AEM faculty spotlight:
Richard James
Read an unabridged version of this interview here.
When an engineer creates a new bridge design, reference tables are consulted. AEM Professor Richard James seeks to create such a reference on a slightly smaller scale, that of atoms and molecules. James, a Distinguished McKnight and Russell J. Penrose Professor, has long been interested in developing unusual new materials. Recently, his work has shifted toward biomaterials, specifically bacteriophage T4. Viruses like T4 are built of components that he calls “objective structures.” To picture an objective structure, imagine a group of identical people sitting in chairs that are arranged in a perfect circle. Each person sees exactly the same environment. Professor James discusses these and more in the following Q&A.
Richard James
My work is about the discovery of new materials. In my lab we make alloys from elemental materials, guided by theoretical developments. My students and I develop theory to understand the behavior of materials. We take theoretical predictions to the lab and make the materials. As you can imagine, it can be a incredibly exciting, as when we actually discover a new material with some unexpected properties, or deeply humbling, when we realize that we have left an important factor out of the theory.
For example?
I hesitate to expose the deeply humbling moments, but much of our work is on shape memory materials, where a large change of shape is induced by changing the temperature. This behavior is caused by a phase transformation. A few years ago, guided by theory, we realized that if a material would have such a phase transformation, and would also be magnetic and satisfy certain other conditions, one should be able to induce the phase transformation by applying a magnetic field. With the collaboration of Professor Shield these materials were then realized in my lab. If one brings a magnet close to this material, it undergoes a big change of shape. We are now thinking about other ways a phase transformation can be used to allow a material to have properties that are impossible in a single phase. A dream material would have a ferroelectric phase and a ferromagnetic phase. There is some indication from theory that one could find materials like that.
How would you look for such a material?
Partly, we rely on collaborations with physicists who do “first principles calculations” to help identify favorable structures for properties like ferromagnetism or ferroelectricity. Another important aspect of these materials is reversibility. Lots of materials have phase transformations, but few are highly reversible. Of course, it is much more interesting when we have this high degree of reversibility, as one can then go easily back and forth between the phases. One of our recent breakthroughs is a new understanding of reversibility, completely contrary to what is written in textbooks. It is a quantitative understanding, so we could go to the lab and systematically change composition to achieve these special conditions that theoretically give high reversibility. My recent Ph.D. student, Jerry Zhang, did this, and the results were amazing: in some cases he decreased the size of the hysteresis (a measure of reversibility) by a factor of 10. There are fascinating new families of shape memory alloys that are emerging from this work.
Tell me a bit about objective structures.
This is a new direction in my research, and, as usual, I am beginning with the development of theory. Imagine a structure which is built of identical molecules, each with, say, 100 atoms, numbered 1 to 100. Imagine that you sit on the 27th atom of one of the molecules, and you look around. Nearby, you see other atoms of the same molecule, and, further away, you see other atoms of the other molecules. Now sit on the 27th atom of a different molecule and, again, look around. If you orient yourself in just the right way, you see exactly the same environment, just as in the circle of chairs. If this happens for corresponding atoms in every molecule of the structure, then I call that an objective structure. Lots of the parts of viruses have these structures. But also, most of the structures adopted by elements in the Periodic Table are objective structures, with one atom per molecule, including exotic things like buckyballs and carbon nanotubes.
What can we learn from such structures?
For one thing, these are the natural structures to search for special physical properties like ferromagnetism and ferroelectricity. For ferromagnetism, if one atom wants to have unpaired spins, that is, to be magnetic, all of the atoms will also want to be magnetic, because of the way objective structures are built. People in biology take natural structures and study them: it is considered uninteresting in biology if one violates conditions that occur in vivo. But I like to think in more of an engineering way about this, and the first step is understanding how they’re put together. Objective structures offer a special window into the building of molecular structures.
How would someone build something like a virus?
When engineers build a bridge, they go to tables of I-beams and trusses and, from stress analysis, they understand how to use these in a reliable, efficient structure. What I would like is to have that kind of quantitative information for molecules, so you could build structures out of molecules like you build bridge structures. You might be able to build a structure which exactly matches some part of a virus. By doing that you may be able to make it so the virus naturally binds the structure, thereby disabling the virus. You might be able to build a tubular structure whose molecules exactly match the inside of a carbon nanotube. Suitably functionalized, it could be a template for the large-scale growth of carbon nanotubes.
How do you find objective structures? Do they all look like carbon nanotubes or viruses?
No, there are many others! Last year, together with Prof. Ryan Elliott and our postdoc Kaushik Dayal, we set ourselves the task of finding every objective structure. I was on sabbatical in Germany, and I think I invested more than 1000 man-hours in this one calculation! But, we succeeded in finding an explicit formula for every objective structure. This is a basis for a systematic study of their properties.
Last Modified: Tuesday, 09-Oct-2007 06:43:46 CDT -- this is in International Standard Date and Time Notation