<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">If the anion stays charged, which is an issue by itself in DFT, the distance will never be large enough, because the slab will generate a macroscopic electric field. sb<br><br><div dir="ltr"><div><span style="background-color: rgba(255, 255, 255, 0);">___</span></div><div><span style="background-color: rgba(255, 255, 255, 0);">Stefano Baroni, Trieste -- http://stefano.baroni.me</span></div></div><div dir="ltr"><br><blockquote type="cite">On 23 Feb 2021, at 07:05, Nam Tran <vnt981@uowmail.edu.au> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Dear QE users,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
I would like to calculate the adsorption energy of a negative anion NO3- with a positive slab (The total system is neutral). I cannot use the convention formula Eds = E(slab+anion) - E(slab) - E(anion) because of the charge compensation when calculating the
energy of charged slab and charge adsorbate. </div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
As the total system (<span style="background-color:rgb(255, 255, 255);display:inline !important">slab+anion</span>) is neutral, I wonder if it is possible to just move the <span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">molecule
far away from the slab (make sure that vacuum in z-direction is large enough), and calculate the energy difference i.e.,
</span><span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">one of them the molecule is far away from the surface and in the other one the molecule adsorbed on the surface.</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<span style="color: rgb(0, 0, 0); font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;"><br>
</span></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Best regards</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
Nam</div>
<div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div id="Signature">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif"></div>
</div>
</div>
<span>_______________________________________________</span><br><span>Quantum ESPRESSO is supported by MaX (www.max-centre.eu)</span><br><span>users mailing list users@lists.quantum-espresso.org</span><br><span>https://lists.quantum-espresso.org/mailman/listinfo/users</span></div></blockquote></body></html>