Determine the repeat distance, linear density, and packing fraction for BCC lithium, which has a lattice parameter of 0.35089 nm, in the [100] , [110] [111] , and directions. Which of these directions is close packed?

3

The band gap of gallium phosphide is 2.26 eV, which makes it appropriate for producing yellow LEDs, although the yellow color is rarely useful on its own (think a yellow laser pointer). One can alter the band gap of GaP, changing the emission color to red or green. Propose the ways to produce these two colors by (1) chemical (compositional) and (2) physical (non-compositional) modifications of the material.

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