Input Block 'String'

Which version of NWChem are you using? The input to the NEB and string codes has changed quite a bit in the last few months, so the input will be highly dependent on what version you're using.

you can also enter extra geometries, i.e. middle and end geometries, to define the path. The labels of these geometries are "midgeom", "endgeom", e.g.

This run never really converges well because the two H's that are doing all the real work pop off to form H2 and do a little dance and then come back to the CH2 group they left behind. Optimizing the details of the little dance is about as likely has finding blinker fluid at the auto parts store

Note that this sends H1 right through the Carbon - atom avoidance code must work



echo

start ch4_string

permanent_dir ./permh
scratch_dir ./permh

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

basis

 * library STO-3G

end

scf

  maxiter 5001

end


string

  #tol  0.004d0

  nhist 10

  stepsize 1.00d0

  nbeads  10

  maxiter 100

  interpol 1

  freeze1 .true.

  freezeN .true.

end
task scf string ignore
task scf string ignore

string

   nbeads 20

end
task scf string ignore

The input I posted is in the development tree and will part of the next release. You can download a development snapshot and use it, or you can use the input in the 6.1 QA. The older version of the string code doesn't converge very quickly, but it should work.