ESP module

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I would like to have a little more information on the ESP module (when using "task ESP"). From what I understand, the plt file produced contains the potential profile to be plotted as an isosurface. What about the grid file generated? Does it contain the potential evaluated at each point of the grid?

How are those properties calculated or could you point me some reference to read about this.

And what about running "task dft property" with the ESP keyword in the property block? Is this the same calculation but evaluating the potential at the atomic coordinates?

Thanks,

Chloe

  • Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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Yes, the grid file should contain the fitted potential at each grid point.

Reference: C. Chipot, B. Maigret, J.-L. Rivail, H.A. Sheraga, J. Phys. Chem., 96 (1992), p. 10276

Yes, the electrostatic potential in the property block is evaluated at the atomic positions only. I.e., no fitting required.

Bert


Quote:Chloe Mar 27th 7:38 pm
I would like to have a little more information on the ESP module (when using "task ESP"). From what I understand, the plt file produced contains the potential profile to be plotted as an isosurface. What about the grid file generated? Does it contain the potential evaluated at each point of the grid?

How are those properties calculated or could you point me some reference to read about this.

And what about running "task dft property" with the ESP keyword in the property block? Is this the same calculation but evaluating the potential at the atomic coordinates?

Thanks,

Chloe

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Is it possible to specify a specific list of grid points for the calculation of the electrostatic potential? I tried supplying a grid file with the desired grid points. The calculation seems to have used these points to calculate the atomic charges, but the potential values (it is what I am interested in) were not written to the grid file. Otherwise, the documentation only explains how to define the range and spacing in the input file, but not the actual grid points.

Thanks,

Chloe

  • Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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Unfortunately this is not possible. With a little bit of coding you should be able to do it though.

Bert

Quote:Chloe Apr 25th 8:35 pm
Is it possible to specify a specific list of grid points for the calculation of the electrostatic potential? I tried supplying a grid file with the desired grid points. The calculation seems to have used these points to calculate the atomic charges, but the potential values (it is what I am interested in) were not written to the grid file. Otherwise, the documentation only explains how to define the range and spacing in the input file, but not the actual grid points.

Thanks,

Chloe

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Hi,

I was wondering what are the units of the potential written to the .grid file.

Thanks,

Chloe

  • Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
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I believe it is atomic units.

Bert


Quote:Chloe Jun 5th 2:10 pm
Hi,

I was wondering what are the units of the potential written to the .grid file.

Thanks,

Chloe

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Hi Bert,

I believe that the potential in the grid file generated by the esp module is simply the actual potential found by integrating the density : \int \frac{\rho(r')}{|r-r'|}dr'
Is it? This explains why it cannot be evaluated at the position of the nuclei.

Now, what I would like to understand is how the "Total Potential" is calculated with the esp keyword in the property block. This potential is evaluated at the atomic position. From the shape of the potential, I would guess that it has something to do with the core potential of the atoms. This gives a potential which is completely different from the one in the grid file and also different from the ESP printed at atomic positions when calling "task esp".

I also really need to know if this potential (in the property block) is expressed in units of energy (hartrees) or potential (some atomic unit equivalent to volts) as both have opposite signs.

Thanks,

Chloe

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Hi Bert,

I am very new to nwchem and I am also interested in obtained esp values at a list of specific points. Would it be possible for you to shed a bit more light on what code I would need to write in order to achieve this?

Thank you

Quote:Bert Apr 26th 9:11 am
Unfortunately this is not possible. With a little bit of coding you should be able to do it though.

Bert

Quote:Chloe Apr 25th 8:35 pm
Is it possible to specify a specific list of grid points for the calculation of the electrostatic potential? I tried supplying a grid file with the desired grid points. The calculation seems to have used these points to calculate the atomic charges, but the potential values (it is what I am interested in) were not written to the grid file. Otherwise, the documentation only explains how to define the range and spacing in the input file, but not the actual grid points.

Thanks,

Chloe

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Yes, the grid file should contain the fitted potential at each grid point.

Reference: C. Chipot, B. Maigret, J.-L. Rivail, H.A. Sheraga, J. Phys. Chem., 96 (1992), p. 10276

Yes, the electrostatic potential in the property block is evaluated at the atomic positions only. I.e., no fitting required.

Bert


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