| Re: DFT-D3 energy changes between v3.9 and v3.8 ( No.1 )|
- Date: 2020/04/22 13:04
- Name: Kylin
- Dear Todorovic,
Actually, there are some program bug on DFT-D3 module with DFTD3.damp=bj and Periodic conditions in the last version (v3.8).
I think the new versions has fixed such problem.
For more discussion, refer to this post: http://www.openmx-square.org/forum/patio.cgi?mode=view&no=2517
| Re: DFT-D3 energy changes between v3.9 and v3.8 ( No.2 )|
- Date: 2020/04/22 17:20
- Name: Milica Todorovic <firstname.lastname@example.org>
- Dear Kylin,
Many thanks for the quick response and the recommended post "(Maybe) fixing Vdw-d3(bj)", I read it carefully.
Just to clarify: I did not use openmx v3.8.5, where VdW energy is really nan (as in the other post). I used v3.8, where I obtained a reasonable -1.817523400790 Ha. With v3.9.2 I obtained -0.075717467476 Ha, which is not so reasonable for a large aromatic molecule (7 benzene rings). Of course, the structures are from earlier work with openmx, but usually openmx backwards compatibility is good and energies and forces are similar. Such large changes are uncommon and I am not sure what to trust.
I know that DFT-D3 energy value in v3.8 was benchmarked against VASP DFT-D3 bj implementation. So I don't know why the v.3.9.2 number is so different - has it been checked or benchmarked? Are there any technical notes on this?
Many thanks and all the best, Milica.
| Re: DFT-D3 energy changes between v3.9 and v3.8 ( No.3 )|
- Date: 2020/04/28 06:00
- Name: Jhon W. Gonzalez <email@example.com>
- Hi Milica,
Just out of curiosity...
When you relax the structures with both versions, do the equilibrium distances also change significantly?
| Re: DFT-D3 energy changes between v3.9 and v3.8 ( No.4 )|
- Date: 2020/06/10 16:39
- Name: T. Ozaki
- Hi Milica-san,
Sorry for my late response.
I performed benchmark calculations of DFT-D3 using v3.8, v3.8.5, and v3.9.2 for a molecular and bulk systems,
and obtained almost the same value of DFT-D3 energy for all the versions.
So, I wonder that some unexpected issue must be happening for your system.
The difference between v3.8.5 and v3.9.2 related to DFT-D3 is the folllowing small modification:
v3.8.5: line 3738 in Total_Energy.c
fdamp = (a1_dftD*sqrt(C8/C6)+a2_dftD);
v3.9.2: line 3406 in Total_Energy.c
fdamp = (a1_dftD*sqrt(C8C6)+a2_dftD);
v3.9.2 analytically evaluates C8/C6 and stores it into the variable: C8C6 so that the division by C6 of zero can
be avoided. If the ill-defined calculation does not appear, both the versions should give the same energy.
To fix the problem you have, could you share your input file with us?
Thank you very much for your cooperation in advance.