Andrew,
The fix move actually worked (Thanks!), but something is still not quite right. The minimization after the soft potential gives infinite pressure (see below), and that persists throughout the integration even though the subsequent trajectory visualization appears normal.
Fred
Setting up minimization ...
Memory usage per processor = 4.58094 Mbytes
Step Temp E_pair E_mol TotEng Press
100000 0.4463571 1.#INF 0.21467385 1.#INF -1.#IND
100001 0.4463571 1.#INF 0.21467385 1.#INF -1.#IND
Loop time of 0.246624 on 2 procs for 1 steps with 1668 atoms
Minimization stats:
Stopping criterion = linesearch alpha is zero
Energy initial, next-to-last, final =
1.#INF 1.#INF 1.#INF
Force two-norm initial, final = 321.956 321.956
Force max component initial, final = 36.2835 36.2835
Final line search alpha, max atom move = 1.64275e-010 5.96046e-009
Iterations, force evaluations = 1 25