The formation of dimerized molecules of C60 and their solids

The formation of dimerized molecules of C₆₀ was studied using the Brenner potential. Several structures are obtained which have been classified into three categories, viz., dumbbells, and fused and coalesced dimers, similar to those obtained earlier, using the Tersoff potential. However, there are differences in the binding energies obtained using these two potentials. From these formations, we chose four forms of the composite dimer molecule as cyclo dumbbell, peanut, capped armchair (5,5) and zigzag nanotubes (10,0) to form crystalline solids. Calculations have been performed by placing them in various crystal structures, i.e. monoclinic, hexagonal and cubic close packed. To obtain stable dimerized crystal structures, the dimer molecules are considered to be rigid, interacting via atom-atom interaction of 6-exponential form. The monoclinic phase has been found to be energetically most stable for each of the dimers. Various structural, thermodynamic and phonon related properties of the stable dimer phases were investigated.