ss 2 angles (and associated cross terms) 
    <LI>
    charmm = harmonic + Urey-Bradley 
    <LI>
    cosine = (1 + cos(theta))
</UL>
<PRE>
define style of angle interactions to use for all 3-body terms
must be used before the &quot;read data&quot; command (if not using the
  default) to tell the program how to read the &quot;Angle Coeffs&quot; entry
  in the data file
can be used after the &quot;read data&quot; command to change the style to none
coefficients for all angle types must be defined in the data