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<p>Dear Davide,</p>
<p><br>
</p>
<p>I am studying several Cu(II)-based systems. One of them is Cu-L-alanine. Crystallographic unit cell of this complex comprises two Cu atoms and four L-alanine molecules. Hyperfine coupling constants on 13C nuclei calculated by QE-GIPAW were comparable to
hyperfine coupling constants calculated by Orca, where the structural model used in Orca consisted of only one Cu atom and two L-alanine molecules.</p>
<p>The next system was one of metal-organic frameworks. Its unit cell, supplied to QE-GIPAW calculations, contained 12 Cu atoms, whereas the model used with Orca comprised 6 Cu atoms. The latter structural model described the same motif as was the one contained
in the unit cell of periodic calculations. Nevertheless, hyperfine coupling constants on 13C nuclei obtained with QE-GIPAW were about 9-times as large as hyperfine coupling constants obtained with Orca:</p>
<p>Orca : QE-GIPAW</p>
<p></p>
<div>-0.9<span style="white-space:pre"> </span>: -7.9</div>
<div>2.4<span style="white-space:pre"> </span>:<span style="white-space:pre"> </span>
21.0</div>
<div>0.3<span style="white-space:pre"> </span>:<span style="white-space:pre"> </span>
3.3</div>
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<div>For another MOF system again a large factor was between the QE-GIPAW and Orca calculated constants.</div>
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<div>Best regards</div>
<div>Gregor</div>
<br>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Davide Ceresoli <davide.ceresoli@cnr.it><br>
<b>Sent:</b> Friday, December 18, 2020 12:44:29 PM<br>
<b>To:</b> users@lists.quantum-espresso.org<br>
<b>Subject:</b> Re: [QE-users] definition of the hyperfine coupling constant in QE-GIPAW</font>
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<div class="PlainText">Dear Gregor,<br>
the hyperfine coupling should be multiplied by the number<br>
of unpaired electrons (2*S_z). It also assumes I=1/2.<br>
<br>
In the past I checked that GIPAW yields the same results of ORCA<br>
and Gaussian for molecules in the case S = I = 1/2. I can re-check that.<br>
<br>
Best.<br>
Davide<br>
<br>
<br>
<br>
On 12/18/20 10:22 AM, Gregor Mali wrote:<br>
> Hello.<br>
> <br>
> <br>
> Isotropic hyperfine coupling constants A_iso, calculated by QE-GIPAW, can differ
<br>
> by a large factor from A_iso, obtained by Orca. The factor depends on the number
<br>
> of unpaired electrons in the unit cell (used in QE) and in the cluster model <br>
> (used in Orca). In Orca, A_iso is proportional to spin-density at the position <br>
> of a nucleus divided by <S_z>. <S_z> is the maximum value of the z component. <br>
> What is the definition of A_iso in QE-GIPAW? Is it perhaps proportional <br>
> to spin-density multiplied by S(S+1)/<S_z>?<br>
> <br>
> <br>
> Thanks in advance!<br>
> <br>
> <br>
> Gregor Mali<br>
> <br>
> National Institute of Chemistry<br>
> <br>
> Ljubljana, Slovenia<br>
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