Past Winner
2006 NSERC Howard Alper Postdoctoral Prize

Nicholas J. Mosey

Mechanical and Aerospace Engineering

Princeton University

Nicholas J. Mosey

Computational chemist Nicholas Mosey is looking for better ways to prevent materials from wearing, and he's going right down to the atomic level to do it. Or, more to the point, he is getting his computer to go down to the atomic level for him.

When it comes to protecting materials from wear, much of the attention today is not so much on the material itself but on sheathing it in a wear-resistant coating, often microscopically thin. Developing a better understanding of how those materials work (and how they break down) under different conditions will in turn lead to being able to design better materials. This is the focus of the research Dr. Mosey will conduct with his NSERC Howard Alper Postdoctoral Prize.

This kind of research has traditionally been done with expensive laboratory experiments, but now it normally starts with computer simulations. Simulations have become widely used in virtually all scientific disciplines over the last two decades as computers have developed more and more capacity to crunch large numbers. Computer models can simulate any aspect of a compound's behaviours, such as the energy generated by a reaction, the formation or breaking of bonds, and even the behaviour of individual electrons in a molecule. Today, no chemist can afford not to have at least some understanding of simulation methods.

Computational chemists have to be jacks of several trades, and with expertise in mathematics, physics and computer science, Dr. Mosey is no exception. Because the field is relatively new, he says there are also no off-the-shelf tools he can use for his particular research. “There are some very well-established techniques,” he says, “but a big part of the field is still in method development.” Ongoing advances in computer technology also continually open up new possibilities.

To find the answers he is looking for, Dr. Mosey has to study both the structure of a material at the molecular level and its behaviour in bulk. When it comes to looking at individual atoms that make up a material, he uses a branch of computational chemistry called quantum chemistry (QC). Analysing a material in bulk, however, is best done with “force-field” (FF) or “continuum-level” methods.

Unfortunately, each method has certain limitations. FF and continuum-level methods are less transferable between systems, but QC methods can be applied only to systems with no more than a few hundred atoms. To overcome those limitations, Dr. Mosey is adopting hybrid methods that combine various simulation methods.

Dr. Mosey's attention is focused specifically on a class of materials that is characterized by “strongly correlated electrons,” which give them certain desirable electromagnetic and surface properties. While his focus is on their wear properties, he says they are also of interest for other applications, including superconductors and nano-scale devices.

This research follows closely on work done for his doctoral thesis on anti-wear additives in motor oil, which won him a 2007 NSERC Doctoral Prize. He found a natural fit for his interests in the research group headed by well-known materials scientist Emily Carter at Princeton University. “This group specializes in looking at failure mechanisms in materials and trying to come up with ways to get around those processes,” he says.

Despite ongoing technical advances, limitations in computer power still place real restrictions on what is possible. “You really have to look at very small systems compared to what people look at in experiments,” he says. “So if we had more and more computers you could go to bigger and more realistic systems. That would reduce the number of approximations that go into our models.”