One class of materials, two incompatible theories
For more than a decade, Richard Dronskowski and Matthias Wuttig, both at RWTH Aachen University in Germany, have been battling about the bonding in chalcogenide phase change materials. They have helped develop – and become rooted to – contrasting theories as to what’s going on at the atomic level. While the pair once worked together to understand these materials, countless heated arguments and published exchanges mean they’re no longer on speaking terms. The few kilometres between their offices are nothing compared to the deep disagreement that separates the two scientists.
One of the reasons why these researchers, as well as others in the UK, Spain, Belgium and South Korea, are so committed to understanding how atoms in these materials bond is to help explain their unusual properties. Phase change materials reversibly convert between an amorphous and crystalline phase in nanoseconds, prompted by a laser or an electrical pulse. Few materials undergo structural changes so quickly – just look at the amorphous silica found in windowpanes, which stays in the same phase for many years.
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