increased electronic coupling with increased distance (weired, anything wrong)


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i'm calculating the electronic coupling between an oxygen atom and an oxygen anion. I change the distance from 3.0, 3.5, 4.0, 4.5 to 5.0 A. The coupling values decrease from 3.0 to 3.5 to 4.0, which is as expected. However, the coupling values then increase from 4.0 to 4.5 to 5.0, which is weired, anything wrong with my input?

ps, i have tried the nofock keyword and several different basis sets. this always happens. Below is my input:

charge 0
geometry noautosym
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
triplet
uhf
maxiter 500
vectors output 0.movecs
end
task scf

charge -1
geometry noautosym
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
doublet
uhf
maxiter 500
vectors output 1.movecs
end
task scf

charge -1
geometry noautosym
O 5.0 0.0 0.0
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
nopen 3
uhf
maxiter 500
vectors input fragment 0.movecs 1.movecs output initial.movecs
end
task scf

charge -1
geometry noautosym
O 5.0 0.0 0.0
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
nopen 3
uhf
maxiter 500
vectors initial.movecs reorder 2 1 output final.movecs
end
task scf

et
vectors reactants initial.movecs 
vectors products final.movecs
end
basis
O library 6-31G*
end
task scf et

Forum Vet
You are not really moving the electron from one atom to the other as you also move the basis functions when you reorder. The following way would be better and correct:

charge 0
geometry noautosym
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
triplet
uhf
maxiter 500
vectors output 0.movecs
end
task scf

charge -1
geometry noautosym
O 0.0 0.0 0.0
end
scf
doublet
uhf
maxiter 500
vectors output 1.movecs
end
task scf

charge -1
geometry noautosym
O 5.0 0.0 0.0
O 0.0 0.0 0.0
end
scf
nopen 3
uhf
maxiter 500
vectors input fragment 0.movecs 1.movecs output initial.movecs
end
task scf

geometry noautosym
O 5.0 0.0 0.0
O 0.0 0.0 0.0
end
scf
nopen 3
uhf
maxiter 500
vectors input fragment 1.movecs 0.movecs output output final.movecs
end
task scf

et
vectors reactants initial.movecs
vectors products final.movecs
end
task scf et

Some notes: You do not have to repeat the basis set block, or the charge every time. NWChem will use the last basis set and charge specified up to that point.

Bert



Quote:Tiechong Nov 13th 10:56 pm
i'm calculating the electronic coupling between an oxygen atom and an oxygen anion. I change the distance from 3.0, 3.5, 4.0, 4.5 to 5.0 A. The coupling values decrease from 3.0 to 3.5 to 4.0, which is as expected. However, the coupling values then increase from 4.0 to 4.5 to 5.0, which is weired, anything wrong with my input?

ps, i have tried the nofock keyword and several different basis sets. this always happens. Below is my input:

charge 0
geometry noautosym
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
triplet
uhf
maxiter 500
vectors output 0.movecs
end
task scf

charge -1
geometry noautosym
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
doublet
uhf
maxiter 500
vectors output 1.movecs
end
task scf

charge -1
geometry noautosym
O 5.0 0.0 0.0
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
nopen 3
uhf
maxiter 500
vectors input fragment 0.movecs 1.movecs output initial.movecs
end
task scf

charge -1
geometry noautosym
O 5.0 0.0 0.0
O 0.0 0.0 0.0
end
basis
O library 6-31G*
end
scf
nopen 3
uhf
maxiter 500
vectors initial.movecs reorder 2 1 output final.movecs
end
task scf

et
vectors reactants initial.movecs 
vectors products final.movecs
end
basis
O library 6-31G*
end
task scf et


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