Livermore scientists reveal details of reactive states of water-to-air interface

Using the latest terascale ASCI computers, scientists at Lawrence Livermore National Laboratory have revealed details of the reactive states and faster relaxation of molecules at the water-to-air interface.

Scientists Christopher Mundy and I-Feng Kuo created the first ab initio calculations of a stable aqueous liquid-vapor interface. The simulations serve as a robust predictive tool in the investigation of electronic properties of molecules at interfaces.

These complex theoretical models have captured surface phenomena of water that have recently been observed experimentally in the group of Professor Rich Saykally at UC-Berkeley. The results are presented in the January 30 edition of Science.

The researchers first stabilized a region of bulk water in the center of a water slab so they could quantify the reactive states and surface relaxation as the bulk water approached the liquid-vapor interface.

Data analysis shows that there is a faster relaxation of water molecules at the interface and the surface contains far more reactive states than the bulk.

“These simulations serve as an important step toward the use of terascale resources to produce simulations of water in complex environments,” Mundy said. “The chemistry and physics of the aqueous liquid-vapor interface have been receiving recent attention because of new experimental techniques to characterize its structure.”

The ab initio simulations of the aqueous liquid/vapor interface have a resolution of approximately 35 angstrom and contain a total of 216 water molecules.

Characterizing water at the liquid-to-air interface produces important results in atmospheric science. The Saykally group experiments on the aqueous liquid-vapor interface have provided additional proof of dangling oxygen-hydrogen bonds present at the surface, strong evidence for surface relaxation, and new structural portions in which both hydrogens are dangling.

The Livermore work seems to have captured all these surface events. Ab initio simulations present an unbiased representation of water in different environments and are ideal for explaining surface conditions.

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Founded in 1952, Lawrence Livermore National Laboratory is a national security laboratory, with a mission to ensure national security and apply science and technology to the important issues of our time. Lawrence Livermore National Laboratory is managed by the University of California for the U.S. Department of Energy’s National Nuclear Security Administration.