UT theoretical chemistry code forum

Again, as I mentioned in your other post, this is supposed to be about EON. In the EON code, you can in fact run the NEB image-by-image. But in VASP it must be parallel. Anyway, see my comments in your other post for possible solutions.

First, this is posted on a forum related to the EON code. Is this really an EON calculation, or standard VASP-NEB? I assume it is the latter. If so, I think your assessment is correct, that you need to run each image on a sufficient number of cores to distribute the memory per core. To help with the...

You can see the current NEB forces using our script nebef.pl.

The time step is controlled by POTIM is you use the built-in vasp-optimizers and by the TIMESTEP tag if you use our vtst optimizers.

There is some art to optimization, but there are also some sensible guidelines. When forces are high, use a conservative optimizer such as IBRION=3 and a small time step < 0.1. Once the forces are below 0.2 eV/Ang, you can switch to a second order optimizer (e.g. IBRION=1).

The problem is your initial paths. You have mechanisms in which molecules are being broken in the gas phase and then a fragment adsorbs on the surface (in the case of CO2 and CH4) or just left in gas phase (H2). If you are trying to understand dissociative adsorption, you need to find stable final s...

Before getting into the dimer calculations, the NEB calculations do not looks right. I see jumps of over 2 eV between images in the first calculation and oscillations in the energy and high forces in the second. Check these paths to see if they are reasonable. I would not be surprised if you are loo...

the command for vasp is:
make veryclean

My concern is that there is an old chain.o object file in the src directory. If you clean the build there should be no .o files in the src subdirectory.

You do not need to modify makefile.include. Make sure that you do a make clean and check that chain.o is removed before making the vtst version.

No, there is no secret rule. I just looked at my own makefile and stated where it was. To be honest, I'm not sure exactly where in the build order the vtst objects should go. I just figured that giving a specific place was better than suggesting that you place it by trial and error.

Make sure to add the VTST objects to your src/.objects file. This can be done by including a first line in the file: VTST_OBJS = bfgs.o dynmat.o instanton.o lbfgs.o sd.o cg.o dimer.o bbm.o \ fire.o lanczos.o neb.o qm.o opt.o chain.o and then add those objects after hamil_rot.o, as in: hamil_rot.o \ ...

With IBRION=5, vasp calculates the Hessian and the normal mode frequencies. Don't you just need the later for thermodynamic properties?

If you use the vtstcode, the dymmatrix.pl script generates the Hessian from forces printed in the OUTCAR file.

Yes, for sure. The dimer calculation should be continued with the CENTCAR file. If you use the vfin.pl script, the CENTCAR will be copied to the POSCAR, ready for another calculation.

Ah, you need a lower ediff for the dimer calculation. Using 1e-4 will result in too much noise in the forces so that the curvature calculation will be unreliable, as well as the dimer calculation. Use 1e-7 or 1e-8.

Well, without having resolved the problems with the dimer calculation, I think that your continued ci-NEB calculation looks pretty good. You have a saddle point geometry at the 05 image with a barrier of 1.4 eV and a residual force of only 0.02 eV/Ang.

This looks strange - did you run the neb2dim.pl script to initialize your dimer calculation? Your dimer calculation starts with a much higher energy and force as compared to image 5 in your NEB calculation. You could try using the geometry from image 05 and a MODECAR generated from 04 and 06 as in: ...