SrZrCu ( = S and Se): two novel layered quaternary mixed transition metal chalcogenides.

Depending on their bandgaps, mixed metal layered chalcogenides are potential candidates for thermoelectric and photovoltaic applications. Herein, we reported the exploratory synthesis of Sr-Zr-Cu- ( = S/Se) systems, resulting in the identification of two novel quaternary chalcogenides: SrZrCuS and SrZrCuSe. These isoelectronic compounds (SrZrCu) crystallized in two different structural types.

BaZrTe: a new complex ternary telluride structure with low thermal conductivity.

Heavier metal-based tellurides with complex structures are of great interest for thermoelectric () applications. Herein, we report the synthesis of a new telluride BaZrTe using high-temperature reactions of elements. Our single-crystal X-ray diffraction study reveals that it crystallizes in the space group 3̄ of the trigonal crystal system and is isostructural to its Se analogue BaZrSe complex.

Polarized Raman, infrared and dielectric spectra of lead-free KNaNbOpiezoelectric system: insights fromtheoretical and experimental studies.

The KNaNbO(KNN) system has emerged as one of the most promising lead-free piezoelectric over the years. In this work, we perform a comprehensive investigation of electronic structure, lattice dynamics and dielectric properties of room temperature phase of KNN by combiningDFT based theoretical analysis and experimental characterization. We assign the symmetry labels to KNN vibrational modes and obtainpolarized Raman spectra, Infrared reflectivity, Born-effective charge tensors, oscillator strengths etc.

Influence of temperature on bandgap shifts, optical properties and photovoltaic parameters of GaAs/AlAs and GaAs/AlSbheterojunctions: insights fromDFT + NEGF studies.

The III-V group semiconductors are highly promising absorbers for heterojunctions based solar cell devices due to their high conversion efficiency. In this work, we explore the solar cell properties and the role of electron-phonon coupling (EPC) on the solar cell parameters of GaAs/AlSb and GaAs/AlAsheterojunctions using non-equilibrium Green function method (NEGF) in combination ofdensity functional theory (DFT). In addition, the band offsets at the heterointerfaces, optical absorption and bandgap shifts (BGSs) due to temperature are estimated using DFT + NEGF approach.

First-principle investigation of structural, electronic, and phase stabilities in chalcopyrite semiconductors: insights from Meta-GGA functionals.

We undertake a comprehensive first-principles investigation into the factors influencing the optoelectronic efficiencies of PQIIIR2VIchalcopyrite semiconductors. The structural attributes, electronic properties, and phase stabilities are explored using various meta-GGA exchange-correlation (XC) functionals within the density functional framework. In particular, we assess the relative performance of these XC functionals in obtaining estimates of various relevant parameters.

BaSiSbTe(Te): hypervalent Te in a new structure type with low thermal conductivity.

Heavier pnictogen (Sb, Bi) containing chalcogenides are well known for their complex structures and semiconducting properties for numerous applications, particularly thermoelectric materials. Here, we report the syntheses of single crystals and polycrystalline phases of a new complex quaternary polytelluride, BaSiSbTe(Te), a high-temperature reaction of elements. A single-crystal X-ray diffraction study showed that it crystallizes in an unprecedented structure type with monoclinic symmetry (space group: 2/).

BaFeAgS: a new antiferromagnetic and semiconducting quaternary sulfide.

The single crystals of a quaternary sulfide, BaFeAgS, have been synthesized by reacting elements at 873 K inside a sealed fused silica tube. The title phase is the first ordered quaternary compound of the Ba-Ag-Fe-S system. The crystal structure of BaFeAgS is characterized by a single-crystal X-ray diffraction study at 298(2) K.

Efficient and improved prediction of the band offsets at semiconductor heterojunctions from meta-GGA density functionals: A benchmark study.

Accurate theoretical prediction of the band offsets at interfaces of semiconductor heterostructures can often be quite challenging. Although density functional theory has been reasonably successful to carry out such calculations, efficient, accurate semilocal functionals are desirable to reduce the computational cost. In general, the semilocal functionals based on the generalized gradient approximation (GGA) significantly underestimate the bulk bandgaps.

Five coordinated Mn in BaMnSiTe: synthesis, crystal structure, physical properties, and electronic structure.

We report the synthesis of single-crystals of a new transition metal-containing quaternary chalcogenide, BaMnSiTe, synthesized by the solid-state method at 1273 K. A single-crystal X-ray diffraction study shows that it crystallizes in the orthorhombic crystal system (space group: ) with cell constants of = 13.4690(6) Å, = 8.

Germanium Antimony Bonding in BaGeSbTe with Low Thermal Conductivity.

A new quaternary telluride, BaGeSbTe, was synthesized at high temperature via the reaction of elements. A single-crystal X-ray diffraction study shows that the title compound crystallizes in its own structure type in the monoclinic 2/ space group having cell dimensions of = 13.984(3) Å, = 13.

Theoretical investigation of lattice dynamics, infrared reflectivity, polarized Raman spectra and nature of interlayer coupling in two-dimensional layered gallium sulfide.

Gallium sulfide (GaS) is a highly promising two-dimensional layered semiconductor owing to its remarkable thickness dependent electronic and physical properties. In this article, we perform a comprehensivestudy of lattice dynamics, mode symmetry assignments, polarized Raman and infrared (IR) reflectivity spectra of GaS system. Polarized Raman spectra are obtained for different light polarization set-ups of incoming and scattered light.

BaLnMnTe (Ln = Pr, Gd, and Yb; x = Ln vacancy): syntheses, crystal structures, optical, resistivity, and electronic structure.

Three new isostructural quaternary tellurides, BaLnMnTe (Ln = Pr, Gd, and Yb), have been synthesized by the molten-flux method at 1273 K. The single-crystal X-ray diffraction studies at 298(2) K showed that BaLnMnTe crystallize in the space group -C2/m of the monoclinic crystal system. There are six unique crystallographic sites in this structure's asymmetric unit: one Ba site, one Ln site, one Mn site, and three Te sites.

First principles theoretical investigations of low Young's modulus beta Ti-Nb and Ti-Nb-Zr alloys compositions for biomedical applications.

High alloyed β-phase stabilized titanium alloys are known to provide comparable Young's modulus as that to the human bones (~30 GPa) but is marred by its high density. In the present study the low titanium alloyed compositions of binary Ti-Nb and ternary Ti-Nb-Zr alloy systems, having stable β-phase with low Young's modulus are identified using first principles density functional framework. The theoretical results suggest that the addition of Nb in Ti and Zr in Ti-Nb increases the stability of the β-phase.

Prediction of a switchable two-dimensional electron gas at ferroelectric oxide interfaces.

The demonstration of a quasi-two-dimensional electron gas (2DEG) in LaAlO3/SrTiO3 heterostructures has stimulated intense research activity in recent years. The 2DEG has unique properties that are promising for applications in all-oxide electronic devices. For such applications it is desirable to have the ability to control 2DEG properties by external stimulus.

Magnetic tunnel junctions with ferroelectric barriers: prediction of four resistance States from first principles.

Magnetic tunnel junctions (MTJs), composed of two ferromagnetic electrodes separated by a thin insulating barrier layer, are currently used in spintronic devices, such as magnetic sensors and magnetic random access memories. Recently, driven by demonstrations of ferroelectricity at the nanoscale, thin-film ferroelectric barriers were proposed to extend the functionality of MTJs. Due to the sensitivity of conductance to the magnetization alignment of the electrodes (tunneling magnetoresistance) and the polarization orientation in the ferroelectric barrier (tunneling electroresistance), these multiferroic tunnel junctions (MFTJs) may serve as four-state resistance devices.