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-boun...@gromacs.org [mailto:gmx-users- > boun...@gromacs.org] On Behalf Of Nilesh Dhumal > Sent: Monday, July 08, 2013 10:32 PM > To: gmx-users@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 > > > > -- > gmx-users mailing list gmx-users@gromacs.org > http://lists.gromacs.org/mailman/listinfo/gmx-users > * Please search the archive at > http://www.gromacs.org/Support/Mailing_Lists/Search before posting! > * Please don't post (un)subscribe requests to the list. Use the > www interface or send it to gmx-users-requ...@gromacs.org. > * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists -- gmx-users mailing list gmx-users@gromacs.org http://lists.gromacs.org/mailman/listinfo/gmx-users * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/Search before posting! * Please don't post (un)subscribe requests to the list. Use the www interface or send it to gmx-users-requ...@gromacs.org. * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists
