Dear amber users
I am trying to understand the cartesian forces calculations in the case
of a dihedral potential. The source code of this calculation is in
dihedrals.f90 module.
I supposed that the following is used
f = - d E(phi) / d r = 1/sin phi * dE(phi)/d phi * d cos phi / d r
and then with special stuff if sin phi tends to zero we, get the
following equation :
f = - df * d cos phi / d r (line 344 in dihedrals.f90 in pmemd in
amber 10)
I do not understand the calculation of the cos phi derivative. But maybe
I can let it for later. I think this calculation
is the one describe in Allen and Tildesley.
I juste would like to know if my previous equation is right. Mainly is
the minus sign correct ?
Thanks for your help.
germain
--
Germain Vallverdu
Doctorant
Laboratoire de Chimie Physique
germain.vallverdu.lcp.u-psud.fr
01 69 15 30 38
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Received on Mon Sep 14 2009 - 13:42:07 PDT
