.

 where n is the number of four-body potentials to be entered. There follows n records, each specifying a particular four-body potential in the following manner:

		 atmnam 1 		 a8 		 first atom type (central site)


atmnam 2 		 a8 		 second atom type


atmnam 3 		 a8 		 third atom type


atmnam 4 		 a8 		 fourth atom type


key 		 a4 		 potential key. See table 4.14


variable 1 		 real 		 potential parameter see table4.14


variable 2 		 real 		 potential parameter see table4.14


variable 3 		 real 		 cutoff range for this potential (Å)

The variables pertaining to each potential are described in table 4.14. Note that the third variable is the range at which the four-body potential is truncated. The distance is in Å, measured from the central atom.

Table 4.14: Four-body Potentials

key	potential type	Variables (1-2)		functional form
harm	Harmonic	$k$	$\phi_0$	$U(\phi)= {1\over 2} k (\phi - \phi_0)^2$
hcos	Harmonic cosine	$k$	$\phi_{0}$	$U(\phi)={k\over 2}(cos(\phi) -cos(\phi_{0}))^{2}$
plan	Planar	$A$		$U(\phi)= A \left [ 1 - \cos (\phi)\right]$
$\phi$ is the inversion angle.