论文标题
硅酸钠玻璃表面的结构和振动特性
Structure and vibrational properties of sodium silicate glass surfaces
论文作者
论文摘要
使用分子动力学模拟，我们研究了钠硅酸盐玻璃表面对钠含量以及表面性质的结构和振动特性的依赖性。考虑了两种类型的玻璃表面：熔体形成的表面（MS），其中具有自由表面的液体已被冷却到玻璃相中，并通过玻璃样品的张拉力负载获得断裂表面（FS）。我们发现，在Na和非桥接氧原子中，MS比FS和散装玻璃更丰富，而FS的结构缺陷浓度更高，例如两元环和不足协调的SI。我们将这些结构性差异与玻璃的生产历史和NA离子的迁移率相关联。还发现，对于Na-poor系统，与幂律的组成和局部原子电荷密度衰减中的波动是距表面距离的函数，而Na-富富的系统显示出指数衰变，典型的衰减长度为$ \ \ \ \ \ \ \ \ 2.3 $ 〜〜。状态的振动密度表明，表面的存在导致系统中特征频率的降低。两元的戒指引起了$ \ of your \ com〜cm $^{ - 1} $的发音频段，这是一个很好的一致性实验观察。
Using molecular dynamics simulations we investigate the dependence of the structural and vibrational properties of the surfaces of sodo-silicate glasses on the sodium content as well as the nature of the surface. Two types of glass surfaces are considered: A melt-formed surface (MS) in which a liquid with a free surface has been cooled down into the glass phase and a fracture surface (FS) obtained by tensile loading of a glass sample. We find that the MS is more abundant in Na and non-bridging oxygen atoms than the FS and the bulk glass, whereas the FS has higher concentration of structural defects such as two-membered rings and under-coordinated Si than the MS. We associate these structural differences to the production histories of the glasses and the mobility of the Na ions. It is also found that for Na-poor systems the fluctuations in composition and local atomic charge density decay with a power-law as a function of distance from the surface while Na-rich systems show an exponential decay with a typical decay length of $\approx2.3$~Å. The vibrational density of states shows that the presence of the surfaces leads to a decrease of the characteristic frequencies in the system. The two-membered rings give rise to a pronounce band at $\approx880$~cm$^{-1}$ which is in good agreement experimental observations.
