Study of the effect of rare earth elements X(Pm, Ce, Pr, La) on the modification of NbN/Fe interface using first-principles calculations

This study presents an investigation of the basic properties of bulk phase NbN and bulk phase Fe as well as the impact of doping with rare earth elements (Pm, Ce, Pr, La) on the degree of bonding at the NbN/Fe interface using first-principles calculations. For each low-index surface of the two bulk phases, calculations were performed and analyzed. Based on the analyses, the selected NbN (211) and Fe (110) surfaces were then combined as the most suitable interface. The analysis reveals a reduced N-Nb bond length at the interface, with an attachment work of -0.21292 J/m2 for the NbN(211)/Fe(110) interface. Furthermore, the interfacial energy is 0.89769 J/m2, and the combination of the two leads to a tighter bonding at the interface. The four rare earth elements are doped into the interface, and the calculation results of the rare earth element atom substitution for Nb are as follows: gamma-Ce is -5.02865 J/m2, gamma-Pr is -3.91418 J/m2, gamma-Pm is -4.65489 J/m2, gamma-La is -4.95645 J/ m2; the rare earth element atom substitutions for Fe are as follows: gamma-Ce is -5.12654 J/m2, gamma-Pr is -6.59452 J/ m2, gamma-Pm is -4.98143 J/m2, and gamma-La is -5.01213 J/m2. The addition of the four rare earth elements can bring the interface closer. Furthermore, substituting rare earth elements for Fe atoms considerably enhances the interface. Notably, the lowest value of doping formation energy is -0.12086 J/m2, which is observed when Pr replaces Fe, and the lowest value of doping solvation energy is -3.08754 eV. Among the four rare-earth elements, replacing Fe atoms with Pr demonstrates the most significant enhancement of interfacial bonding.