Abstract
Terminating the tip of an atomic force microscope with a CO molecule allows data to be acquired with a well-known and inert apex. Previous studies have shown conflicting results regarding the electrostatic interaction, indicating in some cases that the negative charge at the apex of the CO dominates, whereas in other cases the positive charge at the end of the metal tip dominates. To clarify this, we investigated CaF 2(111). CaF 2 is an ionic crystal and the (111) surface does not possess charge inversion symmetry. Far from the surface, the interaction is dominated by electrostatics via the negative charge at the apex. Closer to the surface, Pauli repulsion and CO bending dominate, which leads to an unexpected appearance of the complex 3-atom unit cell. We compare simulated data in which the electrostatics are modeled by point particles versus a charge density calculated by DFT. We also compare modeling Pauli repulsion via individual Lennard–Jones potentials versus a total charge density overlap. In doing so, we determine forcefield parameters useful for future investigations of biochemical processes.
| Original language | English |
|---|---|
| Article number | 14104 |
| Pages (from-to) | 1-12 |
| Number of pages | 12 |
| Journal | Scientific Reports |
| Volume | 10 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 1 Dec 2020 |
| MoE publication type | A1 Journal article-refereed |
Funding
The authors thank A. Foster, F. Huber, J. Berwanger, and K. Pürckhauer for fruitful discussions. A.L. thanks A. Peronio and D. Meuer for support in data acquisition and analysis. Potential conflict of interests: F.J.G. holds patents for the qPlus sensor. A.L., A.J.W. and F.J.G. acknowledge funding from the Deutsche Forschungsgemeinschaft within research project CRC 1277, sub-project A02 and project GRK 1570. P.H. acknowledges support from project number L100101952 of the Czech Academy of Sciences. Open access funding provided by Projekt DEAL.