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We present a new method to synthesize bulk indium nitride by means of a simple solid-state chemical reaction carried out under hydrostatic high pressure/high temperature conditions in a multi-anvil apparatus, not involving gases or solvents during the process. The reaction occurs between the binary oxide $In_2O_3$ and the highly reactive $Li_3N$ as nitrogen source, in powder form. The formation of the hexagonal phase of InN, occurring at 350 {\deg}C and P $\geq$ 3 GPa, was successfully confirmed by powder X-ray diffraction, with the presence of $Li_2O$ as unique byproduct. A simple washing process in weak acidic solution followed by centrifugation, allowed to obtain pure InN polycrystalline powders as precipitate. With an analogous procedure it was possible to obtain pure bulk GaN, from $Ga_2O_3$ and $Li_3N$ at T $\geq$ 600{\deg}C and P $\geq$ 2.5 GPa. These results point out, particularly for InN, a clean, and innovative way to produce significant quantities of one of the most promising nitrides in the field of electronics and energy technologies., Comment: Under revision in a peer-review journal

Copper-doped antimony selenide (Cu-doped Sb2Se3) thin films were deposited as absorber layers in photovoltaic solar cells using the low-temperature pulsed electron deposition (LT-PED) technique, starting from Sb2Se3 targets where part of the Sb was replaced with Cu. From a crystalline point of view, the best results were achieved for thin films with about Sb1.75Cu0.25Se3 composition. In order to compare the results with those previously obtained on undoped thin films, Cu-doped Sb2Se3 films were deposited both on Mo- and Fluorine-doped Tin Oxide (FTO) substrates, which have different influences on the film crystallization and grain orientation. From the current-voltage analysis it was determined that the introduction of Cu in the Sb2Se3 absorber enhanced the open circuit voltage (VOC) up to remarkable values higher than 500 mV, while the free carrier density became two orders of magnitude higher than in pure Sb2Se3-based solar cells.

In this paper, we generalize the projected Jacobi and the projected Gauss–Seidel methods to vertical linear complementarity problems (VLCPs) characterized by matrices with positive diagonal entries. First, we formulate the methods and show that the subproblems that must be solved at each iteration have an explicit solution, which is easy to compute. Then, we prove the convergence of the proposed procedures when the matrices of the problem satisfy some assumptions of strict or irreducible diagonal dominance. In this context, for simplicity, we first analyze the convergence in the special case of VLCPs of dimension $$2n\times n$$ , and we then generalize the results to VLCPs of an arbitrary dimension $$\ell n\times n$$ . Finally, we provide several numerical experiments (involving both full and sparse matrices) that show the effectiveness of the proposed approaches. In this context, our methods are compared with existing solution methods for VLCPs. A parallel implementation of the projected Jacobi method in CUDA is also presented and analyzed.

In this paper, we generalize and analyze the concepts of diagonal dominance and irreducibility in the framework of column and row representative matrices of a set. Our analysis includes the definition of particular sets of M- and H-matrices. We also analyze the form that the matrices of the introduced irreducible sets must have and the implications of the obtained results on the solution of vertical and horizontal linear complementarity problems. In this context, we prove that the projected Jacobi and the projected Gauss-Seidel methods for horizontal linear complementarity problems converge when the matrices of the problem satisfy one of the introduced generalizations of strict diagonal dominance or of irreducible diagonal dominance. This extends current convergence results.

The dynamic behavior of supramolecular organic frameworks (SOFs) based on the rigid tetra-4-(4-pyridyl)phenylmethane (TPPM) organic tecton has been elucidated through 3D electron diffraction, X-ray powder diffraction and differential scanning calorimetry (DSC) analysis. The SOF undergoes a reversible single-crystal-to-single-crystal transformation when exposed to vapours of selected organic solvents, moving from a closed structure with isolated small voids to an expanded structure with solvated channels along the b axis. The observed selectivity is dictated by the fitting of the guest in the expanded SOF, following the degree of packing coefficient. The effect of solvent uptake on TPPM solid-state fluorescence was investigated, evidencing a significant variation in the emission profile only in the presence of chloroform.

The employment of two-dimensional materials, as growth substrates or buffer layers, enables the epitaxial growth of layered materials with different crystalline symmetries with a preferential crystalline orientation and the synthesis of heterostructures with a large lattice constant mismatch. In this work, we employ single crystalline graphene to modify the sulfurization dynamics of copper foil for the deterministic synthesis of large-area Cu9S5 crystals. Molecular dynamics simulations using the Reax force-field are used to mimic the sulfurization process of a series of different atomistic systems specifically built to understand the role of graphene during the sulphur atom attack over the Cu(111) surface. Cu9S5 flakes show a flat morphology with an average lateral size of hundreds of micrometers. Cu9S5 presents a direct band-gap of 2.5 eV evaluated with light absorption and light emission spectroscopies. Electrical characterization shows that the Cu9S5 crystals present high p-type doping with a hole mobility of 2 cm(2) V-1 s(-1).

We present here a method for the quantitative prediction of the spectroscopic specular reflectivity line-shape in anisotropic layered media. The method is based on a 4 &times, 4 matrix formalism and on the simulation from the first principles (through density functional theory&mdash, DFT) of the anisotropic absorption cross-section. The approach was used to simulate the reflectivity at the oxygen K-edge of a 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) thin film on Au(111). The effect of film thickness, orientation of the molecules, and grazing incidence angle were considered. The simulation results were compared to the experiment, permitting us to derive information on the film geometry, thickness, and morphology, as well as the electronic structure.

We examine the asymptotics of the moments of characteristic polynomials of $N\times N$ matrices drawn from the Hermitian ensembles of Random Matrix Theory, in the limit as $N\to\infty$. We focus in particular on the Gaussian Unitary Ensemble, but discuss other Hermitian ensembles as well. We employ a novel approach to calculate asymptotic formulae for the moments, enabling us to uncover subtle structure not apparent in previous approaches., 26 pages

This paper considers several aspects of random matrix universality in deep neural networks. Motivated by recent experimental work, we use universal properties of random matrices related to local statistics to derive practical implications for deep neural networks based on a realistic model of their Hessians. In particular we derive universal aspects of outliers in the spectra of deep neural networks and demonstrate the important role of random matrix local laws in popular pre-conditioning gradient descent algorithms. We also present insights into deep neural network loss surfaces from quite general arguments based on tools from statistical physics and random matrix theory., 42 pages

Multiferroics, showing the coexistence of two or more ferroic orderings at room temperature, could harness a revolution in multifunctional devices. However, most of the multiferroic compounds known to date are not magnetically and electrically ordered at ambient conditions, so the discovery of new materials is pivotal to allow the development of the field. In this work, we show that BaFe

Weak interactions (hydrogen bonds, halogen bonds, CH···π and π-π stacking) can play a significant role in the formation of supramolecular assemblies with desired structural features. In this contribution, we report a systematic investigation on how a halogen bond (XB) can modulate the structural arrangement of silver supramolecular complexes. The complexes are composed of X-phenyl(bispyrazolyl)methane (X = Br, I) and I-alkynophenyl(bispyrazolyl)methane ligands functionalized in meta (L3Br, L3I) and para (L4Br, L4I, L4CCI) positions on a phenyl ring with the purpose of providing different directionalities of the X function with respect to the N,N coordination system. The obtained [Ag(L)2]+ moieties show remarkable geometric similarities, and the L4Br, L4I, and L4CCI ligands exhibit the most conserved types of supramolecular arrangement that are sustained by XB. The increased σ-hole in L4CCI with respect to L4I leads to an occurrence of short (and strong) XB interactions with the anions. [Ag(L4I)2]PF6 and [Ag(L4I)2]CF3SO3 are characterized by the presence of three different phases, and the single-crystal evolution from phase-1 (a honeycomb structure with large 1D cavities) to phase-3 (solventless) occurs by a stepwise decrease in the crystallization solvent content, which promotes an increase in XB interactions in the lattice. The present paper aims to provide useful tools for the selection of appropriate components for the use of coordination compounds to build supramolecular systems based on the halogen bond.

The Temperature Induced Neutral to Ionic phase Transition (TI-NIT) is a rare phenomenon occurring in mixed stack charge transfer (CT) crystals made up of alternating $\pi$-electron Donor (D) and Acceptor (A) molecules. We were able to grow crystals of Tetrathiafulvalene-Fluoranil (TTF-FA), and to show that it undergoes TI-NIT like the prototype CT crystal TTF-Chloranil. We characterized both room and low T phases through IR and Raman spectroscopy and XRD, demonstrating that while TTF-FA is quasi-neutral at room T, its ionicity jumps from 0.15 to 0.7 at low T, therefore crossing the Neutral-Ionic borderline. The transition, occuring around 150K, is first order, with large thermal hysteresis and accompanied by crystal cracking. In the high T phase D and A molecules lie on inversion center, i.e. the stacks are regular, whereas the low T phase is characterized by the loss of the inversion symmetry along the stack as the stacks are strongly dimerized and by the doubling of the unit cell., Comment: 7 pages, 5 figures

Let $O$ be chosen uniformly at random from the group of $(N+L) \times (N+L)$ orthogonal matrices. Denote by $\tilde{O}$ the upper-left $N \times N$ corner of $O$, which we refer to as a truncation of $O$. In this paper we prove two conjectures of Forrester, Ipsen and Kumar (2020) on the number of real eigenvalues $N^{(m)}_{\mathbb{R}}$ of the product matrix $\tilde{O}_{1}\ldots \tilde{O}_{m}$, where the matrices $\{\tilde{O}_{j}\}_{j=1}^{m}$ are independent copies of $\tilde{O}$. When $L$ grows in proportion to $N$, we prove that \begin{equation*} \mathbb{E}(N^{(m)}_{\mathbb{R}}) = \sqrt{\frac{2m L}{\pi}}\,\mathrm{arctanh}\left(\sqrt{\frac{N}{N+L}}\right) + O(1), \qquad N \to \infty.\end{equation*}\ud We also prove the conjectured form of the limiting real eigenvalue distribution of the product matrix. Finally, we consider the opposite regime where $L$ is fixed with respect to $N$, known as the \textit{regime of weak non-orthogonality}. In this case each matrix in the product is very close to an orthogonal matrix. We show that $\mathbb{E}(N^{(m)}_{\mathbb{R}}) \sim c_{L,m}\,\log(N)$ as $N \to \infty$ and compute the constant $c_{L,m}$ explicitly. These results generalise the known results in the one matrix case due to Khoruzhenko, Sommers and \.{Z}yczkowski (2010).

By means of single-crystal X-ray diffraction, we give direct crystallographic evidence of a centrosymmetry breaking below TS = 200 K, concomitant with the onset of a commensurate structural modulation in the quadruple perovskite YMn3Mn4O12. This result, which explains the anomalously large thermal coefficient of the Y3+ ion in previously reported structural models, is attributed to the small size of the Y3+ ion, which causes its underbonding within the dodecahedral coordination polyhedron. The present data are consistent with a commensurate superstructure described by an I-centered pseudo-orthorhombic cell with polar Ia symmetry and a ? aF?2 = 10.4352(7) Å, b ? 2bF = 14.6049(9) Å, c ? cF?2 = 10.6961(7) Å, and ? = 90.110(3)°, where aF ? cF ? 7.45 Å, bF ? 7.34 Å, and ? ? 91° are the unit cell parameters of the I2/m structure observed at room temperature. Consistent with the above polar structure, at lower temperature, T* = 70 K, we observe in polycrystalline samples an anomaly of the direct current (DC) and alternating current (AC) magnetization, concomitant with the appearance of a net electric polarization, as indicated by pyrocurrent and dielectric constant measurements. These results, complemented by electrical transport measurements, suggest a magnetic ferroelectricity driven by short-range magnetic order in YMn3Mn4O12.

A new organic–inorganic hybrid centrosymmetric compound, (C4H12NO3)CdCl3·H2O, was synthesized by the slow evaporation method at room temperature and characterized by single X-ray diffraction (SCXRD). The results of the X-ray diffraction study demonstrated that this material crystallizes in the triclinic system with the space group P 1 ¯ and the following unit cell parameters a = 6.822(6) A, b = 8.96(2) A, c = 10.034(3) A, α = 72.901(3)°, β = 71.927(3)°, γ = 89.099(3)° and Z = 2. In the crystal structure, the atomic arrangement is described as an alternation of organic and inorganic layers along the a-axis. The anionic layers are formed by [CdCl5O]− octahedrons, while the cationic layers are made up of [C4H12NO3]+ cations. The crystal packing is governed by N H⋯Cl, N H⋯O, C H⋯Cl, O H⋯Cl and O H⋯O hydrogen bonds, forming a three dimensional supramolecular network. Hirshfeld surfaces and 2D fingerprint plots were determined for visualizing, exploring and quantifying the intermolecular interactions in the crystal lattice of the title compound. Infrared and Raman spectroscopy were reported at room temperature in the frequency domains 400–4000 cm−1 and 50–500 cm−1, respectively. Differential scanning calorimetry (DSC) revealed one exothermic peak located at around T1 = 368 K. Electrical and dielectric properties were investigated as a function of temperature (300–430 K) in the frequency range 40 Hz–110 MHz. The electrical and dielectric studies were performed by means of impedance spectroscopy and dielectric permittivity e ' , e ' ' . Nyquist curves were well fitted to an equivalent circuit formed by parallel combination resistance and capacity fractal of the bulk. The frequency dependence of the alternative current (AC) conductivity was analyzed using the Jonscher law. Overlapping-large polaron tunneling (OLPT) and non-overlapping small polaron tunneling (NSPT) conduction mechanism models successfully explained the behavior of the exponent n.

In this paper, we extend modulus-based matrix splitting iteration methods to horizontal linear complementarity problems. We consider both standard and accelerated methods and analyze their convergence. In this context, we also generalize existing results on modulus-based matrix splitting iteration methods for (non-horizontal) linear complementarity problems. Lastly, we analyze the proposed methods by numerical experiments involving both symmetric and non-symmetric matrices.

The loss surfaces of deep neural networks have been the subject of several studies, theoretical and experimental, over the last few years. One strand of work considers the complexity, in the sense of local optima, of high dimensional random functions with the aim of informing how local optimisation methods may perform in such complicated settings. Prior work of Choromanska et al (2015) established a direct link between the training loss surfaces of deep multi-layer perceptron networks and spherical multi-spin glass models under some very strong assumptions on the network and its data. In this work, we test the validity of this approach by removing the undesirable restriction to ReLU activation functions. In doing so, we chart a new path through the spin glass complexity calculations using supersymmetric methods in Random Matrix Theory which may prove useful in other contexts. Our results shed new light on both the strengths and the weaknesses of spin glass models in this context., 50 pages, 11 figures; references added for Kac-Rice reduction to RMT method; updates following JSTAT review and publication

We investigated the mixed-stack charge-transfer crystal, N,N'-dimethylphenazine-TCNQ (${\mathrm{M}}_{2}\mathrm{P}$-TCNQ), which is polar at room temperature and just at the neutral-to-ionic interface (ionicity $\ensuremath{\rho}\ensuremath{\approx}0.5$). We detect the typical dielectric signature of a relaxor ferroelectric and an asymmetric positive-up-negative-down behavior. While relaxor ferroelectricity is usually ascribed to disorder in the crystal, we find no evidence for structural disorder in the investigated crystals. To elucidate the origin of ${\mathrm{M}}_{2}\mathrm{P}$-TCNQ's dielectric properties we perform parallel structural and spectroscopic measurements, associated with theoretical modeling and quantum-mechanical calculations. Our combined effort points to a highly polarizable electronic system that is strongly coupled to lattice vibrations. The found indications for polarization reversal imply flipping of the bent conformation of the ${\mathrm{M}}_{2}\mathrm{P}$ molecule with an associated energy barrier of a few tens of an eV, broadly consistent with an Arrhenius fit of the dielectric relaxation times. While the polarization is mostly of electronic origin, its possible reversal implies slow collective motions that are affected by solid-state intermolecular interactions.

A 49-year-old black male was referred to the Emergency Department (ED) after a 24-h history of confusion, progressive blurring of vision and altered mental status. On admission, the patient was confused and showed slurred speech and dyspnea. A history of alcohol abuse, and recent use of non-specified "energy drinks" was reported. The patient was apyretic; blood pressure was 170/80 mmHg, pulse rate 98 beats/min, respiratory rate 38 breaths/min, and peripheral oxygen saturation 99% at room air. Physical examination was unremarkable, but he showed progressive depression of cognitive status with no motor deficits nor nuchal rigidity. Brain CT scan was negative. Arterial blood gas showed high anion gap metabolic acidosis with slightly increased lactate levels (Table 1). Measured osmolality was 301 mOsm/kg, with no evident osmolal gap.