Thermal behavior of modulated haüyne from eifel, germany: In situ high-temperature single-crystal x-ray diffraction study

In-situ high-temperature single-crystal X-ray diffraction experiments on modulated haüyne obtained from Eifel, Germany, were conducted to re-evaluate its thermal behavior. The linearity of its thermal expansion is lost between 600 and 700 °C. Satellite peaks, indicating the modulated structure, were clearly observed up to 600 °C, but disappeared at 700 °C. These results indicate that the modulated haüyne structure changed in this temperature region. In addition, according to the observation of X-ray oscillation images taken at ambient conditions, the modulated structure of the sample heat-treated below 1000 °C remained unchanged, whereas modulation of the parent crystal structure changed when the sample was heat-treated above 1000 °C. This structural change to the unique modulated structure can be attributed to be the possible rearrangement of Al/Si distribution in the tetrahedral sites forming the framework.