Fig. 5: DFT calculations.
From: Mechanochemical ammonia synthesis enhanced by silicon nitride as a defect-inducing physical promoter
a N2 dissociation energy diagram of the Fe(110) and Si3N4/Fed surfaces. b Free energy changes of the N* hydrogenation to ammonia on the clean Fe(110) surface, a Si3N4 cluster on Fe surface (Si3N4/Fe), and Si3N4 cluster on defective Fe (Si3N4/Fed). Optimized geometries of N*, NH*, NH2*, and NH3* on the three different catalyst surfaces are shown with the graph. Color code: Fe—tan, Si—blue, N—light blue, and H—pink. c Comparison of the H* diffusion on the Fe(110) and Si3N4/Fed surfaces. d 2D activity heatmap describing the turnover frequency (TOF) from N* into ammonia.
