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Hydration and reaction mechanisms on sodium silicate glass surfaces from molecular dynamics simulations with reactive force fields
Journal of the American Ceramic Society ( IF 3.9 ) Pub Date : 2020-03-19 , DOI: 10.1111/jace.17059 Thiruvilla S. Mahadevan 1 , Jincheng Du 1
Journal of the American Ceramic Society ( IF 3.9 ) Pub Date : 2020-03-19 , DOI: 10.1111/jace.17059 Thiruvilla S. Mahadevan 1 , Jincheng Du 1
Affiliation
Recent development of reactive force fields have enabled molecular dynamics simulations of interactions between silicate glasses and water at the atomistic scale. While multicomponent silicate glasses encompass a wide variety of compositions and properties, one common structural feature in these glasses is the combination of the network structure that is made up of silica tetrahedra linked through corner sharing interspersed with network modifiers like alkali and alkaline‐earth ions that break up the Si–O–Si linkages by forming nonbridging oxygen. In reactions with water, ion exchange between alkali ions in the glass and proton or hydronium in the solution, as well as hydrolysis reaction of the Si–O–Si linkages and subsequent silanol formation, is observed and well documented. We have used a set of recently developed reactive force field to investigate the reactions between water and the surfaces of silica and sodium silicate glasses of different compositions for reactions up to 8 nanoseconds. Our results indicate sodium leaching into water and diffusion of water molecules up to 25 Å into the glass surface. We examined the structural and compositional changes inside the glass and around the diffused ions and use these to explain the rates of silanol formation at the surface. We also observed proton transport in the glass which has an indirect influence on the silanol formation rates. While the surface of the glass was rough to start with, it undergoes further modification into a hydrated gel‐like structure in the glass for up to 5 Å in the higher alkali containing glasses. It was found that the leached sodium ions remain close to the interface and that fragments of silicate network from the surface is capable of dislodging from the bulk glass and enter the aqueous solution. These simulations thus provide insights into the formation and structure of an alteration layers commonly observed in multicomponent silicate glasses corroded in aqueous solutions.
中文翻译:
利用反作用力场的分子动力学模拟研究硅酸钠玻璃表面的水化反应机理
反作用力场的最新发展使得能够以原子尺度对硅酸盐玻璃与水之间的相互作用进行分子动力学模拟。尽管多组分硅酸盐玻璃包含多种成分和性能,但这些玻璃的一个常见结构特征是网络结构的组合,该网络结构由四角形二氧化硅组成,该四面体通过角共享连接,并散布有诸如碱金属和碱土金属离子之类的网络改性剂。通过形成非桥连氧来破坏Si-O-Si键。在与水的反应中,观察到并充分记录了玻璃中碱离子与溶液中的质子或水合氢离子之间的离子交换,以及Si-O-Si键的水解反应和随后的硅烷醇形成。我们使用了一 组最近开发的反作用力场研究了水与不同组成的二氧化硅和硅酸钠玻璃表面之间的反应,反应时间长达8纳秒。我们的结果表明钠浸入水中,水分子扩散至25Å进入玻璃表面。我们检查了玻璃内部以及扩散离子周围的结构和组成变化,并用这些变化解释了表面上硅烷醇形成的速率。我们还观察到玻璃中的质子传输对硅醇形成速率有间接影响。尽管玻璃表面起初很粗糙,但在含碱度更高的玻璃中,它经过进一步修饰后变成玻璃中的水合凝胶状结构,最高可达到5Å。发现浸出的钠离子保留在界面附近,并且表面的硅酸盐网络碎片能够从块状玻璃中移出并进入水溶液。因此,这些模拟提供了对蚀变层的形成和结构的认识,蚀变层通常在水溶液中腐蚀的多组分硅酸盐玻璃中观察到。
更新日期:2020-04-22
中文翻译:
利用反作用力场的分子动力学模拟研究硅酸钠玻璃表面的水化反应机理
反作用力场的最新发展使得能够以原子尺度对硅酸盐玻璃与水之间的相互作用进行分子动力学模拟。尽管多组分硅酸盐玻璃包含多种成分和性能,但这些玻璃的一个常见结构特征是网络结构的组合,该网络结构由四角形二氧化硅组成,该四面体通过角共享连接,并散布有诸如碱金属和碱土金属离子之类的网络改性剂。通过形成非桥连氧来破坏Si-O-Si键。在与水的反应中,观察到并充分记录了玻璃中碱离子与溶液中的质子或水合氢离子之间的离子交换,以及Si-O-Si键的水解反应和随后的硅烷醇形成。我们使用了一 组最近开发的反作用力场研究了水与不同组成的二氧化硅和硅酸钠玻璃表面之间的反应,反应时间长达8纳秒。我们的结果表明钠浸入水中,水分子扩散至25Å进入玻璃表面。我们检查了玻璃内部以及扩散离子周围的结构和组成变化,并用这些变化解释了表面上硅烷醇形成的速率。我们还观察到玻璃中的质子传输对硅醇形成速率有间接影响。尽管玻璃表面起初很粗糙,但在含碱度更高的玻璃中,它经过进一步修饰后变成玻璃中的水合凝胶状结构,最高可达到5Å。发现浸出的钠离子保留在界面附近,并且表面的硅酸盐网络碎片能够从块状玻璃中移出并进入水溶液。因此,这些模拟提供了对蚀变层的形成和结构的认识,蚀变层通常在水溶液中腐蚀的多组分硅酸盐玻璃中观察到。