  The task of accurately locating fluid phase boundaries by means of computer
simulation is hampered by problems associated with sampling both coexisting
phases in a single simulation run. We explain the physical background to these
problems and describe how they can be tackled using a synthesis of biased Monte
Carlo sampling and histogram extrapolation methods, married to a standard fluid
simulation algorithm. It is demonstrated that the combined approach provides a
powerful method for tracing fluid phase boundaries.
