Plotting orbital densities

[Ruairi Graham]

Dear Dirac experts,

I see that there is an old tutorial for getting a .cube file to visualise orbitals in programs such as avogadro. For context I have done KRCI on a linear diatomic (not symmetric) and want to look at the HOMO and LUMO. Is this tutorial still relevant or is there a different method to run this post processing step. I have tried to look at the **VISUAL section of the manual but not entirely sure how to form the input file so I can obtain the .cube file. 

Kind regards,
Ruairi

[Deniz Kahraman]

Dear Ruairi,

If you are using a relativistic Hamiltonian, spinors are complex, many-component wavefunctions. Standard "red and blue" isosurfaces which represent positive and negative amplitudes are not suitable for them. I think the standard practice is plotting the wavefunction squares, electron densities. Specifically talking about diatomic species, 2D plotting of electron densities gives a very good idea about the specific state. I am attaching the part I use for visualization for doubly occupied 45th state: 

**VISUAL
.DENSITY
DFCOEF
.OCCUPATION
1
1 45 1.0
.2D
-10.0 0.0 -10.0
 10.0 0.0 -10.0
 2000
-10.0 0.0  10.0
 2000

For a heavy molecule, visualizing where the electrons are is the most physically honest thing for me now. I still do not know how to interpret specific wavefunctions chemically and anybody's help is appreciated. Take into account that those values between -10.0 to 10.0 define XYZ and are in bohr radius unit, not angstrom. 

Best wishes!

Deniz

[Visscher, L. (Luuk)]

Dear Ruari,

Please take a look at the new tutorials (in the form of a Python notebook) that were released with DIRAC26. These can be found inside the directory demo_notebooks. The tutorial discusses visualization of the full density (and other related objects) but you can also plot the density of a single orbital by tweajking the input as demonstrated below by Deniz.

best regards,

Luuk

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