[QE-users] users Digest, Vol 207, Issue 11

[toshi1higu at docomo.ne.jp]

Dear Professor, Nishidate,
Thank you very much for your comment.
I am investigating the emission current pattern from carbon nanotubes using
computer simulations. When I investigated the emission current pattern using
both Quantum-Espresso and Octopus, I found differences between the two. To
find out which is correct, I performed calculations using hydrogen, for
which an analytical solution has been obtained. 
In the case of Octopus, the pattern seemed to be s-orbital: spherical,
p-orbital: 2-lobes, d-orbital: 4-lobes. However, in Quantum-Espresso, all
the patterns from the 1st to the 10th orders were spherical. 
I am contacting QE-users to find out if there is something wrong with my
calculation method. 
Since I am using the pw.in file used for carbon nanotubes, I think there are
many strange things such as nbnd, ecutwfc, and size of simulation box.

Best regards,
 Higuchi Toshiharu
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Today's Topics:

   1. Re: The orbitals of a hydrogen atom (Kazume NISHIDATE)


----------------------------------------------------------------------

Message: 1
Date: Sat, 12 Oct 2024 21:38:16 +0900
From: Kazume NISHIDATE <nisidate at iwate-u.ac.jp>
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: Re: [QE-users] The orbitals of a hydrogen atom
Message-ID: <C1A8DFFF-0412-4E85-9AA9-E8B590AA5E50 at iwate-u.ac.jp>
Content-Type: text/plain; charset=utf-8

Dear Higuchi,

> However, the orbitals obtained with Quantum-Espresso (assuming the 
> ILDOS pattern as the orbital) were all spherically symmetric orbitals

>                         nat = 1,
>                        ntyp = 1,

You are considering only one atom in the orthorhombic cell. 
In this case, the orbitals px, py, and pz cannot be separated unambiguously
since the atom cannot distinguish the x, y, or z-axis. 
In other words, there is no way for the hydrogen to determine the particular
axis. Hydrogen is in an ?approximated? vacuum.
Hence, these orbitals are energetically degenerated.


>                     ecutwfc = 26 ,
>                     ecutrho = 156 ,
>                        nbnd = 228,

I can't imagine the necessity of considering the 228 bands for only one
hydrogen in a supercell. Is it an educational purpose?
If so, visualizing the analytically delivered orbital functions should be
sufficient.

Here are some other notes;

The cutoff energy needs to be higher for your purpose. 
The number 'nbnd=228' is almost nonsense.

I?m not sure, but Wannier90 would be able to plot 'molecular orbital'
like crystal orbital. But there will be similar restrictions. 

Or you can try to use the Gaussian or Hondo to produce your higher order
orbitals. In these cases, you will be required to specify these particular
axes.



????
Kazume NISHIDATE Ph.D

Department of Systems Innovation Engineering, Graduate School of Science and
Engineering, Iwate University
4-3-5 Ueda, Morioka, Iwate, 020-8551 JAPAN
Phone:+81-19-621-6391
kazume.nishidate at gmail.com, nisidate at iwate-u.ac.jp
https://sites.google.com/site/nisidatelab/




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