Grid specification for dummy atoms
Just Got Here
2:22:19 PM PDT - Fri, Sep 21st 2012
I am trying to create a dummy atom to mimic hydrogen but with partial atomic charge. An example input file for a dummy atom that acts like a hyrogen

geometry
bqH 0 0 0 charge 1.00 mass 1.007825
end

basis
bqH library H "tzvp"
end

dft
odft
mult 2
xc b3lyp
direct
end
task dft energy

but, when I do this the grid is not specified. I also tried to add this to the grid specification

grid lebedev bqH 100 18

with a read error.

Any suggestions on getting a grid for the dummy atom to work?

Forum Vet
5:19:37 PM PDT - Fri, Sep 28th 2012
The current grid code of NWChem is designed so that if a bq is charged, no grid is assigned.
(I think that the rationale was that bqs with grids are used in BSSE calculations and they don't
have a charge, bqs with charges are point charges, instead).
We will try to see if we can modify the code to accommodate charged bqs with grids.
However, I would like to understand better what you are trying to get.
I don't quite see the difference between using a bqh charged and a real hydrogen atom ...
Let's see the following example:
1) let first try the h2+ molecule, e.g.

charge 1.
geometry
h 0. 0. 0.
h 0. 0. 1.
end

2) the let's replace the second hydrogen with the charged bq

charge 1.
geometry
h 0. 0. 0.
bqh 0 0 0 charge 1.00 mass 1.007825
end

The result is that if you try a HF calculation, the energy are exactly the same, i.e. the charged bqH
behave in the same way as a real hydrogen atom

Please let me know if this example has anything to do with what you are trying to accomplish.

Cheers, Edo

Just Got Here
2:30:09 PM PDT - Fri, Oct 5th 2012
I have switched to doing HF calculations since this doesn't depend on the grid. The big issue I am having is lets say I want, using your example:

charge 1.
geometry
bqh1 0 0 0 charge 1.10 mass 1.007825
bqh2 0 0 1 charge 0.09 mass 1.007825
end

I can only do this with HF.

Gets Around
10:34:50 PM PDT - Thu, May 3rd 2018
Quote:Edoapra Sep 28th 5:19 pm
The current grid code of NWChem is designed so that if a bq is charged, no grid is assigned.
(I think that the rationale was that bqs with grids are used in BSSE calculations and they don't
have a charge, bqs with charges are point charges, instead).
We will try to see if we can modify the code to accommodate charged bqs with grids.
However, I would like to understand better what you are trying to get.
I don't quite see the difference between using a bqh charged and a real hydrogen atom ...
Let's see the following example:
1) let first try the h2+ molecule, e.g.

charge 1.
geometry
h 0. 0. 0.
h 0. 0. 1.
end

2) the let's replace the second hydrogen with the charged bq

charge 1.
geometry
h 0. 0. 0.
bqh 0 0 0 charge 1.00 mass 1.007825
end

The result is that if you try a HF calculation, the energy are exactly the same, i.e. the charged bqH
behave in the same way as a real hydrogen atom

Please let me know if this example has anything to do with what you are trying to accomplish.

Cheers, Edo


In this context I would like to clarify something.
Here you are showing a single H atom, which you want to make a ghost.

Say, if I have 4 H atom and I want to make first 2 of them dummy or ghost (no charge) in my BSSE calculation.

How am I supposed to do that when all atom types are same ??


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