Novel auxetic semiconductors with high carrier mobility: first principles prediction of Janus GeXY (X/Y = S, Se, Te) monolayers.

Recently, auxetic materials have attracted attention due to their unusual behavior and multifunctional applications. A negative Poisson's ratio has been found in some two-dimensional (2D) asymmetric layered materials. In this work, we predict a new class of 2D auxetic materials with the chemical formula GeXY (X/Y = S, Se, Te) using calculations.

Two-dimensional piezoelectric AlSiX (X = N, P, As) semiconductors with Raman activity, favorable band-gap, and high carrier mobility based on first-principles calculations.

In the present work, we attempt to construct two-dimensional AlSiX (X = N, P, As) monolayers and examine their stabilities, Raman activity, piezoelectricity, as well as electronic/transport properties for various applications, using first-principles calculations. All three - AlSiN, AlSiP and AlSiAs - configurations are confirmed to have good dynamic, thermal, and mechanical stabilities from their phonon spectra, molecular dynamics investigations, and attained elastic constants/cohesive energy results. The Raman spectra of the AlSiX monolayers are performed using the finite displacement technique to assess their vibrational properties and Raman activities.

Exploring the versatility of MoSe/WS heterostructures.

Two-dimensional materials and their combined heterostructures have paved the way for numerous next-generation electronic and optoelectronic applications. Herein, we performed first principles calculations to computationally design the MoSe/WS heterostructure and consider its geometric structure, electronic properties and contact behavior, as well as the effects of the electric fields and strain. Our results show that the MoSe/WS heterostructure is energetically, thermodynamically and mechanically stable.

Piezoelectric GaGeX (X = N, P, and As) semiconductors with Raman activity and high carrier mobility for multifunctional applications: a first-principles simulation.

In the present work, we propose GaGeX (X = N, P, As) monolayers and explore their structural, vibrational, piezoelectric, electronic, and transport characteristics for multifunctional applications based on first-principles simulations. Our analyses of cohesive energy, phonon dispersion spectra, and molecular dynamics simulations indicate that the three proposed structures have good energetic, dynamic, and thermodynamic stabilities. The GaGeX are found as piezoelectric materials with high piezoelectric coefficient of -1.

Monolayers SnTeX (X = P, As) as promising materials for photocatalytic water splitting and flexible devices: a DFT study.

First principles calculation was performed to study the SnTeX (X = P, As) monolayers. Structural investigation confirms the stability of the two monolayers with Young's modulus in the range of 30.34-33.

Unveiling Versatile Electronic Properties and Contact Features of Metal-Semiconductor Graphene/γ-GeSSe van der Waals Heterostructures.

Recently, searching for a metal-semiconductor junction (MSJ) that exhibits low-contact resistance has received tremendous consideration, as they are essential components in next-generation field-effect transistors. In this work, we design a MSJ by integrating two-dimensional (2D) graphene as the metallic electrode and 2D Janus γ-GeSSe as the semiconducting channel using first-principles simulations. All the graphene/γ-GeSSe MSJs are predicted to be energetically, mechanically, and thermodynamically stable, characterized by the weak van der Waals (vdW) interactions.

Large piezoelectric responses and ultra-high carrier mobility in Janus HfGeZH (Z = N, P, As) monolayers: a first-principles study.

Breaking structural symmetry in two-dimensional layered Janus materials can result in enhanced new phenomena and create additional degrees of piezoelectric responses. In this study, we theoretically design a series of Janus monolayers HfGeZH (Z = N, P, As) and investigate their structural characteristics, crystal stability, piezoelectric responses, electronic features, and carrier mobility using first-principles calculations. Phonon dispersion analysis confirms that HfGeZH monolayers are dynamically stable and their mechanical stability is also confirmed through the Born-Huang criteria.

P-incorporated CuO/CuS heteronanorods as efficient electrocatalysts for the glucose oxidation reaction toward highly sensitive and selective glucose sensing.

Currently, tremendous efforts have been made to explore efficient glucose oxidation electrocatalysts for enzymeless glucose sensors to meet the urgent demands for accurate and fast detection of glucose in the fields of health care and environmental monitoring. In this work, an advanced nanostructured material based on the well-aligned CuO/CuS heteronanorods incorporated with P atoms is successfully synthesized on a copper substrate. The as-synthesized material shows high catalytic behavior accompanied by outstanding electrical conductivity.

Insights from Experiment and Theory on Peculiarities of the Electronic Structure and Optical Properties of the TlHgGeSe Crystal.

TlHgGeSe crystal was successfully, for the first time, synthesized by the Bridgman-Stockbarger technology, and its electronic structure and peculiarities of optical constants were investigated using both experimental and theoretical techniques. The present X-ray photoelectron spectroscopy measurements show that the TlHgGeSe crystal reveals small moisture sensitivity at ambient conditions and that the essential covalent constituent of the chemical bonding characterizes it. The latter suggestion was supported theoretically by ab initio calculations.

Theoretical and Experimental Advances in High-Pressure Behaviors of Nanoparticles.

Using compressive mechanical forces, such as pressure, to induce crystallographic phase transitions and mesostructural changes while modulating material properties in nanoparticles (NPs) is a unique way to discover new phase behaviors, create novel nanostructures, and study emerging properties that are difficult to achieve under conventional conditions. In recent decades, NPs of a plethora of chemical compositions, sizes, shapes, surface ligands, and self-assembled mesostructures have been studied under pressure by in-situ scattering and/or spectroscopy techniques. As a result, the fundamental knowledge of pressure-structure-property relationships has been significantly improved, leading to a better understanding of the design guidelines for nanomaterial synthesis.

Electronic and optical properties of thiogermanate AgGaGeS: theory and experiment.

The electronic and optical properties of an AgGaGeS crystal were studied by first-principles calculations, where the full-potential augmented plane-wave plus local orbital (APW+lo) method was used together with exchange-correlation pseudopotential described by PBE, PBE+, and TB-mBJ+ approaches. To verify the correctness of the present theoretical calculations, we have measured for the AgGaGeS crystal the XPS valence-band spectrum and the X-ray emission bands representing the energy distribution of the electronic states with the biggest contributions in the valence-band region and compared them on a general energy scale with the theoretical results. Such a comparison indicates that, the calculations within the TB-mBJ+ approach reproduce the electron-band structure peculiarities (density of states - DOS) of the AgGaGeS crystal which are in fairly good agreement with the experimental data based on measurements of XPS and appropriate X-ray emission spectra.

First-principles study on the structural properties of 2D MXene SnSiGeN and its electronic properties under the effects of strain and an external electric field.

The MXene SnSiGeN monolayer as a new member of the MoSiN family was proposed for the first time, and its structural and electronic properties were explored by applying first-principles calculations with both PBE and hybrid HSE06 approaches. The layered hexagonal honeycomb structure of SnSiGeN was determined to be stable under dynamical effects or at room temperature of 300 K, with a rather high cohesive energy of 7.0 eV.

A new family of NaTMGe (TM = 3d transition metals) half-Heusler compounds: the role of TM modification.

Exploring Heusler based materials for different practical applications has drawn more and more attention. In this work, the structural, electronic, magnetic, and mechanical properties of NaTMGe (TM = all 3d transition metals) half-Heusler compounds have been systematically investigated using first-principles calculations. The TM modification plays a determinant role in the fundamental properties.

Electronic structure and interface contact of two-dimensional van der Waals boron phosphide/GaSSe heterostructures.

In this work, we systematically examine the electronic features and contact types of van der Waals heterostructures (vdWHs) combining single-layer boron phosphide (BP) and Janus GaSSe using first-principles calculations. Owing to the out-of-plane symmetry being broken, the BP/GaSSe vdWHs are divided into two different stacking patterns, which are BP/SGaSe and BP/SeGaS. Our results demonstrate that these stacking patterns are structurally and mechanically stable.

Rashba-type spin splitting and transport properties of novel Janus XWGeN (X = O, S, Se, Te) monolayers.

We discuss and examine the stability, electronic properties, and transport characteristics of asymmetric monolayers XWGeN (X = O, S, Se, Te) using density functional theory. All four monolayers of quintuple-layer atomic Janus XWGeN are predicted to be stable and they are all indirect semiconductors in the ground state. When the spin-orbit coupling (SOC) is included, a large spin splitting at the point is found in XWGeN monolayers, particularly, a giant Rashba-type spin splitting is observed around the point in three structures SWGeN, SeWGeN, and TeWGeN.

Antiferromagnetic ordering in the TM-adsorbed AlN monolayer (TM = V and Cr).

In this work, the effects of transition metal (TM = V and Cr) adsorption on AlN monolayer electronic and magnetic properties are investigated using first-principles density functional theory (DFT) calculations. TMs prefer to be adsorbed on-top of a bridge position as indicated by the calculated adsorption energy. V adatoms induce half-metallicity, while Cr adatoms metallize the monolayer.

Theoretical prediction of Janus PdXO (X = S, Se, Te) monolayers: structural, electronic, and transport properties.

Due to the broken vertical symmetry, the Janus material possesses many extraordinary physico-chemical and mechanical properties that cannot be found in original symmetric materials. In this paper, we study in detail the structural, electronic, and transport properties of 1T Janus PdXO monolayers (X = S, Se, Te) by means of density functional theory. PdXO monolayers are observed to be stable based on the analysis of the vibrational characteristics and molecular dynamics simulations.

Outstanding elastic, electronic, transport and optical properties of a novel layered material CF: first-principles study.

Motivated by very recent successful experimental transformation of AB-stacking bilayer graphene into fluorinated single-layer diamond (namely fluorinated diamane CF) [P. V. Bakharev, M.

Long-term characterization of roadside air pollutants in urban Beijing and associated public health implications.

Road traffic constitutes a major source of air pollutants in urban Beijing, which are responsible for substantial premature mortality. A series of policies and regulations has led to appreciable traffic emission reductions in recent decades. To shed light on long-term (2014-2020) roadside air pollution and assess the efficacy of traffic control measures and their effects on public health, this study quantitatively evaluated changes in the concentrations of six key air pollutants (PM, PM, NO, SO, CO and O) measured at 5 roadside and 12 urban background monitoring stations in Beijing.

Layered post-transition-metal dichalcogenide SnGeN as a promising photoelectric material: a DFT study.

First-principles calculations were performed to study a novel layered SnGeN compound, which was found to be dynamically and thermally stable in the 2H phase, with the space group 6̄2 and lattice constant = 3.143 Å. Due to its hexagonal structure, SnGeN exhibits isotropic mechanical properties on the x-y plane, where the Young's modulus is 335.

Novel Janus GaInX (X = S, Se, Te) single-layers: first-principles prediction on structural, electronic, and transport properties.

In this paper, the structural, electronic, and transport properties of Janus GaInX (X = S, Se, Te) single-layers are investigated by a first-principles calculations. All three structures of GaInX are examined to be stable based on the analysis of their phonon dispersions, cohesive energy, and Born's criteria for mechanical stability. At the ground state, The Janus GaInX is a semiconductor in which its bandgap decreases as the chalcogen element X moves from S to Te.

Coarse Grained Modeling of Multiphase Flows with Surfactants.

Coarse-grained modeling methods allow simulations at larger scales than molecular dynamics, making it feasible to simulate multifluid systems. It is, however, critical to use model parameters that represent the fluid properties with fidelity under both equilibrium and dynamic conditions. In this work, dissipative particle dynamics (DPD) methods were used to simulate the flow of oil and water in a narrow slit under Poiseuille and Couette flow conditions.

Novel Janus group III chalcogenide monolayers AlXY(X/Y = S, Se, Te): first-principles insight onto the structural, electronic, and transport properties.

Motivated by the recent successful synthesis of 2D quintuple-layer atomic materials, for the first time, we design and investigate the electronic and transport properties of Janus AlXY(X/Y = S, Se, Te; X ≠ Y) monolayers by using the density functional theory. Our calculations demonstrate that most of the models of AlXY(except for AlSTemonolayer) are dynamically and mechanically stable. By using the hybrid functional, all models of AlXYare semiconductors with an indirect bandgap.