Unit cell => Translation Axes

[ghutchis]

Currently, the unit cell is written as alpha, beta, gamma, a, b, c. But this is 6 degrees of freedom, but many solid state codes use translation vectors.

For use with solid-state codes, it would be ideal if CJSON:

• Always wrote out real-space Cartesian coordinates (in addition to fractional)
• Wrote out the 3x3 translation matrix either in addition to the unit cell parameters or instead of the parameters.

Otherwise, it's hard to implement CP2K or VASP or ABINIT input generators in Avo2 (among other things)

[harsh07051]

I will like to fix this issue

[ghutchis]

This is actually already fixed in avogadrolibs, e.g.

TePb.txt