# ESP module

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 Chloe Member Profile Send PM
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 12:38:14 PM PDT - Tue, Mar 27th 2012 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 Profile Send PM
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 4:35:56 PM PDT - Wed, Apr 4th 2012 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 pmI 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

 Chloe Member Profile Send PM
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 1:35:32 PM PDT - Wed, Apr 25th 2012 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 Profile Send PM
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 9:11:52 AM PDT - Thu, Apr 26th 2012 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 pmIs 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

 Chloe Member Profile Send PM
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 7:10:49 AM PDT - Tue, Jun 5th 2012 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 Profile Send PM
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 11:56:16 AM PDT - Tue, Jun 5th 2012 I believe it is atomic units. Bert Quote:Chloe Jun 5th 2:10 pmHi, I was wondering what are the units of the potential written to the .grid file. Thanks, Chloe

 Chloe Member Profile Send PM
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 7:23:02 AM PDT - Tue, Aug 21st 2012 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

 Hjuinj Member Profile Send PM
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 4:41:07 AM PDT - Sat, Apr 14th 2018 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 amUnfortunately 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 pmIs 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

 Tanghao Member Profile Send PM
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 12:13:05 AM PDT - Mon, May 14th 2018 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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