Polymorphism mediated by electric fields: A first principles study on organic/inorganic interfaces


Organic/inorganic interfaces are known to exhibit rich polymorphism, where different polymorphs often possess significantly different properties. Which polymorph forms during an experiment depends strongly on environmental parameters such as deposition temperature and partial pressure of the molecule to be adsorbed. To prepare desired polymorphs these parameters are varied. However, many polymorphs are difficult to access with the experimentally available temperature- pressure ranges. In this contribution, we investigate how electric fields can be used as an additional lever to make certain structures more readily accessible. On the example of tetracyanoethylene (TCNE) on Cu(111), we analyze how electric fields change the energy landscape of interface systems. TCNE on Cu(111) can form either lying or standing polymorphs, which exhibit significantly different work functions. We combine first-principles calculations with a machine-learning based structure search algorithm and ab-initio thermodynamics to demonstrate that electric fields can be exploited to shift the temperature of the phase transition between standing and lying polymorphs by up to 100 K.

Version notes

The changes include mostly formatting changes and improved wording. Additionally two new plots were added to the supporting information (impact of substrate relaxations and sensitivity analysis for the predicted phase boundaries)


Supplementary material

Supporting information to "Controlling the polymorphism of organic/inorganic interfaces with electric fields"
Convergence tests, more detailed information regarding adsorption geometries and energies of isolated molecules, further discussion of (components of) the monolayer adsorption energy, details regarding SAMPLE structure search, further information regarding approximations made for the ab-initio thermodynamics.

Supplementary weblinks

DFT data
All DFT calculations are available in the NOMAD repository.