Modeling of structural and energetic parameters of р-Er1-xScxNiSb semiconductor

The energy expediency of the existence of Er1-xScxNiSb substitutional solid solution up to the concentration x≈0.10 was established by modeling the variation of free energy ΔG(x) values (Helmholtz potential). At higher Sc concentrations, x> 0.10, there is stratification (spinoidal decomposition of phase). It is shown that in the structure of p-ErNiSb semiconductor there are vacancies in positions 4a and 4c of Er and Ni atoms, respectively, generating structural defects of acceptor nature. The number of vacancies in position 4a is twice less than in position 4c. This ratio also remains for p-Er1-xScxNiSb. Doping of p-ErNiSb semiconductor by Sc atoms by substitution of Er atoms is also accompanied by the occupation of vacancies in position 4a. In this case, Ni atoms occupy vacancies in position 4c, which can be accompanied by the process of ordering the p-Er1-xScxNiSb structure. Occupation of vacancies by Sc and Ni atoms leads to an increase of the concentration of free electrons, an enlarge of the compensation degree of semiconductor, which changes the position of the Fermi level εF and the mechanisms of electrical conductivity.

Spinodal Decomposition in a Polystyren/ Cyclohexane Solution of Critical Composition

Results of experiments are reported demonstrating spinoidal decomposition in a critical mixture of polystyrene and cyclohexane. If time and length are properly scaled using data obtained from static and dynamic light scattering exper­ iments, the time evolution of the “spinodal ring” is repre­sented to a good approximation by an empirical equation proposed by Snyder and Meakin which describes spinodal decomposition for various types of systems.

SPINOIDAL DECOMPOSITION NEAR A LIFSHITZ POINT

Near a Lifshitz point, there is a deep minimum of the electronic energy. This minimum can lead to a spinoidal decomposition for carrier concentrations near the Lifshitz point. Such a two-phase mixture would be an ideal candidate for excitonic superconductivity.