Individual Material Tracking

[ethan-shanahan]

Material properties are currently tracked as a collection of all materials required for the simulation. Instead, we should track individual materials and provide a list of these to the job/utils.

Implementation could be related to #42, via dynamic input namespaces.

Additionally, one could then lookup and use a specific material by name.

[sanathkeshav]

This could be very useful here: https://github.com/nicoguaro/material_database

[ethan-shanahan]

For a submit.py script using the package's utilities, the proposed change to the representation of materials would replace the "material_properties" input with a "material_phases" input.

Old:

"material_properties": {
    "bulk_modulus": [62.5000, 222.222, 62.5000],
    "shear_modulus": [28.8462, 166.6667, 28.8462]
},

New:

"material_phases": {
    "copper": [0, 2],
    "aluminium": [1]
},

This translates to: phase 0 = copper, phase 1 = aluminium, phase 2 = copper. Note, the bulk/shear values above are not representative of these materials.

Under this format, each material would be its own node labelled "copper", "aluminium", etc., and they would be of various MaterialData types that the plugin defines for each supported "matmodel".

Additionally, each job would have a "material_phases" input which defines what materials occupy which phases of the microstructure. If the user were to provide materials inconsistent with the provided "matmodel", utils could reject the input without ever calling AiiDA or FANS.

If an advanced user wishes to use a custom material, they must create the node themselves and provide it a unique label. That label can then simply be used in place of "copper" or "alumininum" above.

[ethan-shanahan]

PR #52 includes some sketched changes to implement this.