.

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

		 atmnam 1 		 a8 		 first atom type 


atmnam 2 		 a8 		 second atom type (central site)


atmnam 3 		 a8 		 third atom type


key 		 a4 		 potential key. See table 4.13

Table 4.13: Three-body potentials

key	potential type	Variables (1-4)				functional form
thrm	Truncated harmonic	$k$	$\theta_{0}$	$\rho$		$U(\theta)= {k\over 2} (\theta - \theta_0)^2 \exp[-(r_{ij}^8 + r_{ik}^8)/\rho^8]$
shrm	Screened harmonic	$k$	$\theta_{0}$	$\rho_{1}$	$\rho_{2}$	$U(\theta)= {k\over 2} (\theta - \theta_0)^2\exp[-(r_{ij}/\rho_1 + r_{ik}/\rho_2)]$
bvs1	Screened Vessal[24]	$k$	$\theta_{0}$	$\rho_{1}$	$\rho_{2}$	$U(\theta)= {k \over 8(\theta-\theta_0)^2}\left\{ \left[ (\theta_0 -\pi)^2 -(\theta-\pi)^2\right]^2\right\}$
						$\exp[-(r_{ij}/\rho_1 + r_{ik}/\rho_2)]$
bvs2	Truncated Vessal[25]	$k$	$\theta_{0}$	$a$	$\rho$	$U(\theta)= k\big[ \theta^a (\theta-\theta_0)^2 (\theta+\theta_0-2\pi)^2 - {a\over 2} \pi^{a-1}$
						$(\theta-\theta_0)^2(\pi - \theta_0)^3\big] \exp[-(r_{ij}^8 + r_{ik}^8)/\rho^8]$
hbnd	H-bond [8]	$D_{hb}$	$R_{hb}$			$U(\theta)=D_{hb}cos^{4}(\theta)[5(R_{hb}/r_{jk})^{12}-6(R_{hb}/r_{jk})^{10}]$
$\theta$ is the a-b-c angle.

		 variable 1 		 real 		 potential parameter see table4.13


variable 2 		 real 		 potential parameter see table4.13


variable 3 		 real 		 potential parameter see table4.13


variable 4 		 real 		 potential parameter see table4.13


variable 5 		 real 		 cutoff range for this potential (Å)

The variables pertaining to each potential are described in table 4.13. Note that the fifth variable is the range at which the three body potential is truncated. The distance is in Å, measured from the central atom.

The specification of four body potentials is initiated by the directive: