Use the method of Villars ^[*] to evaluate the structure likely to be stable for five hypothetical binary compounds of your choice.

Ammonium Chloride has the CsCl structure(B2) in which the NH ₄ ions occupy the body-centered sites and the Cl ions the corner sites of the unit cell. There are two possible orientations for the NH ₄ ions. Above a critical temperature these orientations are randomly distributed among the NH ₄ ions. Below the critical temperature there is a partial long-range order to the distribution of these orientations. Use a Bragg Williams type model to calculate the configurational entropy of a partially long-range-ordered crystal having an excess of one orientation over the other, i.e. in the perfectly ordered crystal there is only one orientation while in the random case there are equal numbers of the two orientations.

Use Figure 1.3 to determine whether the liquid phase of Bi has a lower or higher specific volume than each of solid phases I, VII and VIII.

Suppose by radiation that defects can be introduced into a solid and thereby raise its Gibbs free energy. Use free energy temperature curves to determine the effect of these defects on the melting point of the irradiated solid.

Given a thin film coherent with its substrate. The latter is elastically much stiffer than the film. The film will not deform plastically, but only elastically up to its melting point. Also, it is known that the elastic...