Integrated absolute spin density changes significantly during geometry optimization, and is not reproduced in a subsequent SCF run (no smearing)
marci... at gmail.com
Fri Jan 20 09:03:43 UTC 2017
the total integrated spin density can be different from zero, even if the
multiplicity is stil one, this should not be a problem.
After the geometry optimisation, did you try to restart also the wave
function in addition to the coordinates?
I have noticed that in your scf.inp the SCF_GUESS is set to ATOMIC.
My guess is that the scf ends to be trapped in a metastable state ,due to
the bad starting guess.
On Monday, January 16, 2017 at 2:41:56 AM UTC+1, Ananth Govind Rajan wrote:
> Dear all,
> I am using version 2.5.1 of CP2K for geometry optimizing my system of
> interest, which is a graphene nanoribbon. I have attached the input and
> output files for two separate cases: (a) a geometry optimization
> (geo_opt.inp and geo_opt.out) and (b) an SCF run with the optimized
> geometry (scf.inp and scf.out). Two XYZ files are also attached, the
> initial unoptimized file (zigzag_init.xyz), and the final optimized
> coordinates (optimized_zigzag_initial.xyz)
> As you will see, I am performing a spin polarized (UNRESTRICTED_KOHN_SHAM)
> calculation, with the MULTIPLICITY set to 1. The RELAX_MULTIPLICITY option
> is not turned on (it is set to zero by default). I am *not* using
> smearing. As the geometry optimization proceeds, the integrated absolute
> spin density (IASD) seems to increase significantly (from ~0 to ~18). Is
> this expected? I would imagine that the IASD is related to the specified
> multiplicity and therefore should not change significantly as optimization
> proceeds, because smearing is not turned on.
> In fact, after geometry optimization finished, I ran a simple SCF run to
> compute the energy of the system using the optimized coordinates.
> Surprisingly, this energy is significantly different (~ 5 eV) than the
> energy obtained at the end of the geometry optimization step, despite
> having similar input files. Moreover, the IASD is also different at the end
> of the SCF run (~ 0), compared to at the end of the GEO_OPT run (~18).
> Can anyone please advise what the issue might be? Why are the results so
> different between the SCF and GEO_OPT? Is it okay that the IASD changes
> during GEO_OPT?
> Please let me know if you need any more information for diagnosing the
> Thank you very much
> Best regards,
> Ananth Govind Rajan
> PhD Candidate
> Department of Chemical Engineering, MIT
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