Domain formation and phase transitions in the wurtzite-based heterovalent ternaries: a Landau theory analysis

Characterizing the crystalline disorder properties of heterovalent ternary semiconductors continues to challenge solid-state theory. Here, a Landau theory is developed for the wurtzite-based ternary semiconductor ZnSnN2. It is shown that the symmetry properties of two nearly co-stable phases, with space groups Pmc21 and Pbn21, imply that a reconstructive phase transition is the source of crystal structure disorder via a mixture of phase domains. The site exchange defect, which consists of two adjacent antisite defects, is identified as the nucleation mechanism of the transition. A Landau potential based on the space-group symmetries of the Pmc21 and Pbn21 phases is constructed from the online databases in the ISOTROPY software suite and this potential is consistent with a system that undergoes a paraelectric to antiferroelectric phase transition. It is hypothesized that the low-temperature Pbn21 phase is antiferroelectric within the c-axis basal plane. The dipole arrangements within the Pbn21 basal plane yield a nonpolar spontaneous polarization and the electrical susceptibility derived from the Landau potential exhibits a singularity at the Néel temperature characteristic of antiferroelectric behavior. These results inform the study of disorder in the broad class of heterovalent ternary semiconductors, including those based on the zincblende structure, and open the door to the application of the ternaries in new technology spaces.

Existence of heteroclinic solutions for a class of problems involving the fractional Laplacian

In this paper, we study the existence of heteroclinic solution for a class of nonlocal problems of the type [Formula: see text] where [Formula: see text], [Formula: see text] are continuous functions verifying some technical conditions. For example [Formula: see text] can be asymptotically periodic and potential [Formula: see text] can be the Ginzburg–Landau potential, that is, [Formula: see text].

Existence of a Heteroclinic Solution for a~Double Well Potential Equation in an Infinite Cylinder of ℝ N

This paper is concerned with the existence of a heteroclinic solution for the following class of elliptic equations: -\Delta{u}+A(\epsilon x,y)V^{\prime}(u)=0\quad\mbox{in }\Omega, where {\epsilon>0} , {\Omega=\mathbb{R}\times\mathcal{D}} is an infinite cylinder of {\mathbb{R}^{N}} with {N\geq 2} . Here, we consider a large class of potentials V that includes the Ginzburg–Landau potential {V(t)=(t^{2}-1)^{2}} and two geometric conditions on the function A. In the first condition we assume that A is asymptotic at infinity to a periodic function, while in the second one A satisfies 0<A_{0}=A(0,y)=\inf_{(x,y)\in\Omega}A(x,y)<\liminf_{|(x,y)|\to+\infty}A(x,y)=A% _{\infty}<\infty\quad\text{for all }y\in\mathcal{D}.

On the Temperature Regions of the Phases of BaTiO3

The Landau potential of BaTiO3 should be the invariant of the operations of the group Oh. By using the phase stability conditions, the temperature regions of possible phases are given. The pressure-temperature phase diagram of BaTiO3 has been investigated by using a modification of Landau potential. At low temperature, each phase boundary bends sharply down, and the non-linear behavior is associated with quantum effects. Saturation temperature characterizes the extent of quantum mechanical, and is related to the extent to which changes in the hard phonon modes influence the transition mechanism.

LANDAU POTENTIAL STUDY OF THE CHIRAL PHASE TRANSITION IN A QCD-LIKE THEORY

We investigate the chiral phase transition of a QCD-like theory, based the shape change of the effective potential near the critical point. The potential is constructed with the auxiliary field method, and a source term coupled to the field is introduced in order to compute the potential shape numerically. We also generalize the potential so as to have two independent order parameters, the quark scalar density and the number density. We find a tri-critical point locating at (T, μ) = (97, 203) MeV , and visualize it as the merging point of three potential minima.