ONIOM

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I'm pretty new to NWChem and I would like to see If it is possible to use ONIOM or QM/MM for my system. For example, in a water dimer ONIOM calculation, I want to do the following:

Water molecule #1
Optimize with RI-MP2

Water dimer #2
Freeze it + use MM or an available Force Field on NWChem

so I know the following so far for an input file

start filename

memory 50MW

geometry noautosym units angstrom
O   0.88   -0.01    0.00
H 1.41 0.78 0.00
H 1.30 -0.87 0.00
H -0.07 0.05 0.00
O -1.03 0.11 0.00
H -1.41 -0.76 0.00
end

basis "ri-mp2 basis" print
  1. BASIS SET: (4s,3p,2d,1f)
H    S    8.5128275910           1.0000000        
H S 1.8730891166 1.0000000
H S 0.52618426941 1.0000000
H S 0.28973989936 1.0000000
H P 2.3725491635 1.0000000
H P 1.1804084468 1.0000000
H P 0.60382204241 1.0000000
H D 1.8096373189 1.0000000
H D 1.1439726055 1.0000000
H F 1.8063060576 1.0000000
#BASIS SET: (8s,6p,5d,3f,1g)
O S 366.54531503 1.0000000
O S 76.693314858 1.0000000
O S 24.573835091 1.0000000
O S 8.4165585072 1.0000000
O S 3.0202080356 1.0000000
O S 1.3331563617 1.0000000
O S 0.81250658727 1.0000000
O S 0.36505253662 1.0000000
O P 52.854386423 1.0000000
O P 15.021795824 1.0000000
O P 3.9137719482 1.0000000
O P 2.1678840611 1.0000000
O P 0.97419243984 1.0000000
O P 0.51845615412 1.0000000
O D 15.907733132 1.0000000
O D 5.3799329215 1.0000000
O D 2.9552623921 1.0000000
O D 1.1624458997 1.0000000
O D 0.50353399421 1.0000000
O F 4.6873846701 1.0000000
O F 2.1512789489 1.0000000
O F 1.0894068169 1.0000000
O G 2.3270964878 1.0000000
end

set geometry:actlist 1:3

oniom
high ri-mp2?? basis ???
low ???
end

task oniom optimize

My question at the question marks above in the oniom calc.

I did not see a force field available for oniom calculation. is it possible? or it can be done
with QM/MM



Thanks a lot in advance!

  • Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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I would recommend using QM/MM for this. Don't think MD is a possibility in the ONIOM formalism as implemented.

Bert


Quote: Jun 16th 9:48 pm
I'm pretty new to NWChem and I would like to see If it is possible to use ONIOM or QM/MM for my system. For example, in a water dimer ONIOM calculation, I want to do the following:

Water molecule #1
Optimize with RI-MP2

Water dimer #2
Freeze it + use MM or an available Force Field on NWChem

so I know the following so far for an input file

start filename

memory 50MW

geometry noautosym units angstrom
O   0.88   -0.01    0.00
H 1.41 0.78 0.00
H 1.30 -0.87 0.00
H -0.07 0.05 0.00
O -1.03 0.11 0.00
H -1.41 -0.76 0.00
end

basis "ri-mp2 basis" print
  1. BASIS SET: (4s,3p,2d,1f)
H    S    8.5128275910           1.0000000        
H S 1.8730891166 1.0000000
H S 0.52618426941 1.0000000
H S 0.28973989936 1.0000000
H P 2.3725491635 1.0000000
H P 1.1804084468 1.0000000
H P 0.60382204241 1.0000000
H D 1.8096373189 1.0000000
H D 1.1439726055 1.0000000
H F 1.8063060576 1.0000000
#BASIS SET: (8s,6p,5d,3f,1g)
O S 366.54531503 1.0000000
O S 76.693314858 1.0000000
O S 24.573835091 1.0000000
O S 8.4165585072 1.0000000
O S 3.0202080356 1.0000000
O S 1.3331563617 1.0000000
O S 0.81250658727 1.0000000
O S 0.36505253662 1.0000000
O P 52.854386423 1.0000000
O P 15.021795824 1.0000000
O P 3.9137719482 1.0000000
O P 2.1678840611 1.0000000
O P 0.97419243984 1.0000000
O P 0.51845615412 1.0000000
O D 15.907733132 1.0000000
O D 5.3799329215 1.0000000
O D 2.9552623921 1.0000000
O D 1.1624458997 1.0000000
O D 0.50353399421 1.0000000
O F 4.6873846701 1.0000000
O F 2.1512789489 1.0000000
O F 1.0894068169 1.0000000
O G 2.3270964878 1.0000000
end

set geometry:actlist 1:3

oniom
high ri-mp2?? basis ???
low ???
end

task oniom optimize

My question at the question marks above in the oniom calc.

I did not see a force field available for oniom calculation. is it possible? or it can be done
with QM/MM



Thanks a lot in advance!


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