Update cubic.py

[shubhamachary56821]

done some minor changes for fixing negative shape in Gaussian Cube, if issue still persist, please inform and guide

[Ali-Tehrani]

Thank you for the pull-request and for implementing this feature!
My only other comment is that
"atcoords": coordinates, will also need its unit changed and the method documentation should include that its units are converted to atomic units (Bohr) length.

[Ali-Tehrani]

I recommend extending the precision to 16 digits, since our calculations often rely on 64-bit floating point representations.
Using scipy and mpmath, the value for converting 1 Bohr to Angstrom is 0.529177210902999962.

But since we have SciPy as a prerequisite, i think it's better to do

import scipy.constants as spc
BOHR_TO_ANGSTROM = spc.value('atomic unit of length') / spc.angstrom

[Ali-Tehrani]

@PaulWAyers I think that it is more straightforward to just return a flag, like units: "bohr" (or "angstrom"), to cube_data instead of defaulting to converting everything to atomic units.

If user specifically cares about atomic units, then they can handle the conversion themselves. For example I know in protein-related work, they would prefer to keep the units that they are in.