TORSION ATOMS=2,5,6,7  LABEL=t1
TORSION ATOMS=5,6,7,9  LABEL=t2
ex: EXTENDED_LAGRANGIAN ARG=t1,t2 KAPPA=20,20.0 TAU=0.05,0.05 FRICTION=10,20
PRINT ARG=t1,t2,ex.* STRIDE=1 FILE=colvar FMT=%8.4f
METAD ARG=ex.t1_fict,ex.t2_fict SIGMA=0.2,0.2 HEIGHT=1.0 PACE=10 LABEL=bias  FMT=%14.6f
