AMBER: the total energy is not converge as the cutoff increase

From: thanyarat Udom <thanyarat22.yahoo.com>
Date: Mon, 6 Mar 2006 00:51:46 -0800 (PST)

Dear Amber users
                   I want to run an energy minimization of protein/water/counter ions system. First, I have tested cutoff the value of non-bonded. I summarized the output from the first step (NSTEP = 1) of energy minimization as follows.
  cut off Total Energy(NSTEP=1) BOND ANGLE DIHED VDWAALS EEL
    10 -145910 2629.283 5045.8942 10443.8164 30238.3127 -243907.946
   12 -262380 2629.283 5045.8942 10443.8164 29518.1267 -356388.753
   15 -302340 2629.283 5045.8942 10443.8164 29052.2034 -395395.948
   18 -260040 2629.283 5045.8942 10443.8164 28855.7353 -355521.277
   20 -571410 2629.283 5045.8942 10443.8164 28731.883 -667743.075
  
 Surprisingly, the total energy is not converge as the cutoff increase. Particularly, the results at cutoff = 20 Å look very strange. The minimization has not been employed PBC (ntb =0). Please help me.
                                                               Best Regard
                                                    Thanyarat Udommaneethanakit


                
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Received on Sun Mar 12 2006 - 06:10:07 PST
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