Luntz A C, Persson M
Physics Department, University of Southern Denmark, 5230 Odense M, Denmark.
J Chem Phys. 2005 Aug 15;123(7):074704. doi: 10.1063/1.2000249.
Using density-functional theory we calculate friction coefficients describing the damping of nuclear motion into electron-hole pair excitation for the two best-known examples of activated adsorption: H2 dissociation on a Cu(111) surface and N2 dissociation on a Ru(0001) surface. In both cases, the frictions increase dramatically along the reaction path towards the transition state and can be an order of magnitude larger there than typical in the molecularly adsorbed state. In addition, the frictions for N2/Ru(0001) are typically an order of magnitude larger than for H2/Cu(111). We rationalize these trends in terms of the electron structure as the systems proceed to dissociation along the reaction paths. Combining these friction coefficients with the potential-energy surface in quasiclassical dynamics allows first-principles studies of the importance of the breakdown in the Born-Oppenheimer approximation in describing the chemistry. We find that nonadiabatic effects are minimal for the H2/Cu(111) system, but are quite important for N2/Ru(0001).
利用密度泛函理论，我们计算了摩擦系数，该系数描述了核运动衰减为电子 - 空穴对激发的情况，针对活化吸附的两个最著名例子：H₂ 在 Cu(111) 表面的解离和 N₂ 在 Ru(0001) 表面的解离。在这两种情况下，沿着朝向过渡态的反应路径，摩擦力急剧增加，并且在那里可能比分子吸附态时的典型值大一个数量级。此外，N₂/Ru(0001) 的摩擦力通常比 H₂/Cu(111) 的大一个数量级。当系统沿着反应路径进行解离时，我们根据电子结构对这些趋势进行了合理化解释。将这些摩擦系数与准经典动力学中的势能面相结合，使得能够对玻恩 - 奥本海默近似失效在描述化学反应中的重要性进行第一性原理研究。我们发现，非绝热效应对于 H₂/Cu(111) 系统最小，但对于 N₂/Ru(0001) 却相当重要。
