How much does surface polymorphism influence the work function of organic/metal interfaces?

Andreas Jeindl, Lukas Hörmann, Oliver Hofmann*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Molecules adsorbing on metal surfaces form a variety of different surface polymorphs. How strongly this polymorphism affects interface properties is a priori unknown. In this work we investigate how strongly the surface polymorphism influences the interface work functions for various organic/metal interfaces. To evaluate the whole bandwidth of possible polymorphs, we perform full theoretical structure search, probing millions of polymorph candidates. All of these candidates might be observed in reality, either by kinetic trapping or by thermodynamic occupation. Employing first-principles calculations and machine learning we predict and analyze the work function changes for those millions of candidates for three physically distinct model systems: the weakly interacting naphthalene on Cu(111), the strongly interacting anthraquinone on Ag(111), and tetracyanoethylene, which undergoes a reorientation from lying to standing polymorphs on the Cu(111) surface. These thorough investigations indicate that kinetic trapping of flat-lying molecules can lead to work function differences of a few hundred meV. If the molecules also reorientate, this can increase to a change of several eV. We further show that the spread in work function decreases when working in thermodynamic equilibrium, but thermally occupied phases still lead to an intrinsic uncertainty at elevated temperatures.
Original languageEnglish
Article number151687
Number of pages6
JournalApplied Surface Science
Publication statusPublished - 1 Feb 2022


  • Ab-initio thermodynamics
  • Density functional theory
  • Kinetic trapping
  • Machine learning
  • Structure prediction
  • Temperature dependence

ASJC Scopus subject areas

  • Condensed Matter Physics
  • General Physics and Astronomy
  • Surfaces, Coatings and Films
  • General Chemistry
  • Surfaces and Interfaces


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