ndhumal at andrew.cmu.edu
Tue Jul 9 05:05:49 CEST 2013
Thanks for reply.
Still I have a question why it is -inf (infinity) at the end.
> I would say the problem is too less statistics. In the paper where the
> 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.
>> -----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
>> 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?
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