Interstitial: make

Step 1. For each element in insert_ele list, InterstitialGenerator module in pymatgen.analysis.defects.generators would help to generate interstitial structure. The structure would be appended into a list if it can meet the requirements in conf_filters.

Step 2. If refine is True, we do refine process. If reprod-opt is True (the default is False), we do reproduce process. Else, the vacancy structure (POSCAR) and supercell information (supercell.out) are written in the task directory, for example, in confs/mp-*/interstitial_00/task.000000 with the check and possible removing of the old input files like before.

Step 3. In interstitial by VASP, ISIF = 3. In interstitial by LAMMPS, the same in.lammps as that in EOS (change_box is True) would be generated with scale set to one.