Discovering the details of dissolution

Researchers brought together theoretical and experimental approaches to learn more about the liquid molecules surrounding ions. The knowledge of the structure formed by the ion and the first layer of surrounding solvent molecules has broad applications, from understanding how pollutants move in the soil to how neurotransmitters work in the brain.

Ions in a liquid are like celebrities at a movie opening— surrounded by fans who jostle each other to get as close as the velvet ropes around the red carpet will allow. So it is with ions in water or other liquids or solvents.

At Pacific Northwest National Laboratory and Argonne National Laboratory, researchers brought together an unusual combination of theoretical and experimental approaches to determine the number, relative positions and motions of the liquid molecules surrounding ions. This is an initial step in developing fundamental principles that explain how ions move in complex systems.

By combining two techniques that are not commonly used together, the team created simulations, or short video clips, that show the location of the ions and the water molecules.

The first technique, known as extended x-ray absorption fine structure spectroscopy, uses x-rays to probe the relative positions of atoms in a solution. The second technique uses advanced calculations and molecular modeling to simulate the structure and motion of relevant systems. The team showed the model’s accuracy by comparing it to laboratory measurements.

This research was funded by the Department of Energy Office of Basic Energy Sciences.