<div>Dear Prof. Jürg Hutter, </div><div> </div>Thank you very much for your quick and helpful reply. I ran the tests you suggested; the inputs, outputs and an updated analysis script are in the attached cp2k_GTH-SCAN_report_v2.zip (new section A3 and an extended B1 in the README). Please correct me if I have misread anything. **1. Al: MOLOPT-SR basis** I kept everything else fixed (GAPW + GAPW_ACCURATE_XCINT, all other elements TZV2P-MOLOPT-SCAN / GTH-SCAN) and changed only the Al kind, on the original structure and the three MD frames. Al |ΔF| RMS against the all-electron Al (meV/Å): | Al basis + potential | initial | Al4 | Al5 | Al6 | |---|---|---|---|---| | TZV2P-MOLOPT-SCAN-GTH-q3 + GTH-SCAN-q3 (before) | 306 | 466 | 351 | 333 | | DZVP-MOLOPT-SR-GTH-q3 + GTH-SCAN-q3 | 275 | 410 | 307 | 281 | | TZV2P-MOLOPT-SR-GTH-q3 (BASIS_MOLOPT_UCL) + GTH-SCAN-q3 | 314 | 487 | 368 | 350 | | DZVP-MOLOPT-SR-GTH-q3 + GTH-PBE-q3 | 172 | 245 | 187 | 181 | - With the SR basis the Al difference changes only a little (about −10 % with DZVP-SR, no change with TZV2P-SR), so it does not seem to come from the SCAN basis. - Surprisingly to me, switching only the potential from GTH-SCAN-q3 to GTH-PBE-q3 removes about half of the difference, in the direction of the all-electron result, although the two parameter sets differ by less than 1 %. The trend on the Al–O pairs and on the relative energies of the Al4/5/6 frames is reduced in the same way, but not removed (about 180 meV/Å remains). So the Al forces seem to be very sensitive to the potential parameters. Would you expect this for GTH-SCAN-q3, and would you recommend a different approach for Al in oxides with r2SCAN, for example a potential with 2s2p in the valence (I could not find one for SCAN in POTENTIAL_UZH), or simply the all-electron Al with GAPW? **2/3. Zn grid sensitivity** Following your suggestion, I added GAPW, GAPW_ACCURATE_XCINT and USE_FINER_GRID step by step (1100 Ry, 302 atoms, 4 rigid shifts). Zn force spread, |ΔF| RMS (meV/Å): | Setting | Zn spread | |---|---| | GPW | ~390 | | GAPW + GAPW_ACCURATE_XCINT | 37 | | GPW + USE_FINER_GRID | 28–32 | | GAPW + GAPW_ACCURATE_XCINT + USE_FINER_GRID | 0.7–0.8 | - The full combination works very well: the Zn noise drops below 1 meV/Å. Thank you for this. - I also changed only the Zn basis to TZVP-MOLOPT-SR-GTH and the potential to GTH-PBE-q12; the noise stayed at ~390 meV/Å, so with these choices it seems to come from r2SCAN on the grid rather than from the SCAN basis or potential. May I ask one more question on this? Would it be possible, or sensible at all, to reduce this grid sensitivity on the side of the potential or the basis set, for example a Zn potential/basis built to be smoother on the grid for meta-GGAs? Since the SR basis and the GTH-PBE potential did not change it, I do not know whether this is something the potential or basis can address. Thank you again for your time and help. Best regards, Wei LIU <div class="gmail_quote"><div dir="auto" class="gmail_attr">在2026年10月12日星期一 UTC+9 22:23:26<Jürg Hutter> 写道： </div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi 1) You can try the Al (sr) basis from BASIS_MOLOPT. This text would give a hint if the UZH SCAN basis for Al is in some way corrupted. The SCAN/Hybrid basis sets are less texted than the PBE ones. 2/3) r2SCAN needs higher cutoffs than PBE. If the force wiggles are too large you can try GAPW and accurate_intrgration and finer_grid (in that order, accumulative) regards JH ________________________________________ 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 liu wei <<a href data-email-masked rel="nofollow">whispe...@gmail.com</a>> Sent: Monday, October 12, 2026 2:15 PM To: cp2k Subject: [CP2K:22433] Question about Al (GTH-SCAN-q3) forces with r2SCAN compared with all-electron / PAW results Dear CP2K developers and users, I am a student working on ab initio MD of a ZnO–P2O5–Al2O3 glass (302 atoms, Γ point) with r2SCAN-D3(BJ), the GTH-SCAN potentials and the MOLOPT-SCAN basis sets (CP2K 2026.2). While I was checking my forces against VASP, I noticed a difference on Al that I do not understand, and I would be very grateful for your advice. I may well be missing something in my setup, so please correct me if so. I have attached all inputs and outputs, a short analysis script (numpy only) and a README with the full tables (cp2k_GTH-SCAN_report.zip). **1. Al forces** On one 302-atom structure I obtained the following force differences (|ΔF| RMS per element, meV/Å): | A − B | Zn | O | P | Al | |---|---|---|---|---| | CP2K (GPW, TZV2P-MOLOPT-SCAN, GTH-SCAN, 800 Ry, FINER) − VASP (PAW O_h/P_h/Zn/Al_sv_GW, 1300 eV) | 41 | 55 | 61 | 320 | | CP2K GAPW, Al → ALL + pob-TZVP-rev2 − CP2K GAPW, Al GTH-SCAN-q3 (everything else identical) | 3 | 40 | 11 | 306 | | CP2K GAPW with all-electron Al − VASP Al_sv_GW | 58 | 39 | 61 | 62 | - For Zn, O and P the two codes agree to about 40–60 meV/Å, and the pressure agrees to within 1 kbar, but for Al the difference is about 300 meV/Å. - When I replaced only the Al GTH-SCAN-q3 by an all-electron Al in GAPW, most of this difference (about 94 %) disappeared in my test. - I tried to check a few other possible reasons: USE_FINER_GRID, GPW vs GAPW (0.6 meV/Å on Al), and the frozen 2s2p core on the VASP side (Al vs Al_sv_GW changes the Al forces by 69 meV/Å, in the other direction). None of them seemed to explain it, but I am not sure whether I checked them in the right way. - I also looked at three MD snapshots with 4-, 5- and 6-coordinated Al. On all 6 Al the difference seems to follow the same trend: compared with the all-electron Al, GTH-SCAN-q3 appears to pull the short Al–O bonds (< 1.85 Å) in and push the longer Al–O contacts (2.1 Å and beyond) out; between 1.85 and 2.1 Å the sign varies. Here I project ΔF = F(all-electron) − F(GTH-SCAN-q3) on each Al–O pair as (ΔF_O − ΔF_Al)·u, with u the unit vector from Al to O. A positive value means the all-electron force along the pair is more repulsive than the GTH-SCAN-q3 one (so GTH-SCAN-q3 pulls the pair together), and a negative value means it is more attractive (GTH-SCAN-q3 pushes the pair apart). These are differences, not the total forces. For example, I get +812 meV/Å for a bond of 1.66 Å and −436 meV/Å for a contact of 2.10 Å. - One limitation I am aware of: the all-electron run also uses a different Al basis (pob-TZVP-rev2), so I could not separate the effect of the potential from that of the basis. Changing only the MOLOPT basis (TZVP → TZV2P) moved the Al forces by 87 meV/Å, so I guessed the potential plays the larger role, but I am not confident about this. **2. Zn (a smaller question)** With GPW, r2SCAN + TZVP-MOLOPT-SCAN + GTH-SCAN-q12 gave a Zn force spread of about 390 meV/Å RMS over 4 rigid shifts of the same structure, while PBEsol + TZVP-MOLOPT-SR + GTH-PBE-q12 changed by only about 2 meV/Å when the FFT grid changed (1100 vs 1350 Ry). USE_FINER_GRID reduced the r2SCAN spread to about 30 meV/Å, which works well for me. I did not separate the effects of the functional, the basis and the potential, so I am not sure where this comes from. **My questions** 1. Could you help me understand what might cause the Al difference? Is it something one would expect with GTH-SCAN-q3 (for example, because it was fitted for SCAN rather than r2SCAN), or is there likely a problem in my setup or in the way I compared the results? 2. For Al in oxides with SCAN/r2SCAN, would you recommend a different potential or basis (for example, one with 2s2p in the valence), or another way to check this more carefully? 3. For Zn with r2SCAN, is this grid sensitivity expected, and is there anything you would recommend besides USE_FINER_GRID? I would be happy to run any additional tests you suggest. Thank you very much for your time and for developing CP2K. Best regards, Wei LIU -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href data-email-masked rel="nofollow">cp2k+uns...@googlegroups.com</a><mailto:<a href data-email-masked rel="nofollow">cp2k+uns...@googlegroups.com</a>>. To view this discussion visit <a href="https://groups.google.com/d/msgid/cp2k/189080b0-6d63-4515-9a04-191b65347daan%40googlegroups.com" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=zh-CN&q=https://groups.google.com/d/msgid/cp2k/189080b0-6d63-4515-9a04-191b65347daan%2540googlegroups.com&source=gmail&ust=1791944968631000&usg=AOvVaw3MbiXZiDCyXVi_WiQte2cv">https://groups.google.com/d/msgid/cp2k/189080b0-6d63-4515-9a04-191b65347daan%40googlegroups.com</a><<a href="https://groups.google.com/d/msgid/cp2k/189080b0-6d63-4515-9a04-191b65347daan%40googlegroups.com?utm_medium=email&utm_source=footer" target="_blank" rel="nofollow" data-saferedirecturl="https://www.google.com/url?hl=zh-CN&q=https://groups.google.com/d/msgid/cp2k/189080b0-6d63-4515-9a04-191b65347daan%2540googlegroups.com?utm_medium%3Demail%26utm_source%3Dfooter&source=gmail&ust=1791944968631000&usg=AOvVaw27e_OFBVEP7BTkKK9x0OGi">https://groups.google.com/d/msgid/cp2k/189080b0-6d63-4515-9a04-191b65347daan%40googlegroups.com?utm_medium=email&utm_source=footer</a>>. </blockquote></div> -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>. To view this discussion visit <a href="https://groups.google.com/d/msgid/cp2k/f6b35e26-6305-4de1-abb2-c135735ab583n%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/f6b35e26-6305-4de1-abb2-c135735ab583n%40googlegroups.com</a>.