[gmx-users] positive 1-4 energy sum

[David van der Spoel]

merc mertens wrote:
> hello,
> 
> below are energies calculated for a 10 ns run.
> the sum of the 1-4 terms should not be positive, i think.
> does anyone know what could be the problem? 
> i use these parameters:


yes thats fine. just think of an alkane chain. the 1-4 Coulomb 
interactions are H-H or C-C, all with the same sign and hence positive.
> 
> rlist                        = 0.9 
> coulombtype                  = PME 
> rcoulomb                     = 0.9 
> rvdw                         = 1.0 
> 
> --> g_energy output:
> 
> Statistics over 5000001 steps [ 0.0000 thru 10000.0000 ps ], 7 data sets
> 
> Energy                      Average       RMSD     Fluct.      Drift  Tot-Drift
> -------------------------------------------------------------------------------
> LJ-14                       26332.9    112.725    112.232 -0.00364844   -36.4844
> Coulomb-14                   256395    475.441    412.468  0.0819133    819.133
> LJ-(SR)                      135435    981.874     981.08  0.0136749    136.749
> LJ-(LR)                     -3757.3    3.99437    3.99433 -6.70857e-06 -0.0670857
> Coulomb-(SR)             -1.4232e+06    1538.71    1413.21  -0.210844   -2108.44
> Potential                -1.46317e+06     1119.7    911.325  -0.225359   -2253.59
> Total-Energy             -1.16712e+06    942.923    679.441  -0.226485   -2264.85
> 


-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,  	75124 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://folding.bmc.uu.se
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