# Understanding Gaussian Cube file output by NWChem

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 Kpelzer Member Profile Send PM
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 9:33:08 AM PDT - Mon, Aug 19th 2013 I have been using NWChem to image orbitals in the Gaussian Cube format that I then image in Vesta. I'm a little confused about what the raw numbers that go into the Cube file are. I thought that it was charge density; however, what I get is a file with both positive and negative numbers. Since charge density can't be negative, I am not sure what I am looking at. Could anyone tell me exactly what goes into the cube file? These are for DFT calculations where my dplot section looks like this: dplot gaussian title monomer_4ang1 output monomer_4ang1.cube vectors C70.movecs orbitals view;1;211 LimitXYZ -7.5 7.5 150 -7.5 7.5 150 -8.5 8.5 170  end The orbitals look reasonable in Vesta, they just have positive and negative lobes. I would be grateful for any explanation of what NWChem is outputting here. Thanks in advance for any advice.

 Edoapra Forum:Admin, Forum:Mod, bureaucrat, sysop Profile Send PM
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 12:54:50 PM PDT - Mon, Aug 19th 2013 Kenley, NWChem is outputting the orbitals values, not the charge densities. To get the density corresponding to the orbitals # 117 you selected (i.e. the squared value of the orbital), you need to replace "orbitals view" with "orbitals density", e.g. orbitals density;1;211 

 Kpelzer Member Profile Send PM
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 2:22:00 PM PDT - Mon, Aug 19th 2013 Thanks Edoapra. So the numbers currently being output in the cube file are simply the square roots of the density at each point (times a factor of +/- 1)?

 Edoapra Forum:Admin, Forum:Mod, bureaucrat, sysop Profile Send PM
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 2:47:36 PM PDT - Mon, Aug 19th 2013 Quote:Kpelzer Aug 19th 2:22 pmThanks Edoapra. So the numbers currently being output in the cube file are simply the square roots of the density at each point (times a factor of +/- 1)? No, the correspondence is not so direct. Here is the formula for the charge density ρ(r) in term of the orbitals ψa(r) $\rho(\mathbf{r}) = \sum_{a=1}^{n_{occ}} |\psi_a(\mathbf{r})|^2$ Edited On 2:51:17 PM PDT - Mon, Aug 19th 2013 by Edoapra

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