Extending to continuous potentials a cleaving wall molecular dynamics simulation method recently developed for the hard-sphere system ͓Phys. Rev. Lett. 85, 4751 ͑2000͔͒, we calculate the crystalmelt interfacial free energies, ␥, for a Lennard-Jones system as functions of both crystal orientation and temperature. At the triple point, T*ϭ0.617, the results are consistent with an earlier cleaving potential calculation by Broughton and Gilmer ͓J. Chem. Phys. 84, 5759 ͑1986͔͒, however, the greater precision of the current calculation allows us to accurately determine the anisotropy of ␥. From our data we find that, at all temperatures studied, ␥ 111 Ͻ␥ 110 Ͻ␥ 100 . A comparison is made to the results from our previous hard-sphere calculation and to recent results for Ni by Asta, Hoyt, and Karma ͓Phys. Rev. B 66 100101͑R͒ ͑2002͔͒.

A series of five zeolitic imidazolate frameworks (ZIFs) have been synthesized using zinc(II) acetate and five different 4,5-functionalized imidazole units, namely ZIF-25, -71, -93, -96, and -97. These 3-D porous frameworks have the same underlying topology (RHO) with Brunauer-Emmet-Teller surface areas ranging from 564 to 1110 m(2)/g. The only variation in structure arises from the functional groups that are directed into the pores of these materials, which include -CH(3), -OH, -Cl, -CN, -CHO, and -NH(2); therefore these 3-D frameworks are ideal for the study of the effect of functionality on CO(2) uptake. Experimental results show CO(2) uptake at approximately 800 Torr and 298 K ranging from 0.65 mmol g(-1) in ZIF-71 to 2.18 mmol g(-1) in ZIF-96. Molecular modeling calculations reproduce the pronounced dependence of the equilibrium adsorption on functionalization and suggest that polarizability and symmetry of the functionalization on the imidazolate are key factors leading to high CO(2) uptake.