(a) In the cubic crystal structures, as the values of the Miller indices (h, k, and 1) increase, does the interplanar spacing (daki) increase or decrease? Why?

(a) Magnesium (Mg) has a hexagonal close-packed (HCP) crystal structure with the lattice parameter of a = 0.321 nm and c= 0.521 nm and the atomic radius is 0.173 nm. (i) What is the number of atoms per unit cell in HCP structure? (ii) Determine the atomic packing factor of the Mg unit cell. (iii) Is Mg containing an ideal atomic packing factor? You may justify your answer by evaluating the HCP c/a ratio. Subsequently, will slip be harder in Mg compared to the ideal HCP structure? Justify your answer.

What is face centered cubic unit cell? What is its significance in the field of engineering and chemistry?

In the early days of X-ray crystallography there was an urgent need to know the wavelengths of X-rays. One technique was to measure the diffraction angle from a mechanically ruled grating. Another method was to estimate the separation of lattice planes from the measured density of a crystal. The mass density of NaCl is 2.17 g cm−3 and the (100) reflection using radiation of a certain wavelength occurred at 6.0°. Calculate the wavelength of the X-rays.