CCL: Inquire a cutoff value for degenerate states
- From: Robert Molt <r.molt.chemical.physics=-=gmail.com>
- Subject: CCL: Inquire a cutoff value for degenerate states
- Date: Fri, 18 Sep 2015 10:49:17 -0400
Sent to CCL by: Robert Molt [r.molt.chemical.physics/./gmail.com]
It's going to be dependent on the system. We need more information
the original question poser about the context.
If I said that two electronic states are separated by 0.1 eV, they are
roughly degenerate. If you told me the states were separated by 0.01
I would definitely call those electronic states degenerates. But
lies the issue: relative to the energy scale of electronic states, 0.01
eV is very tiny. By contrast, like Dr. Abrash noted, 0.01 eV is
for certain spectroscopy studies.
On 9/18/15 9:27 AM, Abrash, Samuel sabrasha/richmond.edu wrote:
Sent to CCL by: "Abrash, Samuel" [sabrash,+,richmond.edu]
I don't know the theoretical convention, but from the point of view of a
spectroscopist (my original training), .01 eV is 81 cm-1, and while states
separated by 81 cm-1 will begin to exhibit Fermi resonance, they would not be
considered degenerate. However, the convention for computational chemistry may
be based on other arguments.
Samuel A. Abrash
Associate Professor, Department of Chemistry
Coordinator, Environmental Studies Program
University of Richmond
Cell: (804) 363-2597
"At the time God created the world and desired to reveal the depth of His
being from out of the hidden, the light came from darkness and they were joined
together. Because of this, out of darkness came the light, and out of the
hidden came the revealed and out of the good came evil and out of mercy came
severe judgement, and everything is intertwined with everything else... the good
inclination and the evil inclination, the right and the left." The Zohar
From: owner-chemistry+sabrash==richmond.edu:ccl.net [mailto:owner-chemistry+sabrash==richmond.edu:ccl.net] On Behalf Of Youzhao
Lan lyzhao a aliyun.com
Sent: Thursday, September 17, 2015 9:01 PM
To: Abrash, Samuel
Subject: CCL: Inquire a cutoff value for degenerate states
Sent to CCL by: "Youzhao Lan" [lyzhao,+,aliyun.com] Dear all,
I want to set a small cutoff value for deciding whether two states are
Is there a generally acceptted value in a.u. or eV unit for this cutoff?
e.g., 0.001 a.u. or 0.01 eV?
Any help will be appreciated.
Dr. Robert Molt Jr.
Visiting Associate Professor of Chemistry
Department of Chemistry & Chemical Biology
Indiana University-Purdue University Indianapolis
402 N. Blackford St.
Indianapolis, IN 46202