[gmx-users] g_current

[Nilesh Dhumal]

Thanks for reply.

Still I have a question why it is     -inf  (infinity)  at the end.

Nilesh

> Hi,
>
>  I would say the problem is too less statistics. In the paper where the
> tool
> was introduced, a simulation of 100ns has been performed in order to
> achieved sufficient sampling.
>
> The order of magnitude is given due to the units.
>
> Simulate for a longer time to get rid of the noise. Calculating these kind
> of correlations functions is really not a simple task.
>
> Schroeder et al. have published an article about fitting of dielectric
> spectra for ionic liquids, where this problem is discussed in detail.
>
> Cheers,
> Flo
>
>> -----Original Message-----
>> From: gmx-users-bounces at gromacs.org [mailto:gmx-users-
>> bounces at gromacs.org] On Behalf Of Nilesh Dhumal
>> Sent: Monday, July 08, 2013 10:32 PM
>> To: gmx-users at gromacs.org
>> Subject: [gmx-users] g_current
>>
>> Hello,
>> I am calculating the correlation of rotational and translation dipole
>> moment of ionic liquids. I run the 1 ns simulation and saved the
>> trajectory at 1 fs.
>>
>> g_current -f md.trr -s md.tpr -n index.ndx -mc
>>
>> I selected "system" group.
>>
>> Here I pasted the initial j(t) vales and the final value is infinity.
>>
>> # This file was created Sun Jul  7 20:51:59 2013
>> # by the following command:
>> # g_current -f md.trr -s md.tpr -e 10.0 -mc
>> #
>> # g_current is part of G R O M A C S:
>> #
>> # Gallium Rubidium Oxygen Manganese Argon Carbon Silicon
>> #
>> @    title "M\sD\N - current  autocorrelation function"
>> @    xaxis  label "Time (ps)"
>> @    yaxis  label "< M\sD\N (0)\c7\CJ(t) >  (e nm/ps)\S2"
>> @TYPE xy
>> # time   M_D(0) J(t) acf         Integral acf
>> 0.000   -5.20584e-15             0
>> 0.001   -6.97466e-15    -1.42702e-17
>> 0.002   -6.97511e-15    -5.25081e-17
>> 0.003   -6.97474e-15    -9.07484e-17
>> 0.004   -6.97391e-15    -1.28987e-16
>>
>>
>>
>> Why final value is infinity? If I do autocorrelation function of these
>> values, I get all values 0.
>>
>> Why J(t)values are in range of e-15?
>>
>> Nilesh
>>
>>
>>
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