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Short helpfile for action CENTER
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The input trajectory can be in any of the following formats: 

                  ATOMS - the group of atoms that you are calculating the Gyration 
                          Tensor for. For more information on how to specify lists of atoms 
                          see \ref Group 

The following arguments are compulsory: 

                   TYPE - ( default=RADIUS ) The type of calculation relative to the 
                          Gyration Tensor you want to perform 

In addition you may use the following options: 

                  NOPBC - ( default=off ) ignore the periodic boundary conditions 
                          when calculating distances 
                 PHASES - ( default=off ) use trigonometric phases when computing 
                          position of center 
            SAFE_PHASES - ( default=off ) use trignomentric phases when computing 
                          position of center but also compute the center in ths usual way and 
                          use this when the pbc are not set. There are two reasons for 
                          using this option (1) you are doing something that you know is 
                          really weird or (2) you are an idiot 
                   MASS - ( default=off ) calculate the center of mass 
                WEIGHTS - what weights should be used when calculating the center. If 
                          this keyword is not present the geometric center is computed. If 
                          WEIGHTS=@Masses is used the center of mass is computed. If WEIGHTS=@charges 
                          the center of charge is computed. If the label of an action is 
                          provided PLUMED assumes that that action calculates a list of 
                          symmetry functions that can be used as weights. Lastly, an explicit 
                          list of numbers to use as weights can be provided 


