What you did not show was that the minimization will give different
forces too.
The minimization will stop once the forces are for a couple of times
below 2.0 mRy (case.inM) and the movement is small enough.
Even very small differences between the sp and non-sp calculation will
lead to a different minimization-path and thus mixer will stop by chance
at different positions leading to different EFGs (and E-tot).
In other words: If you would really want to get out the same results in
both runs you need to put the cut-off in case.inM very small, so that
mixer will optimize the positions until the forces are really small in
all cases.
On 04/08/2016 12:41 PM, Marcelo Barbosa wrote:
Dear Sirs,
I did some calculations with GaN (struct file in attachment) to compare the
difference in energy and electric field gradient between the use of
spin-polarization or not.
The calculations were done using the commands
init_lapw -b -ecut -8 -numk 480 -rkmax 7 (-sp)
run(sp)_lapw -p -ec 0.00001 -cc 0.0001 -fc 0.5
and the results were the following
:ENE = -7995.60614872 (no spin-polarization)
:ENE = -7995.60614871 (spin-polarization)
:EFG001 = 0.57937 (no sp)
:EFG001 = 0.57931 (sp)
so they basically give the same.
Then, I relaxed the structure using
run(sp)_lapw -p -ec 0.00001 -cc 0.0001 -fc 0.5 -min
and the results were
:POS001 = 0.66667 0.33333 0.00002 (no sp)
:POS001 = 0.66667 0.33333 0.00000 (sp)
:POS002 = 0.66667 0.33333 0.37662 (no sp)
:POS002 = 0.66667 0.33333 0.37701 (sp)
:ENE = -7995.60615476 (no sp)
:ENE = -7995.60615035 (sp)
:EFG001 = 0.45038 (no sp)
:EFG001 = 0.58801 (sp)
so they gave different final positions and very different :EFG, as a
consequence.
However, if I use the final structure from the minimization without
spin-polarization and do a calculation with spin-polarization (both from the
beginning, using the previous commands), I get equal values
:ENE = -7995.60615467 (no sp)
:ENE = -7995.60615466 (sp)
:EFG001 = 0.45036 (no sp)
:EFG001 = 0.45034 (sp)
and if I use the final structure from the minimization with spin-polarization
and do a calculation without spin-polarization, I also get equal values
:ENE = -7995.60614842 (no sp)
:ENE = -7995.60614842 (sp)
:EFG001 = 0.58272 (no sp)
:EFG001 = 0.58271 (sp)
This means that the only thing that I am getting different between them is the
atomic positions during the minimization, since I always get the same :ENE and
:EFG if both calculations are done with the same struct file.
Is there any reason for this to happen?
Which values for :ENE, :EFG and :POS should I consider the best, the
spin-polarized ones or the ones without spin-polarization?
Best regards,
Marcelo
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