  Two-dimensional classical cluster of particles interacting through a screened
Coulomb potential is studied. This system can be used as a model for "dusty
particles" in high-frequency discharge plasma. For systems consisting of N = 2
- 40 particles and confined by a harmonic potential we find ground-state
configurations, eigenfrequencies and eigenvectors for the normal modes as a
function of the Debye screening length R_D in plasma. Variations in R_D cause
changes in the ground-state structure of clusters, each structural
rearrangement can be considered as a phase transition of first or second order
(with respect to parameter R_D). Monte Carlo and molecular dynamics are used to
study in detail the melting of the clusters as the temperature is increased. By
varying the density and the temperature of plasma, to which the particles are
immersed, one can modulate thermodynamical properties of the system,
transforming it in a controllable way to an ordered (crystal-like),
orientationaly disordered or totally disordered (liquid-like) states. The
possibility of dynamical coexistence phenomena in small clusters is discussed.
