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<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Let me give yet another different answer.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">The initial question was about accuracy, while the parameters it referred to affect not accuracy yet only precision.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Precision = what was called ‘technical convergence’ by Laurence Marks.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Accuracy = difference between the DFT result and the experimental value (exclusively determined by the functional).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">You can have a fully precise calculation with low accuracy. And even if you would have the exact functional (=fully accurate), but would be using a small basis set, your calculation
would not be very precise.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">The Delta test is about precision, not accuracy.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Hence, the better formulation of the initial question would have been ‘high-precision calculations’ (which would have made clear that it was not aiming at the functional).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="mso-fareast-language:EN-US">Stefaan<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="NL">Van:</span></b><span lang="NL"> Wien [mailto:wien-bounces@zeus.theochem.tuwien.ac.at]
<b>Namens </b>Laurence Marks<br>
<b>Verzonden:</b> vrijdag 13 april 2018 16:38<br>
<b>Aan:</b> A Mailing list for WIEN2k users <wien@zeus.theochem.tuwien.ac.at><br>
<b>Onderwerp:</b> Re: [Wien] High accuracy calculations<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Let me give a different answer.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">To perform a high accuracy calculation...use a high accuracy functional.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">The technical convergence of, for instance, energy at a level of 0.01 eV/atom is easy, and the default parameters are close to good enough in most cases. (Phonons may require some care.)<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">The accuracy of some functionals is an order of magnitude larger than this, i.e. 0.1eV/atom or worse.<o:p></o:p></p>
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<p class="MsoNormal">_____<br>
Professor Laurence Marks<br>
"Research is to see what everybody else has seen, and to think what nobody else has thought", Albert Szent-Gyorgi<br>
<a href="http://www.numis.northwestern.edu">www.numis.northwestern.edu</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Fri, Apr 13, 2018, 9:29 AM Gavin Abo <<a href="mailto:gsabo@crimson.ua.edu">gsabo@crimson.ua.edu</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Regarding the SupplMat-WIEN2k.pdf at<br>
<br>
<a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__molmod.ugent.be_deltacodesdft&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=i1cULin_bn1tXhun33udTWyfJa5a0DXu_AhUGpJF-9E&s=d8WhT1rs3NF5IudCJnDFvFy87W1MFRyRUoXvlFeoo20&e=" target="_blank">https://urldefense.proofpoint.com/v2/url?u=https-3A__molmod.ugent.be_deltacodesdft&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=i1cULin_bn1tXhun33udTWyfJa5a0DXu_AhUGpJF-9E&s=d8WhT1rs3NF5IudCJnDFvFy87W1MFRyRUoXvlFeoo20&e=</a><br>
<br>
I could be wrong, but it seems to be referring to lnsmax and lmax in <br>
case.in1 and GMAX in case.in2 as seen in the WIEN2k usersguide [ <br>
<a href="https://urldefense.proofpoint.com/v2/url?u=http-3A__susi.theochem.tuwien.ac.at_reg-5Fuser_textbooks_usersguide.pdf&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=i1cULin_bn1tXhun33udTWyfJa5a0DXu_AhUGpJF-9E&s=9xncYwixf_vmWq4iLvqt1Ac_1AZDwTlEHL8FHaao_20&e=" target="_blank">https://urldefense.proofpoint.com/v2/url?u=http-3A__susi.theochem.tuwien.ac.at_reg-5Fuser_textbooks_usersguide.pdf&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=i1cULin_bn1tXhun33udTWyfJa5a0DXu_AhUGpJF-9E&s=9xncYwixf_vmWq4iLvqt1Ac_1AZDwTlEHL8FHaao_20&e=</a>
].<br>
<br>
<br>
On 4/13/2018 3:33 AM, Nils Longshower wrote:<br>
> Hi!<br>
><br>
> I have a question on some parameters to increase accuracy. In the <br>
> supplementary materials for the delta tests, the following parameters <br>
> are listed:<br>
><br>
> * largest l-value of nonspherical Hamiltonian and overlap matrix<br>
><br>
> * elements inside the spheres largest l-value in expansion of density <br>
> and potential<br>
><br>
> * largest vector in Fourier expansion of charge density<br>
><br>
><br>
><br>
> Where do I set these parameters?<br>
><br>
><br>
> Best,<br>
> Nils<br>
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