Search found 2034 matches

by graeme
Fri Sep 10, 2021 11:57 pm
Forum: VTSTTools
Topic: NEBs converging slowly
Replies: 10
Views: 286

Re: NEBs converging slowly

The algorithm to determine extrema simply goes between each pair of images and fits a cubic function to the energies and forces in that interval. In this case, there is a spurious minimum near the initial state with an energy of -0.000219. The position of 0.047705 is a scaled position along the path...
by graeme
Wed Sep 08, 2021 4:38 pm
Forum: VTSTTools
Topic: NEBs converging slowly
Replies: 10
Views: 286

Re: NEBs converging slowly

Put the OUTCAR from your calculations of the minima in the appropriate folders (00 and NN); our scripts greps those for the energy of the endpoints which is needed for the interpolation.
by graeme
Wed Sep 08, 2021 4:08 pm
Forum: VTSTTools
Topic: NEBs converging slowly
Replies: 10
Views: 286

Re: NEBs converging slowly

No, so we typically run things in the following way: vfin.pl dir (copies the current files to directory dir and sets up a new calculation in the current directory) cd dir nebresults.pl (generates plots of the minimum energy path and calculates extrema along the path) neb2dim.pl (uses the calculated ...
by graeme
Wed Sep 08, 2021 3:43 pm
Forum: VTSTTools
Topic: NEBs converging slowly
Replies: 10
Views: 286

Re: NEBs converging slowly

Formally, you would look at the eigenvalues of the Hessian matrix. But you can also just see it from the structure where you have both stiff C-H bonds in a molecule that is partly dissociating from the surface, so there are also going to be floppy modes associated with bending / torsions / rotation ...
by graeme
Tue Sep 07, 2021 11:16 pm
Forum: VTSTTools
Topic: NEBs converging slowly
Replies: 10
Views: 286

Re: NEBs converging slowly

Goodness, looking at the date stamps on those slurm jobs, these have been epic calculations! I see a few things. First, these calculations have both soft and stiff modes which makes optimization challenging. But also, you are getting just ~20 iterations per run which makes things slow-going. So whil...
by graeme
Mon Sep 06, 2021 11:25 pm
Forum: VTSTTools
Topic: How to converge CI-NEB calculations faster?
Replies: 4
Views: 232

Re: How to converge CI-NEB calculations faster?

There are a few problems with your NEB calculation. First, you have frozen C atoms which are in different geometries along your band. Second, you have put a lot of resources into the electronic structure precision, but have only 3 images to find a saddle geometry. Finally, your POTIM is likely too l...
by graeme
Mon Sep 06, 2021 5:33 pm
Forum: Bader
Topic: Orbital charges calculation
Replies: 1
Views: 118

Re: Orbital charges calculation

Hi Hao,
We currently do not. Many years ago we had this capability with a patch to vasp, but we rarely used it and now it will be incompatible with respect to any current version of vasp. For band decomposed charge densities, you will have to use the spherical volumes implemented in vasp.
Graeme
by graeme
Thu Sep 02, 2021 6:02 pm
Forum: Bader
Topic: problem with convergence of charges
Replies: 6
Views: 423

Re: problem with convergence of charges

Yves, I think I understand and agree with everything that you say. Unfortunately, I have very little to add to answer your questions. I am surprised by the monotonic change in charges with grid density and I don't know if that would be typical of other systems. Following that, I can also not suggest...
by graeme
Tue Aug 31, 2021 11:05 pm
Forum: VTSTTools
Topic: Dimer run...good to 0.03 eV/A, but drifted away
Replies: 1
Views: 212

Re: Dimer run...good to 0.03 eV/A, but drifted away

I did a couple of subsequent calculations and I believe that the dimer calculation has originated near a shoulder in the potential. On a shoulder, there is a negative mode, but when you follow it, it can disappear. Try getting closer with the NEB calculation. You can also post that if you want and I...
by graeme
Tue Aug 31, 2021 3:07 pm
Forum: VTSTTools
Topic: NEB forces units in OUTCAR
Replies: 10
Views: 497

Re: NEB forces units in OUTCAR

The NEB tangent is a single unit vector in the 3N dimensional space of the calculation, describing the direction along the minimum energy path.
by graeme
Tue Aug 31, 2021 2:14 pm
Forum: VTSTTools
Topic: NEB calculation with gpu
Replies: 3
Views: 195

Re: NEB calculation with gpu

Why is it so important to run the NEB with 5 images; why don't you run it with 4?
by graeme
Tue Aug 31, 2021 2:11 pm
Forum: VTSTTools
Topic: NEB forces units in OUTCAR
Replies: 10
Views: 497

Re: NEB forces units in OUTCAR

The NEB tangent is just a unit vector along the path at each image.
by graeme
Mon Aug 30, 2021 4:55 pm
Forum: VTSTTools
Topic: NEB forces units in OUTCAR
Replies: 10
Views: 497

Re: NEB forces units in OUTCAR

All forces are in eV/Ang; there are no Bohr units in the vasp code that I know of.

If you give me a specific force that you are looking at (which image, which iteration) I can help you sort this out. The TOTAL-FORCE does have the NEB projection and spring forces.
by graeme
Mon Aug 30, 2021 3:26 pm
Forum: VTSTTools
Topic: NEB forces units in OUTCAR
Replies: 10
Views: 497

Re: output of forces

The band appears converged, but you have high forces in your 06 endpoint directory. You are certainly allowed to use a non-relaxed endpoint, but make sure that you know what you are doing. The forces on the endpoints are not considered in the NEB calculation. If you are looking at a different image,...