HOLLOW DIAMONDS - STABILITY AND ELASTIC PROPERTIES

We conjecture about the possibility of periodic sp(3)-bonded carbon lattices formed by regular arrays of fullerenic cavities (hollow diamonds (HDs)) as a generalization of clathrates. We describe three infinite series of HDs having Nn(n + 1)(2n + 1)/3 atoms per unit cell, for any natural number n and N = 17 (face center cubic), 20 (hexagonal) or 23 (simple cubic lattices). Each of the series tends to diamond for n --> infinity. Using the semi-empirical many-body Tersoff potential for the carbon-carbon interaction, we have calculated with a simulated annealing procedure the ground-state structure, the total energy and the elastic constants of the smallest HDs (fcc-C-34, hex-C-40 and sc-S-46), comparing the results to diamond.