Elastic and electronic properties of PbO-type FeSe1-xTex (x = 0 - 1.0): A first-principles study

The effect of doping on electronic and other related properties of PbO-type FeSe1-xTex has been investigated theoretically using density functional method. The elastic properties for mono- and poly-crystalline FeSe1-xTex system are predicted for the first time and the results discussed. Analysis of doping dependent band characteristics in conjunction with previous studies reveal that favorable nesting of Fermi surface indicates a possible basis for understanding why Tc in FeSe1-xTex is maximum for x ~ 0.5. Keywords: FeSe superconductors, Substitution effect, Elastic properties, Electronic properties. PACS: 74.62.Dh, 74.70.Dd, 74.20.Pq, 74.25.LdComment: 11 pages, 5 figure

Superconducting MAX phases Nb2AC (A = S, Sn): An ab-initio study

An ab-initio investigation of structural parameters, elastic, electronic, thermodynamic and optical properties of MAX phases Nb2AC (A = S, Sn) has been carried out by the plane wave psedudopotential method based on density functional theory (DFT). The effect on results of substitution of heavier Sn atoms for the lighter S atoms in the nanolaminate network has been made. The analysis of the electronic band structure shows that these compounds are electrical conductors, with contribution predominantly from the Nb 4d states. The temperature and pressure dependence of bulk modulus, Debye temperature, specific heats, thermal expansion coefficient of the nanolaminates are calculated for the first time using the quasi-harmonic Debye model with phononic effects. The estimated values of electron-phonon coupling constants (lambda ~ 0.49, ~0.59) imply that Nb2SC and Nb2SnC are moderately coupled superconductors. Further first time detailed analysis of all optical functions reveals that Nb2SC is a better dielectric material, and also both the phases, having similar reflectivity spectra, show promise as good coating materials in the energy regions 10-16.5 eV. Keywords: Nb2SC; Nb2SnC; First-principles; Mechanical properties; Quasi-harmonic Debye model; Band structure; Thermodynamic properties; Optical propertiesComment: 12 pages, 7 figures, 2 tables. Modification of text and Fig.

Sulvanite Compounds Cu3TMS4 (TM= V, Nb and Ta): Elastic, Electronic, Optical and Thermal Properties using First-principles Method

We present a systematic first-principles study of the structural, elastic, electronic, optical and thermodynamics properties of the sulvanite compounds Cu3TMS4 (TM = V, Nb and Ta). The structural, elastic and electronic properties are in fact revisited using a different calculation code than that used by other workers and the results are compared. The band gaps are found to be 1.041, 1.667 and 1.815 eV for Cu3VS4, Cu3NbS4 and Cu3TaS4, respectively which are comparable to other available calculated results. The optical properties such as dielectric function, refractive index, photoconductivity, absorption coefficients, reflectivity and loss function have been calculated for the first time. The calculated results are compared with the limited measured data on energy dependent refractive index and reflectivity coefficient available only for Cu3TaS4. All the materials are dielectric, transparent in the visible range. The values of plasma frequencies are found to be 15.36, 15.58 and 15.64 eV for Cu3VS4, Cu3NbS4 and Cu3TaS4, respectively. Furthermore, following the quasi-harmonic Debye model, the temperature effect on the bulk modulus, heat capacity, and Debye temperature is calculated reflecting the anharmonic phonon effects and these are compared with both experimental and other theoretical data where available.Comment: 13 page

Newly synthesized Ti5Al2C3: Electronic and optical properties by first-principles method

A theoretical study of the newly identified Ti5Al2C3 belonging to the MAX phases has been performed by using the first-principles pseudopotential plane-wave method within the generalized gradient approximation (GGA). The energy band structure and optical properties are reported for the first time. It is seen that Ti 3d electrons mainly contribute to the DOS at the Fermi level, and should be involved in the conduction properties. The parameters of optical properties (dielectric function, absorption spectrum, conductivity, energy-loss spectrum and reflectivity) for Ti5Al2C3 are calculated and discussed. The material has a large positive static dielectric constant of 130 which indicates it to be a good dielectric material. Further the reflectivity of Ti5Al2C3 is high in the infrared-visible-UV region up to ~ 9.7 eV showing promise as a good coating material to avoid solar heating. Keywords: A: Ti5Al2C3; B: First-principles; C: Electronic structure; C: Optical propertiesComment: 5 pages, 3 figures, 1 tabl

Phase stability and physical properties of hypothetical V4SiC3

We study the phase stability, mechanical, electronic, optical properties and Vicker's hardness of the newly predicted layered compound V4SiC3 using the first-principles method. This hypothetical compound is found to possess higher bulk modulus as well as higher hardness than those of a similar V4AlC3. The Mulliken bond population analysis indicates that the substitution of Al atom with the Si atom increases the Vicker's hardness of this compound. The electronic band structure shows that the conductivity is metallic and the main contribution comes from V 3d states. The partial density of states (PDOS) shows that the hybridization peak of V 3d and C 2s lies lower in energy than that of V 3d and Si 3p states which suggests that the V 3d - C 2s bond is stronger than the V 3d - Si 3p bond. The results are consistent with our bond analysis. Further we have discussed the origin of the features that appear in the optical properties. V4SiC3 is seen as a promising dielectric material showing a much better candidate material as a coating to avoid solar heating than those of V4AlC3, {\alpha}-Nb4SiC3 and Ti4AlN3 compounds. Keywords: MAX phase V4SiC3; Phase stability; Electronic properties; Optical properties; Vicker's hardness. PACS: 61.66.Fn, 62.20.-x, 62.20.Dc, 71.15Mb, 78.20.CiComment: 9 pages, 4 figures, 3 Table, Correction in Fig. 4 (ref 17 changed to ref 21

Structural, elastic, electronic and optical properties of a newly predicted layered-ternary Ti4SiN3: A First-principles study

We study a newly predicted layered-ternary compound Ti4SiN3 in its {\alpha}- and {\beta}-phases. We calculate their mechanical, electronic and optical properties and then compare these with those of other compounds M4AX3 (M = V, Ti, Ta; A = Si, Al; X = N, C). The results show that the hypothetical Ti4SiN3 shows an improved behavior of the resistance to shape change and uniaxial tensions and a slight elastic anisotropy. The electronic band structures for both {\alpha}- and {\beta}-Ti4SiN3 show metallic conductivity in which Ti 3d states dominate. The hybridization peak of Ti 3d and N 2s lies lower in energy than that of Ti 3d and Si 3p states which suggests that the Ti 3d - N 2s bond is stronger than the Ti 3d - Si 3p bond. Using band structure we discuss the origin of different features of optical properties. The {\alpha}-phase of predicted compound has improved behavior in reflectivity compared to those of similar types of compounds. Keywords: Ternary nitride; First-principles; Mechanical properties; Electronic band structure; Optical propertiesComment: 9 pages, 6 figures, 2 table

Synthesized inverse-perovskites Sc3InX (X = B, C, N): A theoretical investigation

We present first-principles density functional theory (DFT) investigations of mechanical, thermodynamic and optical properties of synthesized inverse-perovskites Sc3InX (X = B, C, N). The elastic constants at zero pressure and temperature are calculated and the anisotropic behavior of the compounds is illustrated. All the three materials are shown to be brittle in nature. The computed Peierls stress, approximately 3 to 5 times larger than of a selection of MAX phases, show that dislocation movement may follow but with much reduced occurrences compared to these MAX phases. The Mulliken bonding population and charge density maps show stronger covalency between Sc and X atoms compared with Sc-Sc bond. The Vickers hardness values of Sc3InX are predicted to be between 3.03 and 3.88 GPa. The Fermi surfaces of Sc3InX contain both hole- and electron-like topology which changes as one replaces B with C or N. The bulk modulus, specific heats, thermal expansion coefficient, and Debye temperature are calculated as a function both temperature and pressure using the quasi-harmonic Debye model with phononic effects. The results so obtained are analysed in comparison to the characteristics of other related compounds. Moreover optical functions are calculated and discussed for the first time. The reflectivity is found to be high in the IR-UV regions up to ~ 10.7 eV (Sc3InB, Sc3InC) and 12.3 eV (Sc3InN), thus showing promise as good coating materials. Keywords: Sc3InX, Mechanical properties; Fermi surface; Quasi-harmonic Debye model; Thermodynamic properties; Optical propertiesComment: 14 pages, 8 figures, 2 tables, some text modifications. arXiv admin note: substantial text overlap with arXiv:1208.556

Structural, elastic, thermal and lattice dynamic properties of new 321 MAX phases

A new series of MAX family designated as 321 phases are recently reported with Nb3As2C, V3As2C, Nb3P2C and Ta3P2C. Most of the physical properties of these new MAX phase compounds are unexplored and the present study aims to investigate their structural, elastic, thermal, and lattice dynamical properties. Their mechanical and dynamical stabilities are examined. All the phases are elastically anisotropic and brittle in nature. The Debye temperatures and lattice thermal conductivities have been calculated. Lattice dynamical features are investigated in detail and infrared and Raman modes are identified. High melting temperature of these compounds are favorable for their applications at elevated temperatures

New MAX Phase Compound Mo2TiAlC2: First-principles Study

A theoretical study of Mo2TiAlC2 compound belonging to the MAX phases has been performed by using the firstprinciples pseudopotential plane-wave method within the generalized gradient approximation. We have calculated the structural, elastic, electronic and optical properties of Mo2TiAlC2. To confirm mechanical stability, the elastic constants Cij are calculated. Other elastic parameters such as bulk modulus, shear modulus, compressibility, Young modulus, anisotropic factor, Pugh ratio, Poisson ratio are also calculated. The energy band structure and density of states are calculated and analyzed. The results show that the electrical conductivity is metallic with a high density of states at the Fermi level in which Mo 4d states dominate. Furthermore, the optical properties such as dielectric function, refractive index, photoconductivity, absorption coefficients, loss function and reflectivity are also calculated. Its reflectance spectrum shows that it has the potential to be used as a promising shielding material to avoid solar heating.Comment: 9 page

Response of Some Biochemical and Mineral Constituents of the Postharvest Mango (Mangifera Indica L.) Influenced by Different Levels of Bavistin DF

An investigation was carried out with the postharvest mangoes (viz., the Langra and the Khirshapat) treating with different levels of Bavistin DF solution (namely, 250, 500, and 750 PPM) for obtaining results on the biochemical and mineral content changes as well as storability of postharvest mango. The results of the experiments exhibited that only the single effect of varieties was found to be significant in most of the parameters studied. The Langra enriched a greater quantity of crude fiber, lipid, water-soluble protein, phosphorus, and potassium constituents over the Khirshapat. It is revealed that the expansion of mineral contents in the mango was intimately associated with ripening during storage. The results also noticed to be an increasing trend of lipid and protein content in mango pulp with the advance of storage period using Bavistin DF