PES of H2-H2

[middhap]

Hello,

I was having trouble in specifying the z-matrix if I want to calculate
the complete 2-body PES of for example, H2-H2.  In particular, I want to
fix the H-H bond length of the 2 H2 molecules, and vary the distance and
the angle between the two molecules.  I am getting the error
"Unrecognizable molecule" if I use the z-matrix specified below:


geometry={H1;
                  H2,H1,r1;
                  H3,H2,r(i),H1,theta(i);
                  H4,H3,r1}

Here, r(i) and theta are variable and r1 is fixed

Please advise on a way to accomplish this task

Thanks a lot
Prankuk