Physical properties of newly synthesized noncentrosymmetric TaIr2B2 and NbIr2B2 superconductors: an extensive comparison of GGA and LDA functional investigations.

In recent years, noncentrosymmetric (NCS) structural compounds have received much attention from the scientific community in the exploration for the unconventional nature of superconductivity with exciting physical properties. This study uses the comprehensive generalized gradient approximation (GGA) and local density approximation (LDA) to gain insights into the physical properties of two recently synthesized Ir-based NCS superconductors, TaIr2B2 and NbIr2B2. The structural parameters, mechanical performance, electronic structure, Debye temperature, melting temperature, electronic specific heat, and electron-phonon coupling constant of TaIr2B2 and NbIr2B2 are explored and discussed in detail. Density functional theory (DFT) optimized structural parameters of both NCS phases agree well with experimental observation. Both GGA and LDA calculations show that the compounds are ductile, machinable, mechanically stable, and anisotropic in nature. The elastic moduli and hardness calculations reveal that TaIr2B2 is harder than NbIr2B2. The calculation of the melting temperature reveals that TaIr2B2 is more suitable for high temperature technology applications compared to NbIr2B2. Both GGA and LDA functionals reveal that the optical functions are very similar. Both compounds display a significant amount of reflectivity spectra over a wide range of photon energies. The GGA functional reveals a somewhat higher density of states value compared to that of LDA. The present calculated values of the electron-phonon coupling constant of both compounds are consistent with values previously reported from experimental studies.

DFT Insights into MAX Phase Borides Hf2AB [A = S, Se, Te] in Comparison with MAX Phase Carbides Hf2AC [A = S, Se, Te].

In this work, density functional theory (DFT)-based calculations were performed to compute the physical properties (structural stability, mechanical behavior, and electronic, thermodynamic, and optical properties) of synthesized MAX phases Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, and Hf2TeB and the as-yet-undiscovered MAX carbide phase Hf2TeC. Calculations of formation energy, phonon dispersion curves, and elastic constants confirmed the stability of the aforementioned compounds, including the predicted Hf2TeC. The obtained values of lattice parameters, elastic constants, and elastic moduli of Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, and Hf2TeB showed fair agreement with earlier studies, whereas the values of the aforementioned parameters for the predicted Hf2TeC exhibit a good consequence of B replacement by C. The anisotropic mechanical properties are exhibited by the considered MAX phases. The metallic nature and its anisotropic behavior were revealed by the electronic band structure and density of states. The analysis of the thermal properties-Debye temperature, melting temperature, minimum thermal conductivity, and Grüneisen parameter-confirmed that the carbide phases were more suited than the boride phases considered herein. The MAX phase's response to incoming photons further demonstrated that they were metallic. Their suitability for use as coating materials to prevent solar heating was demonstrated by the reflectivity spectra. Additionally, this study demonstrated the impact of B replacing C in the MAX phases.

Investigation of the Influence of Pressure on the Physical Properties and Superconducting Transition Temperature of Chiral Noncentrosymmetric TaRh2B2 and NbRh2B2.

TaRh2B2 and NbRh2B2 compounds exhibit noncentrosymmetric superconductivity with a chiral structure. Density functional theory-based ab-initio calculations have been executed to analyze the structural properties, mechanical stability, ductility/brittleness behaviors, Debye temperature, melting temperature, optical response to incident photon energy, electronic characteristics, and superconducting transition temperature of chiral TaRh2B2 and NbRh2B2 compounds under pressure up to 16 GPa. Both the chiral phases are mechanically stable and exhibit ductile nature under the studied pressure. The maximum value of the Pugh ratio (an indicator of ductile/brittle behaviors) is observed to be 2.55 (for NbRh2B2) and 2.52 (for TaRh2B2) at 16 GPa. The lowest value of the Pugh ratio is noticed at 0 GPa for both these chiral compounds. The analysis of reflectivity spectra suggests that both the chiral compounds can be used as efficient reflecting materials in the visible energy region. At 0 GPa, the calculated densities of states (DOSs) at the Fermi level are found to be 1.59 and 2.13 states eV-1 per formula unit for TaRh2B2 and NbRh2B2, respectively. The DOS values of both the chiral phases do not alter significantly with applied pressure. The shape of the DOS curve of both compounds remains almost invariant with applied pressure. The pressure-induced variation of Debye temperatures of both compounds is observed, which may cause the alternation of the superconducting transition temperature, Tc, with applied pressure. The probable changing of Tc with pressure has been analyzed from the McMillan equation.

Effect of Pressure on the Superconducting Transition Temperature and Physical Properties of CaPd2P2: A DFT Investigation.

CaPd2P2 is a recently reported superconducting material belonging to the well-known ThCr2Si2-type family. First-principles density functional theory calculations have been carried out to investigate the structural, mechanical, thermophysical, optical, electronic, and superconducting properties of the CaPd2P2 compound under pressure. To the best of our knowledge, this is the first theoretical approach to studying the pressure effect on the fundamental physical and superconducting properties of CaPd2P2. It is mechanically stable under the studied pressures. The applied hydrostatic pressure reveals a noticeable impact on elastic moduli of CaPd2P2. It exhibits ductile nature under the studied pressure. Significant anisotropic behavior of the compound is revealed with/without pressure. The study of melting temperature shows that the compound has a higher melting temperature, which increases with the increasing applied pressure. The investigation of the electronic properties strongly supports the optical function analysis. The reflectivity as well as the absorption spectra shifts to higher energy with the increasing applied pressure. The pressure-dependent behavior of the superconducting transition temperature, T c, is revealed with a pressure-induced increasing trend in Debye temperature.

Semiconducting to metallic transition with outstanding optoelectronic properties of CsSnCl3 perovskite under pressure.

Inorganic non-toxic metal halide perovskites have taken the dominant place in commercialization of the optoelectronic devices. The first principles simulation has been executed with the help of density functional theory to investigate the structural, optical, electronic and mechanical properties of non-toxic CsSnCl3 metal halide under various hydrostatic pressures up to 40 GPa. The analysis of optical functions displays that the absorption edge of CsSnCl3 perovskite is shifted remarkably toward the low energy region (red shift) with enhanced pressure. The absorptivity, conductivity and the value of dielectric constant also increases with the applied pressure. The investigation of mechanical properties reveals CsSnCl3 perovskite is mechanically stable as well as highly ductile and the ductility is increased with increasing pressure. The investigation of electronic properties shows semiconducting to metallic transition occurs in CsSnCl3 under elevated pressure. The Physics behind all these changes under hydrostatic pressure has been analyzed and explained in details within the available Scientific theory.

Narrowing band gap and enhanced visible-light absorption of metal-doped non-toxic CsSnCl3 metal halides for potential optoelectronic applications.

Non-toxic (lead-free) inorganic perovskites have seized the leading position in the race for the commercialization of solar cells and other photovoltaic devices. The present study is the first theoretical approach to show that metal (Cr/Mn)-doped CsSnCl3 perovskites exhibit high optical absorption, high photoconductivity, and high dielectric constant not only in the visible but also in the ultraviolet region of light energy due to the narrowing band gap. We carried out density functional theory (DFT) investigations to find the structural, electronic, optical, and mechanical properties of pristine CsSnCl3, Cr-, and Mn-doped CsSnCl3 samples in detail. The investigation of the optical functions displayed that the absorption edges of both Cr- and Mn-doped CsSnCl3 shifted greatly in the direction of the low photon energy area (red-shift) compared with the pristine sample. An extra very high intensity peak of absorption was noted for both Cr- and Mn-doped CsSnCl3 in the visible energy region. The investigation of the mechanical parameters revealed that both Cr- and Mn-doped CsSnCl3 samples were as mechanically stable and highly ductile as the pure CsSnCl3 sample. The investigation of the electronic properties demonstrated that the creation of intermediate states in the band gap for both the Cr- and Mn-doped CsSnCl3 samples made the transition of excited photoelectrons to the conduction band from the valence band easier. A combined study suggested that Mn-doped CsSnCl3 was better suited for applications in high potency solar cells and other optoelectronic devices than the other inorganic metal halide perovskites.

Correction: Narrowing band gap and enhanced visible-light absorption of metal-doped non-toxic CsSnCl3 metal halides for potential optoelectronic applications.

[This corrects the article DOI: 10.1039/C9RA10407K.].