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<p>Dear all,</p>
<p>thank you for your comments:</p>
<p>1) </p>
<blockquote type="cite">
<pre wrap="">Did you use a Gamma centered k mesh (and enough k points)</pre>
</blockquote>
<br>
<p>I have checked that the same inequality in MLD, appears both
when k-points are shifted or not shifted. So, influence of shift
of k-points can be ruled out.</p>
<p>I have 30x30x30 k-points, which should be enough. When using
46x46x46 k-mesh, the MLD inequality is reduced by about factor
two, but still present. Even when using very fine k-mesh
(90x90x90) for optical calculation, the inequality persists.<br>
</p>
<p><br>
</p>
<p>2) <br>
</p>
<p> </p>
<blockquote type="cite"><span
style="color:rgb(0,0,0);font-size:12.8px">In some cells
shifting the k-point origin with MSR1a leads to slightly
unbalanced forces which are hard to converge to the "right"
symmetric result. If the forces are slightly off, this is an
indication that the density is also slightly off. Exactly why
this occurs I do not know, I suspect very soft modes
associated with numerical errors in finite arithmetic.</span></blockquote>
<br>
<p>Well, for me it is hard to believe, that the problem can
originates from numerical error. The MLD inequality creates
sort-of ghost peaks in MLD spectra which for bcc Fe are very
stable at positions at 4.8 and 6 eV for different calculation
details (as different k-mesh, presence/absence of spin-orbit,
shifted/non-shifted k-mesh). Under all those changes in the
calculations, the position of ghost peaks remains very stable,
just their amplitudes varies. Also, if problem would be just
numerical one, why ghost peaks are not present in simple cubic
or fcc calculations?<br>
</p>
<p><br>
</p>
<p>3)<br>
</p>
<blockquote type="cite"> <br>
It is instructive to repeat the calculation without SO and see
how big the difference between sig_xx and sig_yy (for any M
direction) is then. </blockquote>
<br>
I tried to calculate various combinations of structure,
(with/without SO or sp) using full (non-magnetic) bcc symmetry, or
bcc symmetry reduced by presence of magnetization (i.e. it means
reduction of symmetry + new k-mesh as generated by initso).<br>
In case of spin-polarized calculations without SO, the ghost MLD
peaks appear when going from full bcc symmetry to bcc symmetry
reduced by magnetization.<br>
<br>
<br>
<p> </p>
<table cellspacing="0" border="0">
<colgroup width="312"></colgroup> <colgroup width="85" span="3"></colgroup>
<tbody>
<tr>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left" height="17"><br>
</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">nosp+noso</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">sp+noso</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">sp+so</td>
</tr>
<tr>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left" height="17">bcc
full symmetry without magnetization</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">OK</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">OK</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">X</td>
</tr>
<tr>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left" height="17">bcc
symmetry reduced by magnetization</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">?</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">ghosts</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">ghosts</td>
</tr>
<tr>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left" height="17">(fcc
or simple cubic) reduced by magnetization<br>
</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">?</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">OK</td>
<td style="border-top: 1px solid #000000; border-bottom: 1px
solid #000000; border-left: 1px solid #000000;
border-right: 1px solid #000000" align="left">OK</td>
</tr>
</tbody>
</table>
<p> </p>
<p> </p>
<br>
<br>
<br>
Therefore it seems to me that the ghost MLD peaks appear when
symmetry is reduced in the bcc structure. It seems that SO
coupling is not important in this problem.<br>
It is the lower symmetry itself, which creates the MLD inequality
(ghost MLD peaks).<br>
<br>
For example, can there be some small problem with generation of
k-mesh or related symmetry in bcc+magnetization case?<br>
<br>
<br>
Thank you for your help<br>
With my best regards<br>
Jaroslav<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
<br>
On 26/11/17 18:51, Laurence Marks wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CANkSMZAbwEZWU--JhOm7+Z1K6E_qNe4+750iyjBhgeu+b0_SZg@mail.gmail.com">
<div dir="ltr"><span style="color:rgb(0,0,0);font-size:12.8px">I
will third the comment that not using a shifted cell might be
important (might). In some cells shifting the k-point origin
with MSR1a leads to slightly unbalanced forces which are hard
to converge to the "right" symmetric result. If the forces are
slightly off, this is an indication that the density is also
slightly off. Exactly why this occurs I do not know, I suspect
very soft modes associated with numerical errors in finite
arithmetic.</span>
<div style="color:rgb(0,0,0);font-size:12.8px"><br>
</div>
<div style="color:rgb(0,0,0);font-size:12.8px">N.B., Wien2k is
quite good with these numerical errors. I've noticed that Vasp
calculations that collaborators have done often have much
larger symmetry breaking.</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Sun, Nov 26, 2017 at 11:39 AM,
Karel Vyborny <span dir="ltr"><<a
href="mailto:vybornyk@fzu.cz" target="_blank"
moz-do-not-send="true">vybornyk@fzu.cz</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">I
suppose that this does not have to do (much) with
centering the mesh.<br>
My guess based on other QMO calculations is that some
contributions to<br>
mat. els. of e.g. vx*vx from different parts of the BZ
don't cancel<br>
(numerically) even if they actually should.<br>
<br>
It is instructive to repeat the calculation without SO and
see how big the<br>
difference between sig_xx and sig_yy (for any M direction)
is then.<br>
<br>
Cheers,<br>
<br>
Karel<br>
<br>
<br>
--- x ---<br>
dr. Karel Vyborny<br>
Fyzikalni ustav AV CR, v.v.i.<br>
Cukrovarnicka 10<br>
Praha 6, CZ-16253<br>
tel: +420220318459<br>
<br>
<br>
On Sun, 26 Nov 2017, Fecher, Gerhard wrote:<br>
<br>
> There was a recent discussion on magnetic anisotropy,
With a remark by Peter,<br>
> Did you use a Gamma centered k mesh (and enough k
points)<br>
><br>
> Ciao<br>
> Gerhard<br>
><br>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the
Galaxy:<br>
> "I think the problem, to be quite honest with you,<br>
> is that you have never actually known what the
question is."<br>
><br>
> ==============================<wbr>======<br>
> Dr. Gerhard H. Fecher<br>
> Institut of Inorganic and Analytical Chemistry<br>
> Johannes Gutenberg - University<br>
> 55099 Mainz<br>
> and<br>
> Max Planck Institute for Chemical Physics of Solids<br>
> 01187 Dresden<br>
</blockquote>
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<div dir="ltr"><span
style="font-size:12.8px">Professor
Laurence Marks</span><br>
</div>
<div dir="ltr"><span
style="font-size:12.8px">"Research is to
see what everybody else has seen, and to
think what nobody else has thought", </span><span
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4D: </span><a
href="http://MURI4D.numis.northwestern.edu"
style="font-size:12.8px" target="_blank"
moz-do-not-send="true">MURI4D.numis.northwestern.edu</a>
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<div>Co-Editor, Acta Cryst A</div>
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</blockquote>
<p><br>
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