Search found 39 matches

by xph
Mon Apr 02, 2012 4:59 pm
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

Thanks to your testing, we do find a bug in nebbarrier.pl. It should read enthalpy rather than energy. We are fixing it now.

All the SSNEB calculations are fine, and you just need to run nebresults.pl again when we update the VTSTSCRIPTS.
by xph
Sun Apr 01, 2012 5:26 am
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

Two real negative modes? Then it is a monkey saddle point, though NEB is not designed to find such kind of saddle points. Did you watch the two modes to see what they look like? I have been using SSNEB in TSASE which is also on our website under "code". I have calculated phase transformati...
by xph
Sat Mar 31, 2012 11:03 pm
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

That second last terms are the magnitude of the real forces on images. You can find details of how to grep and calculate them in nebbarrier.pl For the frequency calculation, make sure that you excluded the three translation modes, whose frequencies are close to zero and can be imaginary, when you co...
by xph
Sat Mar 31, 2012 6:37 am
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

Apparently, your climbing images converged to the saddle point, which can be seen from the force in neb.dat (the second last term, climbing image is close to zero). The problem you saw is from spline. That means the path near the saddle needs to be zoomed in. It is mainly because there is a level pa...
by xph
Wed Mar 28, 2012 5:24 pm
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

Seems like another minimum shows up on the path. I would suggest minimize the 6 image at 30 GPa and use it as the new final state.
What happens for the last 3 images? Is this because of translating or the tangent along some ultra soft mode?
by xph
Wed Mar 28, 2012 12:48 am
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

Could you share the neb.dat file?
If the force converged but the path is still not smooth, adding more images usually helps.
Also try to start with your the path converged at 10 GPa. Don't forget to minimize the end points again at 30 GPa.
by xph
Thu Mar 15, 2012 7:36 pm
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

There is no need to insert more images if the resolution is satisfactory. 5 images are enough for most cases. Just checked that PSTRESS was good in the latest VTSTCODE (updated a month ago). About that paper, they were not using our SSNEB method. To repeat their results, I think you can just set lik...
by xph
Wed Mar 14, 2012 5:43 pm
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

Could you try the calculation without any pressure? The SSNEB in VTST has not been tested under pressure. The TSASE version does. Still, if there are intermedia minimums between the initial and final states, it is more difficult to converge. Rather than increase the number of images, it is more effi...
by xph
Wed Mar 14, 2012 2:04 am
Forum: VTSTTools
Topic: solid state CI-NEB, not converge
Replies: 34
Views: 43006

Re: solid state CI-NEB, not converge

I have some suggestions: 1. Use fewer images, usually 5 images between initial and final minimum are enough. More images make it more difficult to converge. 2. Make sure that ENCUT is more than 1.3*ENMAX. ENMAX is the largest ENMAX in POTCAR. 3. Turn off climbing image in the beginning and turn it o...