center-of-mass

Dear Professor,
Now,I am using the lmp11_g++ , I want to output the center-of-mass of the group of atoms (rigid body). And in the manual of the lmp9_g++, I know the command of “fix com command” can calculate it .However, in the manual of the lmp11_g++, after reading the manual , I write the following two commands:
compute 3 tip com
dump 3 tip custom 100 dump.%.displace c_3
However there is an error : Dump custom compute does not compute per-atom info-catch_rsh /opt/mpich2/gnu.
I am puzzled with the problem . Could you give me some guidance , please.
Best regards ,
Liujing.