Abstract

This work is motivated by the results obtained during a study on the tritiated water adsorbed in zeolite [L. Frances et al., J. Phys. Chem. C, 119, 28462 (2015)]. The decomposition of water by radiolysis leads to the production of dioxygen and dihydrogen as main stable products. By studying the evolution of their quantities of matter, one can note an increase in a first stage, followed by a decrease after a few hundred days of storage until complete disappearance. This interesting process depends on the water loading ratios, expressed in mass percentage, lying between 4%, and 19%; such a phenomenon is not observed in saturated zeolite. Our goal is to determine, through numerical simulations, how this disappearance, which is associated with the recombination of the radiolysis products, occurs by making a microscopic study on the adsorption of H₂O, H₂, and O₂ molecules on 4A zeolite (Z4A). Computational physics is useful to understand the effects of molecule adsorption on its structure and also to closely examine the molecule-zeolite and molecule-molecule interactions. Indeed, different simulation methods are used from static to dynamic studies employing both quantum and classical tools with the periodical structure of Z4A. To summarize, the adsorption of molecules from the radiolysis of water are studied according to different points of view (quantum and classical) using various numerical simulation tools, such as density functional theory for ab initio structural optimization and energy calculation, Monte Carlo to study the distribution of the adsorbed molecules in the zeolite, and molecular dynamics to follow the evolution of the system (molecule + zeolite) over time depending on the temperature, in order to extract as much information as possible (structurally, statistically, energy, electronically) to understand the main problematic of this work: How do stable molecules issued from radiolysis recombine in Z4A?

摘要

这项工作是受对during化沸石[L. Frances等，J。Phys。化学 C，119，28462（2015）]。水通过辐射分解而分解，产生了主要的稳定产物二氧和二氢。通过研究其物质量的演变，人们可以注意到第一阶段的物质增加，然后经过数百天的储存直至完全消失，随后逐渐减少。这个有趣的过程取决于载水率（以质量百分比表示），介于4％和19％之间。在饱和沸石中未观察到这种现象。我们的目标是通过数值模拟，通过对H的吸附进行微观研究，确定这种消失与放射分解产物的重组有关如何发生。₂ O，H ₂和O ₂分子在4A沸石（Z4A）上。计算物理学对于理解分子吸附对其结构的影响以及密切检查分子-沸石和分子-分子之间的相互作用非常有用。实际上，从静态研究到动态研究，都采用了具有Z4A周期性结构的量子和经典工具，采用了不同的仿真方法。综上所述，使用各种数值模拟工具（例如从头算结构优化和能量计算的密度泛函理论，蒙特卡洛方法研究）的各种数值模拟工具，根据不同的观点（量子和经典）研究了水辐射分解过程中分子的吸附。吸附分子在沸石中的分布，以及随温度变化随系统演化的分子动力学（分子+沸石），