[gmx-users] Fwd: Frequency dependent dielectric of water

[David van der Spoel]

On 2015-01-05 20:56, Bharat Sharma wrote:
> Hello Experts,
> I am interested to calculate frequency dependent dielectric constant. I
> prepared a dipcorr.xvg file and used g_dielectric function of gromacs to
> calculate frequency dependent dielectric of water.
>
> I used this command.
>
> *g_dielectric_mpi -f dipcorr.xvg -eps0 95 -epsRF 1 -ffn exp_exp -bfit 0.005
> -eint 0.005 -fft*
why do you use epsRF 1? That means vacuum boundary conditions. If you 
used PME you should probably set 0.

Note that you have to know what your are doing with this program and you 
may have to check the source code.
>
> My model gives static dielectric of value 95.
> However the problem is the intersection of real and imaginary dielectric is
> around 500 GHz which is not very realistic. The real value is around 10 GHz.
>
> I am wonder if I am doing something wrong on my command. Any suggestions
> are appreciated.
>
> Thank you.
>
> Bharat
>


-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se