optoelectronics

Si has the diamond and GaAs has the zinc blende crystal structure. Given the lattice parameters of Si

and GaAs, a = 0.543 nm and a = 0.565 nm, respectively, and the atomic masses of Si, Ga, and As as

28.08 g/mol, 69.73 g/mol, and 74.92 g/mol, respectively, calculate the density of Si and GaAs. What is

the atomic concentration (atoms per unit volume) in each crystal?