Seenivasan H, Tiwari Ashwani K
Indian Institute of Science Education and Research Kolkata, Mohanpur 741252, India.
J Chem Phys. 2014 May 7;140(17):174704. doi: 10.1063/1.4873898.
Water adsorption and dissociation on Ni(110) surface is studied in detail and compared with its close packed counterparts using density functional theory calculations. Water adsorption occurs on the top site as found on Ni(100) and Ni(111) but the adsorption is stronger on Ni(110). H and OH preferably adsorb on the short bridge sites (brgshort) opposed to hollow sites on (100) and (111) surfaces. Energy barriers for water molecule dissociation on Ni(110) as obtained from the transition state (TS) calculations were low compared to other Ni low indexed surfaces. TS geometries at different positions of the lattice coordinate, Q, were obtained to study the effect of surface temperature on dissociation of H2O molecules. These calculations revealed that second layer atoms were also involved in the TS. Dissociation probabilities are obtained using a semi-classical approximation by sampling Q for a Boltzmann distribution at different temperatures. Results showed that the increasing surface temperature significantly increases the dissociation probabilities at lower energies and saturates near the barrier for dissociation. Although the contribution from both top and second layers is similar at low surface temperatures, motion of top layer atoms contribute more towards dissociation probability at higher surface temperatures. Dissociation probabilities obtained are more than one order of magnitude higher than that on Ni(100) and Ni(111) surfaces suggesting Ni(110) to be more reactive among the low indexed Ni surfaces.
利用密度泛函理论计算,详细研究了水在Ni(110)表面的吸附和解离,并将其与密排对应物进行了比较。水的吸附发生在顶位,这与在Ni(100)和Ni(111)上发现的情况相同,但在Ni(110)上的吸附更强。与(100)和(111)表面上的空心位相比,H和OH更倾向于吸附在短桥位(brgshort)上。与其他低指数Ni表面相比,通过过渡态(TS)计算得到的Ni(110)表面水分子解离的能垒较低。获得了晶格坐标Q不同位置处的TS几何结构,以研究表面温度对H2O分子解离的影响。这些计算表明,第二层原子也参与了过渡态。通过在不同温度下对玻尔兹曼分布的Q进行采样,使用半经典近似获得解离概率。结果表明,表面温度升高显著增加了较低能量下的解离概率,并在解离势垒附近达到饱和。虽然在低表面温度下顶层和第二层的贡献相似,但在较高表面温度下,顶层原子的运动对解离概率的贡献更大。获得的解离概率比在Ni(100)和Ni(111)表面上的解离概率高一个多数量级,这表明在低指数Ni表面中,Ni(110)更具反应活性。