Di Valentin Cristiana, Pacchioni Gianfranco, Bernasconi Marco
Dipartimento di Scienza dei Materiali, Università di Milano-Bicocca, via R. Cozzi 53, 20125 Milano, Italy.
J Phys Chem B. 2006 Apr 27;110(16):8357-62. doi: 10.1021/jp060815f.
Ab initio molecular dynamics (MD) is used to investigate NO reaction processes on the (001) surface of CaO. A novel path is proposed for the first steps of nitrogen oxides reactivity catalyzed by the CaO surface. The mechanism consists of the formation of anionic dimers, adsorbing on the surface cations, at the expense of oxidized NO species adsorbed on surface anions. The complete charge-transfer process takes place in two steps, producing first monovalent anionic dimers (NO)2- and, later on, divalent anionic dimers (NO)2(2-). These redox processes cause spin quenching and are observed in the short time scale of the ab initio MD simulation at 300 K. The results presented provide a rationalization of a recent electron spin resonance (ESR) investigation indicating that the spectroscopy is silent to most of the nitrogen oxide species adsorbed on CaO powders, despite deposition of paramagnetic NO molecules at room temperature.
采用从头算分子动力学（MD）方法研究一氧化氮（NO）在CaO（001）表面的反应过程。针对CaO表面催化氮氧化物反应的第一步，提出了一条新路径。该反应机理包括以吸附在表面阴离子上的氧化态NO物种为代价，形成吸附在表面阳离子上的阴离子二聚体。完整的电荷转移过程分两步进行，首先生成单价阴离子二聚体(NO)₂⁻，随后生成二价阴离子二聚体(NO)₂²⁻。这些氧化还原过程导致自旋猝灭，且在300K的从头算MD模拟的短时间尺度内被观测到。本文给出的结果为最近的电子自旋共振（ESR）研究提供了一种合理解释，该研究表明，尽管在室温下沉积了顺磁性NO分子，但光谱对吸附在CaO粉末上的大多数氮氧化物物种并不敏感。
