ang1: ANGLE ATOMS=2,6,3
ang2: ANGLE ATOMS=2,6,7,3

UPPER_WALLS ARG=ang1 AT=0.3 KAPPA=20.0 LABEL=uwall
LOWER_WALLS ARG=ang2 AT=0.2 KAPPA=40.0 EXP=4 EPS=0.3 OFFSET=0.1 LABEL=lwall

PRINT ...
  STRIDE=10
  ARG=ang1,ang2,*.bias,*.force2
  FILE=COLVAR FMT=%6.3f
... PRINT

ENDPLUMED

