Resonant Lifetime of Core-Excited Organic Adsorbates from First Principles

Abstract

We investigate by first-principles simulations the resonant electron-transfer lifetime from the excited state of an organic adsorbate to a semiconductor surface, namely, isonicotinic acid on rutile TiO 2 (110). The molecule−substrate interaction is described using density functional theory, while the effect of a truly semi-infinite substrate is taken into account by Green's function techniques. Excitonic effects due to the presence of core-excited atoms in the molecule are shown to be instrumental to understand the electron-transfer times measured using the so-called core-hole-clock technique. In particular, for the isonicotinic acid on TiO 2 (110), we find that the charge injection from the LUMO is quenched, since this state lies within the substrate band gap. We compute the resonant charge-transfer times from LUMO+1 and LUMO+2, and systematically investigate the dependence of the elastic lifetimes of these states on the alignment among adsorbate and substrate states.

Effect of Structural Fluctuations on Elastic Lifetimes of Adsorbate States: Isonicotinic Acid on Rutile(110)

“…18,44 and extensions to MOs in Refs. 19,45. For the calculation of the MOs the hydrogen atom dissociated upon adsorption is added back to the molecule in order to saturate free bonds.…”

“…This is expected to give good results as the coefficients for the hydrogen atom's orbitals are negligible for the MOs of interest 4 here. 19 We subsequently calculate the projected density of states (PDOS) on the reference wavepackets:…”

“…Another difference with respect to the model in Ref. 19 lies in the chosen adsorption site for the dissociated hydrogen, that is put closer to the molecule in the current work, following the CPMD study. 32 However, we explicitly checked that this choice has negligible effect on the reported results.…”

“…The values for the equilibrium adsorption shown in brackets are taken from Ref. 19. All quantities are further defined in the text.…”

“…[28][29][30][31] Along similar lines, in this work, we investigate the elastic lifetimes of the frontier orbitals of isonicotinic acid on rutile TiO 2 (110) in the presence of structural fluctuations by sampling static nuclear configurations from ab-initio molecular dynamics at room temperature. 32 Thereby we extended previous work considering the equilibrium structure (0 K) 19 to include the effect of temperature. This approach does not include non-adiabatic effects explicitly.…”