[gmx-users] Shift and Switch are obsolete!?

Alan Wilter Sousa da Silva alan at biof.ufrj.br
Mon Aug 19 17:18:30 CEST 2002

Hi, pardon if I go straightforward to the question.
	I'm trying to set coulomtype to Shift (or Switch).  This is my
constraints              = h-bonds
constraint-algorithm     = shake
nstenergy                = 0
ns_type                  = simple
coulombtype              = Switch
rlist                    = 1.3
rcoulomb                 = 1.2
rcoulomb_switch          = 1.1
vdwtype                  = Switch
rvdw                     = 1.2
rvdw_switch              = 1.1

GMX manual recommends rlist to be 0.1 to 0.3 nm larger than rcoulomb.  But
I got it from grompp:

ERROR: rcoulomb must be >= rlist
ERROR: rvdw must be >= rlist

Please, one question more.  If I use pure cut-off,  I still do not follow
why rlist must be larger or equal to rcoulomb.  How does GMX couple with
an atom at the exactly distance of cut-off, and atoms beyond?  One cannot
have discontinuity!  So, is a shift function implicit with cut-off?

Best regards,
Alan Wilter S. da Silva
 Laboratório de Física Biológica
  Instituto de Biofísica Carlos Chagas Filho
   Universidade do Brasil/UFRJ
    Rio de Janeiro, Brasil

More information about the gromacs.org_gmx-users mailing list