Investigating Chlorination and Migration Mechanism of NaCl on C−S−H: DFT and AIMD Study**

Abstract

The present study investigates the chlorination and migration mechanism of Tobermorite9 Å through the use of density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD). The findings reveal a negative adsorption energy value of À 2.19488 eV. The results of the charge density difference analysis reveal that the Ca atoms experience electron loss, while the Cl atom undergoes electron gain. The O atom situated at the end of the silicate chain (and silicate chain bridge) exhibits electron gain, and the Na atom experiences electron loss. The results of density of states (DOS) and partial density of states (PDOS) demonstrate that the CaÀ Cl bond was created as a result of the interaction between Ca and Cl orbitals. The evident overlaps between Na-p and O24-p orbitals lead to the formation of NaÀ O bond. In AIMD simulation, the minimum energy barrier and activation energy of sodium chloride molecule are 0.09236 eV and 0.059 eV, respectively. The findings also suggest that chloride ion diffusion is facile on hydrated calcium silicate.

Review of Recent Computational Research on the Adsorption of PFASs with a Variety of Substrates

“…These calculations, however, can be computationally more expensive than classical MD calculations and can be limited in the size of systems that can be efficiently analyzed; moreover, they do not take dispersion forces into account if corrections or other optimized functionals are not used [ 26 ]. Dispersion interactions can be accounted for using nonlocal density functionals (such as vdW-DF1), semiclassical C 6 -methods (such as D3), or one-electron effective potentials (such as atom-centered external potentials) [ 27 , 28 , 29 , 30 , 31 ]. MD analyzes the dynamics of the nuclei of the atoms in a system using classical equations of motion, without taking the electrons into effect.…”