From Dimer to Crystal: Calculating the Cohesive Energy of Rare Gas Solids

An upper-level undergraduate project is described in which students perform high-level ab initio computational scans of the potential energy curves for Ne-2 and Ar-2 and obtain the respective Leonard-Jones (LJ) potential parameters a and e for the dimers, Using this information, along with the summation of pairwise interactions in the face-centered cubic structures of the crystalline solids, the students determine the cohesive energies of solid Ne and Ar. By applying the Debye theory of solids, they then adjust these values to take zero-point vibrational effects into account after obtaining the respective Debye temperatures from published low-temperature heat capacity data. The students also calculate the lattice parameters and solid densities. An assessment of their work is made by comparing their results with experimental data.