| 10:23:36 AM PDT - Tue, Aug 29th 2017 |
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Hi all,
Before I begin, I acknowledge that the following are references that I have reviewed in order to get to this point in my work which I will post:
http://nwchemgit.github.io/Special_AWCforum/st/id305/How_to_get_the_open_shell_sin...
I am attempting to perform a broken symmetry calculation on a large structure. To this end, I found u/Edo's advice using the mixang option in the above link. My issue is that there is a discrepancy in the energy I get following this methodology and that of Gaussian's energy prediction. To converge the energy I follow these steps in order: (beneath each step is an example input file)
1) Optimize geometry of structure (restricted calculation)
start input
memory total 56000 mb
geometry noautoz
- COORDS OMMITED TO CONSERVE SPACE
end
basis
end
driver
xyz outCoord
end
- task dft
dft
CONVERGENCE density 1e-8
XC B3LYP
NOIO
NOPRINT
DIRECT
MAXITER 150
end
task dft optimize
2) Use the wavefunction generated by the previous calculation as vector 'input' to perform a BS (unrestricted) calculation
start input
memory total 56000 mb
geometry noautoz
end
basis
end
dft
CONVERGENCE density 1e-8
xc hfexch
odft
mult 1
DIRECT
MAXITER 650
mulliken
vectors input input.movecs output symm.mos
end
task dft
set mixang 120.
dft
xc b3lyp
adapt off
vectors input symm.mos swap alpha 395 394 output brksymm.mos
end
- task dft
dft
CONVERGENCE density 1e-8
DIRECT
MAXITER 650
xc b3lyp
end
task dft
3) Use the wavefunction generated by the previous BS an vector 'input' to perform another geometry optimization (unrestricted calculation)
start input
memory total 56000 mb
geometry noautoz
end
basis
end
driver
xyz outCoord
end
- task dft
dft
CONVERGENCE density 1e-8
vectors input brksymm.mos output opt2.mos
XC B3LYP
NOIO
NOPRINT
DIRECT
MAXITER 150
end
task dft optimize
4) Finally, use the wavefunction generated in the previous geometry optimization as vector 'input' to perform a final BS (unrestricted) calculation.
start input
memory total 56000 mb
geometry noautoz
end
basis
end
driver
xyz outCoord
end
- task dft
dft
CONVERGENCE density 1e-8
vectors input brksymm.mos output opt2.mos
XC B3LYP
NOIO
NOPRINT
DIRECT
MAXITER 150
end
task dft optimize
Idealistically, I expect the energy of Step 3) and Step 4) (*the second optimization and BS calculation) to be the same, as seen in my Gaussian results. The energy discrepancy I am seeing in these Steps for Nwchem suggest either the wavefunction I am using as input is unstable, or there is an error in my input file. If output files or energy values are necessary, I can provide in another post as I imagine this one is rather lengthy.
Any ideas or help would be greatly appreciated
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