Search found 2255 matches

by graeme
Wed Jun 21, 2023 2:37 pm
Forum: VTSTTools
Topic: Estimated opinion on the simulation results
Replies: 2
Views: 3693

Re: Estimated opinion on the simulation results

It looks good to me; I don't see any problems.
by graeme
Tue Jun 20, 2023 9:45 pm
Forum: VTSTTools
Topic: Visualization of MODECAR?
Replies: 4
Views: 4763

Re: Visualization of MODECAR?

I can't remember the form of the MODECAR, but it should be easy to see if it is direct or Cartesian. Basically, I am just saying that you have a minimum structure and a displaced structure in a dimer calculation, then you can see the difference between them, which is the direction of the MODECAR.
by graeme
Thu Jun 15, 2023 7:54 pm
Forum: VTSTTools
Topic: Visualization of MODECAR?
Replies: 4
Views: 4763

Re: Visualization of MODECAR?

I think that the easiest way to visualize the modecar is to make a 2-image movie - one image at the minimum and the other at the displaced configuration. Going between these images should give you a sense of what the displacement mode is.
by graeme
Wed Jun 14, 2023 6:05 pm
Forum: VTSTTools
Topic: NEB convergence problems
Replies: 3
Views: 4138

Re: NEB convergence problems

I have a somewhat different take on the issue. I'm going to attach 3 tests that I did. In SrAgO3, I used the conservative settings of IOPT=3 TIMESTEP=0.05. After 132 iterations (it is still running) the force on the climbing image has increased from 0.15 up to 0.54 eV/Ang and the barrier remains ove...
by graeme
Sat Jun 10, 2023 11:51 pm
Forum: VTSTTools
Topic: Request for Assistance with CINEB Calculations.
Replies: 2
Views: 4015

Re: Request for Assistance with CINEB Calculations.

I will need to see a calculation where it has completed at least one NEB geometry optimization - what you posted does not have any forces on the images. Other problems: You did not link in our VTST code and so any tags relation to IOPT or LCLIMB will not be considered. Your molecule has frozen coord...
by graeme
Wed Jun 07, 2023 1:50 am
Forum: VTSTTools
Topic: Stuck NEB calculation
Replies: 10
Views: 9085

Re: Stuck NEB calculation

You have to download all of the scripts and add it to your path. You might also need to add the directory to your PYTHONPATH ; that is what you need for scripts to be able to import python modules, such as aselite. By the way, you can also do this through ase.
by graeme
Tue Jun 06, 2023 9:18 pm
Forum: VTSTTools
Topic: Stuck NEB calculation
Replies: 10
Views: 9085

Re: Stuck NEB calculation

The two scripts work the same way. For IDPP, see: https://wiki.fysik.dtu.dk/ase/tutorials/neb/idpp.html
by graeme
Mon Jun 05, 2023 10:08 pm
Forum: VTSTTools
Topic: Migration barrier unexpected too large
Replies: 2
Views: 3739

Re: Migration barrier unexpected too large

The problem is that you have not linked our vtstcode into your vasp binary. So what is happening is that you have turned off vasp optimization with IBRION=3, POTIM=0 but then don't have the vtst code to do the optimization with your IOPT tag. So the reason that the barrier is so high is because it i...
by graeme
Mon Jun 05, 2023 1:53 am
Forum: VTSTTools
Topic: error while creating NEB images
Replies: 3
Views: 3945

Re: error while creating NEB images

It looks fine to me; perhaps your visualizer is showing atoms jumping due to the periodic images?
by graeme
Mon Jun 05, 2023 1:50 am
Forum: VTSTTools
Topic: Stuck NEB calculation
Replies: 10
Views: 9085

Re: Stuck NEB calculation

If you look at image 04, you will see that the migrating Li atom is sitting right on top of another atom. This calculation will never converge. You need a more sensible initial band. One option is to choose a sensible intermediate (04) structure and make two bands that you can put together. Another ...
by graeme
Sun Jun 04, 2023 5:19 am
Forum: VTSTTools
Topic: Stuck NEB calculation
Replies: 10
Views: 9085

Re: Stuck NEB calculation

I don't understand the structure of the files that you sent. I'm expecting a main directory with your INCAR, POTCAR, KPOINTS, and then a set of directories: 00, 01, ... NN, with POSCAR files and OUTCAR files. Then I can see the results of your calculation and what might be wrong. The li4toli3_NEB su...
by graeme
Sun Jun 04, 2023 12:10 am
Forum: VTSTTools
Topic: Stuck NEB calculation
Replies: 10
Views: 9085

Re: Stuck NEB calculation

If you post a .tar.gz of the calculation, I can take a look at it.
by graeme
Thu May 25, 2023 11:33 pm
Forum: VTSTTools
Topic: Vacancy migration
Replies: 6
Views: 5796

Re: Vacancy migration

Normally one would talk about a free energy difference, but let's just assume that the energy is the key component of free energy for solids. So a negative formation energy of a material means that the material is more stable than your reference components. That does not mean that the material is st...
by graeme
Thu May 25, 2023 10:38 pm
Forum: VTSTTools
Topic: Vacancy migration
Replies: 6
Views: 5796

Re: Vacancy migration

No, even if the overall formation energy is negative, that is not what's important: if the vacancy formation energy is negative the system will be unstable to vacancy formation.
by graeme
Wed May 24, 2023 8:24 pm
Forum: VTSTTools
Topic: Vacancy migration
Replies: 6
Views: 5796

Re: Vacancy migration

So first, the vacancy formation energy should be positive in the sense that it costs energy to make a vacancy in a material. If it was negative, the material would not be thermodynamically stable. In terms of a vacancy diffusion barrier, 7 eV sounds pretty high, but I don't know what the material is...