<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Dear Flo,<div>I really fear it is a D3 problem, </div><div>we would have not done the D2 test otherwise.</div><div>We are very familiar with cutoff problems, that’s why here the cutoff is 600 Ry (despite 800 would be better for Pd)</div><div><br></div><div>we are speaking here of 0.07 Ry difference just in dispersion energy..</div><div><br></div><div>Unless, as Leo said, there is something non trivial that we ignore </div><div>i would guess that something with R_CUTOFF is wrong but I cannot imagine what</div><div><br></div><div>Kind regards</div><div><br></div><div>Carlo</div><div><br><div><div>On 06 Oct 2014, at 22:25, Leopold Talirz <<a href="mailto:leopold...@gmail.com">leopold...@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr">Dear Flo,<div><br></div><div>thanks a lot for your reply and the link. Nice table with the cutoff values for the elements by the way :)</div><div><br></div><div>Concerning our question - I completely agree with your point, where it concerns quantities that are computed on the grids. Our question, however, concerns only the *dispersion energy*. As far as I know (please correct me, if I am wrong) both DFT-D2 and DFT-D3 compute the dispersion energy based only on atomic coordinates. </div><div>If the interaction between the periodic replicas of the slab across the vacuum region are set to zero by R_CUTOFF, then the dispersion energy should be completely independent of the amount of vacuum. If you check the values for the DFT-D2, you will find that the dispersion energies for the two different amounts of vacuum are identical up to the last digit.</div><div><br></div><div>Best,</div><div>Leo</div></div><div><br class="webkit-block-placeholder"></div>
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