Modulation of strain on electronic structure and contact type of BP/SnS van der Waals heterostructure

Vertical van der Waals heterostructures(vdWH) composed of two monolayer materials can provide new opportunities for layered electronic devices. Here we present a detailed theoretical investigation about the electronic properties of BP/SnS vdWH by applying in-plane uniaxial and biaxial strains. Our first principles calculations suggest that the direct bandgap of BP/SnS vdWH can be maintained within a large range of uniaxial and biaxial strains. We also find that the bandgap, band alignment and contact type of BP/SnS vdWH can be tuned by uniaxial and biaxial strains. In addition, the Poisson’s ratio exhibits an intense anisotropy with respect to the uniaxial strain along zigzag and armchair directions. The easily tunable electronic properties and highly anisotropic character of BP/SnS vdWH make it to be a promising material in the field of photovoltaic cells, photodetectors, and other functional nano devices.

Impact of Fluoroalkylation on the N-Type Charge Transport of Two Naphthodithiophene Diimide Derivatives

In this work, we investigate two recently synthesized naphthodithiophene diimide (NDTI) derivatives featuring promising n-type charge transport properties. We analyze the charge transport pathways and model charge mobility with the non-adiabatic hopping mechanism using the Marcus-Levich-Jortner rate constant formulation, highlighting the role of fluoroalkylated substitution in α (α-NDTI) and at the imide nitrogen (N-NDTI) position. In contrast with the experimental results, similar charge mobilities are computed for the two derivatives. However, while α-NDTI displays remarkably anisotropic mobilities with an almost one-dimensional directionality, N-NDTI sustains a more isotropic charge percolation pattern. We propose that the strong anisotropic charge transport character of α-NDTI is responsible for the modest measured charge mobility. In addition, when the role of thermally induced transfer integral fluctuations is investigated, the computed electron–phonon couplings for intermolecular sliding modes indicate that dynamic disorder effects are also more detrimental for the charge transport of α-NDTI than N-NDTI. The lower observed mobility of α-NDTI is therefore rationalized in terms of a prominent anisotropic character of the charge percolation pathways, with the additional contribution of dynamic disorder effects.

Arbitrary-order intrinsic virtual element method for elliptic equations on surfaces

We develop a geometrically intrinsic formulation of the arbitrary-order Virtual Element Method (VEM) on polygonal cells for the numerical solution of elliptic surface partial differential equations (PDEs). The PDE is first written in covariant form using an appropriate local reference system. The knowledge of the local parametrization allows us to consider the two-dimensional VEM scheme, without any explicit approximation of the surface geometry. The theoretical properties of the classical VEM are extended to our framework by taking into consideration the highly anisotropic character of the final discretization. These properties are extensively tested on triangular and polygonal meshes using a manufactured solution. The limitations of the scheme are verified as functions of the regularity of the surface and its approximation.

The primitive equations in the scaling-invariant space $$L^{\infty }(L^1)$$

Consider the primitive equations on $$\mathbb {R}^2\times (z_0,z_1)$$ R 2 × ( z 0 , z 1 ) with initial data a of the form $$a=a_1+a_2$$ a = a 1 + a 2 , where $$a_1 \in \mathrm{BUC}_\sigma (\mathbb {R}^2;L^1(z_0,z_1))$$ a 1 ∈ BUC σ ( R 2 ; L 1 ( z 0 , z 1 ) ) and $$a_2 \in L^\infty _\sigma (\mathbb {R}^2;L^1(z_0,z_1))$$ a 2 ∈ L σ ∞ ( R 2 ; L 1 ( z 0 , z 1 ) ) . These spaces are scaling-invariant and represent the anisotropic character of these equations. It is shown that for $$a_1$$ a 1 arbitrary large and $$a_2$$ a 2 sufficiently small, this set of equations admits a unique strong solution which extends to a global one and is thus strongly globally well posed for these data provided a is periodic in the horizontal variables. The approach presented depends crucially on mapping properties of the hydrostatic Stokes semigroup in the $$L^\infty (L^1)$$ L ∞ ( L 1 ) -setting. It can be seen as the counterpart of the classical iteration schemes for the Navier–Stokes equations, now for the primitive equations in the $$L^\infty (L^1)$$ L ∞ ( L 1 ) -setting.

Schwarzschild-like solutions in Finsler–Randers gravity

In this work, we extend for the first time the spherically symmetric Schwarzschild and Schwarzschild–De Sitter solutions with a Finsler–Randers-type perturbation which is generated by a covector $$A_\gamma $$ A γ . This gives a locally anisotropic character to the metric and induces a deviation from the Riemannian models of gravity. A natural framework for this study is the Lorentz tangent bundle of a spacetime manifold. We apply the generalized field equations to the perturbed metric and derive the dynamics for the covector $$A_\gamma $$ A γ . Finally, we find the timelike, spacelike and null paths on the Schwarzschild–Randers spacetime, we solve the timelike ones numerically and we compare them with the classic geodesics of general relativity. The obtained solutions are new and they enrich the corresponding literature.

Magic Angle Spinning and Truncated Field Concept in NMR

In order to thoroughly comprehend and adequtely interpret NMR data, it is necessary to perceive the complex structure of spin Hamiltonian. Although NMR principles have been extensively discussed in a number of distinguished introductory publications, it still remains difficult to find illustrative graphical models revealing the tensorial nature of spin interaction. Exposure of the structure standing behind mathematical formulas can clarify intangible concepts and provide a coherent image of basic phenomena. This approach is essential when it comes to hard to manage, time-dependent processes such as Magic Angle Spinning (MAS), where the anisotropic character of the spin system interactions couple with experimentally introduced time evolution processes. The presented work concerns fundamental aspects of solid state NMR namely: the uniqueness of the tetrahedral angle and evolution of both dipolar D and chemical shield σ coupling tensors under MAS conditions.

Deep Learning Strategies for Differential Expansion Microscopy

Differential expansion microscopy (DiExM) achieves greater than 500-fold volumetric expansion of biological specimens without loss of cellular antigens. The anisotropic character of this expansion, which affects tissues, cells, organelles and even sub-organelle features, requires the application of novel machine learning approaches to extract accurate and meaningful morphological and biochemical information from DiExM images. Here we describe current strategies to achieve this goal.

Magnetic and magnetoresistive properties of nanocomposites based on Co and SiO

A series of thin-film nanocomposites based on ferromagnetic metal Co and insulator SiO were prepared using an electron-beam method. The magnetoresistive and magnetic properties of these structures deposited at room temperature and then annealed to 700 K were investigated. The results showed that at the Co concentration 40 [Formula: see text]x [Formula: see text] 60 at.%, thin-film nanocomposites exhibit magnetoresistance (MR) that is conditional on spin-dependent tunnelling of electrons. This range of concentrations corresponds to the prepercolation area according to the magnetic investigations. For samples with x [Formula: see text] 70 at.%, the anisotropic character of MR peculiar to the homogeneous ferromagnetic materials appears. According to the magnetic properties study, this range of concentrations corresponds to the area after transition through the percolation threshold. The annealing process in temperature range from 300 K to 700 K in the magnetic field slightly influenced the magnetoresistive properties of the thin-film nanocomposites based on Co and SiO for all range of concentrations.

The influence of external electric fields on charge reorganization energy in organic semiconductors

Charge reorganization energies (λ) of inter-ring carbon–carbon (IRCC) bond connected conjugated polycyclics are shown to exhibit an electric-field-driven anisotropic character.