Rigid vs. Nonrigid Molecules
MC and MD can be performed on molecules as already described
- MD moves advance atom positions based on current forces
- MC moves translate atoms and accepts based on energy change
- both are done considering inter- and intra-molecular forces
- limiting distribution has same form
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- if this is all that is done, there is nothing more to say
Often it is much more efficient to use a rigid-bond model
- MD integration then doesn’t have to deal with fast intramolecular dynamics, so a larger time step can be used
- MC can sample configurations more efficiently using rigid-body moves (even if model does not have rigid bonds)
but much care is needed to do this properly