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We have looked into the structural, mechanical, optoelectronic, superconducting state and thermophysical aspects of intermetallic compound Zr$_3$Ir using the density functional theory (DFT). Many of the physical properties, including direction dependent mechanical properties, Vickers hardness, optical properties, chemical bonding nature, and charge density distributions, are being investigated for the first time. According to this study, Zr$_3$Ir exhibits ductile features, high machinability, significant metallic bonding, a low Vickers hardness with low Debye temperature, and a modest level of elastic anisotropy. The mechanical and dynamical stabilities of Zr$_3$Ir have been confirmed. The metallic nature of Zr$_3$Ir is seen in the electronic band structures with a high electronic energy density of states at the Fermi level. The bonding nature has been explored by the charge density mapping and bond population analysis. The tetragonal Zr$_3$Ir shows a remarkable electronic stability, as confirmed by the presence of a pseudogap in the electronic energy density of states at the Fermi level between the bonding and antibonding states. Optical parameters show very good agreement with the electronic properties. The reflectivity spectra reveal that Zr$_3$Ir is a good reflector in the infrared and near-visible regions. Zr$_3$Ir is an excellent ultra-violet (UV) radiation absorber. High refractive index at visible photon energies indicates that Zr$_3$Ir could be used to improve the visual aspects of electronic displays. All the optical constants exhibit a moderate degree of anisotropy. Zr$_3$Ir has a moderate melting point, high damage tolerance, and very low minimum thermal conductivity. The thermomechanical characteristics of Zr$_3$Ir reveal that it is a potential thermal barrier coating material. The superconducting state parameters of Zr$_3$Ir are also explored.

In this work, density functional theory (DFT) based calculations were performed to compute the physical properties (structural stability, mechanical behavior, electronic, thermodynamic, and optical properties) of synthesized MAX phases Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, Hf2TeB, and the as-yet-undiscovered MAX carbide phase Hf2TeC. Calculations of formation energy, phonon dispersion curves, and elastic constants confirmed the stability of the aforementioned compounds. The obtained values of lattice parameters, elastic constants, and elastic moduli of Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, and Hf2TeB showed fair agreement with earlier studies, whereas the values of the mentioned parameters for the predicted Hf2TeC exhibit a good consequence of B replacement by C. The anisotropic mechanical properties are exhibited by the considered MAX phases. The metallic nature and its anisotropic behavior were revealed by the electronic band structure and density of states. The analysis of the thermal properties Debye temperature, melting temperature, minimum thermal conductivity, and Gruneisen parameter confirmed that the carbide phases were more suited than the boride phases considered herein. The MAX phase response to incoming photons further demonstrated that they were metallic. Their suitability for use as coating materials to prevent solar heating was demonstrated by the reflectivity spectra. Additionally, this study demonstrated the impact of B replacing C in the MAX phases., 38 pages

Binary uranium hydrides, UHx (x = 1, 2, 3, 5, 6, 7, 8), with different crystal symmetries are potentially interesting compounds for high-Tc superconductivity and as hydrogen storage systems. In this work we have explored the structural, elastic, mechanical, bonding, and thermophysical properties of these systems under uniform pressure via density functional theory based computations. Most of the results disclosed in this work are novel. From the calculations of the cohesive energy and enthalpy of formation, we have found that the titled compounds are chemically stable. The computed elastic constants at different pressures ensure elastic stability. All the binary hydrides are mechanically anisotropic. Pressure induced brittle-ductile transition takes place under high pressure. The compounds are machinable with the cubic {\alpha}-UH3-Pm-3n showing very high value of the machinability index. All the compounds are fairly hard with cubic UH8 showing superhard character. The Debye temperatures and acoustic velocities of these compounds are high; the highest value is found for the cubic UH8. The melting temperature, Gr\"uneisen parameter, minimal phonon thermal conductivity, and the thermal expansion coefficient of these compounds have also been studied at different pressures. All these parameters show excellent correspondence with the estimated Debye temperature, elastic parameters and bonding characteristics., Comment: arXiv admin note: text overlap with arXiv:2211.09457

BaAgAs is a ternary Dirac semimetal which can be tuned across a number of topological orders. In this study we have investigated the bulk physical properties of BaAgAs using density functional theory based computations. Most of the results presented in this work are novel. The optimized structural parameters are in good agreement with previous results. The elastic constants indicate that BaAgAs is mechanically stable and brittle in nature. The compound is moderately hard and possesses fair degree of machinability. There is significant mechanical/elastic anisotropy in BaAgAs. The Debye temperature of the compound is medium and the phonon thermal conductivity and melting temperature are moderate as well. The bonding character is mixed with notable covalent contribution. The electronic band structure calculations reveal clear semimetallic behavior with a Dirac node at the Fermi level. BaAgAs has a small ellipsoidal Fermi surface centered at the G-point of the Brillouin zone. The phonon dispersion curves show dynamical stability. There is a clear phonon band gap between the acoustic and the optical branches. The energy dependent optical constants conform to the band structure calculations. The compound is an efficient absorber of the ultraviolet light and has potential to be used as an anti-reflection coating. Optical anisotropy of BaAgAs is moderate. The computed repulsive Coulomb pseudopotential is low indicating that the electronic correlations in this compound are not strong., Submitted for publication. arXiv admin note: text overlap with arXiv:2303.01319

In this paper, we have presented a comprehensive study of the physical properties of Kagome superconductor CsV3Sb5 using the density functional theory (DFT). The structural, mechanical, electronic, atomic bonding, hardness, thermodynamic, and optical properties, and their pressure dependences have been investigated for the first time. The calculated ground state lattice parameters and volume are in excellent agreement with available experimental results. The estimated single-crystal elastic constants ensured the mechanical stability of the compound, whereas phonon spectra endorse dynamical stability at zero pressure. The electronic band structure, energy density of states, optical properties confirmed the metallic features. The Pugh ratio, Poisson's ratio of the compound revealed softness and ductility. The hardness, estimated from several formulae, is quite low while the machinability index predicted good machinability with excellent dry lubricating properties. The compound shows tendency towards structural instability at a pressure around 18 GPa. The optical constants have also been studied to correlate those with electronic properties and to predict possible applications of this compound. Both mechanical and optical properties show anisotropy.CsV3Sb5 is predicted to be an efficient absorber of ultraviolet radiation. The compound is also an efficient reflector of visible light.

PbTaSe2 is a non-centrosymmetric topological semimetal. In this work we have explored the structural, elastic, mechanical, bonding, electronic, acoustic, thermal, and optical properties of PbTaSe2. The electronic bond structure calculations confirm semi-metallic character. Fermi surface topology shows both electron and hole sheets. The single crystal elastic constants reveal that PbTaSe2 is elastically stable. The compound is soft, brittle, and highly machinable at the same time. It also possesses very high level of dry lubricity. Various anisotropy indicators suggest that PbTaSe2 is elastically anisotropic with layered character. The phonon dynamics has been investigated. Phonon dispersion plot shows that the compound is dynamically stable with a clear frequency gap between the acoustic and optical branches. The Debye temperature, phonon thermal conductivity, and melting temperature of PbTaSe2 is low. The compound has medium Gr\"uneisen parameter. The bonding character is mainly dominated by ionic bonding with some metallic contribution. The optical parameters have been studied in detail. The optical spectra reveal metallic features. The compound reflects visible light very efficiently (reflectance above 60%). It is also an efficient absorber of the ultraviolet light. The compound exhibits significant optical anisotropy with respect to the polarization directions of the incident electric field.

In this study, we have used density functional theory (DFT) based first-principles investigation of the physical properties of prospective NbAlB compound for the first time. From the analysis of the cohesive energy and enthalpy of formation, it was found that NbAlB is chemically stable. The physical properties of NbAlB have been compared and contrasted with those obtained for MoAlB. Both these MAB phases are elastically anisotropic, mechanically stable, machinable and brittle materials. Structural and elastic features reflect the layered features. The estimated hardness of NbAlB is 19.0 GPa comparable to that of MoAlB (20.8 GPa) suggesting that predicted NbAlB is a hard compound and is suitable for heavy duty industrial applications. NbAlB is more machinable than MoAlB. Electronic band structure calculations reveal conventional metallic behavior with the electronic density of states at the Fermi level arising mainly due to the Nb 4d orbitals in NbAlB. The electronic density of states at the Fermi level is significantly higher in NbAlB in comparison to MoAlB, indicating that NbAlB is expected to exhibit higher level of electrical conductivity. Electronic dispersion is highly anisotropic for both MoAlB and NbAlB with substantially large electronic effective masses in the out-of-plane directions. The bonding features have been elucidated via the analysis of the band structure and charge density distribution. Both the compounds have mixed covalent, ionic and metallic bonding characteristics. The Fermi surfaces of MoAlB and NbAlB consists of electron and hole like sheets. The Debye temperatures of MoAlB and NbAlB are comparable. The estimated melting temperature of NbAlB is somewhat lower than that of MoAlB. NbAlB shows excellent reflection characteristics suitable to be used as an efficient solar reflector. NbAlB is also expected to absorb ultraviolet radiation very effectively.

We present a detailed density functional theory based calculations of the structural, elastic, lattice dynamical, thermophysical, and optoelectronic properties of ternary semiconductors CaZn$_2$X$_2$ (X = N, P, As) in this paper. The obtained lattice parameters are in excellent agreement with the experimental values and other theoretical findings. These elastic constants satisfy the mechanical stability criteria. Moreover, many thermophysical parameters of these compounds are estimated, including the Debye temperature, average sound velocity, melting temperature, heat capacity, lattice thermal conductivity, etc. The comprehensive analysis of the elastic constants and moduli show that CaZn$_2$X$_2$ compounds possess reasonably good machinability, relatively high Vickers hardness and relatively low Debye temperature. The phonon dispersion curves and phonon density of states are investigated for the first time for the compounds CaZn$_2$P$_2$ and CaZn$_2$As$_2$. It is observed from the phonon dispersion curves that the bulk CaZn$_2$X$_2$ (X = N, P, As) compounds are dynamically stable. Electronic properties have been studied through the band structures and electronic energy density of states. The electronic band structures show that CaZn$_2$N$_2$ and CaZn$_2$As$_2$ possess direct band gaps while the compound CaZn$_2$P$_2$ show indirect band gap. The bonding characters of CaZn$_2$X$_2$ (X = N, P, As) compounds are investigated. Energy dependent optical parameters exhibit good correspondence with the electronic energy density of states features. We have thoroughly discussed the reflectivity, absorption coefficient, refractive index, dielectric function, optical conductivity and loss function of these semiconductors. The optical absorption, reflectivity spectra and the refractive index of CaZn$_2$X$_2$ (X = N, P, As) show that the compounds hold promise to be used in optoelectronic devices.

A large number of hitherto unexplored elastic, thermophysical, acoustic, and optoelectronic properties of a double Weyl semimetal SrSi2 have been investigated in this study. Density functional theory (DFT) based methodology has been employed. Analyses of computed elastic parameters reveal that SrSi2 is a mechanically stable, ductile, moderately machinable, and relatively soft material. The compound is predicted to be dynamically stable and possesses significant metallic bonding. Study of thermophysical properties, namely, Debye temperature, Gr\"uneisen parameter, acoustic parameters, melting temperature, heat capacity, thermal expansion coefficient, and dominant phonon mode is also indicative of soft nature of SrSi2. The electronic band structure calculations without and with spin-orbit coupling disclose semimetallic character with clear Weyl nodes close to the Fermi level. The electronic dispersion is anisotropic characterized by nearly flat and linear regions within the Brillouin zone. Optical parameters at different photon energies are investigated. SrSi2 shows excellent nonselective reflection spectrum across an extended range of energy encompassing the visible region implying that the compound under study has significant potential to be used as an efficient solar energy reflector. SrSi2 absorbs ultraviolet light quite efficiently. The compound also possesses high refractive index in the low energy. All these optical features can be useful in optoelectronic device applications.

ZrNCl and HfNCl belong to a class of layered transition metal nitride halides MNCl (M= Zr,H). They are from the space group R-3m (No-166) and crystallize in the rhombohedral structure. Both of these materials have shown promising semiconducting behaviors. Recent studies have shown their versatility as semiconductors and also as superconductors when intercalated with alkaline metals. This paper explores the mechanical, optical and electronic properties of these two semiconducting crystals in depth. A comparative study between the two materials in their elastic constants, anisotropy measures, electronic density of states and band structures, optical spectra has been performed with first principles density functional theory (DFT) based calculations within the local density approximation (with appropriate U for the energy gap calculations in case of HfNCl). HfNCl is more machinable than ZrNCl and is relatively softer as indicated by the lower Debye temperature. ZrNCl has stronger layering due to which it exhibits brittle nature. HfNCl has a larger band gap. ZrNCl is a better reflector of ultraviolet radiation. On the other hand HfNCl is a good ultraviolet absorber. Both materials are anisotropic in regards to structure, electronic energy dispersion and optical parameters. Overall, the degree of anisotropy is more prominent in ZrNCl compared to that in HfNCl. Possible sectors for applications of ZrNCl and HfNCl semiconductors are discussed.

An interesting class of ternary metallic borides, known as the 212 MAX phase borides, is the recent advancement of the MAX phase family. In this article, results from ab-initio calculations on unexplored Ti$_2$PB$_2$, Zr$_2$PbB$_2$, and Nb$_2$AB$_2$ [A = P, S] are reported wherein Ti$_2$PB$_2$ along with its 211 boride phase Ti$_2$PB are predicted for the first time. The stability was confirmed by calculating the formation energy, phonon dispersion curve, and elastic stiffness constants. The obtained elastic constants, elastic moduli, and Vickers hardness values of Ti$_2$PB$_2$, Zr$_2$PbB$_2$, and Nb$_2$AB$_2$ [A = P, S] were found to be significantly larger than those of their counterparts 211 borides and carbides, in a trend similar to other 212 borides. The studied compounds are brittle like most of the MAX and MAB phases. The electronic band structure and density of states revealed the metallic nature of the titled borides. Several thermal parameters were explored, certifying the suitability of Ti2PB2, Zr2PbB2, and Nb2AB2 [A = P, S] compared to their counterparts, and a similar trend was found for the other 212 borides. The obtained results predict that Ti2PB2, Zr2PbB2, and Nb2AB2 [A = P, S] have significant potential for use as efficient thermal barrier coating materials. The response of Ti$_2$PB$_2$, Zr$_2$PbB$_2$, and Nb$_2$AB$_2$ [A = P, S] to the incident photon was studied by computing the dielectric constant (real and imaginary part), refractive index, absorption coefficient, photoconductivity, reflectivity, and energy loss function. The ability to protect from solar heating was revealed from the studied reflectivity spectra. In this work, we have explored the physical basis of the improved thermo-mechanical properties of 212 MAX phase borides compared to their carbide and boride counterparts., Comment: 36 pages

Binary metallic carbides belong to a technologically prominent class of materials. We have explored the structural, mechanical, electronic, optical, and some thermophysical properties of XC (X = Nb, Ta, Ti) binary metallic carbides in details employing first-principles method. Some of the results obtained are novel. A comparative analysis has been made.

Here we have used the density functional theory (DFT) with the GGA-PBE approximation to investigate the structural, mechanical, electronic, hardness, thermal, superconductivity and optoelectronic properties under pressure for monoclinic (P21/m) and orthorhombic (Pmn21) structures of MgVH6. We have studied optical properties of P21/m phase at 0 GPa and Pmn21 phase at 100 GPa only (considering phase stability). Both of the phases of MgVH6 are thermodynamically stable. P21/m phase is mechanically stable but Pmn21 is mechanically unstable in our calculations for the pressures considered. Monoclinic (P21/m) is ductile in nature, on the other hand, orthorhombic (Pmn21) is brittle in nature at 100 GPa and becomes ductile for pressures in the range from 125 GPa to 200 GPa. Hardness calculations indicate superhard character of orthorhombic (Pmn21) structure at 100 GPa. The melting temperature of orthorhombic crystal is very high. This also agrees with the bulk modulus, Debye temperature, and hardness calculations. We have calculated theoretically the superconducting transition temperature Tc at different pressures only for the orthorhombic (Pmn21) structure following a previous study. The estimated values of transition temperatures are within 104.7 K to 26.1 K in the pressure range from 100 GPa to 200 GPa. MgVH6, in both the structures, are elastically and optically anisotropic.

Density functional theory based study of the pressure dependent physical properties of binary SnS compound has been carried out. The computed elastic constants reveal that SnS is mechanically stable and brittle under ambient conditions. With increasing pressure, the compound becomes ductile. The Poisson's ratio also indicates brittle-ductile transition with increasing pressure. The hardness of SnS increases significantly with pressure. The compound possesses elastic anisotropy. The ground state electronic band structure is semiconducting with a small band gap which becomes metallic under pressure. The band becomes more and more dispersive with the increase in pressure while the electronic correlations decrease as pressure is raised. Both the Debye temperature and the phonon thermal conductivity of SnS increase sharply with pressure. The Melting temperature of the compound is low. Mixed bonding characteristics are found with ionic and covalent contributions. SnS is a good absorber of ultraviolet light. The reflectivity of the material increases with the increase in pressure. The reflectivity is nonselective over a wide spectral range. The low energy refractive index is high. All these optical characteristics are useful for prospective optoelectronic device applications. The optical anisotropy is low.

Boron rich chalcogenides have been predicted to have excellent properties for optical and mechanical applications in recent times. In this regard, we report the electronic, optical and mechanical properties of recently synthesized boron rich chalcogenide compounds, B12X (X = S and Se) using density functional theory for the first time. The effects of exchange and correlation functional on these properties are also investigated. The consistency of the obtained crystal structure with the reported experimental results has been checked in terms of lattice parameters. The considered materials are mechanically stable, brittle and elastically anisotropic. Furthermore, the elastic moduli and hardness parameters are calculated, which show that B12S is likely to be a prominent member of hard materials family compared to B12Se. The origin of different in hardness is explained on the basis of density of states near the Fermi level. Reasonably good values of fracture toughness and machinability index for B12X (X= S and Se) are reported. The melting point, Tm for the B12S and B12Se compounds suggests that both solids are stable, at least up to 4208 and 3577 K, respectively. Indirect band gap of B12S (2.27 eV) and B12Se (1.30 eV) are obtained using the HSE06 functional.The electrons of B12Se compound show lighter average effective mass compared to that of B12S compound, which signifies higher mobility of charge carriers in B12Se. The optical properties are characterized using GGA-PBE and HSE06 method and discussed in detail. These compounds possess bulk optical anisotropy and excellent absorption coefficients in visible light region along with very low static value of reflectivity spectra (range: 7.42-14.0% using both functionals) are noted. Such useful features of the compounds under investigation show promise for applications in optoelectronic and mechanical sectors., 34 pages, 13 figures, 6 Tables, This study will be submitted for publication internationally very soon

Tetragonal Mo5PB2 compound, a recently discovered superconductor, belongs to technologically important class of materials. It is quite surprising to note that a large number of physical properties of Mo5PB2, including elastic properties and their anisotropy, acoustic behavior, electronic (charge density distribution, electron density difference), thermo-physical, bonding characteristics, and optical properties have not been carried out at all. In the present work we have explored all these properties in details for the first time with density functional theory based first-principles method. Mo5PB2 is found to be a mechanically stable, elastically anisotropic compound with ductile character. Moreover, the chemical bonding is interpreted by calculating the electronic energy density of states, electron density distribution, elastic properties and Mulliken bond population analysis. Mo5PB2 has a combination of mainly ionic, metallic, and some covalent bonding characteristics. The compound possesses high level of machinability. The band structure along with a large electronic density of states at the Fermi level reveals metallic character. Calculated values of different thermal parameters of Mo5PB2 are closely related to the elastic properties. The energy dependent optical parameters show close assent to the underlying electronic band structure. The optical absorption and reflectivity spectra and the low energy index of refraction of Mo5PB2 show that the compound holds promise to be used in optoelectronic device sector. Unlike the notable anisotropy found in elastic, mechanical properties and minimum thermal conductivity, the optical parameters are found to be almost isotropic with respect to the polarization direction of the incident electric field., Submitted for publication. arXiv admin note: text overlap with arXiv:2103.16027, arXiv:2005.10590

Transition metal dichalcogenides (TMDCs) belong to technologically important compounds. We have explored the structural, elastic, bonding, optoelectronic and some thermo-physical properties of ZrX2 (X = S, Se, Te) TMDCs in details via ab-initio technique in this study. Elastic anisotropy indices, atomic bonding character, optoelectronic properties and thermo-physical parameters including melting temperature and minimum phonon thermal conductivity are investigated for the first time. All the TMDCs under investigation possess significant elastic anisotropy and layered structural features. ZrX2 (X = S, Se, Te) compounds are fairly machinable, and ZrS2 and ZrSe2 are moderately hard. ZrTe2, on the other hand, is significantly softer. Both covalent and ionic bondings contribute in the crystals. Electronic band structure calculations display semiconducting behavior for ZrS2 and ZrSe2 and metallic behavior for ZrTe2. Energy dependent optoelectronic parameters exhibit good correspondence with the underlying electronic energy density of states features. ZrX2 (X = S, Se, Te) compounds absorb ultraviolet radiation effectively. The reflectivity spectrum, R(w), remains over 50% in the energy range from 0 eV to 20 eV for ZrTe2. Therefore, this TMDC has wide band and nonselective high reflectivity and can be used as an efficient reflector to reduce solar heating. Debye temperature, melting point and minimum phonon thermal conductivity of the compounds under study are low and show excellent correspondence with each other and also with the elastic and bonding characteristics.

The discovery of MAX phase borides has added a new dimension for research in the materials science community. In this paper, a first-principles study of the newly known MAX phase borides Zr2AB2 (A = In, Tl) has been carried out. The estimated lattice constants and volumes of the unit cell are found to be consistent with previous study. The dynamical and mechanical stability of the titled compounds have been checked. Fundamental insights into the stiffness constants, elastic moduli, hardness parameters, brittleness and anisotropy indices are presented. The Variation of these mechanical properties was explained based on the Mulliken population analysis and charge density mapping (CDM). The electronic properties have been dealt with by considering electronic band structure and density of states (DOS) which confirmed the metallic nature of Zr2AB2 (A = In, Tl). The lowly dispersive energy bands along the c-direction confirmed anisotropy in conductivity. The analysis of DOS revealed the dominant contribution from Zr-d orbitals to the conductivity with a small contribution from the In/Tl-p states contributing at the Fermi level. The Debye temperature (Theta-D), minimum thermal conductivity (Kmin), Gruneisen parameter and melting temperature (Tm) have been calculated. The higher values of Theta-D and Tm, and lower value of Kmin for Zr2AB2 (A = In, Tl) compared to those of Zr2AC (A = In, Tl). Besides, the specific heat capacities, thermal expansion coefficient, and different thermodynamic potential functions have been calculated. The optical constants have been studied to reveal their possible relevance for application purposes. The reflectivity spectra revealed the applicability of Zr2AB2 (A = In, Tl) as cover materials to diminish the solar heating. The studied physical properties of Zr2AB2 (A = In, Tl) are compared with those of other relevant 212 and 211 MAX phase nanolaminates., Comment: 33 pages, 9 figures

Binary metallic phosphide, Nb2P5, belongs to technologically important class of materials. Quite surprisingly, a large number of physical properties of Nb2P5, including elastic properties and their anisotropy, acoustic, electronic (DOS, charge density distribution, electron density difference), thermo-physical, bonding characteristics, and optical properties have not been investigated at all. In the present work we have explored all these properties in details for the first time employing density functional theory based first-principles method. Nb2P5 is found to be a mechanically stable, elastically anisotropic compound with weak brittle character. The bondings among the atoms are dominated by covalent and ionic contributions with small signature of metallic feature. The compound possesses high level of machinability. Nb2P5 is a moderately hard compound. The band structure calculations reveal metallic conduction with a large electronic density of states at the Fermi level. Calculated values of different thermal properties indicate that Nb2P5 has the potential to be used as a thermal barrier coating material. The energy dependent optical parameters show close agreement with the underlying electronic band structure. The optical absorption and reflectivity spectra and the static index of refraction of Nb2P5 show that the compound holds promise to be used in optoelectronic device sector. Unlike notable anisotropy in elastic and mechanical properties, the optical parameters are found to be almost isotropic.

In the present study, the structural, electronic, optical and thermoelectric properties of two isostructural chalcogenide materials, NaInS2 and NaInSe2 with hexagonal symmetry (R-3m) have been studied using the first principles method. A very good agreement has been found between our results with the available experimental and theoretical ones. The studied materials are semiconducting in nature as confirmed from the electronic band structure and optical properties.The strong hybridizations among s orbitals of Na, In and Se atoms push the bottom of the conduction band downward resulting in a narrower band gap of NaInSe2 compared to that of NaInS2 compound. Different optical (dielectric function, photoconductivity, absorption coefficient, reflectivity, refractive index and loss function) and thermoelectric (Seebeck coefficient, electrical conductivity, power factor and thermal conductivity) properties of NaInX2 (X = S, Se) have been studied in detail for the first time. It is found that all these properties are significantly anisotropic due to the strongly layered structure of NaInX2 (X = S, Se). Strong optical absorption with sharp peaks is found in the far visible to mid ultraviolet (UV) regions while the reflectivity is low in the UV region for both the compounds. Such features indicate feasibility of applications in optoelectronic sector.The calculated thermoelectric power factors at 1000 K for NaInS2 and NaInSe2 along a-axis are found to be 151.5 micro Watt /cmK2 and 154 micro Watt/cmK2, respectively and the corresponding ZT values are ~0.70. The obtained thermal conductivity along a-axis for both compounds is high (~22 W/mK).This suggests that the reduction of such high thermal conductivity is important to achieve higher ZT values of the NaInX2(X = S, Se) compounds., 23 pages, 8 figures, 4 Tables

In this work, we have explored via first principles study of mechanical properties including Vickers hardness and mechanical anisotropy, electronic charge density distribution, Fermi surface, thermodynamic and optical properties of the recently predicted thermodynamically stable MAX phase boride Hf3PB4 for the first time. The calculated lattice constants of the optimized cell are consistent with those found by the predicted data available. Mechanical properties such as C44, B, G, Y, Hmacro and Hmicro of Hf3PB4 boride are compared with those of existing MAX phases. None of the MAX compounds synthesized so far has higher Hmacro and/or Hmicro than that of the predicted Hf3PB4 nanolaminate. Calculations of stiffness constants (Cij) indicate that Hf3PB4 is mechanically stable. The extraordinarily high values of elastic moduli and hardness parameters are explained with the use of density of states (DOS) and charge density mapping (CDM). The high stiffness of Hf3PB4 arises because of the additional B atoms which results in the strong B B covalent bonds in the crystal. The band structure and DOS calculations are used to confirm the metallic properties with dominant contribution from the Hf-5d states to the electronic states around the Fermi level. The technologically important thermal parameters such Debye temperature, minimum thermal conductivity, Gruneisen parameter and melting temperature of Hf3PB4 are calculated. It has been found that the estimated melting temperature of Hf3PB4 is also the highest among all the MAX phase nanolaminates. The important optical constants are calculated and analyzed in detail and their relevance to possible applications in the optoelectronic sectors is discussed. Our study reveals that Hf3PB4 has the potential to be the hardest known MAX phase based on the values of C44, Hmacro and Hmicro., 37 pages

Binary carbides demonstrate attractive set of physical properties that are suitable for numerous and diverse applications. In the present study, we have explored the structural properties, electronic structures, elastic constants, acoustic behaviors, phonon dispersions, optical properties, and various thermophysical properties of binary orthogonal and hexagonal Mo2C compounds in details via first-principles calculations using the density functional theory (DFT). The calculated ground state lattice parameters in both the symmetries are in excellent agreement with available experimental results. The calculated electronic band structure, density of states, and optical properties of Mo2C in both structures reveal metallic features. The orthorhombic crystal shows higher level mechanical and thermal anisotropy compared to that in the hexagonal phase. The elastic constants and phonon dispersion calculations show that, in both structures, Mo2C is mechanically and dynamically stable. A comprehensive mechanical and thermophysical study shows that both phases possess high structural stability, reasonably good machinability, ductile nature, high hardness, low compressibility, high Debye temperature and high melting temperature. Moreover, the electronic energy density of states, electron density distribution, elastic properties, and Mulliken bond population analyses indicate that the structures under consideration consist of mixed bonding characteristics with ionic and covalent contributions. High reflectivity over wide spectral range makes the compound suitable as reflecting coating. Both the structures are efficient absorber of ultraviolet radiation. The refractive indices are quite high in the infrared to visible range.

In the present study we have investigated the structural properties, electronic band dispersion, elastic constants, acoustic behavior, phonon spectrum, optical properties, and a number of thermophysical parameters of binary topological semimetal BaGa2 in details via first-principles calculations using the density functional theory (DFT) based formalisms. The electronic band structure and density of states calculations with spin orbit coupling reveal semimetallic nature with clear topological signature. The minimum thermal conductivities and anisotropies of the compound are calculated. The elastic constants, phonon dispersion calculations show that the compound under study is both mechanically and dynamically stable. Comprehensive study of elastic constants and moduli shows that BaGa2 possesses fairly isotropic mechanical properties, reasonably good machinability, low Debye temperature and melting point. The chemical bonding in BaG2 is interpreted via the electronic energy density of states, electron density distribution, elastic properties and Mulliken bond population analysis. The compound possesses both ionic and covalent bondings. The reflectivity spectra show strong anisotropy with respect to polarization of the incident electric field in the visible to mid-ultraviolet regions. High reflectivity over wide spectral range makes BaGa2 suitable as a reflecting material. BaGa2 is also an efficient absorber of ultraviolet radiation. Furthermore, the refractive index is quite high in the infrared to visible range. All the energy dependent optical parameters show metallic features and are in complete accord with the underlying bulk electronic density of states calculations. Most of the results presented in this study are novel and should serve as useful reference for future study.

In this work, we have studied the structural, elastic, mechanical, electronic, bonding, acoustic, thermal and optical properties of TaX (X = P, As) in detail via first-principles method using the density functional theory. A comprehensive study of elastic constants and moduli shows that both TaP and TaAs possesses low to medium level of elastic anisotropy (depending on the measure), reasonably good machinability, mixed bonding characteristics with ionic and covalent contributions, brittle nature and relatively high Vickers hardness with a low Debye temperature and melting temperature. The minimum thermal conductivities and anisotropies of TaX (X = P, As) are calculated. Bond population analysis supports the bonding nature as predicted by the elastic parameters. The bulk electronic band structure calculations reveal clear semi-metallic features with signature Dirac cone-like dispersions near the Fermi level. A pseudogap in the electronic energy density of states at the Fermi level separating the bonding and the antibonding states indicates significant electronic stability of tetragonal TaX (X = P, As). The reflectivity spectra show almost non-selective behavior over a wide range of photon energy encompassing visible to mid-ultraviolet regions. High reflectivity over wide spectral range makes TaX suitable as reflecting coating. TaX (X = P, As) are very efficient absorber of ultraviolet radiation. Both the compounds are moderately optically anisotropic owing to the anisotropic nature of the electronic band structure. The refractive indices are very high in the infrared to visible range. All the energy dependent optical parameters show metallic features and are in complete accord with the underlying bulk electronic density of states calculations., Comment: Submitted for publication

The structural, electronic, mechanical and thermodynamic properties of (Ti1-xMox)2AlC (0 < x < 0.20) were explored via density functional theory. The obtained lattice constants agree well with the experimental values. The electronic band structure confirms the metallic nature. Strengthening of covalent bonds due to Mo substitution is confirmed from the study of band structure, electronic density of states and charge density mapping. The elastic constants satisfy the mechanical stability criteria. Strengthening of covalent bonds leads to enhanced mechanical properties. (Ti1-xMox)2AlC compounds are found to exhibit brittle behavior. The anisotropic nature of (Ti1-xMox)2AlC is revealed from the direction dependent Young's modulus, compressibility, shear modulus and Poisson's ratio as well as the shear anisotropic constants and the universal anisotropic factor. The Debye temperature, minimum thermal conductivity, Gruneisen parameter and melting temperature of (Ti1-xMox)2AlC have been calculated for different Mo contents. Our calculated values are compared with reported values, where available., Submitted for publication

A topological insulator possesses a bulk energy gap splitting the lowest empty band from the highest occupied electronic band. The electronic states at the surface (or edge in two dimensions), on the other hand, of a topological insulator are gapless and are protected by the time reversal symmetry. Such systems are promising for variety of optoelectronic, superconducting, thermoelectric and quantum computation related applications. We have studied elastic, mechanical, electronic, optical properties, bonding character and the electronic charge density distribution of ternary Bi2Te2Se topological insulator. The compound under study is mechanically stable and elastically anisotropic. The electronic band structure calculations reveal high degree of anisotropy in the energy dispersion. Electronic effective mass is high in the c-direction compared to that in the ab-plane. The optical constants show moderate level of variation with respect to the polarization of the electric field of the incident radiation. The optical spectra are consistent with the electronic band structure and electronic density of states features. Both electronic band structure and optical constants show clear indications of a direct band gap of 0.610 eV for Bi2Te2Se. It is also found that Bi2Te2Se possesses high refractive index at low photon energies in the infrared and visible region. It has low reflectivity in the ultraviolet region. Bi2Te2Se absorbs photons strongly in the ultraviolet energies. All these features make Bi2Te2Se suitable for diverse class of optoelectronic device applications., Comment: Submitted for publication

Density functional theory (DFT) based first-principles investigations of structural, elastic, electronic band structure, and optical properties of superconducting ternary phosphides (BaM2P2; M = Ni, Rh) have been carried out in this study. This is the first detailed pressure dependent study of these properties for the titled compounds. The calculated ambient condition properties are compared with existing experimental and theoretical results, where available. The pressure dependent variations of the electronic density of states at the Fermi level, N(EF), and the Debye temperature, thetaD, have been studied and their effect on superconducting transition temperature have been explored. N(EF) shows nonmonotonic pressure dependence in BaNi2P2. The pressure dependence of N(EF) for BaRh2P2, on the other hand, is monotonic; decreasing with increasing pressure up to 15 GPa and saturating at higher pressure. Pressure dependence of N(EF) is reflected in the pressure dependent superconducting transition temperature. The Debye temperature increases with increasing pressure. The variation of the optical parameters (real and imaginary parts of the dielectric constant, refractive indices, reflectivity, absorption coefficient, and loss function) with photon energy show metallic behavior complementing the features of electronic band structure calculations. The absorption spectra of BaNi2P2 show strong optical absorption in the ultraviolet region, while BaRh2P2 absorbs photons over a wider energy band including the entire visible range. The reflectivity spectra for both BaNi2P2 and BaRh2P2 reveal that these materials are very strong reflectors of visible spectrum and particularly BaNi2P2 have significant potential to be used as coating material to reduce solar heating.

212 MAX phase borides are new additions to the MAX phase family with enhanced thermo-mechanical properties. In this article, first-principles calculations have been carried out to explore the mechanical properties, Vickers hardness, elastic anisotropy, thermal properties, and optical properties of predicted thermodynamically stable MAX compounds Hf2AB2 (A = In, Sn). The structural properties are compared with the available data to assess the validity of calculations. The mechanical stability of Hf2AB2 (A = In, Sn) compounds is established with the help of the computed stiffness constants (Cij). The possible reason for enhanced mechanical properties and Vickers hardness of Hf2SnB2 is explained based on the analysis of bonding strength, followed by the electronic density of states. Higher mechanical strength and Vickers hardness of Hf2AB2 (A = In, Sn) compared to Hf2AC (A = In, Sn) are also indicated in the light of charge density mapping. The values of Pugh ratio, Poissons ratio and Cauchy pressure predict brittle character of the studied compounds. Besides, the anisotropic nature of the titled borides is investigated by 2D and 3D plots of elastic moduli along with some well established anisotropy indices. Thermal properties were investigated by calculating the Debye temperature, minimum thermal conductivity, Gr\"uneisen parameter, and melting temperature. The thermal properties of Hf2AB2 (A = In, Sn) are also superior to Hf2AC (A = In, Sn). The optical constants such as real and imaginary parts of the dielectric function, refractive index, extinction coefficient, absorption coefficient, photoconductivity, reflectivity, and loss function are investigated., Comment: 30 pages, 10 figures, 6 tables

Hole concentration in the CuO2 plane largely controls all the properties in the normal and superconducting states of high-Tc cuprates. The critical current density, Jc, is no exception. Previous hole content dependent studies have demonstrated that the role of intrinsic depairing current density in determining the observed critical current density in copper oxide superconductors. It is also widely agreed upon that the temperature and magnetic field dependent vortex pinning energy plays a major role the Jc of a system.This pinning energy depends directly on the superconducting condensation energy. Superconducting condensation energy, on the other hand, is proportional to the Cooper pair density (superpair density), which is found to be highly dependent on the hole concentration, p, within the CuO2 plane. We have calculated the Cooper pair density, rho_s, of YBCO (Y123), a typical hole doped cuprate, as a function of p, in this study. A triangular pseudogap (PG), pinned at the Fermi level, in the quasiparticle spectral density has been considered. The low-temperature critical current density of a number of Y(Ca)BCO superconductors over wide range of compositions and hole concentrations have been explored. The normalized values of the superpair density and the critical current density exhibit a clear correspondence as the in-plane hole content is varied. This systematic behavior provides us with strong evidence that the critical current density of hole doped cuprates is primarily dependent on the superpair density, which in turn depends on the magnitude of the PG energy.The agreement between the estimated p-dependent superpair density and the previously experimentally determined superfluid density of Y(Ca)BCO is quite remarkable., 17 pages, 4 figures

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.

The superconducting critical current density, Jc, in hole doped cuprates show strong dependence on the doped hole content, p, within the copper oxide plane(s). The doping dependent Jc mainly exhibits the variation of the intrinsic depairing critical current density as p is varied. Jc(p) tends to peak at p ~ 0.185 in copper oxide superconductors. This particular value of the hole content, often termed as the critical hole concentration, has several features putative to a quantum critical point (QCP). Very recently, pressure dependences of the superconducting transition temperature (Tc) and the critical current (Ic) in pure CeRhIn5 and Sn doped CeRhIn5 heavy fermion compounds have been reported (Nature Communications (2018) 9:44, DOI: 10.1038/s41467-018-02899-5). The critical pressure demarcates an antiferromagnetic quantum critical point where both Tc and Ic are maximized. We have compared and contrasted this behavior with those found for Y1-xCaxBa2Cu3O7-d in this brief communication. The resemblance of the systematic behavior of the critical current with pressure and hole content between heavy fermion systems and hole doped cuprates is significant. This adds to the circumstantial evidence that quantum critical physics probably plays a notable role beyond the unconventional normal and superconducting state properties of copper oxide superconductors., 14 pages, 8 figures, 1 table, submitted for publication

Samples of superconducting composite (100-x)YBa2Cu3O7-{\delta} + xNi (x = 1, 2.5, 5, 7.5, 10 and 15 wt.%) were synthesized. Scanning electron microscope (SEM) images revealed that the grain size of YBCO reduces gradually as Ni content is increased. At the same time segregation of Ni as NiO in patches forms throughout the composite. At low Ni wt.%, it was found that the superconducting state properties improved and then dropped with higher Ni wt.%. Segregated patches of NiO on different length scales were observed. The change in the structural and superconducting state parameters of YBCO and the variation of the magnetic critical current density with improved flux pinning in some composites with Ni additives were ascribed to the Jahn-Teller (JT) distortions and pinning of vortices due to antiferromagnetic NiO patches within the samples.

The effects of M atomic species mixing on the physical properties of newly synthesized MAX phase (Zr1-xTix)2AlC solid solutions have been studied by means of density functional theory (DFT) calculations. The lattice constants in good accord with the experimental results, are found to decrease with Ti content. The elastic constants, Cij, and the other polycrystalline elastic moduli have been calculated. The elastic constants satisfy the mechanical stability conditions of these solid solutions. The constants C11, C33 and C44 are found to increase with Ti contents up to x = 0.67, thereafter these decrease slightly. A reverse trend is followed by C12 and C13. The elastic moduli are also found to increase up to x = 0.67, beyond which these moduli go down slightly. Pughs ratio and Poissons ratio both confirm the brittleness of (Zr1-xTix)2AlC. Different anisotropy factors revealed the anisotropic character of these solid solutions. A non-vanishing value of the electronic energy density of states (EDOS) at the Fermi level suggests that (Zr1-xTix)2AlC are metallic in nature. A mixture of covalent, ionic and metallic bonding has been indicated from the electronic structure with dominant covalent bonding due to hybridization of Zr-4d states and C-2p states. The variation of elastic stiffness and elastic parameters with x is seen to be correlated with partial DOS (PDOS) and charge density distribution. The calculated Debye temperature and minimum thermal conductivity are found to increase with Ti contents, while melting temperature is the highest for x = 0.67. The solid solution with x = 0.67 shows improved mechanical and thermal properties compared to that of the two end members Zr2AlC and Ti2AlC. The study of charge transport properties of (Zr1-xTix)2AlC reveals the metallic nature with saturated resistivity. The maximum power factor is obtained at 400 K for (Zr1-xTix)2AlC., 16 pages, 7 figures, submitted to Journal of Alloys and Compounds

The elastic, thermodynamic, electronic, and optical properties of recently discovered and potentially technologically important transition metal boride NbRuB, have been investigated using the density functional formalism. Both generalized gradient approximation (GGA) and local density approximation (LDA) were used for geometrical optimization and for estimation of various elastic moduli and constants. The optical properties of NbRuB have been studied for the first time with different photon polarizations. The frequency (energy) dependences of various optical constants compliment quite well to the essential features of the electronic band structure calculations. Debye temperature of NbRuB has been estimated form the thermodynamical study. All these theoretical estimates have been compared with published results, where available, and discussed in detail. Both electronic band structure and optical conductivity reveal robust metallic characteristics. NbRuB possesses significant elastic and electronic anisotropy. The effects of electronic band structure and Debye temperature on the emergence of superconductivity have also been analyzed., Submitted to Journal of Alloys and Compounds

Using first-principles calculations, the structural, elastic and electronic properties of MoAlB have been investigated for the first time. The optimized lattice constants exhibit fair agreement with the experimental values. The computed elastic constants satisfy the mechanical stability conditions for the MoAlB. The Mo-based boride MoAlB is elastically anisotropic and can be classified as brittle material. This boride is expected to show reasonable thermal conductivity due to its high Debye temperature of 693 K. The metallic electrical conductivity of this compound is predicted from the electronic band structure calculations. The chemical bonding in MoAlB is basically covalent in nature which is supported by the calculated electronic density of states (DOS), Mulliken population, and charge density distribution. The estimated hardness value of 11.6 GPa for MoAlB suggests that it is softer compared to many other borides. The Fermi surface is formed due to low dispersive Mo 4d-like bands, which makes the compound a conductive one.

In the present study we employed density functional theory calculations to investigate the mechanical behavior, bonding nature and defect processes of the new ordered MAX phase Mo2ScAlC2. The mechanical stability of the compound is verified with its single crystal elastic constants. The new phase Mo2ScAlC2 is anticipated to be prone to shear along the crystallographic b and c axes, when a rational force is applied to the crystallographic a axis. The compressibility along the direction under uniaxial stress is expected to be easier in Mo2ScAlC2. Additionally, the volume deformation should be easier in Mo2ScAlC2 than in the isostructural Mo2TiAlC2. Mo2ScAlC2 is predicted to behave in a brittle manner. Due to its higher Debye temperature, Mo2ScAlC2 is expected to be thermally more conductive than Mo2TiAlC2. The cross-slip pinning procedure should be significantly easier in Mo2ScAlC2 as compared to Mo2TiAlC2. The new ordered MAX phase Mo2ScAlC2 has a mixed character of strong covalent and metallic bonding with limited ionic nature. Both Mo-C and Mo-Al bonds are expected to be more covalent in Mo2ScAlC2 than those of Mo2TiAlC2. the level of covalency of Sc-C bond is somewhat low compared to a similar bond Ti-C in Mo2TiAlC2. Due to its reduced hardness, Mo2ScAlC2 should be softer and more easily machinable compared to Mo2TiAlC2. Fermi surface topology of the new compound is formed mainly due to the low-dispersive Mo 4d-like bands. The intrinsic defect processes reveal that the level of radiation tolerance in Mo2ScAlC2 is not as high as in other MAX phases such as Ti3AlC2., Submitted to Journal of Alloys and Compounds

In this paper, we have presented the density functional theory (DFT) based calculations performed within the first-principles pseudopotential method to investigate the physical properties of the newly discovered superconductor LaRu2As2 for the first time. The optimized structural parameters are in good agreement with the experimental results. The calculated independent elastic constants ensure mechanical stability of the compound. The calculated Cauchy pressure, Pugh's ratio as well as Poisson's ratio indicate that LaRu2As2 should behave as a ductile material. Due to low Debye temperature, LaRu2As2 may be used as a thermal barrier coating (TBC) material. The new compound should exhibit metallic nature as its valence bands overlap considerably with the conduction bands. LaRu2As2 is expected to be a soft material and easily machineable because of its low hardness value of 6.8 Gpa. The multi-band nature is observed in calculated Fermi surface. A highly anisotropic combination of ionic, covalent, and metallic interactions is expected in accordance with charge density calculations., To appear in Chinese Physics B

In the present paper, DFT (Density Functional Theory) based first-principles methods are applied to investigate the mechanical and bonding properties of newly synthesized T2 phase superconductor Ta5GeB2 for the first time. The calculated lattice constants are in reasonable agreement with the experiment. The elastic constants (Cij), bulk modulus (B), shear modulus (G), Young's modulus (Y), Poisson ratio (nu), Pugh ratio (G/B), and elastic anisotropy factor, A, of Ta5GeB2 are calculated 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 Ta5GeB2., Comment: To appear in Physica Status Solidi B (2016)

First-principles calculations within the density functional theory (DFT) with GGA-PBE exchange-correlation scheme have been employed to predict the structural, the elastic and the electronic properties of newly discovered lithium silicide superconductor, Li2PtSi3, for the first time. All the theoretical results are compared with those calculated recently for isostructural Li2IrSi3. The present study sheds light on the effect of replacement of transition metal element Ir with Pt on different mechanical, electronic, and superconducting properties. The effect of spin-orbit coupling on electronic band structure was found to be insignificant for Li2PtSi3. The difference in superconducting transition temperatures of Li2PtSi3 and Li2IrSi3 arises primarily due to the difference in electronic energy density of states at the Fermi level. Somewhat reduced Debye temperature in Li2PtSi3 plays a minor role. We have discussed the implications of the theoretical results in details in this study., Comment: Submitted for publication

The structural, elastic, and electronic properties of newly synthesized Zr2(Al0.58Bi0.42)C, Zr2(Al0.2Sn0.8)C, and Zr2(Al0.3Sb0.7)C MAX nanolaminates have been studied using first-principles density functional theory (DFT) calculations for the first time. Theoretical Vickers hardness has also been estimated for these compounds. All the calculated results are compared with experimental data and also with that of recently discovered Zr2AlC phase, where available. Zr2(Al0.58Bi0.42)C and Zr2(Al0.2Sn0.8)C are the two first Bi and Sn containing MAX compounds. The calculated structural parameters are found to be in good agreement with the experimental data. The single crystal elastic constants Cij and other polycrystalline elastic coefficients have been calculated and the mechanical stabilities of these compounds have been theoretically confirmed. The bulk modulus increases and the shear modulus decreases due to partial Bi/Sn/Sb substitution for Al in Zr2AlC. The calculated elastic moduli show that these Bi/Sn/Sb containing MAX phases are more anisotropic than Zr2AlC, and have a tendency towards ductility. The Vickers hardness decreases in the Bi/Sn/Sb containing compounds. Further, the electronic band structures and electronic density of states (EDOS) are calculated and the effects of different elemental substitution on these properties are investigated. The electronic band structures show metallic characteristics with contribution predominantly coming from the Zr 4d orbitals. Partial presence of Bi/Sn/Sb atoms increases the EDOS at the Fermi level to some extent. Possible implications of the theoretical results for these recently discovered MAX nanolaminates have been discussed in detail in this paper., Comment: Submitted to Computational Materials Science

We have investigated Vickers hardness and the thermodynamic properties of the recently discovered nanolaminate carbide Ti3SnC2 polymorphs using the first-principles calculations. The chemical bonding shows a combination of covalent, ionic and metallic types. The strong covalent bonding is mainly responsible for high Vickers hardness of Ti3SnC2 polymorphs. Thermodynamic properties are studied using the quasi-harmonic Debye model. The variation of bulk modulus, thermal expansion co-efficient, specific heats, and Debye temperature with applied pressure (P) and temperature (T) are investigated systematically within the ranges of 0 - 50 GPa and 0 - 1000 K. The calculated results have been compared with available experimental and theoretical data., 8 pages

The structural, elastic, and electronic properties of the very recently discovered ternary silicide superconductor, Li2IrSi3, have been calculated using ab-initio technique. We have carried out the plane-wave pseudopotential approach within the framework of the first-principles density functional theory (DFT) implemented within the CASTEP code. The calculated structural parameters show a reasonable agreement with the experimental results. Elastic moduli of this interesting material have been calculated for the first time. The electronic band structure and electronic energy density of states indicate the strong covalent Ir-Si and Si-Si bonding which lead to the formation of the rigid structure of Li2IrSi3. Strong covalency give rise to a high Debye temperature in this system. We have discussed the theoretical results in detail in this paper., Submitted to Current Applied Physics

Ab intio calculations were done to investigate the structural, elastic, electronic and optical properties of the Cd-containing theoretically predicted MAX phase, Ti2CdN, in comparison with the isostructural and already synthesized phase, Ti2CdC. These calculations reveal that the substitution of C by N affects the lattice parameter c, whereas the lattice parameter a, remains almost unchanged. All the elastic constants and moduli increase when carbon is replaced by nitrogen. The elastic anisotropy in Ti2CdC is higher in comparison with that of Ti2CdN. Both these nanolaminates are brittle in nature. The calculated electronic band structures and density of states suggest that the chemical bonding in these two ternary compounds is a combination of covalent, ionic and metallic in nature. Electrical conductivity of Ti2CdC is found to be higher than that of Ti2CdN. The calculated reflectivity spectra show that both the MAX phases Ti2CdC and Ti2CdN have the potential to be used as coating materials to minimize solar heating., Comment: To appear in Computational Materials Science

We present results of ab-initio calculations of the electronic band structure, lattice dynamical properties, and elastic constants of LaOFeAs, the parent compound of the recently discovered superconducting iron-oxypnictide (LaO1-xFxFeAs). The total and partial electronic density of states (EDOS) of the undoped LaOFeAs (in the insulating or metallic state) are extracted from the electronic band structure. The phonon dispersion and the phonon density of states (PDOS) are also studied. Possible implications of the band structure, EDOS, and PDOS of LaOFeAs on the eventual appearance of high-Tc superconductivity upon carrier doping are discussed. The values of various independent elastic constants for both insulating and metallic states are estimated and discussed., 9 pages, 5 figures, references with DOI information, corrected typos (Table 2, and sections 3.1 and 3.4)