  An elastic rod model for semi-flexible polymers is presented. Theory for a
continuum rod is reviewed, and it is shown that a popular discretised model
used in numerical simulations gives the correct continuum limit. Correlation
functions relating to both bending and twisting of the rod are derived for both
continuous and discrete cases, and results are compared with numerical
simulations. Finally, two possible implementations of the discretised model in
the multi-purpose molecular dynamics software package LAMMPS are described.
