Just one rack of the Blue Gene/Q supercomputer, seen here with its complex wiring and cooling tubes exposed, will rapidly perform complex tasks that would require 18 racks of the previous generation of IBM supercomputers. Image: Brookhaven National Laboratory |
Heavy construction projects demand precision and planning,
particularly if the end products need to perform a specific function. The
degree of complexity increases as the raw materials become smaller and more
specific: Just consider the difference between constructing a house, a car, or
the tiny circuitry within a computer. The challenges and opportunities of
ground-up design are rarely more pronounced than on the nanoscale where atoms
and molecules are the basic building blocks.
Atomic-level tailoring promises important breakthroughs in
energy technology, such as the development of new materials that will make
efficient fuel cells inexpensive enough for widespread use. But nanoscale
engineering requires cutting-edge facilities and expertise in the dizzying laws
of quantum mechanics that govern the interactions between atoms. The sheer
number of variables in effect during any chemical reaction would make complete
understanding impossible without another essential tool: a powerful computer to
connect the atomic dots.
This spring a new supercomputer will come online at the United
States Department of Energy’s Brookhaven National Laboratory, arming its
scientists and engineers with a cutting-edge tool to advance their research.
Brookhaven’s Center for Functional Nanomaterials (CFN) and the Chemistry
Department will use this big boost in computing power, called Blue Gene/Q, to
tease out new ways to put nanoscale materials to work. In particular, Blue
Gene/Q will decode and map out the complex array of chemical reactions that can
occur on a single nanoparticle with greater speed and precision than ever
before.
“Computer modeling is the key to the rational design of
catalysts,” said Mark Hybertsen, who leads the Theory and Computation Group at
CFN. “This machine will more rapidly advance the development of new
electrocatalysts for use in clean-burning fuel cells.”
The new Blue Gene/Q, the latest version in the IBM supercomputer
series that includes Brookhaven Lab’s Blue Gene/L, will add 600 teraflops, or
floating operations per second, of processing power. Only three racks of the
new Blue Gene/Q will soon complete operations that required 18 racks of the
previous generation machine. The system consists of two racks for the RIKEN BNL
Research Center (RBRC) operated with Japan, and a third belonging
exclusively to Brookhaven and run by the Computational Science Center (CSC). It
all boils down to handling more complex data at faster speeds and giving
scientists throughout Brookhaven access to that computational power.
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.”
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.
Upgrades like Blue Gene/Q will help take nanoconstruction along
a similar path, Hybertsen said. With greater processing speed, breakthroughs in
energy technology may become both more frequent and more innovative.