<html><head></head><body><div style="font-family: Verdana;font-size: 12.0px;"><div>Dear gromacs users,<br/></div><div><br/></div><div><br/></div><div>I have a comprehension question to g_dist with the lifetime(-lt) option.<br/></div><div><br/></div><div>I want to determine the lifetime of a certain sidechain - ion contact (I use all ions as a group) within a radis of 0.6 nm.<br/></div><div><br/></div><div>output:<br/></div><div><br/></div><div>@ title "a_538 - K within 0.6 nm"<br/>@ xaxis label "Time (ps)"<br/>@ yaxis label "Number of contacts"<br/>@TYPE xy<br/> 0.000 1.183<br/> 200.000 1.088<br/> 400.000 1.048<br/> 600.000 1.024<br/> 800.000 1.000<br/> 1000.000 0.975<br/> 1200.000 0.958<br/> 1400.000 0.941<br/> 1600.000 0.924<br/> 1800.000 0.906<br/> 2000.000 0.888<br/> 2200.000 0.870<br/> 2400.000 0.851<br/> 2600.000 0.832<br/> 2800.000 0.812<br/> 3000.000 0.793<br/> 3200.000 0.773<br/> 3400.000 0.752<br/>etc.<br/></div><div><br/></div><div>I have difficulties in understanding why the number of contacts decreases to below zero, though at least one ion is constantly within a raidus of 0.6 nm. Is this a correlation function? Is it possible to look up how this is calculated here?<br/></div><div><br/></div><div>this says the help option :<br/></div><div><br/></div><div><em>With options <tt>-lt</tt> and <tt>-dist</tt> the number of contacts
of all atoms in group 2 that are closer than a certain distance
to the center of mass of group 1 are plotted as a function of the time
that the contact was continously present.</em><br/></div><div><br/></div><div>Thank you very much.<br/></div><div>Markus<br/></div><div><br/></div><div><br/></div></div> <br><br><table cellpadding="0" cellspacing="0" border="0"><tr><td style="font-family:verdana; font-size:12px; line-height:17px;border-top:1px solid #000000">Ihr WEB.DE Postfach immer dabei: die kostenlose WEB.DE Mail App für iPhone und Android. <br><a href="https://produkte.web.de/freemail_mobile_startseite/"><b>https://produkte.web.de/freemail_mobile_startseite/</b></a></td></tr></table>
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