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The properties such as structural, mechanical, electronic structure, magnetic, optical and transport properties of the half-Heusler alloys of Rhodium RhFeZ(Z = P, As, Sb, Sn, Si, Ge, Ga, In, Al) are investigated at normal pressure. The alloys RhFeSb, RhFeSn, RhFeGe, RhFeGa, RhFeIn and RhFeAl are more stable in γ-phase. But the alloys RhFeP, RhFeAs and RhFeSi exhibit stability in β-phase under normal pressure. Among the investigated alloys, RhFeSn and RhFeGe are half-metallic at normal pressure. All the other half-Heusler alloys, RhFeP, RhFeAs, RhFeSb, RhFeSi, RhFeGa, RhFeIn and RhFeAl are ferromagnetic at normal pressure. To understand the transport properties, Seebeck coefficients, electrical conductivity, thermal conductivity and power factor are examined. The investigation infers that the alloys RhFeSn and RhFeGe possess remarkable transport properties and find potential applications in thermoelectric devices. [ABSTRACT FROM AUTHOR]

The structural, electronic, mechanical and magnetic properties of Fe2-xCoxTiSn (x = 0, 0.5, 1, 1.5, 2) Heusler alloys in L21 (Cu2MnAl prototype) and XA (Hg2CuTi) phases are analysed. The structural optimization confirms the stability of these alloys in L21 phase. As the pressure is increased, the structural phase transition from L21 to XA phase is predicted at the pressures of 123.34, 74.27, 47.22, 43.18 and 31.25 GPa in Fe2TiSn, Fe1.5Co0.5TiSn, Fe1.0Co1.0TiSn, Fe0.5Co1.5TiSn and Co2TiSn, respectively. Fe2TiSn is identified as a non-magnetic semiconductor using electronic structure calculation. The effect of substitution of Co for Fe on electronic structure and magnetic property of Fe2TiSn is investigated. It is found that Co substituted Fe1.5Co0.5TiSn, Fe1.0Co1.0TiSn and Fe0.5Co1.5TiSn are found to be half-metallic ferromagnetic Heusler alloys. The elastic constants are calculated to ensure mechanical stability. This study opens a way out for the potential application of these alloys as spintronic materials. [ABSTRACT FROM AUTHOR]

The half-metallic and ferromagnetic properties of Co2TiZ (Z = Al, Ga, In) Heusler alloys are investigated. The structural stability is analyzed among the two possible structures, namely, L21 (Cu2MnAl phase) and XA (Hg2CuTi phase) structures. It is found that these alloys are stable in L21 (Cu2MnAl phase) structure. The electronic structure of Co2TiZ reveals that these alloys exhibit half-metallic ferromagnetism with small spin-flip gap at the minority spin state. As the pressure is increased, ferromagnetic to non-magnetic phase transition is observed at the pressures of 380.9, 363.0 and 317.8 GPa for Co2TiAl, Co2TiGa and Co2TiIn, respectively. Half-metallic to metallic phase transition occurs in Co2TiAl, Co2TiGa and Co2TiIn at the pressures of 76.5 GPa, 73.1 GPa and 63.9 GPa respectively. [ABSTRACT FROM AUTHOR]

The electronic structure of silicon carbide with increasing germanium content have been examined using first principles calculations based on density functional theory. The structural stability is analysed between two different phases, namely, cubic zinc blende and hexagonal phases. The zinc blende structure is found to be the stable one for all the Si1-xGexC semiconducting carbides at normal pressure. Effect of substitution of Ge for Si in SiC on electronic and mechanical properties is studied. It is observed that cubic SiC is a semiconductor with the band gap value 1.243 eV. The band gap value of SiC is increased due to the substitution of Ge and the band gap values of Si 0.75 Ge 0.25 C, Si 0.50 Ge 0.50 C, Si 0.25 Ge 0.75 C and GeC are 1.322 eV, 1.413 eV, 1.574 eV and 1.657 eV respectively. As the pressure is increased, it is found that the energy gap gets decreased for Si1-x GexC (X = 0, 0.25, 0.50, 0.75, 1). The elastic constants satisfy the Born - Huang elastic stability criteria. The bulk modulus, shear modulus, Young's modulus and Poisson's ratio are also calculated and compared with the other available results. [ABSTRACT FROM AUTHOR]

First-principles calculations based on density functional theory was performed to analyse the structural stability of transition metal carbides TMC (TM = Ru, Rh, Pd, Os, Ir, Pt). It is observed that zinc-blende phase is the most stable one for these carbides. Pressure-induced structural phase transition from zinc blende to NiAs phase is predicted at the pressures of 248.5 GPa, 127 GPa and 142 GPa for OsC, IrC and PtC, respectively. The electronic structure reveals that RuC exhibits a semiconducting behaviour with an energy gap of 0.7056 eV. The high bulk modulus values of these carbides indicate that these metal carbides are super hard materials. The high B/G value predicts that the carbides are ductile in their most stable phase. [ABSTRACT FROM AUTHOR]

The structural stability of chromium nitride (CrN) and manganese nitride (MnN) is investigated among four different structures, namely, NaCl (Fm3m), zinc blende (F4-3m), orthorhombic (Pnma) and tetragonal (I4/mmm). It is found that the most stable phase is the zinc blende phase for CrN and MnN. The structural phase transition from zinc blende to orthorhombic phase is predicted at high pressure. At normal pressure, CrN and MnN are found to be antiferromagnetic. As the pressure is increased, antiferromagnetic-to-nonmagnetic phase transition is observed at the pressures of 169.5 GPa in CrN and 206 GPa in MnN. The elastic constants obey the Born--Huang criteria, suggesting that they are mechanically stable. The calculatedB/Gvalues indicate that CrN and MnN are ductile in nature. [ABSTRACT FROM PUBLISHER]

The high-pressure structural phase transition, electronic, superconducting and elastic properties of group III nitrides (ScN, YN and LaN) are investigated by first principles calculation with the density functional theory. The calculated lattice parameters are in good agreement with the experimental and other theoretical values. Electronic structure reveals that these materials are semiconductors with an indirect band gap of 1.4, 0.87 and 0.65 eV for ScN, YN and LaN, respectively. The obtained cubic NaCl structure is energetically the most stable structure at ambient pressure. A pressure-induced structural phase transition from NaCl to CsCl structure is predicted. The structural phase transition of ScN, YN and LaN occurs at a pressure of 158, 132 and 26.5 GPa, respectively. On further increase in the pressure, semiconductor-to-metallic transition and superconductivity is observed in these nitrides. The estimatedTcvalues as a function of pressure for ScN, YN and LaN are 31.79, 15.50 and 12.84 K, respectively. [ABSTRACT FROM PUBLISHER]