Single crystal XRD investigation of a critical point terminated phase boundary in solid oxygen

Our research proposal is to study the region of the phase diagram of oxygen extending between 8 and 50 GPa at room and low temperatures using the diamond anvil cell coupled to flux cryostats in order to clarify the open issues present in literature and to confirm and extend to low temperatures the results of our recent diffraction experiment at room temperature (Petra, I-20200536 EC). In particular we plan to investigate and verify the existence of a phase boundary within the region of the epsilon phase at low temperatures, separating the epsilon1 (made of O8 molecules=4XO2 molecules having spin 1) from the epsilon0 (made of O8 molecules=4XO2 molecules having spin 0) as it has been recently proposed by simulations. We have recently obtained in Petra the evidence of important structural changes in the epsilon phase at room temperature which might be the epsilon1 to epsilon0 transition and which needs to be confirmed and studied also at low temperatures.

本研究拟采用金刚石对顶砧（diamond anvil cell）结合磁通低温恒温器（flux cryostats），在室温及低温条件下探究氧气相图中8至50吉帕斯卡（GPa）压力区间的区域，旨在厘清文献中存在的未解决问题，并确认且将我们近期室温衍射实验（Petra，I-20200536 EC）的结果扩展至低温条件。具体而言，我们计划研究并验证低温下epsilon相区域内是否存在相边界——该边界可将epsilon1相（由O8分子即4个O2分子组成，自旋为1（spin））与epsilon0相（由O8分子即4个O2分子组成，自旋为0）分隔开，这一假设是近期模拟研究提出的。我们近期在Petra实验中已观测到室温下epsilon相存在重要结构变化的证据，这可能对应epsilon1相至epsilon0相的转变，需在低温条件下进一步确认与研究。