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The structural property, electronic structure and optical properties of lead-based halide perovskites CsPbF3-yIy (y = 0, 1, 2) are investigated. The computed electronic structure profile of CsPbF3-yIy (y = 0, 1, 2) reveals that these materials exhibit semiconducting behavior at normal pressure. The energy gap of CsPbF3 is tuned by substituting iodine atoms for fluorine atoms. The optical parameters, such as dielectric function, electron energy loss function, refractive index and reflectivity, are computed. The optical properties of these lead-based halide perovskites against the incident photon energy radiation indicate that these materials can be effective candidates for the solar cell applications. [ABSTRACT FROM AUTHOR]

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 halide perovskites are attractive for solar cells due to their excellent power conversion efficiency and low cost. The structural properties of Sn-based halide perovskites CsSnI3−y Fy (y = 0, 1, 2, 3) are investigated using first-principles calculation based on density functional theory. The computed electronic structure profile reveals that these materials exhibit semiconducting behavior. The energy gap value of CsSnI3 is tuned by substituting fluorine atom for iodine atom. It is observed that when the halogen atom fluorine is substituted for iodine atom in CsSnI3, the energy gap values are changed. As the pressure is increased, the energy gap value of these materials decreases and at high pressure, a semiconductor to metallic transition is observed. The optical properties of these Sn-based compounds indicate that these materials may be the effective candidates for the solar cell applications. [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 structural, elastic, magnetic and electronic properties of titanium-based alloys Ti 2 XIn (X = Fe , Co and Ni) are investigated by the first-principles calculations based on density functional theory using the Vienna ab-initio simulation code. The lattice constants of Ti 2 XIn (X = Fe , Co and Ni) alloys are optimized for the two possible structures such as Cu 2 MnAl and Hg 2 CuTi. It is found that at ambient pressure Ti 2 XIn (X = Fe , Co and Ni) alloys are stable in Hg 2 CuTi -type crystal structure. The total magnetic moments (M t ) and the energy gap (E g ) of Ti 2 XIn (X = Fe , Co and Ni) alloys are calculated for various pressures. The total magnetic moments of Ti 2 XIn (X = Fe , Co and Ni) alloys in Hg 2 CuTi structure follow the rule μ t = Z t − 1 8 and agree with the Slater–Pauling (SP) curve quite well. In both structures ( Cu 2 MnAl and Hg 2 CuTi) , the calculated magnetic moment of Ti 2 XIn (X = Fe , Co and Ni) alloys decreases with increase in pressure. Density of states shows the metallic nature of Ti 2 XIn (X = Fe , Co and Ni) alloys in Cu 2 MnAl structure and half-metallic (HM) behavior in Hg 2 CuTi structure, i.e., majority spin channel is strongly metallic and the minority spin maintains the gap at the Fermi level at the equilibrium lattice constant. [ABSTRACT FROM AUTHOR]

Lead-based halide perovskites are attractive substrates for solar cells because of their excellent power conversion efficiency and low cost. The ground-state properties, electronic structure, as well as optical and phonon properties of lead-based halide perovskites (CsPbCl3−yIy (y = 0, 1, 2, 3) are investigated by first-principles calculations based on density functional theory. Their electronic structure indicates that CsPbCl3−y Iy (y = 0, 1, 2, 3) compounds exhibit semiconducting behaviour at normal pressure. The energy gap of CsPbCl3 can be tuned by substituting iodine atoms for chlorine atoms. The energy gap values are found to be 3.06, 2.681, 2.330, and 2.030 eV using HSE06 calculations for CsPbCl3, CsPbCl2I, CsPbClI2, and CsPbI3, respectively. Also, it is found that the energy gap values of these materials decrease with increase in pressure and that a semiconductor-to-metallic phase transition is observed at high pressure. The optical properties of these Pb-based compounds are analysed. The dynamical stability of these perovskites is analysed by their phonon dispersion curves. [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 structural, elastic, magnetic and electronic properties of titanium-based alloys TiX2 (X = Cr, Mn) are investigated by the first-principles calculations based on density functional theory using the Vienna ab-initio simulation code. The lattice constants of TiX2 (X = Cr, Mn) alloys are optimized for various possible structures such as hexagonal, tetragonal and orthorhombic. TiX2 (X = Cr, Mn) alloys are highly stable in hexagonal structure with the space group P63/mmc at ambient pressure. A pressure-induced structural phase transition from hexagonal structure to the tetragonal structure is observed in TiCr2 at 443.3 GPa and in TiMn2 hexagonal structure to orthorhombic structure is at 295.05 GPa. The electronic structure shows that TiX2 (X = Cr, Mn) alloys are metallic in nature at all pressures. The magnetic property of nonmagnetic TiX2 (X = Cr, Mn) alloys are analyzed by doping with ferromagnetic materials (Fe, Co and Ni) using the stoichiometries of TiX 2 − z Y z (X = Cr, Mn; Y = Fe, Co and Ni; z = 0.5,1,1.5). It is seen that the magnetic moment is induced by the substitution of ferromagnetic materials with TiX2 alloys. [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]

The halide perovskites-based solar cells have been attractive due to their excellent power conversion efficiency and low cost. The structural, electronic and optical properties of Sn-based cesium halide perovskites CsSnI 3 − y Br y (y = 0, 1, 2, 3) are investigated based on density functional theory. The computed electronic structure profile of CsSnI 3 − y Br y (y = 0, 1, 2, 3) reveals that these materials exhibit semiconducting behavior at normal pressure. The energy gap of CsSnI3 is tuned by the substitution of bromine atom for iodine atom. Also, it is found that the energy gap values of these materials decrease with increase in pressure and a semiconductor to metallic phase transition is observed at high pressure. The optical properties of these Sn-based halide perovskite compounds against the incident photon energy radiation indicate that these materials can be effective candidates for solar cell applications. The dynamical stability of these perovskites is analyzed by phonon dispersion curve. [ABSTRACT FROM AUTHOR]

Halide perovskite-based solar cells are attractive due to their excellent power conversion efficiency and low cost. Sn-based halide perovskites CsSnI3−yCly (y = 0, 1, 2, 3) are investigated in this work using first-principles calculations based on density functional theory. The computed electronic structure profile reveals that these materials exhibit semiconducting behavior. The energy gap value of CsSnI3 is tuned by substituting Cl atom for iodine atom. As the pressure is increased, the energy gap value of these materials decreases, and a semiconductor to metallic transition is observed at high pressure. The optical properties of these Sn-based compounds, including the real and imaginary parts of the dielectric function, electron energy loss function, refractive index, and reflectivity, are computed. The dynamical stability of these perovskites is analyzed based on the phonon dispersion curve. [ABSTRACT FROM AUTHOR]

The search for emerging materials with ferromagnetic and spin flip properties has attracted widespread interest in material science. Ni based half Heusler alloys have been one of the benchmark half metallic ferromagnetic material owing to their magnetic interaction and promising figure of merit in magnetic memory element. A systematic pathway to design novel Heusler materials is by analyzing structural phase stability, electronic structure, mechanical and magnetic properties. Specifically, we carried out first principles calculations to identify the ferromagnetic and half-metallic properties of Ni based half Heusler alloys XYZ (X = Ni; Y = Cr; Z = Si, Ge, Ga, Al, In, As). The predicted phase stability shows that α-phase is found to be the lowest energy phase compared with β and γ phases. A pressure-induced structural phase transitions from α-phase to γ-phase in NiCrSi, NiCrGe, NiCrGa, NiCrAl, NiCrIn and α-phase to β-phase in NiCrAs are found. Due to the presence of d 8 and d 5 electronic configuration within Ni 2+ and Cr 2+ ions respectively, all the Heusler materials show half metallic behavior. Furthermore, the magnetic moments for these half Heusler alloys in all the three different phases (α, β and γ) have been reported. Our work paves the way for designing novel Heusler materials at normal and high pressure. [ABSTRACT FROM AUTHOR]

The structural, elastic, magnetic and electronic properties of titanium-based ferromagnetic (FM) Ti X ( X = Fe, Co, Ni) alloys are investigated by the first principles calculations based on density functional theory using the Vienna ab initio simulation code. At ambient pressure, all the three alloys TiFe, TiCo and TiNi are highly stable in CsCl structure. The calculated lattice parameters and ground state properties are in good agreement with the available theoretical and experimental results. The density of states explains that these alloys possess the metallic nature at normal and high pressures. A pressure-induced structural phase transitions from CsCl to NaCl phase at 46 GPa and NaCl to ZB phase at 49 GPa in TiFe, CsCl to ZB phase in TiCo at 52 GPa, CsCl to hexagonal phase at 22 GPa and hexagonal to ZB phase at 66 GPa in TiNi are observed. The calculated Debye temperatures of Ti X ( X = Fe, Co, Ni) alloys are in good agreement with earlier reports. Binding energy shows that the TiCo is the most stable alloy. The magnetic property of Ti X ( X = Fe, Co, Ni) alloys reveals that TiFe is stable in nonmagnetic phase and the other two alloys, TiCo and TiNi, are stable in FM phase at normal pressure. [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 search for stable half-metallic ferromagnetic materials remains a high priority in condensed matter Physics. Ab initio calculations are performed using density functional theory to analyze the structural phase stability, electronic structure, mechanical and magnetic properties of Mn based half Heusler alloys XYZ (X = Ir, Pt, Au; Y = Mn; Z = Sn, Sb) for three different phases namely α, β and γ phases of C1 b crystal structure. This work aims to identify the ferromagnetic and half-metallic behavior of XYZ (X = Ir, Pt, Au; Y = Mn; Z = Sn, Sb) half Heusler alloys. To accomplish this, density functional theory (DFT) with generalized gradient approximation formulated by Perdew, Burke and Ernzerhof (GGA-PBE) and the Hubbard formalism (GGA-PBE + U) are used to describe the strong correlations present in these alloys. Among the considered phases, α-phase is found to be the lowest energy phase for IrMnSn, IrMnSb, PtMnSn, PtMnSb, AuMnSn and AuMnSb at normal pressure. A pressure-induced structural phase transition is observed in IrMnSn, IrMnSb, PtMnSn, PtMnSb, AuMnSn and AuMnSb at the pressures of 62.1 GPa, 47.8 GPa, 26.1 GPa, 25.3 GPa, 23.7 GPa and 14.0 GPa respectively. The electronic structure reveals that these materials are metals at normal pressure whereas half metals at high pressure. The magnetic moments for these half Heusler alloys in all the three different phases (α, β and γ) are estimated. [ABSTRACT FROM AUTHOR]

The structural stabilities of cobalt mononitride (CoN) and nickel mono-nitride (NiN) were investigated among the crystal structures, namely, NaCl (B1), CsCl (B2), and zinc blende (B3). It was found that the zinc blende (B3) phase was the most stable phase for both nitrides. A pressure-induced structural phase transition from B3 to B1 phase was predicted in these nitrides. The computed lattice parameter values were in agreement with the experimental values and other theoretical values. The electronic structures reveal that these nitrides are metallic at zero pressure. The computed elastic constants indicate that CoN and NiN are mechanically stable in the B1 and B3 phases. The variations of the elastic constants, bulk modulus, shear modulus, Poisson's ratio, and elastic anisotropy factor with pressure were investigated. The Debye temperature θD values are reported for both the nitrides in their B1 and B3 phases. The high-pressure NaCl phase of both CoN and NiN were found to be ferromagnetic. [ABSTRACT FROM AUTHOR]

The structural stability of Alkali metal hydrides AMH 4 (A=Li, Na; M=B, Al) is analyzed among the various crystal structures, namely hexagonal (P6 3 mc), tetragonal (P4 2 /nmc), tetragonal (P-42 1 c), tetragonal (I4 1 /a), orthorhombic (Pnma) and monoclinic (P2 1 /c). It is observed that, orthorhombic (Pnma) phase is the most stable structure for LiBH 4 , monoclinic (P2 1 /c) for LiAlH 4 , tetragonal (P4 2 /nmc) for NaBH 4 and tetragonal (I4 1 /a) for NaAlH 4 at normal pressure. Pressure induced structural phase transitions are observed in LiBH 4 , LiAlH 4 , NaBH 4 and NaAlH 4 at the pressures of 4 GPa, 36.1 GPa, 26.5 GPa and 46 GPa respectively. The electronic structure reveals that these metal hydrides are wide band gap insulators. The calculated elastic constants indicate that these metal hydrides are mechanically stable at normal pressure. [ABSTRACT FROM AUTHOR]

The structural, electronic, elastic and magnetic properties of gadolinium and its hydrides GdH x ( x =1, 2, 3) are investigated by using Vienna ab-initio simulation package with the generalized gradient approximation parameterized by Perdew, Burke and Ernzerhof (GGA-PBE) plus a Hubbard parameter (GGA-PBE+ U ) in order to include the strong Coulomb correlation between localized Gd 4f electrons. At ambient pressure all the hydrides are stable in the ferromagnetic state. The calculated lattice parameters are in good agreement with the experimental results. The bulk modulus is found to decrease with the increase in the hydrogen content for the gadolinium hydrides. A pressure-induced structural phase transition is predicted to occur from cubic to hexagonal phase in GdH and GdH 2 and from hexagonal to cubic phase in GdH 3 . The electronic structure reveals that mono and di-hydrides are metallic, whereas trihydride is half-metallic at normal pressure. On further increasing the pressure, a half-metallic to metallic transition is also observed in GdH 3 . The calculated magnetic moment values of GdH x ( x =1, 2, 3) are in accord with the experimental values. [ABSTRACT FROM AUTHOR]

The crystal structure, structural stability, electronic and mechanical properties of ReN and TcN are investigated using first principles calculations. We have considered five different crystal structures: NaCl, zinc blende (ZB), NiAs, tungsten carbide (WC) and wurtzite (WZ). Among these ZB phase is found to be the lowest energy phase for ReN and TcN at normal pressure. Pressure induced structural phase transitions from ZB to WZ phase at 214 GPa in ReN and ZB to NiAs phase at 171 GPa in TcN are predicted. The electronic structure reveals that both ReN and TcN are metallic in nature. The computed elastic constants indicate that both the nitrides are mechanically stable. As ReN in NiAs phase has high bulk and shear moduli and low Poisson's ratio, it is found to be a potential ultra incompressible super hard material. [ABSTRACT FROM AUTHOR]

First principles calculations are performed to investigate the structural stability, electronic and mechanical properties of ZnN and CdN for various structures: NaCl, CsCl, zinc blende, and NiAs. The local density and generalized gradient approximations are used for exchange and correlation effects. Our calculations indicate that zinc blende (ZB) phase is the lowest energy phase for ZnN while it is the NaCl phase for CdN at normal pressure. A pressure induced structural phase transition from zinc blende to NiAs phase is predicted in ZnN, whereas NaCl to zinc blende phase and then zinc blende to NiAs phase is observed in CdN. The ground state properties like lattice parameters, bulk modulus and cohesive energy are calculated. Electronic structure reveals that both ZnN and CdN are metallic. The computed elastic constants show that these nitrides are mechanically stable in their most stable phase. The shear modulus, Young’s modulus, Poisson’s ratio and Debye temperature are also calculated. The low bulk modulus value indicates that ZnN and CdN are more compressible compared to other transition metal nitrides. [ABSTRACT FROM AUTHOR]

The structural stability, electronic structure, elastic and superconducting properties of noble metal nitrides MN 2 (M = Ru, Rh, Pd) are investigated in tetragonal (P4/ mbm ), fluorite (Fm3m), orthorhombic ( Pnnm ), pyrite ( Pa-3 ) and hexagonal (P6/ mmm ) phases using first principles calculations. The calculated lattice parameters are in good agreement with other theoretical results. Among the considered structures, RhN 2 and PdN 2 are found to be most stable in tetragonal structure, whereas RuN 2 is stable in fluorite structure. A sequence of structural phase transition is predicted under high pressure in these metal nitrides. The electronic structure reveals that these nitrides are metallic. These metal nitrides are found to be covalent, ionic and metallic in the stable phase. The observations show that these metal nitrides are mechanically stable at ambient condition. The superconducting transition temperatures for RuN 2 , RhN 2 and PdN 2 are found to be 1.65 K, 5.01 K and 8.7 K respectively. [ABSTRACT FROM AUTHOR]

The structural stability, electronic structure and mechanical properties of platinum group metal nitrides PGMN (PGM = Os, Ir, Pt) are investigated using the first principles calculation. The structural stability is analyzed among six different crystal structures namely, NaCl, CsCl, zinc blende, NiAs, WC and wurtzite structures. The zinc blende structure is found to be the most stable one for all the three nitrides at normal pressure. A structural phase transition from zinc blende to the NiAs structure is predicted at the pressures of 71 GPa, 41 GPa and 24 GPa for OsN, IrN and PtN respectively. The electronic structure reveals that these nitrides are metallic. The high bulk modulus values of OsN, IrN and PtN indicate that these metal nitrides are super hard materials. Moreover, a positive value of calculated Cauchy pressure and a high B/G value predict that these materials are ductile in nature. The Debye temperature values are also reported for these nitrides. [ABSTRACT FROM AUTHOR]

Ab initio calculations are performed to investigate the structural stability, electronic structure and elastic properties of noble metal sub-nitrides M2N (M = Ru, Rh, Pd). The metal nitrides, Ru2N and Rh2N are found to be stable in anti-fluorite structure, whereas Pd2N is stable in tetragonal structure. In Ru2N and Rh2N, structural phase transition is predicted from antifluorite to orthorhombic phase whereas tetragonal to antifluorite and then antifluorite to pyrite phase transitions are predicted in Pd2N under high pressure. The electronic structure reveals that these nitrides are metallic. The calculated elastic constants indicate that these materials are mechanically stable at ambient condition. The Debye temperature values are reported for all the phases of these nitrides. The high bulk modulus indicates that these materials are super hard materials. They are ductile in nature at normal and high pressures. The bonding nature of these materials is found to be a mixture of covalent, metallic and ionic attribution at ambient condition. [ABSTRACT FROM AUTHOR]

Abstract: Ab initio calculations are performed to investigate the structural stability, electronic, structural and mechanical properties of 4d transition metal nitrides TMN (TM=Ru, Rh, Pd) for five different crystal structures, namely NaCl, CsCl, zinc blende, NiAs and wurtzite. Among the considered structures, zinc blende structure is found to be the most stable one among all three nitrides at normal pressure. A structural phase transition from ZB to NiAs phase is predicted at a pressure of 104GPa, 50.5GPa and 56GPa for RuN, RhN and PdN respectively. The electronic structure reveals that these nitrides are metallic. The calculated elastic constants indicate that these nitrides are mechanically stable at ambient condition. [Copyright &y& Elsevier]

A theoretical investigation of the structural, electronic and elastic properties of the transition metal monoxides Zinc monoxide (ZnO) and Cadmium monoxide (CdO) in the cubic B1 (rock-salt) B2 (CsCl) and B3 (zinc blende) phases are performed using the first-principles calculations. The optimized lattice parameters and their bulk modulus values are found to be in accord with the available experimental and other theoretical values. To understand the electronic properties of ZnO and CdO, their electronic band structures are analyzed. A pressure induced structural phase transition occurs from B3 to B1 at a pressure of 11.2 GPa and from B1 to B2 at even higher pressure of 243.3 GPa occurs in ZnO; whereas the transition is from B1 to B2 phase at a pressure of 88.5 GPa in CdO. The elastic constants are computed to investigate the mechanical stability at normal and elevated pressures. The pressure dependence of the various moduli, Poisson's ratio, anisotropy and the hardness of ZnO and CdO are also analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The structural, electronic, elastic and magnetic properties of three rare earth nitrides (RENs: RE=Gd, Dy, Ho) are investigated by first principles calculation using Vienna ab-initio simulation code (VASP). At ambient pressure all the three nitrides are stable in the ferromagnetic state (FM) with cubic NaCl(B1) structure. The calculated lattice parameters are in good agreement with experimental and other theoretical values. Electronic structure reveals that these materials are half metallic ferromagnets at normal pressure. A pressure induced structural phase transition from NaCl to wurtzite phase in GdN at 18.2GPa and from NaCl to CsCl phase in DyN at 104GPa and HoN at 138GPa is also predicted. The half metallicity has been retained in GdN, DyN and HoN even after the phase transition but it vanishes at 73.18GPa, 118GPa and 141GPa respectively. Ferromagnetism is quenched in all the three nitrides at a pressure of 252GPa (GdN), 242GPa (DyN) and 236.7GPa (HoN). [Copyright &y& Elsevier]

Highlights: [•] Electronic, structural and elastic properties of group IB nitrides are investigated. [•] A pressure induced structural phase transition is predicted under high pressure. [•] Electronic structure reveals that these materials exhibit metallic behavior. [•] Computed elastic moduli obey traditional mechanical stability condition. [•] The Debye temperature values are computed for Group IB metal mono and di-nitrides. [ABSTRACT FROM AUTHOR]

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]

Abstract: The electronic, structural, mechanical and superconducting properties of group VB mononitrides are investigated by means of first principles calculation based on density functional theory with generalized gradient approximation. The calculated ground state properties are in good agreement with previous experimental and theoretical results. Among the three crystallographic structures that have been investigated, the hexagonal WC phase is found to more stable than the cubic ones. Under high pressure, a series of structural phase transition from WC → NaCl → CsCl phase is also predicted in VN, NbN and TaN. The calculated elastic constants indicate that all the three nitrides are mechanically stable at ambient pressure. The estimated Zener ratio and linear compressibility coefficients K c /K a reveals that these materials exhibit elastic anisotropy. The estimated superconducting transition temperature (T c ) values as a function of pressure for VN, NbN and TaN are 35.5, 37.5 and 30.5 K respectively. [Copyright &y& Elsevier]

First principles calculations are performed by using Vienna ab initio simulation package within the framework of density functional theory to understand the electronic and structural properties of yttrium, zirconium and niobium hydrides. The equilibrium lattice constant, the bulk modulus, the total density of states and charge density distribution are analyzed in comparison with the available experimental and theoretical data. The X-ray diffraction pattern is also simulated to estimate the lattice constants of these hydrides. The formation energies are computed for rock-salt and fluorite structures using density functional theory. The calculated elastic constants obey the necessary stability conditions. A detailed analysis of the changes in density of states and electron density upon hydride formation has allowed us to understand the formation of these hydrides. [ABSTRACT FROM AUTHOR]

Abstract: The structural, elastic, and electronic properties of molybdenum nitride are investigated by first principles calculation with density functional theory. The obtained hexagonal WC structure is energetically the most stable structure at an ambient pressure. A pressure induced structural phase transition from hexagonal WC to cubic NaCl structure is predicted. The estimated superconducting transition temperature (T c ) of molybdenum nitride is 14.0037K. As pressure increases the superconducting transition temperature also increases. [Copyright &y& Elsevier]

Abstract: First-principles calculation was performed using tight-binding LMTO method with local density approximation (LDA) and atomic sphere approximation (ASA) to understand the electronic properties of rhenium nitride. The equilibrium geometries, the electronic band structure, the total and partial DOS are obtained under various pressures and are analyzed in comparison with the available experimental data. The most stable structure of ReN is NiAs like structure. Our results indicate that ReN can be used as a super-hard conductor. We estimated the average electron–phonon coupling constant to be 1.65 and superconducting transition temperature (T c) is 5.1K. The T c value increases with the increase in pressure. [Copyright &y& Elsevier]

Abstract: First principles calculation was performed using tight-binding LMTO method with local density approximation (LDA) and atomic sphere approximation (ASA) to understand the electronic properties of chromium nitride. The equilibrium geometries, the magnetic moment, the electronic band structure, the total and partial DOS are obtained under various pressures and are analyzed in comparison with the available experimental data. The most stable structure of CrN is NaCl structure in the FM state. A pressure-induced second order magnetic phase transition from ferromagnetic (FM) to non-magnetic (NM) at very high pressure of 0.5549Mbar is predicted. Our results indicate that CrN can be used as a hydrogen storage material. [Copyright &y& Elsevier]

• Structural properties of lead based cesium halide perovskites CsPbBr 3−y I y (y = 0, 1, 2, 3) are investigated. • These perovskites exhibit semiconducting behavior at normal pressure. • Semiconductor to metallic phase transition is observed at high pressure. • The optical properties of these Pb-based halide perovskite compounds are computed. The halide perovskites based solar cells have been attractive due to their excellent power conversion efficiency and low cost. The structural properties of lead based cesium halide perovskites CsPbBr 3−y I y (y = 0, 1, 2, 3) are investigated using first principles calculations based on density functional theory. The computed electronic structure profile of CsPbBr 3−y I y (y = 0, 1, 2, 3) reveals that these materials exhibit semiconducting behavior at normal pressure. The energy gap of CsPbBr 3 is tuned by the substitution of iodine atom for bromine atom in CsPbBr 3. Also, it is found that the energy gap values of these materials decrease with increase in pressure and a semiconductor to metallic phase transition is observed at high pressure. The optical properties of these Pb-based halide perovskite compounds against the incident photon energy radiation indicate that these materials can be the effective candidates for the solar cell applications. [ABSTRACT FROM AUTHOR]