<div>Hello everyone,</div><div>i had the same diffuculties with xtb in my calculations.</div><div>I was not able to fully solve the problem but i found some tricks to reduce this effect.</div><div>The following keywords were helpful in my case:<br><br>&DFT<br>&SCF<br>SCF_GUESS MOPAC<br>ADDED_MOS 1000<br>&SMEAR<br>ELECTRONIC_TEMPERATURE 5000<br>&END SMEAR<br></div><div><br></div><div>I would assume xtb is more sensetive to the starting occupation than other methods.</div><div>In my experience the first few iteration steps are crucial and afterwards an reasenoble guess can be made based on the previous iterations.<br></div><div><br></div><div>With best regards,</div><div>Maxim<br></div><br><div class="gmail_quote"><div dir="auto" class="gmail_attr">mpol schrieb am Freitag, 5. Juli 2019 um 10:22:32 UTC+2:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div dir="ltr">Dear Juerg,<div><br></div><div>Thanks for the reply. Notably, I had no such problem with small clusters and molecules.</div><div><br></div><div>Unfortunately, I have to pass on the idea to use GFN-xTB for now, in this case.</div><div><br></div><div>With best regards,</div><div>Mikhail</div><div><br>четверг, 4 июля 2019 г., 19:01:42 UTC+3 пользователь jgh написал:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"></blockquote></div></div><div dir="ltr"><div><blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex">Hi
<br>
<br>we also found that xTB is rather unstable for some systems/atom types.
<br>We think this is mainly due the 3rd order Coulomb term and the
<br>value of gamma (its proportionality factor).
<br>Currently, I don't have an easy solution ready. In your case I would
<br>start with some test calculations on the simple molecules, e.g. CaF2.
<br>You can then try to re-parameterize the atoms (or just the metal?).
<br>You can add the parameters to the input file (see examples in the regtests)
<br>for easy changes.
<br>
<br>regards
<br>
<br>Juerg
<br>--------------------------------------------------------------
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<br>Universität Zürich E-mail: <a rel="nofollow">h...@chem.uzh.ch</a>
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<br>CH-8057 Zürich, Switzerland
<br>---------------------------------------------------------------
<br>
<br>-----<a rel="nofollow">c...@googlegroups.com</a> wrote: -----
<br>To: "cp2k" <<a rel="nofollow">c...@googlegroups.com</a>>
<br>From: "mpol"
<br>Sent by: <a rel="nofollow">c...@googlegroups.com</a>
<br>Date: 07/04/2019 10:57AM
<br>Subject: [CP2K:11946] Ionic crystals with GFN-xTB
<br>
<br>Dear CP2k developers and users,
<br>
<br>Have anyone encountered a problem with GFN-xTB when modeling ionic crystals? If I set
<br>
<br>CHECK_ATOMIC_CHARGES .TRUE.
<br>
<br>When performing CELL_OPT of a CaF_2 supercell, the program stops with the following warning:
<br>
<br>*** WARNING in xtb_matrices.F:1088 :: Atomic charges outside chemical ***
<br> *** range were detected. Switch-off CHECK_ATOMIC_CHARGES keyword in the ***
<br> *** &xTB section if you want to force to continue the calculation. ***
<br>
<br>Setting CHECK_ATOMIC_CHARGES .FALSE. makes the calculation divergent. As I get it, the charges on Ca and F become more and more unphysical in every SCF procedure, and, concomitantly, the total energy becomes lower and lower. I have attached the input and output of the divergent calculation to this message.
<br>
<br>Could anyone give a hint on what to do in this situation? I am interested in MD of solid-liquid interfaces with ionic crystals. GFN-xTB seems the best choice.
<br>
<br>With best regards,
<br>Mikhail
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<br>[attachment "test1.inp" removed by Jürg Hutter/at/UZH]
<br>[attachment "opt.cif" removed by Jürg Hutter/at/UZH]
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<br>[attachment "test1.out" removed by Jürg Hutter/at/UZH]
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