## MC simulations of molecules include rotation moves

- must do this to sample orientations of rigid molecules
- not strictly necessary for non-rigid molecules, but very helpful
- very easy to do this incorrectly

## Trial rotation of a linear molecule

- Let present orientation be given by vector u
- Generate a unit vector v with random orientation
- Let new trial orientation be given by where g is a fixed scale factor that sets the size of the perturbation

## Nonlinear molecule

- same procedure, but do perturbation on the 4-dimensional vector of quaternions

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