在液体硫中S8环含量由X射线衍射确定
Chris Benmore1, Maria Bokova2, Eugene Bychkov3
1X-ray Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA, Lemont, Illinois, 60439, United States.
概括
液体硫含有S8环比以前认为的要少,大约三分之一在化时破裂. 这一发现挑战了现有的硫模型.
科学领域:
- 材料科学 材料科学 材料科学
- 物理化学 物理化学
- 凝聚物质物理学 凝聚物质物理学
背景情况:
- 液体硫的结构,特别是S8环的分量,对于理解其独特的聚合行为至关重要.
- 已建立的模型表明,液体硫主要由Lambda转换温度 (Tλ) 以下的S8环组成.
研究的目的:
- 在广泛的温度范围内 (-55~330°C) 量化确定液体硫中的S8环含量.
- 研究液硫中的结构变化和环形动力学,挑战现有的模型.
- 要将S8环分数与Tλ的聚合机制相关联.
主要方法:
- 在4.47 Å进行X射线对分布函数 (PDF) 分析,以探测S8环结构.
- 三种不同的方法 (缩放,线性组合合适,直接集成) 来计算S8环分数.
- 第一原则分子动力学 (MD) 模拟,以调查动态环扭曲和结合角度.
主要成果:
- 大约三分之一的S8环在化时解离,形成短链 (平均长5±2原子).
- S8环分数随温度变化:在超冷液体 (-30oC) 中为76±10%,在高温 (330oC) 中为23±3%.
- MD计算证实了动态环扭曲,并支持低温液硫中存在短链.
结论:
- 该研究与既有模型相矛盾,揭示了在低温液体硫中显著的S8环解离.
- 短链的存在对于键交换机制在Tλ.驱动聚合时至关重要.
- 这项研究提供了对液体硫结构及其在聚合过程中的作用的修订理解.
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