Rotation assisted diffusion of water trimers on Pd{111}

SURFACE SCIENCE

卷:648

Article

Ranea, Victor A.¹  de Andres, P. L.² 

[1] Univ Nacl La Plata, CCT La Plata CONICET, Inst Invest Fisicoquim Teor & Aplicadas INIFTA, Fac Ciencias Exactas, Calle 64 & Diagonal 113, RA-1900 La Plata, Buenos Aires, Argentina

[2] Donostia Int Phys Ctr, C Manuel de Lardizabal 4, Donostia San Sebastian 20018, Spain

关键词: Water;    Pd{111};    Trimer;    Diffusion;    Rotations;    Density functional theory;   

DOI  :  10.1016/j.susc.2015.10.052

来源: Elsevier

【 摘 要 】

Diffusion barriers for a cluster of three water molecules on Pd{111} have been estimated from ab-initio Density Functional Theory. A model for the diffusion of a cluster of three water molecules (trimer) based in rotations yields a simple explanation of why the cluster can diffuse faster than a single water molecule by a factor approximate to 10(2) [1]. This model is based on the differences between the adsorption geometry for the three molecules forming the timer. One member interacts strongly with the surface and sits closer to the surface (d) while the other two interact weakly and stay at a larger separation from the surface (u). The trimer rotates nearly freely around the axis determined by the d-like monomer. Translations of the whole trimer imply breaking the strong interaction of the d-like molecule with the surface with a high energy cost. Alternatively, thermal fluctuations can exchange the position of the molecule sitting closer to the surface with a lower energetic cost. Rotations around different axis yield a diffusion mechanism where the strong interaction is maintained along the diffusion path, therefore lowering the effective activation barrier. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

Free