# ReaxFF – Analyze surface reactions

In the ReaxFF development version it is now possible to detect if a molecule is adsorbed to a surface and even distinguish between different adsorbed species. The new species detection allows for an easy tracking of surface reactions throughout a ReaxFF trajectory in particular when used from the GUI.
If we apply this tracking to our water on aluminum ReaxFF GUI tutorial, adsorbed and gaseous waters will be distinguished:

The “H2O(ads)” must be understood as a water molecule adsorbed on a surface via its oxygen atom.
If the molecule is adsorbed on the surface via more than one atom, the naming is adjusted accordingly:

The only input required is a SUPPORT keyword in the geo file (BGF format):

SUPPORT startAtom endAtom


startAtom and endAtom are the first and last atom indices of the support (surface+bulk) part of the model system. Multiple SUPPORT keys are allowed in the input file. If this key is present the molfra.out file will contain something like this (taking the Al-water test as an example and treating the Al slab as support):

Iteration    Freq.   Molecular formula                 Molecular mass
0      120 x  Al                                      26.9820
0       61 x  H2O                                     18.0150