Should we always passivate the dangling bonds when we deal with thin-film interface ?
I would like to know when it is mandatory to proceed with passivation of dangling bonds when we target the calculation of the electronic structure and magnetic moment of thin films, using DFT.
If the 2D surface are periodic like infinite 2D graphene or silicence sheet. There is no need of passivation however to confine the periodicity in particular directions consequent to dangling or under coordinated atoms like in graphene ribbon or other 2D ribbon. Since the undercordinted or danglin atoms have unshared electrons these free electron accomdate in non-bonding orbitals which are spurious and in energy eigen value space comes in between VBM and CBM. It must be relaized that free electron or quasi-free electro are more enegetic than bonded or shared electrons. I think its obvious if passivation is complete keeping the hybridization of structural geometry in view no magnetic moment comes in existance. Otherwise depending upon passivation that leaves odd or even electrons magnetic moment may or may-not exist. Sorry if u didn't satisfy of this explanation.
I would like to add that on the other hand if you have an interface between thick two slabs then you may compare the calculations with and without compensating dangling bonds and see if the compensation affect the interface properties. Also, it is important to know that the choice of either using supercell or slab model (with vacuum) strongly affect the polarization. Due to different relaxations, correct polarization is obtained using slab model. Now, if you care about polarization then compensating dangling bonds or not will also affect your results. For instance, if you calculate the critical thickness required to drive polar catastrophe, then you should not compensate dangling bonds as it will destroy the electric field.
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