  A numerical model for a 2D-monolayer plasma crystal was established using the
Box_tree code. Box_tree is a Barnes_Hut tree code which has proven effective in
modeling systems composed of large numbers of particles. Thermally excited
waves in this plasma crystal were numerically simulated and dispersion
relations for both the longitudinal and transverse wave modes were found. These
were compared with the dispersion relations extrapolated from experiment as
well as a theory based on harmonic approximation. The results were found to
agree with theoretical dispersion relations under different wave propagation
directions with different particle charges and over a range of 0.9<k<5.
