I want to compute the ZPE and entropic terms for my platinum slab covered by a bilayer of water (network). I have performed a phonon calculation on a 3x3 q-point grid (my unit cell is ~ 4 Å long)
The calculation is finished and now I am not sure about a few things:
I keep reading in the literature that one must calculate the ZPE/entropic terms using the adsorbate's vibration modes, the thing is that all the modes are coupled with the substrate, it is not possible to "isolate" the adsorbate's vibration.
I am pretty sure I need to average these quantities over the q-points grid but I can't find information about that.
One of my colleagues tells me that I should compute the ZPE/entropic terms of the substrate alone and then subtract them to get the contribution of the adsorbate alone.
Could someone give more details?