Thickness-dependent oxygen chemisorption behaviors on (1 1 1) surfaces of two-dimensional FCC metals Al and Cu: First-principles study.

In this paper, we have studied the different surface oxygen chemisorption behaviors of two-dimensional FCC metal surfaces of Al and Cu with increasing thickness N by first-principles calculations. The charge transfer from substrate to adsorbate O atom is mainly contributed by surface atoms in the Al system, but by surface associated with sub-surface atoms in the Cu system. The shorter Al-O bonding length shows stronger bond strength and interaction than that of Cu O bonding. The thickness-dependence of the binding energy E b , work function Φ, and surface energy E surf in Al(1 1 1) not Cu(1 1 1) shows a periodical oscillation due to QSEs. the oscillations of Al_3 p z PDOS mainly contribute to that of TDOS around E F , thus giving an oscillatory energy state contribution to periodic surface energies and reactivities. Further investigation suggests that QSEs are not only z-direction thickness N but also wavevector-dependence, which is maximum at Γ ¯ point resulting from the strong interlayer coupling interaction between 3 p z orbitals. Besides, the wavevector of Al(1 1 1) is maximum at Γ ¯ point resulting from a strong interlayer coupling interaction between 3 p z states but could become quite small at other symmetry points due to weak intralayer coupling between 3 p x,y states. However, because d-band metals like Cu(1 1 1) have complex Fermi surfaces causing incremental Fermi wavelength anisotropy and larger-amplitude fluctuation of Cu_t 2g at E F , QSEs will be generally canceled. Our systematical calculation results present the oscillations of different periodicity in chemisorption behaviors and physical properties like electronic properties, which can be adapted to tailor catalytic performance, chemical reactions, and even corrosion protection processes in two-dimensional nanostructured film materials. [Display omitted] Oxygen chemisorption is one of the crucial factors to understand the performance of metal materials under special service environments. Here, we investigate the thickness-dependent O chemisorption behaviors on two-dimensional Al(1 1 1) and Cu(1 1 1) films based on first-principles calculations. It is found that the charge transfer from substrate to adsorbate O atom is mainly contributed by surface atoms in the Al system, but by surface associated with sub-surface atoms in the Cu system. Moreover, the thickness-dependent surface energy, work function, and O adsorption energy show an approximate three-monolayer oscillation for the Al surface, but not for the Cu surface. It results from quantum size effects (QSEs) in Al, which are related not only to z-direction size but also to wavevector: the QSEs reach their maximum at Γ ¯ point resulting from strong interlayer coupling interaction between 3 p z orbitals. The oscillations of Al_3 p z PDOS mainly contribute to that of TDOS around E F , thus giving an oscillatory energy state contribution to periodic surface energies and reactivities. However, because d-band metals like Cu(1 1 1) have complex Fermi surfaces causing incremental Fermi wavelength anisotropy and larger-amplitude fluctuation of Cu_t 2g at E F , QSEs will be generally canceled. Our findings may shed light on modeling the chemisorption and intrinsic physical properties, and thereby the distinct surface behaviors of low-dimensional metallic films. [ABSTRACT FROM AUTHOR]