A molecular picture of water-hydroxide solutions
What is it about?
All chemists know that liquid water changes significantly upon addition of a strong base - like sodium hydroxide . This happens because the hydroxide ions become surrounded ("solvated") by water molecules, forming aggregates whose structure was intensively debated before our study. Here, we modeled the water-hydroxide liquid solution and validated our results by comparing them with experimental data. This allowed us to propose, for the first time, a consistent molecular-level picture of the structure of the hydroxide-water complexes in acqueous solutions.
Why is it important?
This was one of the first modeling studies of acqueous solutions based on accurate (but also very time expensive) computational techniques - first-principles molecular dynamics, in the present case. I remember that it took us really a huge lot of time just to run the simulations that we needed to collect the data - actually, around the year 2000, machines weren't as fast as today, of course ;-) Anyway, such an effort was rewarded because we've got quite a few interesting tips on how the most important liquid on earth behaves when a strong base is added. For example, for both the sodium-hydroxide and potassium hydroxide acqueous solutions, we found that the so-familiar tetrahedral coordination geometry of water is completely missing at high concentrations of the hydroxide. This indicates that hydroxide anions have a massive effects on the hydrogen-bond network of water.
The following have contributed to this page: Gloria Tabacchi