Hi All
I am trying to perform transition state searches for oxidations of small molecules. I am very familiar with how this is done in the program Turbomole. I am now in a position where I am using NWchem for the same task and I have problems with the syntax of the transition state search.
The example here is a phenolic hydrogen abstraction of acetaminophen. I am using a methoxy radical as the reactive specie.
My workflow is:
constrained geometry optimization
geometry
load geometry.xyz
end
memory 1000 mb
basis
* library 6-31g
end
dft
xc b3lyp
mult 2
iterations 300
direct
end
geometry adjust
zcoord
bond 13 21 1.21 constant
bond 9 13 0.94 constant
end
end
driver
xyz test
maxiter 50
end
task dft optimize
frequency calculation
restart consgeo
memory 1000 mb
geometry adjust
zcoord
bond 13 21 1.21
bond 9 13 0.94
end
end
freq
animate
end
task dft freq
transition state search
restart consgeo
memory 1000 mb
task dft saddle
This is the first line of output frequencies:
Frequency -339.75 -54.43 5.32 9.09 12.46 15.11
The first frequency is along the reaction coordinates, however, these frequencies does not match what I expect for a hydrogen abstraction - is there a way to increase precision?
My transition state search finishes just fine however the geometry and energy does not match the ones I used to get with Turbomole using the same functional and basis. I am not sure that the saddle task uses the information from the frequency calculation. How can I specify to the program that it is the first imaginary frequency on which I want to perform the saddle point search?
Thanks and best regards,
Rasmus
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