Showing papers by "Robert Evans published in 2021"

Primitive model electrolytes in the near and far field: Decay lengths from DFT and simulations

Abstract: Inspired by recent experimental observations of anomalously large decay lengths in concentrated electrolytes, we revisit the Restricted Primitive Model (RPM) for an aqueous electrolyte We investigate the asymptotic decay lengths of the one-body ionic density profiles for the RPM in contact with a planar electrode using classical Density Functional Theory (DFT) and compare these with the decay lengths of the corresponding two-body correlation functions in bulk systems, obtained in previous Integral Equation Theory (IET) studies Extensive Molecular Dynamics (MD) simulations are employed to complement the DFT and IET predictions Our DFT calculations incorporate electrostatic interactions between the ions using three different (existing) approaches: one is based on the simplest mean-field treatment of Coulomb interactions (MFC), while the other two employ the Mean Spherical Approximation (MSA) The MSAc invokes only the MSA bulk direct correlation function, whereas the MSAu also incorporates the MSA bulk internal energy Although MSAu yields profiles that are in excellent agreement with MD simulations in the near field, in the far field, we observe that the decay lengths are consistent between IET, MSAc, and MD simulations, whereas those from MFC and MSAu deviate significantly Using DFT, we calculated the solvation force, which relates directly to surface force experiments We find that its decay length is neither qualitatively nor quantitatively close to the large decay lengths measured in experiments and conclude that the latter cannot be accounted for by the primitive model The anomalously large decay lengths found in surface force measurements require an explanation that lies beyond primitive models

Gerhard Findenegg (1938-2019)

Abstract: On 12 December 2019, our colleague and friend Professor Dr. Gerhard H. Findenegg (cf. Figure 1) passed away after just having completed the eighty-first year of his life. He leaves behind his wife ...