[gmx-users] rvdw-switch

[sadhna]

hi all,
        I am pretty confused about the use of rvdw_switch.
I have gone through few mdp files where different values are given to this
switch.
 mdp1:
rlist               =1.0
coulombtype         =  cut-off
rcoulomb-switch     =  0
rcoulomb            =  1.2      ; electrostatic cutoff in nm
vdwtype             =  cut-off
rvdw-switch         =  0
rvdw                =  1.0      ; vdw/lj cutoff in nm
;

mdp2:

    rlist    = 1.4
coulomb type = cutoff
rcoulomb     = 1.4
rcoulom_switch = 1.0
vdwtype      =cut-off
rvdw        = 1.4
rvdwswitch  = 1.0

mdp3

     rlist = 1.0
coulombtype =PPPM
rcoulomb_switch =0
rcoulomb =0.85
rvdw_switch =1.0
rvdw =1.0

mdp4
    rlist =1.5
coulombtype =shift
rcoulomb =1.4
rcoulomb_switch =1.0
vdwtype = shift
rvdw =1.4
rvdw_switch = 1.0

Could anyone detail how the vdw potential varies between rvdw_switch and
rvdw in the cases above, especially mdp2 and mdp3 are very confusing.
Does the potential decrease smoothly between rvdw_switch and rvdw even
when the vdwtype=cut-off as in the mdp2 file?
if the user does not specify rvdw_switch in the mdp file does it take any
default value?.

thanks for the patience
sadhna





Sadhna Joshi
Research Scholar
Dept of Chemical Engg
Indian Institute of Technology,Powai
Mumbai-400076
India