From owner-chemistry@ccl.net Fri May 1 07:46:00 2009 From: "Stephen.Garrison]=[srnl.doe.gov" To: CCL Subject: CCL: One unpaired electron - Zero integrated spin density? Message-Id: <-39216-090501074444-1458-dM9ws74t6jBB00yOO4sZrQ###server.ccl.net> X-Original-From: Stephen.Garrison*|*srnl.doe.gov Content-Type: multipart/alternative; boundary="=_alternative 0040813C852575A9_=" Date: Fri, 1 May 2009 07:44:34 -0400 MIME-Version: 1.0 Sent to CCL by: Stephen.Garrison~!~srnl.doe.gov This is a multipart message in MIME format. --=_alternative 0040813C852575A9_= Content-Type: text/plain; charset="US-ASCII" Could someone explain to me how a system can have one unpaired electron, but nearly zero integrated spin density? I am using CASTEP (LDA functional) and am working on a periodic metallic system with 189 electrons. I start the calculation with an estimate of 5 unpaired electrons. The SCF convergence cycle for the initial geometry finds a solution with the following spin densities: 2*Integrated Spin Density = -0.533909E-01 2*Integrated |Spin Density| = 0.972315 The final, optimized geometry has the following spin densities: 2*Integrated Spin Density = -0.337735E-03 2*Integrated |Spin Density| = 0.612583E-02 This does not make much physical sense to me. How can a system have an unpaired electron but zero integrated absolute value(spin density)? What am I missing? Thanks for you help and clarification. Stephen -- Stephen L. Garrison, Ph.D. Senior Engineer Engineering Modeling and Simulation Savannah River National Laboratory Savannah River Site 773-42A, Room 181 Aiken, SC 29808 803-725-2404 Stephen.Garrison]|[SRNL.doe.gov --=_alternative 0040813C852575A9_= Content-Type: text/html; charset="US-ASCII"
Could someone explain to me how a system can have one unpaired electron, but nearly zero integrated spin density?

I am using CASTEP (LDA functional) and am working on a periodic metallic system with 189 electrons.

I start the calculation with an estimate of 5 unpaired electrons. The SCF convergence cycle for the initial geometry finds a solution with the following spin densities:

 2*Integrated Spin Density   =   -0.533909E-01
 2*Integrated |Spin Density| =    0.972315    

The final, optimized geometry has the following spin densities:

 2*Integrated Spin Density   =   -0.337735E-03
 2*Integrated |Spin Density| =    0.612583E-02

This does not make much physical sense to me. How can a system have an unpaired electron but zero integrated absolute value(spin density)? What am I missing?

Thanks for you help and clarification.

Stephen

--
Stephen L. Garrison, Ph.D.
Senior Engineer
Engineering Modeling and Simulation
Savannah River National Laboratory
Savannah River Site
773-42A, Room 181
Aiken, SC 29808
803-725-2404
Stephen.Garrison]|[SRNL.doe.gov
 --=_alternative 0040813C852575A9_=--