CLASSICAL DOUBLE-LAYER ATOMS - ARTIFICIAL MOLECULES

The ground-state configuration and the eigenmodes of two parallel two- dimensional classical atoms are obtained as a function of the interato mic distance (d). The classical particles are confined by identical ha rmonic wells and repel each other through a Coulomb potential. As a fu nction of d we find several structural transitions which are of first or second order. For first (second) order transitions the first (secon d) derivative of the energy with respect to d is discontinuous, the ra dial position of the particles changes discontinuously (continuously), and the frequency of the eigenmodes exhibits a jump (one mode becomes soft, i.e., its frequency becomes zero).