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首页> 外文期刊>Physical review >Adsorption Of Chlorine On Ag(111): No Subsurface Cl At Low Coverage
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Adsorption Of Chlorine On Ag(111): No Subsurface Cl At Low Coverage

机译：氯在Ag（111）上的吸附：低覆盖率下无地下Cl

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The adsorption of molecular and atomic chlorine on perfect Ag(111) surface has been studied and characterized by means of extensive density-functional-theory calculations. For the molecular adsorption, we find that the dissociation of Cl_2 proceeds with an almost vanishing barrier. As for the adsorption of atomic Cl, on-surface, subsurface, and substitutional adsorptions are considered as a function of the coverage. At coverage lower than 1/2 ML, the on-surface adsorption displays the most exothermic chemisorption energies, whereas the mixed on-surface+subsurface and on-surface + substitutional adsorption modes become competitive with pure on-surface adsorption at about 1/2 ML of coverage and at higher coverages even preferred. The analysis of the adsorption free energy as a function of chlorine chemical potential reveals that the on-surface (3~(1/2) × 3~(1/2))R30° adsorption phase is thermodynamically the most stable over a very broad range of Cl chemical potential. The mixed adsorption modes become thermodynamically more stable at high coverage for values of the Cl chemical potential that are substantially larger than those needed to form silver chloride. This finding seems to indicate that the formation of mixed adsorption phases, if they would ever occur, cannot be due to thermodynamic equilibrium but can only result from kinetic effects. We also find that the presence of open surface steps does not stabilize the subsurface Cl adsorption at low coverage. However due to the stronger Cl-surface interaction near steps, the mixed on-surface+subsurface adsorption on Ag(210) at high coverage becomes thermodynamically the most stable phase at Cl chemical potential close to that needed for the formation of bulk AgCl.
机译：研究了分子和原子氯在完美的Ag（111）表面上的吸附，并通过大量的密度泛函理论计算对其进行了表征。对于分子吸附，我们发现Cl_2的离解以几乎消失的势垒进行。至于原子Cl的吸附，表面，亚表面和替代吸附被视为覆盖率的函数。当覆盖率低于1/2 ML时，表面吸附显示出最大的放热化学吸附能，而混合的表面+次表面和表面+替代吸附模式在大约1/2的情况下与纯表面吸附竞争最好是ML覆盖率和更高的覆盖率。分析吸附自由能与氯化学势的关系，发现在很宽的范围内，表面（3〜（1/2）×3〜（1/2））R30°吸附相在热力学上最稳定Cl化学势的范围。对于高得多的Cl化学势值，混合的吸附模式在热力学上变得更加稳定，因为Cl化学势的值明显大于形成氯化银所需的那些。这一发现似乎表明，混合吸附相的形成（如果会发生的话）不能归因于热力学平衡，而只能由动力学效应引起。我们还发现，在低覆盖率下，开放表面台阶的存在并不能稳定地下Cl的吸附。但是，由于台阶附近的Cl-表面相互作用更强，因此在高覆盖率下Ag（210）上混合的表面+亚表面吸附在热力学上成为Cl化学势最稳定的相，接近于形成整体AgCl所需的相。

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