ITITL : the title of the current run, from the AMBER
parameter/topology file
The following is sequentially dropped for each snapshot of the
trajectory:
FORMAT(10F8.3) (X(i), Y(i), Z(i), i=1,NATOM)
X,Y,Z : coordinates or velocities
IF periodic box [4.0 and previous: only if constant pressure]:
FORMAT(10F8.3) BOX(1), BOX(2), BOX(3)
BOX : size of periodic box