UT theoretical chemistry code forum

A student here is working on a routine to identify bond critical points and report the density and the curvatures at these points. We did not have plans to explicitly report the paths between these points and the charge density maxima. If there was a good reason to do this, it could be added to the ...

When you use the climbing image, the highest energy image will try to climb right to the saddle point. As long as you have enough images to resolve the reaction pathway near the saddle, the climbing image will rigorously converge to the saddle. Then there is no need to add more images. You do not ne...

This is very strange. I suggest that you look at the electronic convergence. Did the 3rd image converge within the 600 electronic iterations that you allowed? If not, the energy can be nonsense. What about the spin state? Has the 3rd image in the NEB is converging to a different spin state than the ...

The minimum should have only positive modes. The negative mode has a small magnitude -- is it possible that you have no frozen atoms so that the system can translate? If yes, than you can remove the near-zero modes from both the minimum and saddle point freq.dat files and recalculate the prefactor. ...

1. Yes, both transition state and initial state can use the same DISPLACECAR. 2. In the dymseldsp.pl, the number of atoms is required; it will select that number of atoms that are displaced the most between the initial state and saddle point. An even simpler way of running is to select all of the no...

The second description is most appropriate for getting started. This is when you are calculating your finite difference forces one after the other. It is also possible to run vasp with multiple images (NN>1) so that the finite difference forces are calculated in parallel, but this is a more advanced...

We often use VMD to load the CHGCAR files directly. There is also an older program called vaspview which can load CHGCAR files as well. Both of these programs are free and can plot isosurfaces.

Changing the spring constant will probably not make any difference. What do you mean by not finding a reasonable MEP? Is the barrier too high? If there is a qualitatively different mechanism than the one you are finding starting from a linear NEB, see if you can help it get there. Look for intermedi...

The spring force will have almost no effect on the calculation; you can safely leave it at the default.

A force criteria is 0.08 is probably ok, but going to 0.01 would be safer.

This calculation looks like it's converging to a saddle, but it's not finished yet.
Convergence should speed up now that the rotation is settled down.

The neb2dim.pl should be run without an argument, but it does require some information about the neb calculation -- the location of the saddle point. First run 'nebresults.pl' and this information will be created and stored in the exts.dat file. Then the neb2dim.pl script will run. A message about t...

This will be coming soon.

Try two things:

First, you have to type the .pl, so use:

vasp2xyz.pl POSCAR

Second, that small script was not well written - it assumed a location for the perl binary. I've fixed it, so try downloading a new version of the scripts and run the command again.

There isn't really a problem. A program such as jmol will load that xyz file but it won't know what the atom types are. The reason is that the (vasp4.x) CONTCAR/POSCAR files do not contain the atomic identities. To fix this, replace the first line in your CONTCAR file with a list of the atom types i...

Right, it should be over the entire band. But there has to be some limit to the energy of the unoccupied states included in the average. Otherwise, as you add more unoccupied states in your calculation, the center of the d-band will continue to increase.