Development of a simple, molecular dynamics‐based method to estimate the thickness of electrical double layers. Issue 2 (26th February 2020)

• Record Type: Journal Article
• Authors: Gu, Peike; Yang, Sen; Liu, Xiantang; Yang, Gang
• Is Part Of: Soil Science Society of America Journal. Volume 84:Issue 2(2020)
• Page Start: 494
• Page End: 501
• Publication Date: 2020-02-26
• Subjects: Soils -- United States -- Periodicals; Soil science -- Periodicals; Periodicals; 631.4973
• DOI: 10.1002/saj2.20040
• Languages: English
• ISSNs: 0361-5995

Abstract

Abstract: Electrical double layers (EDL) exist for all interfaces and determination of EDL thicknesses remains a difficult task. In this study, molecular dynamics (MD) simulations are employed aiming to develop a simple method for effective evaluation of EDL thicknesses. The EDL thicknesses at clay minerals/water interfaces are calculated by MD simulations and empirical Debye lengths, considering different electrolyte solutions (NaCl, KCl, CsCl, PbCl2 and CaCl2 ), electrolyte concentrations (0∼1.28 mol/L) and charge locations (tetrahedral and octahedral substitutions). Both methods predict the comparable EDL thicknesses at very low concentrations and more EDL compressions at higher concentrations, while MD simulations show the significant improvements in three aspects, as more rational declining trends with increase of concentrations (Critical for estimating EDL thicknesses especially in highly concentrated solutions), inclusion of ion‐specific effects (More EDL compression for divalent than univalent metal ions, and distinct EDL thicknesses for different alkali ions) and reflection of strong dependence on charge locations (EDL thicknesses differ for montmorillonite and beidellite and have a milder declining rate for montmorillonite). Insights are also offered regarding the microstructure of EDLs, and results promote the understanding of EDLs that determine all interfacial properties and processes.