吸附诱导表面应力的分子动力学模拟

应用分子动力学方法结合镶嵌原子势,模拟研究了同质吸附Cu/Cu(100)和异质吸附Al/Ni(100)纳米薄膜中的吸附诱导表面应力.结果表明吸附原子对表面应力的影响主要源于两种原子间的相互作用;吸附原子和底物表面原子的结合将导致底物表面原子之间的化学键的强度减弱和平衡键长增加,从而导致表面压应力增加;吸附原子之间的相互作用也导致表面应力的变化,吸附原子间的吸引作用导致表面拉应力,而排斥作用导致表面压应力.这两种原子间相互作用所引起的表面应力与吸附原子的密度密切相关,吸附原子与底物表面原子的结合所引起的表面应力的大小与吸附原子的密度成线性关系,而吸附原子间的相互作用所引起的表面应力与吸附原子密度间呈非单调的依赖关系.

Molecular dynamics simulation of adsorbate-induced surface stress

Molecular dynamics simulations combined with embedded-atom method(EAM) potentials were carried out on two adsorbate-covered nanofilms,i.e.Cu/Cu(001) and Al/Ni(001),to investigate adsorbate-induced surface stress.Results show that adatoms alter surface stress in two ways.Local interactions of chemisorpted adatoms with the underlying surface atoms result in a reduction of bond strength and an increase in equilibrium bond length between neighboring atoms in the surface,thus giving rise to compressive surface stress.Adatom-adatom interactions also give significant contribution to surface stress.Attractive adatom-adatom interactions give rise to tensile surface stress,while repulsive adatom-adatom interactions give rise to compressive surface stress.The contribution from these two types of atomic interaction to the surface stress exhibits a close association with adatom density.The surface stress induced by the adatom-substrate cohesion linearly associated with the adatom density,while the surface stress induced by the adatom-adatom interactions exhibits a nonmonotonic dependence on the adatom density.