由一个流行的权重计划引起的偏见
1DataQ Intelligence UG, Fichtelgebirgsstrasse 66, Germany.
概括
流行的SHELXL权重方案可能会导致晶体结构分析的偏差,如果强度标准的不确定性被低估. 这种偏差可能会扭曲结果,正如模拟所显示的那样,低估的不确定性导致等价位移参数增加.
科学领域:
- 晶体学 晶体学是指结晶学.
- 材料科学 材料科学 材料科学
- 计算化学计算化学
背景情况:
- SHELXL精炼程序在X射线晶体学中广泛用于确定晶体结构.
- 在结晶学提炼中权衡方案对于准确的结构确定至关重要.
- 标准不确定性的低估 (s.u.) 在观察到的强度是一个常见的问题.
研究的目的:
- 调查低估的标准不确定性对SHELXL类权重方案中的残留物的影响.
- 量化这种低估在晶体学数据中引入的偏差.
- 评估对关键精炼参数的影响,例如等效位移参数 (U_equiv).
主要方法:
- 进行了模拟,以建模低估强度标准不确定性的影响.
- 该研究的重点是通过类似SHELXL的加权方案产生的残留物.
- 分析了残余的对称性和U_equiv的平均增加.
主要成果:
- 将标准不确定性值低估为5的因素显著偏差剩余值.
- 这种低估破坏了零周围残余的对称性.
- 模拟显示,相当位移参数 (U_equiv) 的平均增加为3.35%.
结论:
- 在强度数据中低估标准不确定性的常见做法引入了使用SHELXL类方法的晶体学精炼中显著的偏差.
- 这种偏差可能导致结构参数不准确,特别是影响原子位移参数.
- 仔细评估和准确估计标准不确定性对于可靠的晶体结构分析至关重要.
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