Low-energy dynamics and emergent excitations in the cubic NTE material Cd(CN)2

Cadmium cyanide is a negative thermal expansion material: it shrinks – rather than expands – when heated. We are proposing to carry out an inelastic neutron scattering experiment on the MARI spectrometer. This experiment will allow us to work out exactly how the structure of cadmium cyanide responds to temperature. We are trying to answer the question: when the material is heated, how do its atoms vibrate? Answering this will allow us to work out the mechanism responsible for its negative thermal expansion effect. This question might have been asked (and answered) many years ago, were it not for the fact that cadmium absorbs neutrons incredibly strongly. What's changed is that we now have access to a sample made from a single isotope of cadmium that is actually a good neutron scatterer, rather than a good neutron absorber.

氰化镉（Cadmium cyanide）是一种负热膨胀（negative thermal expansion）材料：受热时会发生收缩而非膨胀。我们计划在MARI谱仪上开展一项非弹性中子散射（inelastic neutron scattering）实验，以精准探明氰化镉的结构如何随温度变化。我们旨在解答如下问题：当该材料受热时，其原子会如何振动？解答该问题将帮助我们明确其负热膨胀效应背后的作用机制。若非氰化镉对中子具有极强的吸收能力，该问题或许早在多年前就已被提出并得到解答。如今情况已发生改变：我们已能获取由单一镉同位素制成的样品，这类样品实则是优良的中子散射体（neutron scatterer），而非中子吸收体（neutron absorber）。