Structural, electronic and optical properties of the wide-gap Zn1-xCdxTe ternary alloys

International audienceThe II-VI compounds CdTe and ZnTe form a complete series of solid solutions with a cubic Zinc Blende structure. The room temperature band gap of these materials can be tuned from 1.5 eV in CdTe to 2.3 eV in ZnTe by controlling the alloy composition. This material is used as the window layer in thin-film solar cells. Using first-principles calculations, we investigated the structural and electronic properties of two binary CdTe and ZnTe for several compositions with various ordered structures (Cu3Au, luzonite) of Zn1-xCdxTe alloys using the theory of order-disorder transformation. An investigation was also conducted using the first-principles total-energy formalism based on the hybrid full potential augmented plane wave plus local orbital (APW + lo) method, within the local-density approximation (LDA) for the exchange and correlation potential. The 3d orbitals of the Zn atoms and 4d orbitals of the Cd atoms were treated as valence bands in every case. We analyzed the effect of alloying a small amount of ZnTe with CdTe; the fundamental direct band gap energy of the alloys was found to decrease per atomic percent of cadmium

Electronic and Thermoelectric Properties of Li-Based Half-Heusler Alloys: A DFT Study

In this paper, we have studied the electronic, elastic and thermoelectric properties of the half-Heusler LiCrZ (Z = C, N, Si, and P) materials in Type II phase, in this structure the atomic occupations are X (1/2,1/2,1/2), Y (0,0,0) and Z(1/4,1/4,1/4). The ferromagnetic state of Type II structure was found to be the most stable phase for all studied alloys. After calculating the elastic constants, we found out that the conditions of mechanical stability were verified only for LiCrSi and LiCrP alloys in Type II phase, at both equilibrium a0 and half metallic ahm lattice constants, which indicates that these two compounds can be synthesized experimentally. We should also mention that the half metallic behavior in Type II structure, for LiCrSi and LiCrP compounds, was obtained by straining the equilibrium lattice constants by 2% and 6%, respectively. At ahm, these two systems were identified to be true half metals due to their complete spin polarization and integer value of total magnetic moment. These last ones have reached 3μB per unit cell when Z = Si, and 4μB when Z = P. Using the mean field approximation (MFA), the Curie temperatures of Type II structure were also determined, where the values are estimated to be 456.2 K and 302.8 K, respectively. Finally, the thermoelectric performance has been explored by the classical Boltzmann theory. At low temperatures, the figure of merit has reached 0.73 and 0.93 for LiCrSi and LiCrP, respectively. The considerable ZT values and all calculated physical properties make these two systems promising candidates for thermoelectric applications

Ab‐initio study of half‐metallic ferromagnetism in the XCsSr (X=C, Si, Ge, and Sn) half‐Heusler compounds

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Theoretical Study of the Electronic Properties of X2YZ (X = Fe, Co; Y = Zr, Mo; Z = Ge, Sb) Ternary Heusler: Abinitio Study

In the purpose of exploring new Heusler alloys with different magnetic applications, we have employed first principles calculations method within density functional theory. After checking the structural stability of X2YZ Heusler alloys (X = Fe, Co; Y =Zr, Mo and Z = Ge, Sb), we found that Cu2MnAl type structure is more favorable for most compounds except for X2MoGe and Co2MoSb, were the Hg2CuTi structure is energetically more stable. The trends in magnetic and electronic structures can be predicted by the structure types as well as the different kinds of hybridizations between the constituents. Among the two series only two compounds were identified to be true half metals with potential applications in spintronic devices. While one compound was classified as a nonmagnetic semiconductor with a small band gap. For the rest of materials, we found that the metallic behavior is dominant. These materials show possible interesting features in technical applications as well. The effect of distortion on the magnetic properties of Co2ZrGe and Fe2ZrSb showed that the half metallic character was preserved within a moderate range of volume changes, which makes it possible to grow these materials as thin films with modern techniques

Electronic and Thermoelectric Properties in Li-Based Half-Heusler Compounds: A First Principle Study

In this paper, we performed a first principle study for new half-Heusler LiSrX(X= N, P, and As) working with WIEN2k code in the frame work of the density functional theory, and the Boltzmann theory. We estimated the exchange-correlation potential by the generalized gradient approximation (GGA). Energetically, the three compounds show a high stability in structure type2, we notice that the lattice constant increased while bulk modulus decreased in replacing the ions of size increasing. Based on our calculations, LiSrN, LiSrP, and LiSrAs compounds are mechanically stable, and show semiconductor nature with indirect band gaps of 1.21, 1.75 for LiSrN and LiSrAs, and direct band gap of 1.94 eV for LiSrP. The thermoelectric properties are calculated for LiSrX (X=N, P, and As) and they found a high power factor for the p-type doping concentration

The effect of pressure and alloying on half‐metallicity of quaternary Heusler compounds CoMnYZ (Z = Al, Ga, and In)

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First‐principles study of structural, elastic, thermodynamic, electronic and magnetic properties for the quaternary Heusler alloys CoRuFeZ (Z = Si, Ge, Sn)

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Structural, magneto-electronic and thermophysical properties of the new d(0) quaternary heusler compounds ksrcz (z =p, as, sb)

International audienceInvestigation of band structure and thermo-physical response of the d0 new quaternary Heusler compounds KSrCZ (Z = P, As, Sb) within the frame work of density functional theory with full potential linearized augmented plane wave method has been analyzed. Results showed that type-Y3 is the most favorable atomic arrangement. All the compounds are found to be half-metallic ferromagnetic materials with an integer magnetic moment of 2.00 μB and a half-metallic gap EHM of 0.292, 0.234, and 0.351 eV, respectively. The half-metallicity of KSrCZ (Z = P, As, Sb) compounds can be kept in a quite large hydrostatic strain. Thermoelectric properties of the KSrCZ (Z = P, As, Sb) materials are additionally computed over an extensive variety of temperature and it is discovered that all compounds demonstrates higher figure of merit. The properties of half-metallicity and higher Seebeck coefficient makes these materials a promising candidates for thermoelectric and spintronic device applications

First‐principle studies of the structural, electronic and optical properties of the intermetallics semiconducting compounds RuAl <inf>2</inf>, RuGa <inf>2</inf> and OsAl <inf>2</inf>

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