Electronic and crystal structure of the Pt(111)-(√3 × √3)R30°-K system

We present the density functional calculation results for K adsorption on Pt(111) in a (√3 × √3)R30° structure. The site preference, surface relaxation, work function, and electron structure of the system are analyzed. The hcp hollow position is found to be the most favorable for K adsorption. The calculated surface relaxations and adsorption geometry are in agreement with available experimental data. It is demonstrated that the K adsorption leads to the disappearance of a number of platinum surface and resonance states in the energy region above −2 eV and to the appearance of new platinum surface features, as well as bands that are significantly localized at the adsorbate. It is found that the K adsorption 1) transforms the Shockley surface state lying in the bulk band gap near the Γ¯ point on the clean Pt surface into the state localized at the K adlayer and 2) pushes this state up in energy by about 0.17 eV relative to the bottom of the bulk band gap. It is shown that the Rashba spin-orbit strength parameter in this state is surprisingly greater than the respective parameter in the Shockley surface state on Au(111) and Bi(111).
We acknowledge the Tomsk State University competitiveness programme (Project No. 8.1.01.2017) and partial support by the Saint Petersburg State University (Project No. 15.61.202.2015). Y.M.K. acknowledges the Russian Foundation for Basic Research (Project No. 15-02-02717-a) and the Fundamental Research Program of the State Academies of Sciences for 2013–2020. E.V.C. acknowledges the Spanish Ministry of Science and Innovation (Grant No. FIS2016-75862-P).