• Extra heterogeneous dopants further aggravate S- or P-induced embrittlement.
• Aggravation mainly originates from repulsions between P-doping and S-doping.

A first-principles investigation of the interplay of S and P and their role on the cleavage rupture of γ-Ni/γ′-Ni3Al interface is conducted. Trace elements S and P can coexist in the γ-Ni/γ′-Ni3Al interfacial region and their site preferences are scarcely changed by another heterogeneous element. S and P in duplex doping systems tend to simultaneously replace for a Ni and occupy an octahedral interstice adjacent to substituted sub-lattice site to form a doping atom pair, but the interaction between S-doping and P-doping varies with their distributions along or across the interfacial layer. The cleavage fracture of duplex doping interfaces generally occurs in the region between S-doped and P-doped atomic layers, and an extra heterogeneous dopant will further aggravate S- or P-induced embrittlement. It is revealed a strong repulsive interaction between P-doping and S-doping is responsible for the descent of cleavage fracture strengths caused by extra heterogeneous dopants.