Surface diffusion

Figure 1. Model of a single adatom diffusing across a square surface lattice. Note the frequency of vibration of the adatom is greater than the jump rate to nearby sites. Also, the model displays examples of both nearest-neighbor jumps (straight) and next-nearest-neighbor jumps (diagonal). Not to scale on a spatial or temporal basis.

Figure 2. Diagram of the energy landscape for diffusion in one dimension. x is displacement; E(x) is energy; Q is the heat of adsorption or binding energy; a is the spacing between adjacent adsorption sites; Ediff is the barrier to diffusion.

Figure 3. Model of six adatoms diffusing across a square surface lattice. The adatoms block each other from moving to adjacent sites. As per Fick’s law, flux is in the opposite direction of the concentration gradient, a purely statistical effect. The model is not intended to show repulsion or attraction, and is not to scale on a spatial or temporal basis.

Figure 4. Model of an atomic exchange mechanism occurring between an adatom (pink) and surface atom (silver) at a square surface lattice (blue). The surface atom becomes an adatom. Not to scale on a spatial or temporal basis.

Surface diffusion is a general process involving the motion of adatoms, molecules, and atomic clusters (adparticles) at solid material surfaces. The process can generally be thought of in terms of particles jumping between adjacent adsorption sites on a surface, as in figure 1. Just as in bulk diffusion, this motion is typically a thermally promoted process with rates increasing with increasing temperature. Many systems display diffusion behavior that deviates from the conventional model of nearest-neighbor jumps. Tunneling diffusion is a particularly interesting example of an unconventional mechanism wherein hydrogen has been shown to diffuse on clean metal surfaces via the quantum tunneling effect.

单词	Surface diffusion
释义	Surface diffusion 英语百科 Surface diffusion Surface diffusion is a general process involving the motion of adatoms, molecules, and atomic clusters (adparticles) at solid material surfaces. The process can generally be thought of in terms of particles jumping between adjacent adsorption sites on a surface, as in figure 1. Just as in bulk diffusion, this motion is typically a thermally promoted process with rates increasing with increasing temperature. Many systems display diffusion behavior that deviates from the conventional model of nearest-neighbor jumps. Tunneling diffusion is a particularly interesting example of an unconventional mechanism wherein hydrogen has been shown to diffuse on clean metal surfaces via the quantum tunneling effect.
随便看	psoriasis valgaris的意思 psoriasis verruciformis的意思 psoriasis verrucosa的意思 psoriasis vulgaris的意思 Psoriasis with arthropathy的意思 Psoriasis with pustules的意思 psoriasis zosteriformis的意思 psoriatic的意思 psoriatic arthritis的意思 Psoriatic arthropathy的意思 Psoriatic erythroderma的意思 psoriatic exfoliative dermatitis的意思 psoriatic onycholysis的意思 psoriatic的意思 Psoriazin的意思 psoric的意思 Psorigel的意思 Psorinail的意思 psoris的意思 psorocomium的意思 psoroid的意思 psoroma sphinctrinum的意思 psoromic acid的意思 Psorophora的意思 Psorophora columbiae的意思