[gmx-developers] [Fwd: coulomb SR in 3.3cvs]

[David]

On Tue, 2005-07-19 at 15:14 +0200, Michel Cuendet wrote:
> Hi David,
> 
> >You should only compare the first step. The virial (pressure) will tell
> >you whether forces are correct.
> >

How did you make the tpr file? Is it from one and the same tpr file? If
so, please send it to me.

> Allright, here it is :
> 
> -------------------------------------------------------------------------
> First step:  Virial XX, YY, ZZ, EKin, Pressure :
> 3.2.1 :
>     0.000000  68261.312500  75314.625000  68934.000000   216638.687500   
> 44.703457
> 3.3 :
>     0.000000  68055.515625  75127.718750  69873.421875   218547.906250   
> 75.353340
> 
> -------------------------------------------------------------------------
> Energies at first step :
> @ s0 legend "G96Bond"
> @ s1 legend "G96Angle"
> @ s2 legend "Proper Dih."
> @ s3 legend "Improper Dih."
> @ s4 legend "LJ-14"
> @ s5 legend "Coulomb-14"
> @ s6 legend "LJ (SR)"
> @ s7 legend "Coulomb (SR)"
> @ s8 legend "Coul. recip."
> @ s9 legend "Potential"
> 
> 3.2.1  :
>   0.000000  6909.100586  10166.941406  4475.063477  3269.806641  
> 820.055969  62880.343750  166514.671875  -1203442.750000  
> -188707.640625  -1137114.375000
> 3.3 :
>   0.000000  6909.088867  10166.948242  4475.061523  3269.804443  
> 820.041321  62880.359375  166517.578125  -1203541.000000  
> -188709.156250  -1137211.375000
> -------------------------------------------------------------------------
> 
> We see that the energies are all accurate at least up to the 5th digit 
> (can we expect more frome single precision?). The virials diverge 
> already from the third digit. So do the kinetic energies, and the 
> pressures differ...
> 
> I don't know what conclusions to draw from that.
> 
> Thanks for your assistance.
> 
-- 
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://xray.bmc.uu.se/~spoel
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