Theoretical study of Fe-based biomimetic complexes interaction with nitrogen and hydrogen: energetics, QTAIM analysis, and the performance of xTB

Abstract

Nitrogen and hydrogen binding in three types of Peters systems (borane, alkyl, and silyl) is investigated in this work. Peters systems are studied in the perspective of an environmentally friendly ammonia synthesis alternative to the Haber-Bosch process. The problem that lowers the effectiveness of the Peters system-based catalysis is the poisoning of the catalyst itself, due to hydrogen evolution reaction. Herein, we examine how nitrogen and hydrogen molecule interact with the Peters systems using density functional theory (DFT), QTAIM analysis, and xTB methods. The energetics of the interaction and reaction, bond distances, and QTAIM parameters are considered. The xTB method is used for geometry optimization and is compared with the results of the DFT method. It is found that the xTB H0 Hamiltonian tuning needs to be employed to improve performance of this approach when compared against DFT (e.g. to avoid the dissociation of the H-H bond).