Researchers Discover The Cause Of İrradiation-induced İnstability İn Materials Surfaces

A new discovery about the dynamic impact of individual energetic particles into a solid surface improves our ability to predict surface stability or instability of materials under irradiation over time. The finding may lead to the design of improved structural materials for nuclear fission and fusion power plants, which must withstand constant irradiation over decades. It may also accelerate the advent of fusion power, which does not produce radioactivity.

Publishing in Nature Communications, Michael Aziz, Gene and Tracy Sykes Professor of Materials and Energy Technologies, and Michael Brenner, Glover Professor of Applied Mathematics and Applied Physics, both at the Harvard School of Engineering and Applied Sciences (SEAS), and colleagues developed a new rigorous mathematical theory that is "fed" the measured shape of the average crater resulting from the impact of an energetic particle.

The impacts, lasting a few trillionths of a second, are simulated using intensive computer calculations. The theory then "up-scales" the cumulative effect of individual energetic particle impacts to predict surface topography evolution over thousands of seconds or longer.

"Our results illustrate how large-scale computer simulations can be combined with rigorous mathematical analysis to yield precise predictions of new phenomena on length and timescales that would otherwise be computationally impossible," says Brenner.

The researchers were surprised to discover that stability/instability is not determined by the atoms that are blasted away, but instead by the atoms that are knocked around and re-settle nearby.

"Our discovery overturns a long-held paradigm about what causes surfaces to erupt into patterns under energetic particle bombardment. The blasting away of individual atoms from energetic particle impacts has long been thought to determine whether a surface is stable or unstable," says Aziz.

"The effect of atoms blasted away turns out to be so small that it is essentially irrelevant. The lion's share of the responsibility of what makes a surface stable or unstable under irradiation comes from the cumulative effect of the much more numerous atoms that are just knocked to a different place but not blasted away."