Curious Mechanism of the Dissociative Chemisorption of Ammonia on Ru(0001)

Abstract

Dissociative chemisorption of polyatomic molecules on metals, which is relevant to heterogeneous catalysis, usually proceeds through a rotationally adiabatic or rotational sudden mechanism. The reaction is usually either direct or proceeds through a trapped molecular chemisorbed state. Here, ab initio molecular dynamics is used to model the dissociative chemisorption of ammonia on Ru(0001). The reaction mechanism is neither rotationally adiabatic nor rotational sudden, with clearly distinct and nonstatistical initial and time-of-reaction orientation distributions. A reasonably good agreement is obtained between the computed and previously measured sticking probabilities. Under the conditions investigated, the reaction of NH3 goes through a molecular chemisorption-like state, but the reaction is direct.