[xcrysden] Saving the grid for an expanded system

[Tone Kokalj]

On Fri, 2021-04-23 at 17:02 +0200, Juan Jose Melendez Martinez wrote:
> Dear all
> 
> I have generated a supercell by expanding a single unit cell along
> each crystal axis; xcrysden behaves very nicely for this. I can also
> expand a 3D grid defined for the unit cell to the whole supercell,
> and then I can see the charge distribution within the latter, for
> instance. Once I got the grid (say the charge density) in the whole
> supercell, I saved it via the "Save Grid" command. And then I found a
> couple of issues:
> 
> 1) The xsf file saved from the previous procedure contains the atoms
> in the supercell. However, when I load the file, I get the unit cell,
> not the supercell that I expected. 

This is the programmed behavior. If you want to load the structure with
the same setting, use File-->Current State and Structure instead. But
beware that in case of datagrids, this will make very large file.

> 
> 2) I realized that the grid was saved for the unit cell only, not for
> the whole supercell. I can expand the grid again, but I cannot use it
> to compute charge differences, for instance. 

This is also the programmed behavior. Why would you save more than is
needed, especially with datagrids which results in large files? I do
not understand the problem you are describing about the charge
differences.

> Did any of you experience something like this before? Any help,
> please?

Of course: this is how it is meant to be.

Best regards, Tone
-- 
Jožef Stefan Institute, Ljubljana, Slovenia