Performance parameters of infra-red and visible-active MXene photocatalysts for water splitting.

Water splitting reactions through photocatalysis are an efficient and sustainable technique for the generation of green energy. Ability to simultaneously generate hydrogen and oxygen, along with efficiency of utilizing charge carriers, conversion of solar energy to hydrogen, fast migration, and low recombination rates of carriers are the parameters that decide a photocatalyst's suitability in water splitting. In the literature, comprehensive calculation and analysis of all these performance parameters for a potential photocatalyst are rare.

Tunable magnetism in nitride MXenes: consequences of atomic layer stacking.

We have performed density functional theory (DFT) based calculations to investigate the effects of stacking patterns on the electronic and magnetic properties of several nitride MXenes. MXenes, a relatively new addition to the family of two-dimensional materials, have exhibited fascinating properties in several occasions, primarily due to their compositional flexibility. However, compared to carbide MXenes, nitride MXenes are much less explored.

Strain aided drastic reduction in lattice thermal conductivity and improved thermoelectric properties in Janus MXenes.

Surface and strain engineering are among the cheaper ways to modulate structure property relations in materials. Due to their compositional flexibilities, MXenes, the family of two-dimensional materials, provide enough opportunity for surface engineering. In this work, we have explored the possibility of improving thermoelectric efficiency of MXenes through these routes.

Symmetry lowering through surface engineering and improved thermoelectric properties in Janus MXenes.

Despite ample evidence of their influence on the transport properties of two-dimensional solids, the interrelations of reduced symmetry, electronic and thermal transport have rarely been discussed in the context of thermoelectric materials. With the motivation to design new thermoelectric materials with improved properties, we have addressed these by performing first-principles density functional theory based calculations in conjunction with semi-classical Boltzmann transport theory on a number of compounds in the MXene family. The symmetry lowering in parent MCO (M = Ti, Zr, Hf, Mo) MXenes is achieved by replacing the transition metal M on one surface, resulting in Janus compounds MMCO (M = Ti, Zr, Hf and M' = Mo, Zr, Hf; M ≠ M').

Manipulation of electrochemical properties of MXene electrodes for supercapacitor applications by chemical and magnetic disorder.

The potential of two-dimensional MXenes as electrodes in supercapacitor applications has been studied extensively. However, the role of chemical and magnetic disorder in their electrochemical parameters, , capacitance, has not been explored yet. In this work, we have systematically addressed this for VMnCO MXene solid solutions with an analysis based upon the results from first-principles electronic structure calculations.

Two-dimensional bismuth oxyselenide quantum dots as nanosensors for selective metal ion detection over a wide dynamic range: sensing mechanism and selectivity.

Bismuth oxyselenide (BiOSe) nanosheets, a new 2D non-van der Waals nanomaterial having unique semiconducting properties, could be favorable for various sensing applications. In the present report, a top-down chemical approach was adopted to synthesize ultrathin BiOSe quantum dots (QDs) in an appropriate solution. The as-prepared 2D BiOSe QDs with an average size of ∼3 nm, exhibiting strong visible fluorescence, were utilized for heavy-metal ion detection with high selectivity.

Experimental and theoretical study of europium-doped organometal halide perovskite nanoplatelets for UV photodetection with high responsivity and fast response.

Herein, we investigate the role of Eu doping on CHNHPbBr nanoplatelets (NPLs) in terms of their optoelectronic properties and photodetection application through a combined experimental and theoretical approach. The introduction of EuCl in the CHNHPbBr crystal structure by a facile solvothermal method enabled the tuning of the lateral and vertical dimensions of the NSs to form large-area NPLs and finally monolayer nanocrystals. The appearance of low-angle diffraction peaks with Eu doping, which are observed in layered perovskite structures, confirms the formation of quasi-2D NPLs.

Understanding the interfacial charge transfer in the CVD grown BiOSe/CsPbBr nanocrystal heterostructure and its exploitation in superior photodetection: experiment theory.

Efficient charge transfer in a 2D semiconductor heterostructure plays a crucial role in high-performance photodetectors and energy harvesting devices. Non-van der Waals 2D BiOSe has enormous potential for high-performance optoelectronics, though very little is known about the interfacial charge transport at the corresponding 2D heterojunction. Herein, we report a combined experimental and theoretical investigation of interfacial charge transfer in the BiOSe/CsPbBr heterostructure through various microscopic and spectroscopic tools corroborated with density functional theory calculations.

Tailoring the electronic structure and magnetic properties of pyrochlore CoTiGeO: a GGA +study.

We report the electronic structure and magnetic properties of CoTiGeO(0 ⩽⩽ 1) spinel by means of the first-principle methods of density functional theory involving generalized gradient approximation along with the on-site Coulomb interaction () in the exchange-correlation energy functional. Special emphasis has been given to explore the site occupancy of Ge atoms in the spinel lattice by introducing the cationic disorder parameter () which is done in such a way that one can tailor the pyrochlore geometry and determine the electronic/magnetic structure quantitatively. For all the compositions (), the system exhibits weak tetragonal distortion (/≠ 1) due to the non-degeneratedz2anddx2-y2states (orbitals) of the B-site Co.

Site occupancy, composition and magnetic structure dependencies of martensitic transformation in MnNi Sn.

A delicate balance between various factors such as site occupancy, composition and magnetic ordering seems to affect the stability of the martensitic phase in [Formula: see text] [Formula: see text] [Formula: see text]. Using first-principles DFT calculations, we explore the impacts of each one of these factors on the martensitic stability of this system. Our results on total energies, magnetic moments and electronic structures upon changes in the composition, the magnetic configurations and the site occupancies show that the occupancies at the 4d sites in the inverse Heusler crystal structure play the most crucial role.

New quaternary half-metallic ferromagnets with large Curie temperatures.

New magnetic materials with high Curie temperatures for spintronic applications are perpetually sought for. In this paper, we present an ab initio study of the structural, electronic and magnetic properties of Quaternary Heusler compounds CoX'Y'Si where X' is a transition metal with 4d electrons and Y' is either Fe or Mn. We find five new half-metallic ferromagnets with spin polarisation nearly 100% with very high Curie temperatures.

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr Mn )O.

Cation disorder over different crystallographic sites in spinel oxides is known to affect their properties. Recent experiments on Mn doped multiferroic [Formula: see text] indicate that a possible distribution of Mn atoms among tetrahedrally and octahedrally coordinated sites in the spinel lattice give rise to different variations in the structural parameters and saturation magnetisations in different concentration regimes of Mn atoms substituting the Cr. A composition dependent magnetic compensation behaviour points to the role conversions of the magnetic constituents.

Systematic analysis of structural and magnetic properties of spinel CoB2O4 (B = Cr, Mn and Fe) compounds from their electronic structures.

The structural and magnetic properties of spinel compounds CoB2O4 (B  =  Cr, Mn and Fe) are studied using the DFT+U method and generalized gradient approximation. We concentrate on understanding the trends in the properties of these materials as the B cation changes, in terms of relative strengths of crystal fields and exchange fields through an analysis of their electronic densities of states. We find that the electron-electron correlation plays a significant role in obtaining the correct structural and electronic ground states.

First-principles study of the lattice instabilities in Mn2NiX (X = Al, Ga, In, Sn) magnetic shape memory alloys.

Using first-principles based density functional theory, we have investigated the structural instabilities in the austenite phases of Mn(2)NiX (X = Al, Ga, In, Sn) magnetic shape memory alloys. A complete softening is observed in the acoustic TA(2) branches for all the materials along [ξξ0] directions leading to instability in the austenite structure which effectively stabilizes into martensitic structure. The reasons behind this softening are traced back to the repulsion from the optical T(2g) branches and to the nesting features in the Fermi surfaces.

Magnetic properties of Mn2NiSn shape memory alloy.

In this paper, we present the magnetic properties of the inverse Heusler Mn2NiSn alloy computed by ab initio density functional theory (DFT) calculations in order to understand the large magnetic moments observed in experiments in contrast to smaller values obtained in previous ab initio calculations. Our results show that the magnetization in this system is quite sensitive to volume and atomic ordering in the sublattices. The observed variations in the magnetizations are explained from the features in the electronic structures of the Mn d-bands.

First-principles computation of structural, elastic and magnetic properties of Ni2FeGa across the martensitic transformation.

The structural stabilities, elastic, electronic and magnetic properties of the Heusler-type shape memory alloy Ni(2)FeGa are calculated using density functional theory. The volume conserving tetragonal distortion of the austenite Ni(2)FeGa find an energy minimum at c/a = 1.33.

Ab initio study of the phonon spectrum, entropy and lattice heat capacity of disordered Re-W alloys.

The Re(1-x)W(x) alloy is formed by continuous neutron bombardment of W, the core material making up the shield in fusion devices. Here, we present an ab initio study of the lattice dynamical properties of this commercially important alloy. The dynamical (force constant) matrix was obtained through a first-principles, density functional perturbation theory.

A new first principles approach to calculate phonon spectra of disordered alloys.

The lattice dynamics in substitutional disordered alloys with constituents having large size differences is driven by strong disorder in masses, inter-atomic force constants and local environments. In this paper, a new first principles approach based on special quasirandom structures and an itinerant coherent potential approximation to compute the phonon spectra of such alloys is proposed and applied to Ni₀.₅Pt₀.

First-principles prediction of shape memory behavior and ferrimagnetism in Mn2NiSn.

Using first-principles density functional theory, we show that, in Mn(2)NiSn, an energy lowering phase transition from the cubic to tetragonal phase occurs which indicates a martensitic phase transition. This structural phase transition is nearly volume-conserving, implying that this alloy can exhibit shape memory behavior. The magnetic ground state is a ferrimagnetic one with antiparallel Mn spin moments.

Complex magnetic interactions in off-stoichiometric NiMnGa alloys.

Using first-principles density functional theory, the magnetic pair interactions between various pairs of chemical specie have been calculated and the trends in magnetism with varying compositions and chemical ordering are analyzed for three off-stoichiometric NiMnGa alloys in their austenite phases. The experimentally observed trend of decreasing magnetization with increasing Mn concentration is attributed to the antiferromagnetic interactions among Mn atoms occupying sublattices other than the original Mn one. The role of chemical ordering on magnetization is also analyzed by total energy results and exchange interactions.

Phonon spectra of Pd(x)Fe(1-x) alloys with transferable force constants.

The transferable force constant model of van de Walle et al (2002 Rev. Mod. Phys.

The phonon spectra and elastic constants of Pd(x)Fe(1-x): an understanding from inter-atomic interactions.

Understanding the role of the inter-atomic force constants in lattice dynamics of random binary alloys is a challenging problem. Addressing these inter-atomic interactions accurately is a necessity to obtain an accurate phonon spectrum and to calculate properties from them. Using a combination of ab initio density functional perturbation theory (DFPT) and the itinerant coherent potential approximation (ICPA), an analytic, self-consistent method for performing configuration averaging in random alloys, we model the inter-atomic force constants for Pd(0.

Ab initio calculation of lattice dynamics in FePd intermetallics.

The lattice dynamics of FePd and FePd(3) intermetallics have been investigated using an ab initio electronic structure method. The phonon dispersions and the contribution of each of the components to each branch of dispersion for three symmetry directions, along with the phonon densities of states, are calculated and compared with experiments. The force constants between various pairs of atoms in these intermetallics are obtained from first-principles calculations and the results are discussed based upon analysis of these data.