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Tomas Diaz de la Rubia

Tomás Díaz de la Rubia
Associate Director for Chemistry and Materials Science

We Will Always Need Strong Basic Science

BASIC science often deals with the study of the fundamental behavior of the materials in our world. Whether the material being examined is plutonium or human biological tissue or an optical material or an anthrax spore, its structure and properties must be fully understood for researchers to be confident in predicting performance.
I believe strongly that a place like the Laboratory excels in part because for us basic science is not an end in itself, but rather a means to an end. At Livermore, we strive for strong basic science, but we do so in areas that are driven by our mission as an applied science laboratory serving the national interest.
Plutonium, for instance, with its six crystal forms, is a highly idiosyncratic element, and understanding its properties remains one of the most challenging problems in condensed matter and materials physics. At the same time, plutonium is arguably the most important material in the nuclear weapons stockpile. For most of the last 50 years, the Laboratory has relied heavily on underground nuclear testing to verify weapon performance and gather selected information about the behavior of plutonium. The data were used to adjust our computer codes so that over the years they would become increasingly better predictors of weapon performance. However, many of the intricacies of plutonium behavior remained a mystery. More recently, through the National Nuclear Security Administration’s Stockpile Stewardship Program and our own discretionary investments, Livermore researchers have been developing new theoretical and experimental approaches aimed at understanding the fundamental properties of plutonium in exquisite detail. Undoubtedly, the advances being made through these basic science efforts will eventually result in improved models in the weapons codes and, therefore, in increased confidence in our ability to simulate the reliability and performance of the nuclear weapons stockpile.
The article entitled When Semiconductors Go Nano is another example of the basic science at which Livermore excels. In this instance, experimentalists and simulations experts are delving into the behavior of semiconductors at the nanoscale. Specifically, they are examining silicon, germanium, and nanodiamond, a form of carbon. The electronic and optical properties of these materials are very different at the nanoscale than they are in those same materials in the bulk form, thanks to a phenomenon known as quantum confinement. Silicon and germanium emit light at the nanoscale, which they do not do in the bulk form. And the small size of these nanoparticles—just tens of nanometers across, far smaller than the width of a human hair—means that a large percentage of their atoms is at the surface.
By exposing nanoparticles of silicon and germanium to the x rays of huge synchrotron facilities, experimentalists have produced new data about the structure of these materials. At the same time, computer models have revealed insights about how changes to the surface of semiconductor dots produce dramatic changes in their electronic and optical properties. This synergy of experiments and simulations is adding to the growing body of knowledge about these fascinating elements.
Recent simulations of nanodiamond were the first ever performed anywhere. They have shown that at the nanoscale, a molecule of diamond can become a buckyball, the soccer-ball-shaped molecule named for R. Buckminster Fuller, inventor of the geodesic dome. The full ramifications of this unexpected finding are not yet understood, but we can be sure that Livermore’s scientists will soon learn.
The nanoworld is an exciting, unexplored scientific frontier. We strive to consistently offer a range of exciting basic research ventures to attract excellent young scientists to this Laboratory. We understand that any dedicated scientist finds basic science research to be fascinating and profoundly satisfying. We sometimes don’t know where or how the basic research will be applied. But we know that when basic science is inspired by the mission-driven priorities of the Laboratory, applications will abound.

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Lawrence Livermore National Laboratory
Operated by the University of California for the U.S. Department of Energy

UCRL-52000-03-11 | November 7, 2003