First principles prediction of two-dimensional metal-organic framworks: strong interplay between long-range dispersion and charge transfer

When molecules strongly interact with interfaces, they exchange charge. Large organic moelcules interfaces are additionally stabilised by long-range dispersion forces. Correctly describing the interplay of charge-transfer and dispersion interactions at metal-organic interfaces is of paramount importance to correctly describe the structure, stability and electronic properties of such interfaces. In comparison with experiment, we will investigate the ability of dispersion-inclusive Density Functional Theory to describe the adsorption structure of strong donors such as alkali atoms and acceptor molecules such as TCNQ adsorbed at varying facets of Ag. In comparison to NIXSW measurment data on vertical adsorption heights, we find that all recently proposed dispersion-inclusive DFT methods fail to corrrectly capture the adsorption height of alkali ions at metal surfaces. Upon analysis, we propose a rescaling of dispersion parameters to correctly account for the change of atomic polarisability due to charge transfer in this system. Taking this into account gave rise to accurate structural models which enabled further analysis of the energetics and energy level alignment for adsorbed alkali-organic metal-organic frameworks. [1]
[1] P. J. Blowey, B. Sohail, et al. ACS Nano,XXXX 2020.