High-refractive index and mechanically cleavable non-van der Waals InGaS3

The growing families of two-dimensional crystals derived from naturally occurring van der Waals materials offer an unprecedented platform to investigate elusive physical phenomena and could be of use in a diverse range of devices. Of particular interest are recently reported atomic sheets of non-van der Waals materials, which could allow a better comprehension of the nature of structural bonds and increase the functionality of prospective heterostructures. Here, we study the optostructural properties of ultrathin non-van der Waals InGaS3 sheets produced by standard mechanical cleavage. Our ab initio calculation results suggest an emergence of authentically delicate out-of-plane covalent bonds within its unit cell, and, as a consequence, an artificial generation of layered structure within the material. Those yield to singular layer isolation energies of around 50 meVA-2, which is comparable with the conventional van der Waals material's monolayer isolation energies of 20 - 60 meVA-2. In addition, we provide a comprehensive analysis of the structural, vibrational, and optical properties of the materials presenting that it is a wide bandgap (2.73 eV) semiconductor with a high-refractive index (higher than 2.5) and negligible losses in the visible and infrared spectral ranges. It makes it a perfect candidate for further establishment of visible-range all-dielectric nanophotonics

Interface-induced perpendicular magnetic anisotropy of Co nanoparticles on single-layer h-BN/Pt(111)

Ferromagnetism with perpendicular magnetic anisotropy (PMA) was observed at room temperature in cobalt nanoparticles (NPs) grown on hexagonal boron nitride (h-BN) on a Pt(111) surface. It was shown that the Co NPs have planar hexagonal shapes with a mean diameter of ∼20 nm and a mean height of ∼1.6 nm. The depth-resolved analysis of X-ray magnetic circular dichroism at the Co L2,3-edges revealed that in the ferromagnetic Co NPs, the ratio of the orbital magnetic moment to the spin magnetic moment in the out-of-plane direction becomes larger at the Co NP/h-BN interface than the ratio in bulk Co. The B and N K-edge near edge X-ray absorption fine structures showed the orbital hybridization between the π orbitals of h-BN and d orbitals of Co at the interface, as an origin of the orbital magnetic moment enhancement possibly giving rise to PMA in the Co NPs

Spontaneous doping of the basal plane of MoS2 single layers through oxygen substitution under ambient conditions

The chemical inertness of the defect-free basal plane confers environmental stability to MoS2 single-layers, but it also limits their chemical versatility and catalytic activity. The stability of the pristine MoS2 basal plane against oxidation under ambient conditions is a widely accepted assumption in the interpretation of various studies and applications. However, single-atom level structural investigations reported here reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS2 single layers during ambient exposure. Our scanning tunneling microscopy investigations reveal a slow oxygen substitution reaction, upon which individual sulfur atoms are one by one replaced by oxygen, giving rise to solid solution type 2D MoS2-xOx crystals. O substitution sites present all over the basal plane act as single-atomic active reaction centers, substantially increasing the catalytic activity of the entire MoS2 basal plane for the electrochemical H2 evolution reaction.Comment: 6 pages, 5 figure

Raman Spectroscopy of Janus MoSSe Monolayer Polymorph Modifications Using Density Functional Theory

Two-dimensional transition metal dichalcogenides (TMDs) with Janus structures are attracting increasing attention due to their emerging superior properties in breaking vertical mirror symmetry when compared to conventional TMDs, which can be beneficial in fields such as piezoelectricity and photocatalysis. The structural investigations of such materials, along with other 2D materials, can be successfully carried out using the Raman spectroscopy method. One of the key elements in such research is the theoretical spectrum, which may assist in the interpretation of experimental data. In this work, the simulated Raman spectrum of 1H-MoSSe and the predicted Raman spectra for 1T, 1T’, and 1H’ polymorph modifications of MoSSe monolayers were characterized in detail with DFT calculations. The interpretation of spectral profiles was made based on the analysis of the lattice dynamics and partial phonon density of states. The presented theoretical data open the possibility of an accurate study of MoSSe polymorphs, including the control of the synthesized material quality and the characterization of samples containing a mixture of polymorphs

High-pressure phases of sulfur: Topological analysis and crystal structure prediction

We apply density functional theory (DFT) and evolutionary structure prediction algorithms to study the high-pressure behavior of sulfur above 100 GPa. Based on DFT calculations, we determined the energetic relations between experimentally observed S-III, S-V, and b-Po structures. S-V is found to be unstable and transforms to S-III under optimization. The second order character of transformation from S-III to b-Po is theoretically justified and calculations yield a pressure of about 250 GPa. b-Po structure is not stable in trigonal symmetry below 250 GPa and spontaneously transforms into a mono-clinic structure identical to S-III. The calculations yield pressures of 333 and 460 GPa for the transitions from b-Po to simple cubic (sc) and from simple cubic to body centered cubic (bcc) structures of sulfur, respectively

CLINICAL EFFICACY AND SAFETY OF SEIZING PAROXYSMS OF ATRIAL FIBRILLATION WITH PROPAPHENON

The study was made to evaluate clinical efficacy, safety and electrophysiological effects of Propaphenon in seizing paroxysms of atrial fibrillation (AF)45 patients have been evaluated, with AF paroxysms lasting up to 48 hours. To restore sinus rhythm (SR) single oral intake of 600 mg Propaphenon (PRO. MED. CS Praha a.s. ) was used. AF paroxysms were seized under the control of ECG Hotter and BP monitoring.Antiarrhythmic effect was evaluated based on the results of dynamics of electrophysiological parameters determined by means of transesophageal heart electrophysiology studies (ТЕ EPS) in 12 patients.A comparative analysis of results obtained has shown that Propanorm is an effective antiarrhythmic drug to treat AF paroxysms. Heart sinus rhythm (SR) restoration takes place in 88. 9 % cases whereas electrophysiological criteria for antiarrhythmic response include: increased value of rate threshold of induction (RTI) by 140 impulses per minute, disappearance of atrial vulnerability zone and prolonged AV node effective refractory period by 50 ms

High-pressure phases of sulfur: Topological analysis and crystal structure prediction

We apply density functional theory (DFT) and evolutionary structure prediction algorithms to study the high-pressure behavior of sulfur above 100 GPa. Based on DFT calculations, we determined the energetic relations between experimentally observed S-III, S-V, and b-Po structures. S-V is found to be unstable and transforms to S-III under optimization. The second order character of transformation from S-III to b-Po is theoretically justified and calculations yield a pressure of about 250 GPa. b-Po structure is not stable in trigonal symmetry below 250 GPa and spontaneously transforms into a mono-clinic structure identical to S-III. The calculations yield pressures of 333 and 460 GPa for the transitions from b-Po to simple cubic (sc) and from simple cubic to body centered cubic (bcc) structures of sulfur, respectively