A reactive molecular dynamics simulation of the silica-water interface
A reactive molecular dynamics simulation of the silica-water interface
复制标题
DOI：
10.1063/1.3407433
复制
发表时间：
2010-05-07
影响因子：
4.4
通讯作者：
Pandit, Sagar A.
中科院分区：
文献类型：
--
作者：
Fogarty, Joseph C.;Aktulga, Hasan Metin;Pandit, Sagar A.
我们报告了我们的研究二氧化硅-水界面使用反应分子动力学。这种史无前例的模拟达到了研究该系统的详细化学成分所需的长度和时间尺度。我们的分子动力学方法是基于van Duin的ReaxFF力场[J]。理论物理。化学。[j].农业工程学报，2003,19(3)。具体的ReaxFF实现（SERIALREAX）和力场首先在纯二氧化硅和水系统的结构特性上进行了验证。通过研究界面化学成分的变化，分析了新切割的二氧化硅表面上活性水与悬垂键之间的化学反应。在我们的模拟中，涉及硅醇基团的反应在大约250ps的时间内达到化学平衡。我们观察到，水分子通过我们称之为“跳氢”的质子转移过程穿透二氧化硅膜，这与Grotthuss机制类似。在这个过程中，氢原子通过与大块二氧化硅中的氧原子结合和解离来穿过薄膜，而不是完整的水分子扩散。这个过程的有效扩散常数，取氢原子在二氧化硅中的扩散常数，计算为1.68 × 10(-6) cm(2)/s。在靠近二氧化硅表面的水分子的极化也被观察到。随后偶极子的排列导致硅板和水之间的电位差约为10.5 V。(C) 2010年美国物理研究所。(doi: 10.1063/1.3407433)
We report our study of a silica-water interface using reactive molecular dynamics. This first-of-its-kind simulation achieves length and time scales required to investigate the detailed chemistry of the system. Our molecular dynamics approach is based on the ReaxFF force field of van Duin [J. Phys. Chem. A 107, 3803 (2003)]. The specific ReaxFF implementation (SERIALREAX) and force fields are first validated on structural properties of pure silica and water systems. Chemical reactions between reactive water and dangling bonds on a freshly cut silica surface are analyzed by studying changing chemical composition at the interface. In our simulations, reactions involving silanol groups reach chemical equilibrium in similar to 250 ps. It is observed that water molecules penetrate a silica film through a proton-transfer process we call "hydrogen hopping," which is similar to the Grotthuss mechanism. In this process, hydrogen atoms pass through the film by associating and dissociating with oxygen atoms within bulk silica, as opposed to diffusion of intact water molecules. The effective diffusion constant for this process, taken to be that of hydrogen atoms within silica, is calculated to be 1.68x10(-6) cm(2)/s. Polarization of water molecules in proximity of the silica surface is also observed. The subsequent alignment of dipoles leads to an electric potential difference of similar to 10.5 V between the silica slab and water. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3407433]