单原子碘的多晶型现象
Polymorphism of monatomic iodine
AI总结：
本文通过同步辐射单晶X射线衍射和第一性原理计算，在48-51 GPa激光加热I-N2混合物中合成两种原子碘相，发现新的包合型Pm-3n结构及低压fcc相，推进了对卤素高压相变序列的理解。
摘要：
我们应用金刚石对顶砧中的同步辐射单晶X射线衍射（48-51 GPa）和第一性原理理论计算，研究了高压下固态原子碘的晶体结构。我们报道了通过激光加热I-N2混合物在48-51 GPa下合成两种原子碘相。与熟悉的单原子I4/mmm结构（由晶体学上等价的原子组成）不同，新的Pm-3n结构属于包合型，具有两种不同的原子：一个中心脱离原子和形成线性链的外围原子。此外，我们观察到熟悉的高压面心立方（fcc）结构的结晶，尽管与冷压缩碘相比，其压力要低得多。碘中Pm-3n结构的发现标志着理解卤素中压力诱导相变序列的重要一步。
英文摘要：
We applied synchrotron single-crystal X-ray diffraction in a diamond anvil cell at 48-51 GPa and first-principles theoretical calculations to study the crystal structure of solid atomic iodine at high pressure. We report the synthesis of two phases of atomic iodine at 48-51 GPa via laser heating of I-N2 mixtures. Unlike the familiar monatomic I4/mmm structure, which consists of crystallographically equivalent atoms, a new Pm-3n structure is of inclusion type, featuring two distinct kinds of atoms: a central detached one and peripheral ones forming the linear chains. Moreover, we observe crystallization of the familiar high-pressure face centered cubic (fcc) structure, albeit at much lower pressures compared to cold compressed iodine. The discovery of Pm-3n structure in iodine marks an important step in understanding of the pressure induced phase transition sequence in halogens.
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