.cube Files (Output for Dplot)

From NWChem

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Hi,

I am having trouble finding a program that will open the .cube file. I've tried Molden and gopenmol and none of them are working on my machine. I'm running LINUX MINT and Windows 7.

Does anyone know if there are other programs for this?

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Avogadro (http://avogadro.cc/wiki/Main_Page) can read the cube files generated by NWChem and is free and cross-platform.

Load the cube file, under Extensions choose Create Surfaces, under Surface Type choose Cube file generated by NWChem. At least that is what worked for me.

Best,
Sean

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How do you initially open the .cube file though? DO you go to open or input molecular file??

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Open the cube file directly.

Best,
Sean

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Avagadro crashes when I go to Creat Surfaces :/ Mainly what I want to do is to calculate the differences in energy between the HOMO and LUMO orbitals.

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I believe Jmol can also open cube files; although, I do not know the specifics of that.

I do not understand what you mean by calculating the difference in energy between the HOMO and LUMO orbitals in this context.

Best,
Sean

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Energy Difference
I would like to get a plot of the density of states for the HOMO and LUMO orbitals so that I may calculate the band gap between the two.

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The phase "density of states for the HOMO and LUMO orbitals" does not make any sense. A single orbital cannot have a density of states associated with it. DPLOT generates a representation of either the charge density or a molecular orbital in space and is not related to the density of states. You could estimate a density of states by discretizing the energy span of the molecular orbitals and counting how many orbitals have an energy that falls within each bin, i.e. creating a histogram of molecular orbital energies. If all you are interested in is the band gap, a simple approximation can be obtain by simply taking the difference in energy of the HOMO and LUMO, whose energies should be listed in the output file from the calculation.

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I would like to use NWchem to generate something like what is on page 4 of this paper:

http://pubs.acs.org/doi/pdf/10.1021/cm200679y

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I would like to use NWchem to generate something like the graphs which are on page 4 of this paper:

http://pubs.acs.org/doi/pdf/10.1021/cm200679y

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To create a plot similar to Figure 3 of that paper, you would just need to create a histogram of the molecular orbital energies. You could also use kernel density estimation if you wanted a smoother estimation of the density of states. The orbital energies should appear in the output file from a standard calculation. The gap would just be the LUMO energy minus the HOMO energy.


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