Dielectric and Structural Properties of Aqueous NaCl Solutions: A Molecular Dynamics Study Using the Novel Flexible TIP4P/ϵ Flex Model of water

In this work, we investigate the structural and dielectric behaviour of water in sodium chloride (NaCl) solutions, ranging from low concentrations to levels approaching the solubility limit. Specifically, we examine concentrations from [NaCl] = 1m to [NaCl] = 6m, where 6.1m represents the solubility threshold of NaCl in H ₂ O. For the water model, we employ the exible TIP4P/ϵFlex model, which offers an enhanced reproduction of various properties compared to other exible models and non- polarisable rigid models. This includes improvements in the prediction of the infrared spectrum. For the ions, we utilise two distinct models: NaCl/Madrid and NaCl/ϵ, allowing for a comparative analysis of their impact on the system's behaviour.