THE PROBLEM OF ATOMIC DENSITY IN A 6-DIMENSIONAL MODEL OF AN ICOSAHEDRAL QUASI-CRYSTAL

The atomic density in a model of a face centred icosahedral (FCI) quas icrystal is perturbed by Monte Carlo 'phason' annealing. While the fir st-neighbour bond concentration, n(1), is a monotonically increasing f unction of the atomic density, as expected, the second-neighbour bond concentration, n(2), exhibits a maximum at a critical atomic density, rho<p(c)<rho(max),. Assuming a simple Hamiltonian, E = -n(1) - alpha n (2), it was found that any ground state structure has an atomic densit y in the interval(rho(c), p(max)). In the particular case of a FCI qua sicrystal model, the critical atomic density exceeds that of the curre nt rho (max) six-dimensional model by 1%.