c1: COORDINATIONNUMBER SPECIES=1-512 SWITCH={EXP D_0=4.0 R_0=0.5} 
cf: MFILTER_MORE DATA=c1 SWITCH={RATIONAL D_0=2.0 R_0=0.1} LOWMEM 
cc: CENTER_OF_MULTICOLVAR DATA=cf

DUMPATOMS ATOMS=cc FILE=cluster-com.xyz PRECISION=5

d1: DISTANCE ATOMS=cc,21
r: RESTRAINT ARG=d1 AT=13.0 KAPPA=0.5
