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Tradition Turns Ideas into Reality
Associate Director of Physics and Advanced Technologies
THE preeminent goal of physics
in the 20th century was to understand the workings of the world
at the most fundamental level. This moving target shifted to ever-smaller
scales as the technology of observationdriven in turn by advances
in physicsbecame more and more powerful.
As physicists studied atoms
and their constituents, they learned that Newtons laws of
motion did not apply. For example, the particles that make up water
molecules evidently do not follow the same set of rules as bulk
samples of water. Convinced, however, that the world becomes more
understandable as its basic constituents and interactions are exposed,
physicists rarely considered systems of more than two interacting
particles, unless they skipped directly to infinity. This reductive
approach led to the triumphs of modern physics, including quantum
mechanics and the standard model of the strong nuclear, weak nuclear,
and electromagnetic interactions. To this day, however, many bulk
properties of water remain a mystery.
As we enter a new century,
geometric growth in computing poweralso engendered by modern
physicshas positioned physicists to address anew the complexities
of many particles interacting to produce the bulk properties of
materials. Using Advanced Simulation and Computing (ASCI) supercomputers
to simulate the quantum mechanics of matter being shocked, researchers
can now see in detail the dynamic activity of the atoms and molecules
in the sample.
article beginning on p. 4 describes the first-ever quantum molecular
dynamics simulations of shocked hydrogen. Those simulations, the
largest ab initio simulations ever done on the ASCI White computers,
sought to find physical reasons for differing results from two sets
of high-pressure experiments on deuterium, an isotope of hydrogen.
Other simulations have examined the mechanical properties of water
molecules under ambient conditions and at extreme pressures. For
stewardship of the nations nuclear stockpile as well as for
other programmatic applications, knowledge of how materials shock
and fracture at the molecular level is essential.
An especially exciting area
for quantum simulations is in the growing field of nanoscience.
Nanomaterialsone nanometer is a billionth of a meter, or 100,000
times smaller than the width of a human hairare the ultimate
challenge to the way physicists count: one, two, . . . infinity.
Ranging from around 10 to 1,000 atoms in size, nanoparticles behave
in a complex way that is different from the behavior of both their
atomic constituents and bulk matter. For the silicon nanoparticles
known as quantum dots, quantum simulations reveal unique optical
properties that vary with size and surface characteristics. Not
only will lasers made of silicon be possible for the first time,
but silicon dots may also be useful as fluorescent markers in biological
research and as biological sensors. Quantum simulations are also
exploring the behavior of DNA and how best to exploit a cancer-fighting
As a tool for biological
research, quantum simulation may engender progress akin to the advances
in structural biology that followed the introduction of another
physics tool, x-ray diffraction using synchrotron light sources.
In fact, quantum simulations will play a key role in advancing biological
imaging using fourth-generation light sources to illuminate proteins
with the worlds most brilliant x-ray pulses. But thats
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