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Short helpfile for action UWALLS
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The following arguments are compulsory: 

                   DATA - certain actions in plumed work by calculating a list of 
                          variables and summing over them. This particular action can be used 
                          to calculate functions of these base variables or prints them 
                          to a file. This keyword thus takes the label of one of those 
                          such variables as input. 
                     AT - the radius of the sphere 
                  KAPPA - the force constant for the wall. The k_i in the expression 
                          for a wall. 
                 OFFSET - ( default=0.0 ) the offset for the start of the wall. The 
                          o_i in the expression for a wall. 
                    EXP - ( default=2.0 ) the powers for the walls. The e_i in the 
                          expression for a wall. 
                    EPS - ( default=1.0 ) the values for s_i in the expression for a 
                          wall 

In addition you may use the following options: 

  NUMERICAL_DERIVATIVES - ( default=off ) calculate the derivatives for these 
                          quantities numerically 
                 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 

