In the present paper, density functional theory (DFT) based firstprinciples methods are applied to investigate the mechanical and bonding properties of the newly synthesized T 2 phase superconductor Ta 5 GeB 2 for the first time. The calculated lattice constants are in reasonable agreement with the experiment. The elastic constants (C ij ), bulk modulus (B), shear modulus (G), Young's modulus (Y), Poisson's ratio (v), Pugh ratio (G/B), and elastic anisotropy factor A of Ta 5 GeB 2 are calculated and used to explore the mechanical behavior of the compound. To give an explanation of the bonding nature of this new ternary tetragonal system, the band structure, density of states, and Mulliken atomic population are investigated. The estimated Debye temperature and Vickers hardness are also used to justify both the mechanical and bonding properties of Ta 5 GeB 2 .

We report the first principles study of structural, elastic, electronic, optical and thermoelectric properties of newly synthesized K 2 Cu 2 GeS 4 . The structural parameters are found to be in good agreement with experimental results. The single crystal elastic constants (C ij ) are calculated and K 2 Cu 2 GeS 4 is found to be mechanical stable. The analysis of polycrystalline elastic constants reveals that the compound is expected to be soft in nature. The values of Pugh and Poisson ratios suggested that the compound lies in the border line of ductile/brittle behavior. The chemical bonding is primarily ionic, the inter-atomic forces are central in nature and the compound is mechanically anisotropic. The computed electronic band profile shows semiconducting characteristics and the estimated band gap is strongly dependent on the functional used representing the exchange correlations. The nature of chemical bonding is explained using electronic charge density mapping. Important optical constants such as dielectric constants, refractive index, absorption coefficient, photoconductivity, reflectivity and loss function are calculated and discussed in detail. Optical conductivity is found to be in good qualitative agreement with the results of band structure calculations. The Seebeck coefficients are positive for the entire temperature range used in this study, suggesting the presence of p-type charge carriers. We have obtained large Seebeck coefficent, 681 V/K at 100 K and 286 V/K at 300 K. At room temperature, the electrical conductivity and electronic thermal conductivity are 1.83×10 18 ms) -1 and 0.5×10 14 W/mK.s, respectively. The dimensionless figure of merit of K 2 Cu 2 GeS 4 is evaluated as ~1.0 at 300 K. This suggests that K 2 Cu 2 GeS 4 is a potential candidate for thermoelectric applications.

For the first time, we have reported in this study an ab initio investigation on elastic properties, Debye temperature, Mulliken population, Vickers hardness, and charge density of the two recently synthesized superconducting ScRhP and ScIrP pnictides. The optimized cell parameters show fair agreement with the experimental results. The mechanical stability of both ternary phosphides is confirmed via the calculated elastic constants. Both compounds are ductile in nature and damage tolerant. ScIrP is expected to be elastically more anisotropic than ScRhP. The estimated value of Debye temperature predicts that ScRhP is thermally more conductive than ScIrP and the phonon frequency in ScRhP is higher than that in ScIrP. Both pnictides are soft and easily machinable due to their low Vickers hardness. Moreover, the hardness of ScRhP is lower due to the presence of antibonding Rh–Rh in ScRhP. The metallic conductivity of ScRhP reduces significantly when Rh is replaced with Ir. The main contribution to the total density of states (TDOS) at Fermi‐level (EF) comes from d‐electrons of Sc and Rh/Ir in both pnictides. These two ternary compounds are characterized mainly by metallic and covalent bonding with little ionic contribution. The calculated superconducting transition temperatures fairly coincide with the reported measured values.

A new series of MAX family designated as 321 phases are recently reported with Nb 3 As 2 C, V 3 As 2 C, Nb 3 P 2 C and Ta 3 P 2 C. Most of physical properties of these new MAX phase compounds are unexplored and the present study aims to investigate their structural, elastic, thermal and lattice dynamic properties. Their mechanical and dynamical stabilities are examined. Though all the phases are elastically anisotropic and brittle in nature, Nb 3 As 2 C is the most anisotropic and Ta 3 P 2 C is the most brittle. V 3 As 2 C compared to Nb 3 As 2 C and Ta 3 P 2 C compared to Nb 3 P 2 C should exhibit superior mechanical properties, as they possess larger elastic constants and moduli. Shear strength, bond covalency as well as the average bond strength and materials' brittleness are predicted to follow the order: Ta 3 P 2 C > Nb 3 P 2 C > V 3 As 2 C > Nb 3 As 2 C. The estimated Debye temperature and lattice thermal conductivity are highest for Nb 3 As 2 C. Lattice dynamical features are investigated in details and the infrared and Raman active modes are identified. High melting temperatures of these compounds are favorable for their potential applications at elevated temperatures.

The performance of a sustainable green concrete with fly ash (FA), rice husk ash (RHA), and stone dust (SD) as a partial replacement of cement and sand was experimentally explored. FA and RHA have a high silica content, are highly pozzolanic in nature and have a high surface area without any treatment. These by-products show filler effects, which enhance concrete’s density. Results showed that the FA and RHA materials have good hydration behaviour and effectively develop strength at an early age of concrete. SD acts as a stress transferring medium within concrete, thereby allowing the concrete to be stronger in compression, and bending. Consequently, water absorption capacity of the sustainable concrete was lower than that of the ordinary one. However, a little reduction in strength was observed after the replacement of the binder and aggregate using the FA, RHA and SD, but the reduction was insignificant. The reinforced structure with sustainable concrete containing the FA, RHA, and SD generally fails in concrete crushing tests initiated by flexural cracking followed by shear cracks. The sustainable concrete could be categorized as a perfect material with no significant conciliation in strength properties and can be applied to design under-reinforced elements for a low-to-moderate service load.