Hello,<div><br /></div><div>many thanx for the answers.</div><div><br /></div><div>Yes, I found the DFTB3 examples in the test files and I tried those inputs, but to no avail. I played around with some of the settings and I think I found something that works, but I'm no sure it gives the right barrier.</div><div><br /></div><div>With the settings below (the rest of the input is the same, as the uploaded in the first post) I get broken calculations - either the reagent breaks or different H atoms (one from the MM region, one from the QM) get way too close and the calculation stops:</div><div><br /></div><div>DFTB3 + D3(BJ) with default D3BJ_SCALING from the test files, no HB_SR_GAMMA (as per the test files) and no EWALD (as per the test files) - eventually the reagent (QM region) breaks in pieces:</div><div> &DFTB<br /> DIAGONAL_DFTB3 T<br /> !ORTHOGONAL_BASIS F<br /> SELF_CONSISTENT T<br /> DO_EWALD F<br /> DISPERSION T<br /> !HB_SR_GAMMA T<br /> &PARAMETER<br /> PARAM_FILE_PATH ${LIBPATH}/DFTB/3ob-3-1<br /> PARAM_FILE_NAME param_file<br /> DISPERSION_TYPE D3(BJ)<br /> DISPERSION_PARAMETER_FILE ${LIBPATH}/dftd3.dat<br /> D3BJ_SCALING 1.0 0.4 1.5 4.0<br /> !HB_SR_PARAM 4.0<br /> &END PARAMETER<br /> &END DFTB<br /></div><div>----</div><div><br /></div><div>DFTB3 + D3(BJ) with default D3BJ_SCALING from the test files + HB_SR_GAMMA (= 4.2, as per the original paper) and no EWALD (as per the test files) - H atoms get way too close (< 1 A) and the calculations stops:</div><div> &DFTB<br /> DIAGONAL_DFTB3 T<br /> !ORTHOGONAL_BASIS F<br /> SELF_CONSISTENT T<br /> DO_EWALD T<br /> DISPERSION T<br /> HB_SR_GAMMA T<br /> &PARAMETER<br /> PARAM_FILE_PATH ${LIBPATH}/DFTB/3ob-3-1<br /> PARAM_FILE_NAME param_file<br /> DISPERSION_TYPE D3(BJ)<br /> DISPERSION_PARAMETER_FILE ${LIBPATH}/dftd3.dat<br /> D3BJ_SCALING 1.0 0.4 1.5 4.0<br /> HB_SR_PARAM 4.2<br /> &END PARAMETER<br /> &END DFTB<br /></div><div>----</div><div><br /></div><div>DFTB3 + D3(BJ) with original D3BJ_SCALING from the original paper + HB_SR_GAMMA (= 4.2, as per the original paper), no EWALD (as per the test files) - H atoms get way too close (< 1 A) and the calculations stops:</div><div> &DFTB<br /> DIAGONAL_DFTB3 T<br /> !ORTHOGONAL_BASIS F<br /> SELF_CONSISTENT T<br /> DO_EWALD F<br /> DISPERSION T<br /> HB_SR_GAMMA T<br /> &PARAMETER<br /> PARAM_FILE_PATH ${LIBPATH}/DFTB/3ob-3-1<br /> PARAM_FILE_NAME param_file<br /> DISPERSION_TYPE D3(BJ)<br /> DISPERSION_PARAMETER_FILE ${LIBPATH}/dftd3.dat<br /> D3BJ_SCALING 1.0 .5719 .5883 3.6017<br /> HB_SR_PARAM 4.2<br /> &END PARAMETER<br /> &END DFTB</div><div>---</div><div><br /></div><div>ORTHOGONAL_BASIS T always breaks the calculation from the beginning (not a single geometry in the output), so I guess 3ob-3-1 does not have an orthogonal basis or DFTB3 simply does not use one. As I can see - the default in CP2K is FALSE, anyway.</div><div>DO_EWALD F breaks even DFTB2 calculations - the reagent (QM region) breaks in pieces</div><div>---</div><div><br /></div><div>However, the following setup seems to work, although I'm not sure I can trust the barrier (it is very sensitive to intermolecular interactions and it seems kind of high, and there is no available experimental value):</div><div><br /></div><div>DFTB3 + D3(BJ), no D3BJ_SCALING keyword (I let cp2k determine s6, sr6, s8 automatically, as suggested in a recent new thread in this google group) + HB_SR_GAMMA (=4 as usual default), with EWALD - it seems to work:</div><div> &DFTB<br /> DIAGONAL_DFTB3 T<br /> SELF_CONSISTENT T<br /> DO_EWALD T<br /> DISPERSION T<br /> HB_SR_GAMMA T<br /> &PARAMETER<br /> PARAM_FILE_PATH ${LIBPATH}/DFTB/3ob-3-1<br /> PARAM_FILE_NAME param_file<br /> ! UFF_FORCE_FIELD uff_table<br /> DISPERSION_TYPE D3(BJ)<br /> DISPERSION_PARAMETER_FILE ${LIBPATH}/dftd3.dat<br /> HB_SR_PARAM 4<br /> &END PARAMETER<br /> &END DFTB</div><div>---</div><div><br /></div><div>Next I will try to explicitly provide the Hubbard parameters with in the input with DFTB3_PARAM.</div><div><br /></div><div>Thank you again for the help.</div><div>If you can think of anything else - please - tell me.</div><div><br /></div><div>Best Regards,</div><div>Dobromir</div><div><br /></div><div> </div><div class="gmail_quote"><div dir="auto" class="gmail_attr">On Monday, February 2, 2026 at 11:23:58 AM UTC+2 Jürg Hutter wrote:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi
<br>
<br>1) and 2) Have a look in "tests/DFTB/regtest-vdw" . There you find some examples on how to use D3 with DFTB.
<br>3) The D3(BJ) parameters have to be given in the input file. The data file only contains the atom specific parameters,
<br> not the method parameters.
<br>4) Yes, this is the DFTB3 parameter. I don't know if CP2K can read the parameter from the DFTB parameter file. I would have to check.
<br>5) You need the keyword. According to the manual the default is not to use it.
<br>6) I cannot answer this question.
<br>
<br>regards
<br>JH
<br>
<br>________________________________________
<br>From: <a href data-email-masked rel="nofollow">cp...@googlegroups.com</a> <<a href data-email-masked rel="nofollow">cp...@googlegroups.com</a>> on behalf of Dobromir A Kalchevski <<a href data-email-masked rel="nofollow">dobro...@gmail.com</a>>
<br>Sent: Saturday, January 31, 2026 11:21 AM
<br>To: cp2k
<br>Subject: [CP2K:22073] DFTB3 D3(BJ) GAMMA
<br>
<br>Hello valued developers and users,
<br>
<br>I am trying to setup DFTB3 with D3 correction and GAMMA damping and I can't find the answers to all of my questions in the forum threads. Also some answers are not completely clear to me.
<br>
<br>1) If I am to use the D3 correction - is it enough to include
<br> DISPERSION_TYPE D3(BJ)
<br> DISPERSION_PARAMETER_FILE ${LIBPATH}/dftd3.dat
<br>
<br>or should I also include the &VDW_POTENTIAL section and where if I am not using DFT (&XC section)
<br>
<br>2) does D3(BJ) work with DFTB3 or does only D3 work
<br>
<br>3) are both the D3 and the D3(BJ) parameters in the dft3d.dat file. If not - for D3(BJ) I can find only a1, a2 and s8, but I can't find anywhere the fourth one. Why are the default values set to 0
<br>
<br>4) is the keyword DFTB3_PARAM in KIND the Hubbard parameter and is it necessary. The 3ob .skf files technically include it, basically does CP2K read it from the .skfs.
<br>
<br>5) is using 3ob enough for DFTB3 or do I have to include the keyword DIAGONAL_DFTB3 in &DFTB
<br>
<br>6) if HB_SR_GAMMA is the GAMMA damping for hydrogen bonds, is its use recommended for general organics at the moment or it would rather worsen the results, as before
<br>
<br>I am attaching an example input file for QM/MM Metadynamics.
<br>
<br>Best Regards,
<br>Dobromir
<br>
<br>
<br>
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