Tchoń D, Makal A
Biological and Chemical Research Centre, Faculty of Chemistry, University of Warsaw, Żwirki i Wigury 101, 02-089 Warszawa, Poland.
IUCrJ. 2021 Oct 15;8(Pt 6):1006-1017. doi: 10.1107/S2052252521009532. eCollection 2021 Nov 1.
Sufficiently high completeness of diffraction data is necessary to correctly determine the space group, observe solid-state structural transformations or investigate charge density distribution under pressure. Regrettably, experiments performed at high pressure in a diamond anvil cell (DAC) yield inherently incomplete datasets. The present work systematizes the combined influence of radiation wavelength, DAC opening angle and sample orientation in a DAC on the completeness of diffraction data collected in a single-crystal high-pressure (HP) experiment with the help of dedicated software. In particular, the impact of the sample orientation on the achievable data completeness is quantified and proved to be substantial. Graphical guides for estimating the most beneficial sample orientation depending on the sample Laue class and assuming a few commonly used experimental setups are proposed. The usefulness of these guides has been tested in the case of luminescent 1,3-diacetylpyrene, suspected to undergo transitions from the α phase () to the γ phase (2 ) and δ phase (112/) under pressure. Effective sample orientation has ensured over 90% coverage even for the monoclinic system and enabled unrestrained structure refinements and access to complete systematic extinction patterns.
足够高的衍射数据完整性对于正确确定空间群、观察固态结构转变或研究压力下的电荷密度分布是必要的。遗憾的是，在金刚石对顶砧（DAC）中进行的高压实验所产生的数据集本质上是不完整的。本工作借助专用软件，系统地研究了DAC中辐射波长、DAC开口角度和样品取向对单晶高压（HP）实验中收集的衍射数据完整性的综合影响。特别是，量化了样品取向对可实现的数据完整性的影响，并证明其影响很大。提出了根据样品劳厄类并假设一些常用实验装置来估计最有利样品取向的图形指南。这些指南的实用性已在发光的1,3 - 二乙酰芘的情况下进行了测试，该物质在压力下可能从α相（ ）转变为γ相（2 ）和δ相（112/ ）。有效的样品取向即使对于单斜晶系也能确保超过90%的覆盖率，并能够进行无约束的结构精修以及获得完整的系统消光图案。
