Investigation into the physical characteristics of the compounds XBiSe2 (X = Li, Na or K).

CONTEXT: As new materials, the ternary chalcogenides have recently brought scientists' attention. These materials are a novel class of semiconducting chemical compounds. They allow the increase of the photo-conversion efficiency, the performance, and the cheap energy cost. Such materials also provide a wide range of physical and chemical applications. METHODS: The used investigation employs Density Functional Theory (DFT) implemented in the Wien2k package to systematically characterize the physical properties of ternary chalcogenide compounds XBiSe2 (X = Li, Na and K). Such method emphasizes their applicability to energy conversion technologies. Scrutinizing their electronic, optical, and thermoelectric properties elucidates the effect of alkali metal substitution on performance metrics. The results not only advance knowledge of these materials' physicochemical behaviors but also reveal their potential for tailored functionalization in next-generation energy and optoelectronic systems, marking a significant stride in material science and application-oriented research.

Edge wetting of an Ising three-dimensional system.

The effect of edge on wetting and layering transitions of a three-dimensional spin-1/2 Ising model is investigated, in the presence of longitudinal and surface magnetic fields, using mean field theory and Monte Carlo simulations. For T=0, the ground state phase diagram shows that there exist only three allowed transitions, namely, surface and bulk transition, surface transition, and bulk transition. However, there exist a surface intralayering temperature T(s)(L), above which the surface and the intralayering surface transitions occur. While the bulk layering and intralayering transitions appear above another finite temperature T(b)(L)(>or=T(s)(L)). These surface and bulk intralayering transitions are not seen in the perfect surfaces case. Numerical values of T(s)(L) and T(b)(L), computed by Monte Carlo method are found to be smaller than those obtained using mean field theory. However, the results predicted by the two methods become similar, and are exactly those given by the ground state phase diagram, for very low temperatures. On the other hand, the behavior of the local magnetizations as a function of the external magnetic field, shows that the transitions are of the first order type. T(s)(L) and T(b)(L) decrease when increasing the system size and/or the surface magnetic field. In particular, T(b)(L) reaches the wetting temperature T(w) for sufficiently large system sizes.