<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">not necessarily, if there is a barrier (after all, there are plenty of exothermic chemical reactions, without which no fire would exist!) — Stefano B<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On 8 Mar 2018, at 15:50, Laurens Siemons <<a href="mailto:laurenssiemons@hotmail.be" class="">laurenssiemons@hotmail.be</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div id="divtagdefaultwrapper" dir="ltr" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; font-size: 12pt; font-family: Calibri, Helvetica, sans-serif;" class=""><p style="margin-top: 0px; margin-bottom: 0px;" class=""><span id="ms-rterangepaste-start" class=""></span></p><div class="">Dear all,<div style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></div><div style="margin-top: 0px; margin-bottom: 0px;" class="">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:</div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></div>E<sub class="">surface + adsorbate<span class="Apple-converted-space"> </span></sub>=<span class="Apple-converted-space"> </span><span class="">-4301.05337244</span><div style="margin-top: 0px; margin-bottom: 0px;" class="">E<sub class="">surface<span class="Apple-converted-space"> </span></sub>=<span class="Apple-converted-space"> </span><span class="">-4258.9387474</span><br class=""></div><div style="margin-top: 0px; margin-bottom: 0px;" class="">E<sub class="">adsorbate<span class="Apple-converted-space"> </span></sub>=<span class="Apple-converted-space"> </span><span class="">-42.37757742</span><br class=""></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></div><div style="margin-top: 0px; margin-bottom: 0px;" class="">So E<sub class="">ads<span class="Apple-converted-space"> </span></sub>=<span class="Apple-converted-space"> </span><span class="">E<sub class="">surface + adsorbate</sub></span><span class="Apple-converted-space"> </span>- (E<sub class="">surface<span class="Apple-converted-space"> </span></sub>+ E<sub class="">adsorbate</sub>) = 0.26<br class=""></div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></div><div style="margin-top: 0px; margin-bottom: 0px;" class="">Now this seems wrong. If E<sub class="">ads</sub><span class="Apple-converted-space"> </span>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.</div><div style="margin-top: 0px; margin-bottom: 0px;" class=""><br class=""></div><div style="margin-top: 0px; margin-bottom: 0px;" class="">Thanks in advance,</div><div style="margin-top: 0px; margin-bottom: 0px;" class="">Laurens Siemons</div><div style="margin-top: 0px; margin-bottom: 0px;" class="">Master student chemistry</div>University of Antwerp</div><br class=""><p style="margin-top: 0px; margin-bottom: 0px;" class=""></p></div><span id="cid:301FFB32-6873-4E28-8297-9ADEB8FDEA54@sissa.it"><a001cti.rx.in></span><span id="cid:0ACC6E41-D182-4FF4-9F44-127C34781DEC@sissa.it"><anatase001-2x2-4.rx.in></span><span id="cid:48C4C340-C837-4E9D-9F16-EB90BE9696E6@sissa.it"><ethyl-anion.rx.in></span><span style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">_______________________________________________</span><br style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; float: none; display: inline !important;" class="">users mailing list</span><br style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="mailto:users@lists.quantum-espresso.org" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">users@lists.quantum-espresso.org</a><br style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><a href="https://lists.quantum-espresso.org/mailman/listinfo/users" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" class="">https://lists.quantum-espresso.org/mailman/listinfo/users</a></div></blockquote></div><br class=""><div class="">
<div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="orphans: auto; text-align: start; text-indent: 0px; widows: auto; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="orphans: auto; text-align: start; text-indent: 0px; widows: auto; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div style="orphans: auto; text-align: start; text-indent: 0px; widows: auto;"><span style="font-size: 12px;" class="">—</span></div><div style="orphans: auto; text-align: start; text-indent: 0px; widows: auto;"><span style="font-size: 12px;" class="">Stefano Baroni - SISSA, Trieste - <a href="http://stefano.baroni.me" class="">http://stefano.baroni.me</a>, stefanobaroni (skype)</span></div><div style="orphans: auto; text-align: start; text-indent: 0px; widows: auto;"><span style="font-size: 12px;" class=""><br class=""></span></div><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; font-variant-caps: normal; orphans: auto; text-align: start; text-indent: 0px; widows: auto;"><span style="font-size: 12px;" class="">There are two ways of doing a theoretical calculation: you should have either a clear physical model in mind, or a rigorous mathematical basis. You have neither. [E. Fermi to F.J. Dyson, as humbly reported by the latter]</span></div></div></div></div></div></div>
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