硅（111）-7×7表面卤代烷围捕形成及表面卤化的分子动力学

Molecular dynamics of haloalkane corral formation and surface halogenation at Si(111)-7 x 7.

作者信息

Dobrin S, Harikumar K R, Jones R V, McNab I R, Polanyi J C, Waqar Z, Yang J S Y

机构信息

Lash Miller Chemical Laboratories, Department of Chemistry and Institute of Optical Science, University of Toronto, 80 St. George Street, Ontario M5S 3H6, Canada.

出版信息

J Chem Phys. 2006 Oct 7;125(13):133407. doi: 10.1063/1.2352745.

DOI:10.1063/1.2352745

PMID:17029481

Abstract

Long-chain organic molecules, 1-halododecane, RX (X = Cl,Br), adsorbed on Si(111)-7 x 7 were shown to form stable dimeric corrals; type I around corner holes and type II around corner adatoms S. Dobrin et al. [Surf. Sci. Lett. 600, L43 (2006)]. Here we examine the molecular dynamics of corral formation, in which mobile physisorbed adsorbates spontaneously convert to immobile. At high coverage the mechanism gives evidence of involving collisions between mobile vertical monomers, giving types I and II immobile horizontal dimers, vD +vD -->h2 (I, II). At low coverage mobile vertical monomers collide with immobile horizontal ones to form largely type-II corrals, vD + h-->h2 (II). Thermal reaction of corrals with X = Br brominates the surface by two distinct molecular pathways, thought to have more general applicability: "daughter-mediated" reaction of vertical v(A) with a low activation energy (here Ea approximately 5 kcal mol(-1)) and "parent-mediated" reaction of horizontal h or h2 with high activation energy (here Ea = 29 kcal mol(-1)).

摘要

研究表明，吸附在Si(111)-7×7上的长链有机分子1-卤代十二烷RX（X = Cl、Br）会形成稳定的二聚体围栏；一种是围绕角孔的I型，另一种是围绕角位吸附原子的II型（S. Dobrin等人，《表面科学快报》600, L43 (2006)）。在此，我们研究了围栏形成的分子动力学，即移动的物理吸附吸附质自发转变为固定吸附质的过程。在高覆盖度下，该机制表明涉及移动的垂直单体之间的碰撞，形成I型和II型固定的水平二聚体，vD + vD --> h2 (I, II)。在低覆盖度下，移动的垂直单体与固定的水平单体碰撞，主要形成II型围栏，vD + h --> h2 (II)。当X = Br时，围栏的热反应通过两种不同的分子途径使表面溴化，这两种途径被认为具有更广泛的适用性：垂直v(A)的“子介导”反应，活化能较低（此处Ea约为5 kcal mol⁻¹），以及水平h或h2的“母介导”反应，活化能较高（此处Ea = 29 kcal mol⁻¹）。