Add support for INTERFACE FF

[taidbui]

Current version supports only ClayFF. I'm wondering if we can include INTERFACE FF as well since this has been shown as a very accurate FF for simulating various inorganic-organic systems. Below is the original paper:

https://pubs.acs.org/doi/10.1021/la3038846

[punkpony]

Hi taidbui,

Both ClayFF and Interface are fantastic force fields for simulation of mineral-organic interactions. ClayFF is a non-bonded force field (with exception of O-H bonds), while Interface is fully bonded.

Currently, ClayCode only supports non-bonded force field type (due to the way unit cells are replicated). While it is possible to introduce addition of bonds between the unit cells to support integration of Interface (and similar), this is not yet in our priority for the development.

Thank you for your feedback!