From owner-chemistry.,at,.ccl.net Fri Sep 18 12:45:01 2015 From: "Robert Molt r.molt.chemical.physics{:}gmail.com" To: CCL Subject: CCL: Inquire a cutoff value for degenerate states Message-Id: <-51753-150918104924-11572-fXiAtCTXmcEsuf3eAk9hyw(!)server.ccl.net> X-Original-From: Robert Molt Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=windows-1252; format=flowed Date: Fri, 18 Sep 2015 10:49:17 -0400 MIME-Version: 1.0 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 from 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 eV, I would definitely call those electronic states degenerates. But therein 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 pathetic 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 > sabrash:richmond.edu > Cell: (804) 363-2597 > www.richmond.edu/~sabrash > "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 > > -----Original Message----- >> 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 degenerate. > 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. > > Lanhttp://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt> > -- Dr. Robert Molt Jr. Visiting Associate Professor of Chemistry Department of Chemistry & Chemical Biology Indiana University-Purdue University Indianapolis LD 326 402 N. Blackford St. Indianapolis, IN 46202