cale = thermostat a group of atoms by rescaling their velocities 
    <LI>
    hoover/drag = thermostat a group of atoms by the Hoover method 
    <LI>
    langevin = thermostat a group of atoms by the Langevin method 
    <LI>
    springforce = apply a spring force to each atom in group 
    <LI>
    dragforce = drag each atom in group to a specified position 
    <LI>
    shake = apply bond length constraints to certain bonds, enabling longer 
    timesteps 
</UL>
<PRE>
coeffs:  none
               no oth