code: @Override
      public void setCrystal(ICrystal crystal) {
          if (this.crystal != null) this.crystal.removeListener(this);
          this.crystal = crystal;
          if (this.crystal != null) this.crystal.addListener(this);
          notifyChanged();
      }
docs: Sets the Crystal contained in this ChemModel.
  
  @param   crystal  the Crystal to store in this model
  
  @see      #getCrystal