Nature of hydrogen bond and its lifetime in alkali hydroxides (LiOH, NaOH, KOH) in water

Hydrogen bonding, its structure and the lifetime in aqueous solutions of alkali hydroxides (LiOH, NaOH, and KOH) are investigated using quantum molecular dynamics simulations over a concentration range of 1–10 moles. Intermolecular charge density overlap is evaluated using the density functional theory with SCAN meta-GGA exchange-correlation functional to characterize hydrogen bond interactions. The results show that increasing ionic radius r(Li⁺ )+ )+ ) and higher solute concentrations progressively disrupt the hydrogen bond network, leading to a systematic decrease in hydrogen bond lifetime. However, for all the systems studied, based on charge density overlap, the maximum length of the hydrogen bond is found to be 2.1 Å. Hydrogen bond correlation functions are computed based on different definitions to quantify hydrogen bond lifetimes in each system. Our results based on the H-bond characterized by charge density overlap provide a molecular level understanding of concentration and ion-specific effects on the hydrogen bond network in alkaline aqueous environments.