d1: DISTANCE ATOMS=1,2 COMPONENTS
d1m: DISTANCE ATOMS=1,2

RESET_CELL

DUMPATOMS ATOMS=1,2 FILE=after.xyz

d2: DISTANCE ATOMS=1,2 COMPONENTS
d2m: DISTANCE ATOMS=1,2

PRINT ARG=d1.x,d1.y,d1.z,d2.x,d2.y,d2.z FILE=colvar

#RESTRAINT ARG=d2.x,d2.y,d2.z AT=0,0,0 KAPPA=1,2,3
RESTRAINT ARG=d2m KAPPA=1.0 AT=0.0
c: CELL 
#RESTRAINT ARG=c.ay KAPPA=1.0 AT=0.0
