Scheme of supercells employed in the DFT calculations using the example of W(110): bulk lead (a) and surface slab (b). W atoms are depicted by blue spheres. The purple (dark) volume corresponds to the metallic lead, the green (light) volume to the scattering region. The atoms in the unshaded part of the slab supercell serve as a decoupling region from the adjacent vacuum layer.
Richardson-Dushman plot of thermionic emission from a close-packed tungsten surface with experimental data (•) from Ref. 24 and DFT results (■) based on the RPBE functional.
Calculated thermionic current densities for cesiated W(110) based on the RPBE functional. The red (solid) line shows a fit of the DFT data to the Richardson-Dushman equation for monolayer Cs-coverage, the blue (dashed) line for (near optimal) 0.69 monolayer coverage.
Brillouin zone-resolved thermionic emission from clean (a) and cesiated (0.69 ML) W(110) (b) at k B T = 0.17 eV obtained from RPBE calculations. The Brillouin zone of the cesiated system is smaller due to the 3×2 W(110) surface area.
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