Data Grids for examples in Probe Particle Atomic Force Microscopy simulation program (ppafm)

These files are used for running the examples for [ppafm](https://github.com/Probe-Particle/ppafm/) program. The grids are stored in in [.xsf](http://www.xcrysden.org/doc/XSF.html) and [.cube](https://paulbourke.net/dataformats/cube/) format. The data set compiles both the new examples used in paper [Advancing scanning probe microscopy simulations: A decade of development in probe-particle models](https://www.sciencedirect.com/science/article/pii/S0010465524002649) as well as older examples. Notice that the structure does not exactly reflect the directory structure in the [example folder of ppafm](https://github.com/Probe-Particle/ppafm/tree/main/examples) to prevent possible redudancy, but is instead flatenized and sorted by molecules.