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

                    MOL - The numerical indices of the atoms in the molecule. The 
                          orientation of the molecule is equal to the vector connecting the first 
                          two atoms specified. If a third atom is specified its position 
                          is used to specify where the molecule is. If a third atom is 
                          not present the molecule is assumed to be at the center of the 
                          vector connecting the first two atoms. You can use multiple 
                          instances of this keyword i.e. MOL1, MOL2, MOL3... 

The following options are available

  NUMERICAL_DERIVATIVES - ( default=off ) calculate the derivatives for these 
                          quantities numerically 
                  NOPBC - ( default=off ) ignore the periodic boundary conditions 
                          when calculating distances 
                 SERIAL - ( default=off ) do the calculation in serial. Do not use 
                          MPI 
                 LOWMEM - ( default=off ) lower the memory requirements 
                TIMINGS - ( default=off ) output information on the timings of the 
                          various parts of the calculation 
                   MEAN - take the mean of these variables. The final value can be 
                          referenced using <em>label</em>.mean. You can use multiple instances 
                          of this keyword i.e. MEAN1, MEAN2, MEAN3... The corresponding 
                          values are then referenced using <em>label</em>.mean-1, 
                          <em>label</em>.mean-2, <em>label</em>.mean-3... 
                  VMEAN - calculate the norm of the mean vector. The final value can 
                          be referenced using <em>label</em>.vmean. You can use multiple 
                          instances of this keyword i.e. VMEAN1, VMEAN2, VMEAN3... The 
                          corresponding values are then referenced using <em>label</em>.vmean-1, 
                          <em>label</em>.vmean-2, <em>label</em>.vmean-3... 


