problem with initial path in neb calculation
Clicked A Few Times
2:40:53 AM PST - Fri, Mar 4th 2016
Starting a neb calculation with TWO points ( start and end) is OK. However starting with TREE points gives an initial path with is wrong. Along the path the molecule collapses towards the geometric centre, this a the middle point, and start to expand towards a normal molecule but which is not the endpoint. I could verify that with the test in /nwchem-6.6/QA/tests/ch4_zts. If you the test with the spline method this is ok, the same test with NEB is wrong.
  1. Now with a TS guess


geometry geometry nocenter
 symmetry c1
C 0.000000 0.000000 0.000000
H 0.000000 0.000000 1.089000
H 1.026719 0.000000 -0.363000
H -0.513360 -0.889165 -0.363000
H -0.513360 0.889165 -0.363000
end

geometry endgeom nocenter
 symmetry c1
C 0.000000 0.000000 0.000000
H 0.000000 0.000000 -1.089000
H 1.026719 0.000000 0.363000
H -0.513360 -0.889165 0.363000
H -0.513360 0.889165 0.363000
end

geometry midgeom nocenter
 symmetry c1
C 0.000000 0.000000 0.000000
H 0.000000 1.000000 0.000000
H 1.026719 0.000000 0.000000
H -0.513360 -0.889165 0.000000
H -0.513360 0.889165 0.000000
end

basis
 * library STO-3G
end

  1. print low

neb
print
kbeads 0.001
stepsize 0.2
nbeads 11
maxiter 2
hasmiddle
impose
end

task neb scf


Could you help?
thank you very much
jean-louis

Just Got Here
8:43:37 AM PST - Mon, Jan 9th 2017
Same problem on standard Nwchem on debain Jessie
Any news on this bug?

Clicked A Few Times
5:31:05 AM PST - Mon, Feb 13th 2017
Hi,

The very same thing happened to me (and this is related: [1] and [2]).

Two inputs using the very same options and geometries, one using NEB and the other using the ZTS method can be found here: [3]
The complete outputs and initial paths can also be found in the zip file.

Observe that NEB fails due to linear dependencies at some intermediate geometry, which is no surprise if you see the initial path: atoms eventually colapse to the origin.
ZTS method works fine.

Commenting the "hasmiddle" line produces the expected result from both methods.


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