Speaker
Description
Despite years and efforts, determining the structure of highly concentrated aqueous solutions is still a challenge. The complete description of the structure of a 4-component system (anion, cation, water oxygen, water hydrogen) at the two-particle correlation level would require the combination of ten independent experimental data sets. However, the number of available data sets is significantly lower. The low partial weights of the ion-related partials in the measured data (especially in dilute solutions) can be another problem.
Several solutions have been investigated previously in our group. Initially, attempts were made to determine the structure by fitting only diffraction data with RMC. Due to the lack of information, the shape of several partial radial distribution functions (PRDFs) was not well defined. Later, PRDFs calculated from MD simulations were added to the data sets to be fitted. This technique contributes highly to the determination of the structure, but the appropriateness of the interaction potential (force field, FF) used fundamentally determines the validity of the results obtained.
This problem can be solved by examining and combining several FFs. By comparing the models, a better description of the structure can be obtained even if no FF has been found that reproduces the structural functions from diffraction measurements with sufficient accuracy.
By further refining the model configurations with RMC_POT simulations, particle configurations can be obtained that are compatible with the diffraction data, while their potential energy is minimal and their structure is as close as possible to that obtained from MD simulations.
In this presentation, the structure determination technique based on the application of many FFs will be presented by investigating LiCl, CsCl, and CsF solutions.
