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<p style="margin-top:0;margin-bottom:0">Thank you all for your quick response.</p>
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<p style="margin-top:0;margin-bottom:0">I'm running a calculation now like Evren Ataman suggested. By doing this the problem of the compensating background should be resolved as well.
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<p style="margin-top:0;margin-bottom:0">The reason I'm not using vdw corrections is based on an article (<span>doi: 10.1021/jz501050f</span>) where they did calculations with and without these corrections. There conclusion is that the corrections are negligible.</p>
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<p style="margin-top:0;margin-bottom:0">Kind regards,</p>
<p style="margin-top:0;margin-bottom:0">Laurens Siemons<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" color="#000000" face="Calibri, sans-serif"><b>Van:</b> users <users-bounces@lists.quantum-espresso.org> namens Stefano de Gironcoli <degironc@sissa.it><br>
<b>Verzonden:</b> donderdag 8 maart 2018 16:19<br>
<b>Aan:</b> users@lists.quantum-espresso.org<br>
<b>Onderwerp:</b> Re: [QE-users] Wrong adsorption energy</font>
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<p><tt>two things I think might be the origin of strange results.</tt></p>
<p><tt> </tt></p>
<p><tt>your ethyl-anion is charged. the code introduce a compensating background that should cancel out when you calculate the adsortion energy but you are using different cells in the two charged configurations. so something does not cancel out as it should.</tt></p>
<p><tt> </tt></p>
<p><tt>there might be some vdW interaction contributing to the physisorption. I see no inclusion of vdW corrections or use of vdW-aware functionals in your calculations.
<br>
</tt></p>
<p><tt><br>
</tt></p>
<p><tt>best<br>
</tt></p>
<p><tt><br>
</tt></p>
<p><tt>stefano</tt><br>
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<div class="x_moz-cite-prefix">On 08/03/2018 15:50, Laurens Siemons wrote:<br>
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<div>Dear all,
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<p style="margin-top:0; margin-bottom:0">I'm calculating parameters like adsorption energy, geometric parameters, NMR chemical shifts of adsorbates on a surface. In this specific case I calculated the adsorption energy of an ethyl anion on an anatase 001 surface
of titania. I got the following energies:</p>
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E<sub>surface + adsorbate </sub>= <span>-4301.05337244</span>
<p style="margin-top:0; margin-bottom:0">E<sub>surface </sub>= <span>-4258.9387474</span><br>
</p>
<p style="margin-top:0; margin-bottom:0">E<sub>adsorbate </sub>= <span>-42.37757742</span><br>
</p>
<p style="margin-top:0; margin-bottom:0"><br>
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<p style="margin-top:0; margin-bottom:0">So E<sub>ads </sub>= <span>E<sub>surface + adsorbate</sub></span> - (E<sub>surface
</sub>+ E<sub>adsorbate</sub>) = 0.26<br>
</p>
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<p style="margin-top:0; margin-bottom:0">Now this seems wrong. If E<sub>ads</sub> is positive, so adsorption is not favourable, then the ethyl-anion should migrate away from the surface in the relax calculation of a001cti. correct? I executed the three calculations
with the exact same parameters as the other ones so I don't see how this is possible. I attached my input files of the calculations. I hope someone can guide me through this.</p>
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<p style="margin-top:0; margin-bottom:0">Thanks in advance,</p>
<p style="margin-top:0; margin-bottom:0">Laurens Siemons</p>
<p style="margin-top:0; margin-bottom:0">Master student chemistry</p>
University of Antwerp</div>
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