[Pw_forum] Volumetric data units in CUBE file format

[Alberto Otero de la Roza]

Hi Kayahan,

> I would like to write a script in order to manipulate cube files that are
> output in quantum espresso. 

Check out this program: http://gatsby.ucmerced.edu/wiki/Critic2 . You
can do complex arithmetic computations using cubes with it easily.

> However, although I find general information about how cube files
> are ordered,(http://paulbourke.net/dataformats/cube/), but there is
> not much information about the unit of electron charges on each grid
> point for volumetric density. Normally, when I sum all the charge
> density values on grid points in a loop, multiply with volume and
> divide by number of grid points I should have the total number of
> electrons in the system, but it is not working out for me.

I just tried it with the SVN version of espresso on Si and it worked
just fine. Can you please provide more details?

> I would be happy if someone provide some information or
> documentation which tells how to correctly integrate over volumetric
> density in cube files to find total number of electrons.

Essentially, what you did is what it is, as far as I understand
it. Sum all values, times the volume divided by the number of points.

Best,

A.

---
Dr. Alberto Otero de la Roza
National Institute for Nanotechnology,
National Research Council of Canada,
11421 Saskatchewan Drive, Edmonton,
Alberta T6G 2M9, Canada