UT theoretical chemistry code forum

code: vasp5.2, PBE+D2 calculation, CNEB

>nebef.pl
0 0.00000000 -670.54295300 0.00000000
1 0.03416700 -670.54117300 0.00178000 ! It shows the image 1 is at an extrema.
2 0.03161900 -670.54493200 -0.00197900
3 0.04730700 -670.56123200 -0.01827900
4 0.02543000 -670.58572300 -0.04277000

But ...

(1) In the dimer example provided in the website, CG (OPTIM = 2) was used.

Could I change to LBFGS or other NEB optimizer?

In my dimer run when CG optimizer employed, it did not seem to be aggressive because only 0.001 ev or even lower energy decreases for steps.

(2) It seems that the EDIFF ...

When I set the DdR to 0.01, the Torque decreases to a much small value around 1 drastically, with a minus curvature.

Everything seems to be going well.

In the page http://theory.cm.utexas.edu/vtsttools/dimer/

It suggests to incease the finite difference distance DNdR to 0.01 to make the Torque drop systematically as the dimer rotates.

I can not find any DNdR in the OUTCAR file. Does it mean DdR (the dimer separation)?

In my dimer run, the Angle ...

>cp CONTCAR POSCAR
>cp NEWMODECAR MODECAR ?

My dimer run had been converged to 0.03 eV/Angstrom and there were three imaginary frequencyies f/i: 80 cm-1, 118 cm-1 and 256 cm-1. The displacements for 256 cm-1 is in the direction of NEB reaction chain to form product configuration.

Main tags for ...

Thanks. This is my first dimer run.

This is my dimer calucaltion after having been converged to 0.02.

Does it seem to be converging?

Some tags of My INCAR:

EDIFF = 1E-7
EDIFFG = -0.001
IBRION = 3
POTIM = 0
NSW = 300

IOPT = 2
DRotMax = 5
DdR = 1E-2

PW91 + U is considered with a single Gamma point for my 83 atoms supercell.

I have converge my CNEB to 0.05 with a single Gamma K-point.

When I switched the saddle image to SCF total energy calculation with more K points (3 * 3 * 1), the latter is higher at ~ 0.1 eV in energy.

And, the total force of scf calulation is seem to be unconverged (for some free atom, the force ...

What does the DFT + U matter to the dimer calculation?

Is there any problem comparing to DFT without U correction?

Prof. Liu = Liu Zhipan?

Graeme, the line (NEB: no climbing image found) disappeared when I set the EFIRST to a value between the energy 01 image and 04.

I think I have got your points in EFIRST and ELAST in INCAR.

Cheers ~

Dear Graeme, you are so helpful! I love you! ~

I put a small molecule in the slab vacuum 4 Angstrom from the surface. The molecule will be adsorbed to the surface and react with pre-adsorbed surface species. In this process, there is a energy barrier.

So the initial geometry is true acting as a ...

[attachment=0]CNEB.png[/attachment]

I am running a Cl-NEB run and now the nebef.pl results read like above. We can find two extrema in energy: the local minimum of image 2 at -0.0675 and the maximum of image 4 at -0.0299 ref to initial image 00.

When I check the OUTCAR of all the images, I am ...

“We recommend using CG or LBFGS when accurate forces are available. This is essential for evaluating curvatures. For high forces (far from the minimum) or inaccurate forces (close to the minimum) the quick-min or FIRE methods are recommended. These two methods do not rely on curvatures, and tend to ...

For a freqence-aimed run by IBRION = 5 with several involved atoms movable, we can get real several frequences and an intensive imaginary freqence.
Each of the frequences (fi):

ZPEi=0.5hfi

ZPE(total)=sum of all the ZPEi

E(corrected)= E+ZPE(total)

Is it right? And how to treat about the ...