A combined DFT and AIMD study: The effect of nitrogen on Tobermorite9 Å

Abstract

Through the ab initio molecular dynamics (AIMD) and density functional theory (DFT) calculation, the research on the N atom and N 2 molecule on the Tobermorite9 Å (0 0 1) surface is conducted. The findings demonstrate that the most constant adsorption position for the N 2 molecule is the top location of the Ca 5 atom. Electrons are (a) lost by the Ca atom and (b) gained by the N atom, according to the charge density difference results. Then, outcomes from the partial density of states highlight that the formation of an especially weak Ca-N bond resulted from the imperceptible orbital hybridization between the N-p and Ca-d orbitals. Among the upper atoms, the deformation of the calcium atom in the Z direction is the largest, and the value is 0.02341 Å. At 1473 K, the AIMD results show that the N 2 gradually develops from adsorption to desorption on the surface. The adsorption of N 2 molecule on the surface is a physical adsorption. Nitrogen produces elastic deformation on hydrated calcium silicate. These findings provide profound views in understanding the N 2 on hydrated calcium silicate. • The most constant adsorption position is the top location of the Ca 5 atom. • Electrons are lost by the Ca atom and gained by the N atom. • The PDOS highlight that the formation of an especially weak Ca-N bond. • Nitrogen produces elastic deformation on hydrated calcium silicate. • N 2 develops from adsorption to desorption on the surface at AIMD simulation.