Tarmyshov Konstantin B, Müller-Plathe Florian
Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstrasse 20, 64287 Darmstadt, Germany.
J Chem Phys. 2007 Feb 21;126(7):074702. doi: 10.1063/1.2472357.
A molecular dynamics model and its parametrization procedure are devised and used to study adsorption of isopropanol on platinum(111) (Pt(111)) surface in unsaturated and oversaturated coverages regimes. Static and dynamic properties of the interface between Pt(111) and liquid isopropanol are also investigated. The magnitude of the adsorption energy at unsaturated level increases at higher coverages. At the oversaturated coverage (multilayer adsorption) the adsorption energy reduces, which coincides with findings by Panja et al. in their temperature-programed desorption experiment [Surf. Sci. 395, 248 (1998)]. The density analysis showed a strong packing of molecules at the interface followed by a depletion layer and then by an oscillating density profile up to 3 nm. The distribution of individual atom types showed that the first adsorbed layer forms a hydrophobic methyl "brush." This brush then determines the distributions further from the surface. In the second layer methyl and methine groups are closer to the surface and followed by the hydroxyl groups; the third layer has exactly the inverted distribution. The alternating pattern extends up to about 2 nm from the surface. The orientational structure of molecules as a function of distance of molecules is determined by the atom distribution and surprisingly does not depend on the electrostatic or chemical interactions of isopropanol with the metal surface. However, possible formation of hydrogen bonds in the first layer is notably influenced by these interactions. The surface-adsorbate interactions influence the mobility of isopropanol molecules only in the first layer. Mobility in the higher layers is independent of these interactions.
设计并使用了一个分子动力学模型及其参数化程序，以研究不饱和和过饱和覆盖度条件下异丙醇在铂（111）（Pt(111)）表面的吸附情况。还研究了Pt(111)与液态异丙醇之间界面的静态和动态性质。在不饱和覆盖度下，吸附能的大小在较高覆盖度时会增加。在过饱和覆盖度（多层吸附）时，吸附能降低，这与Panja等人在其程序升温脱附实验中的发现一致[《表面科学》395, 248 (1998)]。密度分析表明，界面处分子紧密堆积，随后是一个耗尽层，然后是高达3纳米的振荡密度分布。单个原子类型的分布表明，第一个吸附层形成了一个疏水的甲基“刷”。这个“刷”随后决定了离表面更远的分布。在第二层中，甲基和次甲基基团更靠近表面，随后是羟基；第三层则具有完全相反的分布。这种交替模式从表面延伸到约2纳米。分子的取向结构作为分子距离的函数，由原子分布决定，令人惊讶的是，它不依赖于异丙醇与金属表面的静电或化学相互作用。然而，第一层中可能形成的氢键受到这些相互作用的显著影响。表面 - 吸附质相互作用仅影响第一层中异丙醇分子的迁移率。较高层中的迁移率与这些相互作用无关。
