Averages with Constraints 1.
- Very stiff coordinates are sometimes treated as rigidly constrained
- e.g., the bond length L in the diatomic may be held at a constant value
- MC and MD have different ways to enforce this constraint
- Regardless of simulation technique, the constrained-system ensemble average may differ from the unconstrained value
- even when compared to the limit of an infinitely stiff bond!
- Why the difference?
- A rigid constraint implies no kinetic energy in vibration
- Examine the Lagrangian