surface <surface-statement> end

<surface-statement> :==

  mode=access|contact
  --{Mode for surface area calculation. Default=access}
  rh2o=<real>
  --{Radius of the water molecule probe in Angstroms.}
  accuracy=<real>
  --{Accuracy of calculation.}
  selection=<atom-selection>
  --{Select atoms for surface area calculation.}
  radius=sigma|vdw
  --{Type of radius to use for atoms. Default=sigma.}

  --{The surface area of each atom is stored in the atom property rmsd array.}