<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Generator" CONTENT="MS Exchange Server version 6.5.7650.28">
<TITLE>RE: [gmx-users] Stepsize too small, or no change in energy</TITLE>
</HEAD>
<BODY>
<!-- Converted from text/plain format -->
<P><FONT SIZE=2>Dear Dhiraj,<BR>
<BR>
You're using single precision GROMACS which means that there is a limit to how small your forces can go, if you want to minimise further you will need to use double precision GROMACS (which will decrease the machiene precision allowing you minimisation to run for longer). You will have to recompile GROMACS to double precision and reinstall it following the instructions in the manual. Then you call the higher precision GROMACS by appending an '_d' to the end of the names of all the programs (eg grompp_d and mdrun_d).<BR>
<BR>
Regards<BR>
<BR>
Ella Gale<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: gmx-users-bounces@gromacs.org on behalf of Srivastava, Dhiraj (UMC-Student)<BR>
Sent: Tue 7/18/2006 6:13 AM<BR>
To: Discussion list for GROMACS users<BR>
Subject: [gmx-users] Stepsize too small, or no change in energy<BR>
<BR>
Hi all<BR>
<BR>
when i am trying to minimize my structure, i am getting following error.<BR>
<BR>
Stepsize too small, or no change in energy.<BR>
Converged to machine precision,<BR>
but not to the requested precision Fmax < 1000<BR>
<BR>
Double precision normally gives you higher accuracy.<BR>
<BR>
writing lowest energy coordinates.<BR>
<BR>
Back Off! I just backed up prodh_em.trr to ./#prodh_em.trr.2#<BR>
<BR>
Back Off! I just backed up prodh_wb.pdb to ./#prodh_wb.pdb.4#<BR>
<BR>
Steepest Descents converged to machine precision in 45 steps,<BR>
but did not reach the requested Fmax < 1000.<BR>
Potential Energy = -1.8373166e+06<BR>
Maximum force = 1.5158329e+04 on atom 519<BR>
Norm of force = 3.1759754e+04<BR>
<BR>
<BR>
i have tried the conjugated gradient, constraint none and also included flexible water but still i am getting the same error.<BR>
<BR>
what should i do to solve this problem?<BR>
<BR>
Thanks in advance for help.<BR>
<BR>
_______________________________________________<BR>
gmx-users mailing list gmx-users@gromacs.org<BR>
<A HREF="http://www.gromacs.org/mailman/listinfo/gmx-users">http://www.gromacs.org/mailman/listinfo/gmx-users</A><BR>
Please don't post (un)subscribe requests to the list. Use the<BR>
www interface or send it to gmx-users-request@gromacs.org.<BR>
Can't post? Read <A HREF="http://www.gromacs.org/mailing_lists/users.php">http://www.gromacs.org/mailing_lists/users.php</A><BR>
<BR>
</FONT>
</P>
</BODY>
</HTML>