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Using the Nanohub Crystal Viewer, visualize the crystal structures of GaAs $($zinc$-$blende$)$ and

NaCl $($rock$-$salt$).$ Determine the atomic densities and packing efficiencies for these materials.

Discuss similarities and distinctions of these two structures and their genesis.

Visualize the major atomic planes $\{100\},\{110\},$ and $\{111\}.$ Determine their densities in terms of

atoms$/($unit cell$)$ and calculate their atomic density in $(a\frac{t}{c}{m}^2).$