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We present a theoretical study of the transport properties of two-dimensional hole gas (2DHG) in Ge channel modulation-doped square quantum wells, with very high room-temperature drift mobilities. Within the variational approach, we obtain analytic expressions for the carrier distribution, and autocorrelation functions for various scattering mechanisms. The results were used to determine the hole mobility where only the relevant scattering processes, namely acoustic phonons (Deformation potential and Piezoelectric coupling), ionized impurity, surface roughness were considered. The partials and total mobility dependences on temperature were found. It is shown that acoustic phonon and surface roughness scattering are the dominant mechanism. The interpretation of these results is carried out and the scattering mechanisms limiting the 2DHG mobility in Ge quantum wells of SiGe heterostructure are discussed.

Recently, covalent organic frameworks (COFs) - a new class of highly ordered organic crystalline porous polymers, have attracted huge research interest because of their unique structures and potential applications in gas separation/storage, catalysis, energy strorage and optoelectronic materials development. We have studied several structure’s series of hexagonal shapes to explore the applicability of the formation of two-dimensional (2D) COFs from various pre-defined individual building blocks using Density Functional based tight-binding (DFTB) method. Different high-symmetry stackings, e.g. AA and AB stacking sequence are also designed and investigated. The designed series’s band gaps are found to be ranging from 1.7 to 4.0 eV. Further, the COF series, revealing a variety of promising mechanical and electronic properties, which can potentially find future realistic applications.

In the last decades, covalent organic frameworks (COFs) – the class of highly ordered organic crystalline porous, have attracted huge research interest because of their unique structures and potential applications in gas separation/storage, catalysis, energy storage and optoelectronic materials device. In this works, we proposed several series of triangular topologies to study the applicability of the formation of two-dimensional (2D) COFs from various pre-defined individual building blocks using Density Functional based tight-binding (DFTB) method. Different high-symmetry stacking, e.g. AA and AB stacking sequence are also designed and investigated. The designed series band gaps are found to be ranging from 0 eV to 2.93 eV. Furthermore, the COF series, revealing a variety of promising mechanical and electronic properties, which can potentially find future realistic applications.

We illustrate, with the examples of a few evolved stars, the results of considerations which we have developed with the aim of easing the modelling of their gas envelopes

Polymorphs or phases - different inorganic solids structures of the same composition usually have widely differing properties and applications, thereby synthesizing or predicting new classes of polymorphs for a certain compound is of great significance and has been gaining considerable interest. Herein, we perform a density functional theory based tight binding (DFTB) study on theoretical prediction of several new phases series of II-VI semiconductor material ZnO nanoporous phases from their bottom-up building blocks. Among these, three phases are reported for the first time, which could greatly expand the family of II- VI compound nanoporous phases. We also show that all these generally can be categorized similarly to the aluminosilicate zeolites inorganic open-framework materials. The hollow cage structure of the corresponding building block ZnkOk (k= 9, 12, 16) is well preserved in all of them, which leads to their low-density nanoporous and high flexibility. Additionally the electronic wide-energy gap of the individual ZnkOk is also retained. Our study reveals that they are all semiconductor materials with a large band gap. Further, this study is likely to be the common for II-VI semiconductor compounds and will be helpful for extending their range of properties and applications.