• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Environmental Science: Processes & Impacts >Diverging effects of isotopic fractionation upon molecular diffusion of noble gases in water: mechanistic insights through ab initio molecular dynamics simulations
【24h】

Diverging effects of isotopic fractionation upon molecular diffusion of noble gases in water: mechanistic insights through ab initio molecular dynamics simulations

机译：同位素分馏对水中惰性气体分子扩散的发散作用：通过AB Initio分子动力学模拟的机械洞察

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Atmospheric noble gases are routinely used as natural tracers to analyze gas transfer processes in aquatic systems. Their isotopic ratios can be employed to discriminate between different physical transport mechanisms by comparison to the unfractionated atmospheric isotope composition. In many applications of aquatic systems molecular diffusion was thought to cause a mass dependent fractionation of noble gases and their isotopes according to the square root ratio of their masses. However, recent experiments focusing on isotopic fractionation within a single element challenged this broadly accepted assumption. The determined fractionation factors of Ne, Ar, Kr and Xe isotopes revealed that only Ar follows the prediction of the so- called square root relation, whereas within the Ne, Kr and Xe elements no mass- dependence was found. The reason for this unexpected divergence of Ar is not yet understood. The aim of our computational exercise is to establish the molecular- resolved mechanisms behind molecular diffusion of noble gases in water. We make the hypothesis that weak intermolecular interactions are relevant for the dynamical properties of noble gases dissolved in water. Therefore, we used ab initio molecular dynamics to explicitly account for the electronic degrees of freedom. Depending on the size and polarizability of the hydrophobic particles such as noble gases, their motion in dense and polar liquids like water is subject to different diffusive regimes: the inter- cavity hopping mechanism of small particles (He, Ne) breaks down if a critical particle size achieved. For the case of large particles (Kr, Xe), the motion through the water solvent is governed by mass- independent viscous friction leading to hydrodynamical diffusion. Finally, Ar falls in between the two diffusive regimes, where particle dispersion is propagated at the molecular collision time scale of the surrounding water molecules.
机译：大气惰性气体经常用作天然示踪剂，以分析水生系统中的气体转移过程。通过与未分叉的大气同位素组合物相比，可以使用它们的同位素比来区分不同的物理运输机制。在水生系统的许多应用中，认为分子扩散是根据其质量的平方根比例引起惰性气体和它们同位素的质量依赖性分馏。然而，最近的实验重点关注单一元素内的同位素分级挑战这种广泛接受的假设。确定Ne，Ar，Kr和Xe同位素的确定分馏因子显示，仅在所谓的平方根关系中仅遵循AR，而在NE，Kr和Xe元素内没有发现浓度。尚未理解ar的这种意外分歧的原因。我们的计算练习的目的是建立在水中惰性气体分子扩散背后的分子分辨机制。我们使分子间相互作用弱的假设与溶解在水中的惰性气体的动态性质相关。因此，我们使用AB Initio分子动力学明确占电子自由度。取决于疏水性颗粒如惰性气体的尺寸和极化性，它们在水中的致密和极性液体中的运动受到不同的扩散制度：小颗粒的间腔跳跃机制（他，NE）如果一个关键则分解粒径达到。对于大颗粒（KR，XE）的情况，通过水溶剂的运动受到导致流体动力学扩散的大规模粘性摩擦的管辖。最后，AR落在两个扩散的方案之间，其中颗粒分散在周围水分子的分子碰撞时间标度下繁殖。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号