 by LAMMPS, one line at a time. 
Each command causes LAMMPS to take some action. Usually it simply 
causes some internal variable(s) to be set. Or it may cause a data file 
to be read in or a simulation to be run. Note that most commands have 
default settings, which means you only need use a particular command if 
you do not want the default setting.</P>
<P>
Each LAMMPS input script contains exactly one &quot;read data&quot; (or 
&quot;read restart&quot;) command which defines the problem to be 
simulated.