Monte Carlo Rotations

• 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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