Theoretical study on the influence of salts on the stability of N-methane hydrate

Using first-principles calculations rooted in density functional theory, this study systematically investigates the structural stability, electronic properties, and mechanical behavior of N-methane hydrate upon introduction of predominant marine salts (e.g., chlorides and sulfates). Key findings include: 1)Both NaCl- and KCl-containing S-positions demonstrate negative binding energies, whereas Mg2+, Ca2+, and SO42- destabilize the N-water cages through strong electrostatic interactions, steric constraints, and charge redistribution; 2 The incorporation of NaCl and KCl results in the semiconductor properties of N-methane hydrates, thereby enhancing their conductivity.; 3) The density of states of NaCl-containing N-water cages shifts slightly toward lower energies, indicating lower energy states and higher formation tendency, consistent with binding energy analysis; 4)The hydration of both Na+ and K+ weakens hydrogen bonds, with K+ having a stronger effect, as confirmed by differential charge density analysis; 5)Both S-positions satisfy the mechanical stability criteria in their elastic constants. The KCl-containing S-position exhibits enhanced ductility through lattice expansion and hydrogen bond weakening, but with reduced rigidity and shear resistance, while NaCl shows minimal impact on mechanical properties.