The Structure of Cerium at Ultra-High Pressures

Despite having a rich structural complexity and an unusual electron band configuration, cerium (Ce) has only been studied up to 208 GPa, using energy-dispersive x-ray diffraction techniques. We propose to perform angle-dispersive x-ray diffraction measurements on Ce metal, obtaining high-quality compression data to at least 300 GPa. Preliminary work conducted by our group has indicated that the c/a ratio of the body-centred tetragonal (bct) phase stable above 12 GPa starts to decrease above 200 GPa. We have also seen abnormal compressive behaviour at pressures above 250 GPa, which may be a result of shear stress effects or pressure gradients. These data were acquired using a relatively large ~2µm FWHM beam, making it difficult to draw definitive conclusions. We therefore aim to repeat this experiment using the superior facilities at ID27.

尽管铈（Ce）具备丰富的结构复杂性与独特的电子能带构型，但目前针对该元素的研究仅推进至208吉帕斯卡（GPa），且采用的是能量色散X射线衍射（energy-dispersive x-ray diffraction）技术。本研究拟对金属铈开展角度色散X射线衍射（angle-dispersive x-ray diffraction）测量，以获取至少至300吉帕斯卡的高质量压缩实验数据。本团队前期研究显示，在12吉帕斯卡以上稳定存在的体心四方（body-centred tetragonal, bct）相，其c/a轴比在200吉帕斯卡以上时开始下降。我们还在250吉帕斯卡以上的压力区间内观测到异常压缩行为，该现象可能由剪切应力效应或压力梯度所致。此前的实验采用了半高全宽（Full Width at Half Maximum, FWHM）约2微米的较宽光束，这使得我们难以得出确定性结论。因此，本研究计划依托ID27的先进实验设施重复该实验。