code: public static final Atom getCenterVector(Atom[] atomSet){
  		Atom centroid = getCentroid(atomSet);
  
  		return getCenterVector(atomSet,centroid);
  
  	}
docs: Returns the Vector that needs to be applied to shift a set of atoms to
  the Centroid.
  
  @param atomSet
  array of Atoms
  @return the vector needed to shift the set of atoms to its geometric
  center