Like many scientific disciplines, building and understanding nanomaterials requires teamwork and strong integration of experiment and theory. Experimental work provides tremendous data, but often the theoretical computer analyses point the way toward future innovations.

“Over the past decade, growing computational power has transformed the practice of catalysis science,” said Alex Harris, Chair of Brookhaven’s Chemistry Department. “Calculations of atomic and electronic structure can now give reliable insight to guide the design of better catalysts. We’re excited to see what Blue Gene/Q can do, and we appreciate the effort of the CSC to get the key software tools for catalyst modeling up and running.”

Brookhaven chemist Ping Liu, who helps guide the integration of computational theory and experimentation, sits in front of an open Blue Gene/Q supercomputer rack, showing a schematic of a platinum-shell electrocatalyst designed at the CFN.

As scientists seek to discover the most efficient catalysts for specific applications, they audition many new compounds. Platinum, for example, is an excellent catalyst for many applications, but it is both rare and expensive. One innovation pioneered at Brookhaven reduced the platinum to a one-atom thick layer coating over a less-expensive metal such as palladium. On the atomic scale, the individual platinum atoms then “felt” the influence of the palladium atoms below, instead of platinum atoms. Difficult questions arose about whether or not the chemical reactions on the surface would still produce the same reactions, and if the palladium nanoparticles with their fancy platinum coats would remain stable or shed their new skin.

Experiments showed that not only was this novel core-shell structure stable, but it was an even better catalyst than pure platinum particles in fuel cells. In a surprising discovery, nanoparticles with a partially hollow palladium core actually functioned even more efficiently. That’s when the power of computer simulations came into the picture to explain those results, led by Ping Liu of the Chemistry Department and the CFN.

“The computer calculations revealed to us why the hollow core-shell nanoparticle was the most stable and the best catalyst at the same time. The thin palladium layer in the core led to strain and electronic effects throughout that not only stabilized the catalyst, but promoted the catalytic activity of platinum.” Liu said. “In fact, we learned that the stability of these particles depends on their size, and in the future we will need to study and model even more complex particles with hundreds or thousands of atoms.”

With the detailed information about the atomic-scale interactions available from the computer simulations, the scientists can examine how the catalyst might be improved by small changes, such as substituting gold atoms for palladium atoms in these core-shell particles. The new Blue Gene/Q will make these challenging calculations feasible, allowing theory to guide future experimentation.