[gmx-users] Warning: correlations not long enough

Apramita Chand apramita.chand at gmail.com
Fri Sep 7 11:10:46 CEST 2018

Dear All,
In my simulations ,I have a Peptide in aqueous solution with a cosolvent.
I'm trying to calculate the forward hydrogen bond lifetime with g_hbond and
-ac flag.

For more number of hydrogen bonds like peptide water, water-water, there
are no warnings

But for Peptide cosolvent, there are 315 hydrogen bonds and it does the acf
as 315/315...

It shows warning: correlations not long enough

My original time step was 0.002 and I changed it to 0.0005 and even lowered
the output frequency of coordinates

Doing so gave me a 80GB output file!

Still the problem persists..

The lifetime that is output on the screen is 45 ps.

Since it writes that the lower half of the correlation function was fitted
and then this is calculated, can I quote this lifetime? Is it accurate?

Please help

Yours sincerely

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