On the Vibrational Spectrum and the Vibrational Specific Heat of a Binary Superlattice Alloy

The change in the vibrational modes of a binary superlattice alloy due to the change in its own degree of order has previously been discussed. It was then expected that the vibrational specific heat of the superlattice alloy would change in response to the change in its own degree of order. Using the result obtained formerly, we have applied, in the present paper. Houston\u27s approximate method of finding the frequency distribution function N(ν) to the calculation of the vibrational specific heat of β-brass in the state of any specified degree of order. It is shown that the vibrational specific heat of the disordered alloy is generally larger than that of the ordered one at oridnary temperatures. If two kinds of atoms which are the components of alloy are nearly equal in mass, the vibrational specific heat of the ordered alloy becomes larger than that of the disordered one at low temperatures

On the Lattice Vibrations of a Binary Superlattice Alloy

It is expected that the vibrational modes of a superlattice alloy would change in response to the change in its own degree of order, and hence its vibrational specific heat and thermal conductivity of lattice for the ordered state would be different from those for the disordered one. In the present paper the result of a theoretical calculation on the vibrational modes of a beta brass alloy (CuZn) for the state of any degree of order which was carried out in accordance with the method of Born and von Karman is given. The sixth order secular equation finally obtained was solved with respect to the three principal directions [100], [110], and [111]. The ν-σ curves for the state of several specified values of the degree of order in the three principal directions were plotted. Owing to the fact that the ratio of masses of two kinds of atoms in beta brass is nearly unity, we cannot see a remarkable change in the ν-σ curves in response to the change in the degree of order. However, a similar calculation in regard to Cu_3Au would reveal a more remarkable change in the ν-σ curves accompanying the change in the degree of order than that which appears in the present paper. The influence of the degree of order on the frequency distribution function and the vibrational specific heat of beta brass will be discussed in the paper to be published before long