SYNOPSIS

g_potential -f traj.xtc -n index.ndx -s topol.tpr -o potential.xvg -oc charge.xvg -of field.xvg -[no]h -[no]version -nice int -b time -e time -dt time -[no]w -xvg enum -d string -sl int -cb int -ce int -tz real -[no]spherical -ng int -[no]correct

DESCRIPTION

g_potential computes the electrostatical potential across the box. The potential is calculated by first summing the charges per slice and then integrating twice of this charge distribution. Periodic boundaries are not taken into account. Reference of potential is taken to be the left side of the box. It is also possible to calculate the potential in spherical coordinates as function of r by calculating a charge distribution in spherical slices and twice integrating them. epsilon_r is taken as 1, but 2 is more appropriate in many cases.

FILES

-f traj.xtc Input
 Trajectory: xtc trr trj gro g96 pdb cpt 

-n index.ndx Input
 Index file 

-s topol.tpr Input
 Run input file: tpr tpb tpa 

-o potential.xvg Output
 xvgr/xmgr file 

-oc charge.xvg Output
 xvgr/xmgr file 

-of field.xvg Output
 xvgr/xmgr file 

OTHER OPTIONS

-[no]hno
 Print help info and quit

-[no]versionno
 Print version info and quit

-nice int 19
 Set the nicelevel

-b time 0
 First frame (ps) to read from trajectory

-e time 0
 Last frame (ps) to read from trajectory

-dt time 0
 Only use frame when t MOD dt = first time (ps)

-[no]wno
 View output  .xvg,  .xpm,  .eps and  .pdb files

-xvg enum xmgrace
 xvg plot formatting:  xmgrace,  xmgr or  none

-d string Z
 Take the normal on the membrane in direction X, Y or Z.

-sl int 10
 Calculate potential as function of boxlength, dividing the box in nr slices.

-cb int 0
 Discard first nr slices of box for integration

-ce int 0
 Discard last nr slices of box for integration

-tz real 0
 Translate all coordinates distance in the direction of the box

-[no]sphericalno
 Calculate spherical thingie

-ng int 1
 Number of groups to consider

-[no]correctno
 Assume net zero charge of groups to improve accuracy

KNOWN PROBLEMS

- Discarding slices for integration should not be necessary.