[gmx-users] Including quadrupole-charge interaction in GROMACS

[Erik Marklund]

Hi,

For neutral species, I think it's straightforward (unless the paper Ran Friedman mentioned says otherwise). Just use the definition of the quadrupole moment to figure out where to put the charges and what magnitude to assign to them. The electric field from a quadrupole declines like r^-3, however, so its importance for graphene interactions seem very small to me.

Erik


16 jun 2011 kl. 17.10 skrev WU Yanbin:

> Hi, Erik,
> 
> Thanks for the information.
> 
> Regarding using more than two partial charges to mimic quadrupole explicitly, is there a one-to-one relation between the quadrupole moments and "position and magnitude" of the partial charges? For example, if I would like to include quadrupole moment for carbon in graphene, which has only non-zero Q20 quadrupole component, how should I place partial charges to mimic that quadrupole moment?
> 
> Any hint or direction for literature is appreciated.
> 
> Best,
> Yanbin
> 
> On Thu, Jun 16, 2011 at 3:24 AM, Erik Marklund <erikm at xray.bmc.uu.se> wrote:
> Quadrupole interactions are implicit whenever you have a molecule withe more than two partial charges. You don't have to include it explicitly. There are, however, multipole expansion techniques to speed up electrostatics calculations, but that's another story.
> 
> Erik
> 
> 15 jun 2011 kl. 23.45 skrev WU Yanbin:
> 
> > Dear GMXers,
> >
> > Is there a way in GROMACS to include quadrupole-charge interaction?
> > Or is there a standard to way to mimic quadrupole moment using partial charge?
> >
> > Thank you.
> >
> > Best,
> > Yanbin
> > --
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> -----------------------------------------------
> Erik Marklund, PhD student
> Dept. of Cell and Molecular Biology, Uppsala University.
> Husargatan 3, Box 596,    75124 Uppsala, Sweden
> phone:    +46 18 471 4537        fax: +46 18 511 755
> erikm at xray.bmc.uu.se
> http://www2.icm.uu.se/molbio/elflab/index.html
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-----------------------------------------------
Erik Marklund, PhD student
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,    75124 Uppsala, Sweden
phone:    +46 18 471 4537        fax: +46 18 511 755
erikm at xray.bmc.uu.se
http://www2.icm.uu.se/molbio/elflab/index.html

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