Quantitative relation between the thermionic contrast of metal surfaces and their degree of monocrystallization

▶ We calculate effective work functions (ϕ+,ϕe) for ionic and electronic emissions. ▶ All of ϕ+,ϕe and contrast (Δϕ* ≡ ϕ+ − ϕe) agrees well with experimental data. ▶ Δϕ* = 4c δm (1 − δm) for monocrystallization degree (δm) of 0.5-1. ▶ For W, Δϕ* = c = 0.53 ± 0.09 eV for δm ≲ 0.5, agreeing with experimental data. ▶ Our theoretical model gives a clue to clarify the peculiarity of work function.