A MATTERS Can Exascale Computing Help Us Understand Extreme Materials? Some things are diffi cult to understand—higher math, relationships, the appeal of reality TV—whereas other things are understood to be diffi cult—brain surgery, two-year olds, learning to speak Finnish. Then there’s the response of a mate- rial hit by a shock wave, which is not only diffi cult to under- stand, but trying to simulate it, even using the world’s most powerful computers, is suffi ciently diffi cult that it currently can’t be done. A shock wave is an extremely energetic disturbance that moves through matter at supersonic speeds. Like a flash flood tearing through a slot canyon, it arrives without warning. Matter suddenly finds itself immersed in the wild pressure and temperature maelstrom that trails the wall-like shock front. As the shock propagates through, say, a solid, it generates enormous mechanical stresses that can deform, crack, even shatter the material. Even if there is no structural damage, will the material properties be the same as they were before? Only select groups of people—demolition experts, makers of body armor, certain types of physicists—know that the answer to that question is “We don’t know” and are frustrated by it. But the much larger materials-science community is similarly frustrated by a related problem: the inability to produce the next generation of so-called extreme materials that can survive and function in extreme environ- ments. The core of an advanced nuclear reactor is an extreme environment. So is the radiation-filled vacuum of near-Earth space or any environment where a shock wave comes to visit. Extreme materials deserve our attention because if researchers could create polymers that withstand high temperatures and pressures, alloys that resist corrosion, or Earth-friendly materials that can tolerate excessive exposure to chemicals, radiation, or electromagnetism, then a bevy of already-thought-of advanced technologies could come off the drawing boards and possibly turn our world into the sustain- Tim Germann with his gigascale computer 10 1663 los alamos science and technology magazine june 2012