The full-potential linearized augmented plane wave method with the generalized gradient approximation for the exchange-correlation potential (FLAPW-GGA) is used to predict the electronic and elastic properties of the newly discovered superconducting nanolaminate Ti2InC. The band structure, density of states and Fermi surface features are discussed. The optimized lattice parameters, independent elastic constants, bulk and shear moduli, compressibility are evaluated and discussed. The elastic parameters of the polycrystalline Ti2InC ceramics are estimated numerically for the first time.
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 …
The first-principles FLAPW-GGA calculations of the elastic properties of recently discovered superconducting LiFeAs are reported. The independent elastic constants (Cij), bulk modulus, compressibility, and shear modulus are evaluated and discussed. Additionally, numerical estimates of the elastic parameters of the polycrystalline LiFeAs ceramics are performed for the first time.
MAX phases are nanolaminated ternary materials that combine metallic and ceramic properties. Currently, the A-site elements replacement in traditional ones by later transition-metals opens a door to explore new types of MAX phases. In this work, we performed a systematic first-principle study to explore trends in stability, electronic structure and mechanical properties of 288 compositions of M2AX phases (M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W; A=Al, Si, P, S, Ga, Ge, As, Se, In, Sn, Sb, Te, Tl, Pb, Bi, Mn, Fe, Co, Ni, Cu, Zn, Tc, Ru, Rh, Pd, Ag, Cd, Os, Ir, Pt, Au, Hg; X=C). Such a dataset, combi…
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 nat…
Graphene has been widely used in the form of micro-flakes to fabricate composite materials with enhanced mechanical properties. Due to the small size of the inclusions and their random orientation within the matrix, the superior mechanical properties of graphene cannot be fully exploited. Recently, attempts have been made to fabricate nanolaminate composites by interleaving large sheets of chemical vapor deposition (CVD) monolayer graphene between thin layers of polymer matrices. However, CVD graphene is inevitably accompanied by wrinkles that are formed in the synthesis process, and it remain…
The elastic, electronic and optical properties of MNNi3 (M= Zn, Sn and Cu) have been calculated using the plane-wave ultrasoft pseudopotential technique which is based on the first-principles density functional theory (DFT) with generalized gradient approximation (GGA). The optimized lattice parameters, independent elastic constants (C11, C12, and C44), bulk modulus B, Compressibility K, shear modulus G, and Poisson's ratio \u{psion}, as well as the band structures, total and atom projected densities of states and finally the optical properties of MNNi3 have been evaluated and discussed. The e…
Using the ab initio approaches, the comparative stability, structural, elastic, and electronic properties of three polymorphs of the superconducting disilicide YIr2Si2, which differ in the atomic configurations of [Ir2Si2] (or [Si2Ir2]) blocks, were examined. For these YIr2Si2 polymorphs, the optimized structural data, elastic parameters, electronic bands, total and partial densities of states, Fermi surface topology, and chemical bonding have been obtained and analyzed. Our studies showed that although ThCr2Si2- and CaBe2Ge2-type polymorphs are mechanically stable and relatively hard material…
First principles pseudopotential calculations have been performed for the first time to investigate the phonon dispersion, thermodynamic and optical properties including charge density, Fermi surface, Mulliken population analysis, theoretical Vickers hardness of predicted MAX phase Sc2InC. We revisited the structural, elastic and electronic properties of the compound which assessed the reliability of our calculations. The analysis of the elastic constants and the phonon dispersion along with phonon density of states indicates the mechanical stability and dynamical stability of the MAX phase. T…
This is a critical review of MAX-phase carbides and nitrides from an electronic-structure and chemical bonding perspective. This large group of nanolaminated materials is of great scientific and technological interest and exhibit a combination of metallic and ceramic features. These properties are related to the special crystal structure and bonding characteristics with alternating strong M-C bonds in high-density MC slabs, and relatively weak M-A bonds between the slabs. Here, we review the trend and relationship between the chemical bonding, conductivity, elastic and magnetic properties of t…
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…
RbFe2As2 has recently been reported to be a bulk superconductor with Tc = 2.6 K in the undoped state, in contrast to undoped BaFe2As2 with a magnetic ground state. We present here the results of the first-principles calculations of the structural, elastic and electronic properties for this newest superconductor and discuss its behaviour in relation to other related systems. Keywords: RbFe2As2, Electronic structure; Elastic constant; Superconductivity. PACS: 74.70.Dd, 74.10.+v, 74.20.Pq, 75.25.Ld
In order to understand the unexpected superconducting behavior of MgB$_2$ compound we have made electronic structure calculations for MgB$_2$ and closely related systems. Our calculated Debye temperature from the elastic properties indicate that the average phonon frequency is very large in MgB$_2$ compared with other superconducting intermetallics and the exceptionally high $T_c$ in this material can be explained through BCS mechanism only if phonon softening occurs or the phonon modes are highly anisotropic. We identified a doubly-degenerate quasi-two dimensional key-energy band in the vicin…
We study the ac electric potential induced by the electron sound wave (a perturbation of the electron distribution function propagating with the Fermi velocity) in single crystals of high purity gallium. The potential and the elastic components of the electron sound demonstrate qualitatively different dependencies on the electron relaxation rate: while the phase of the potential increases with temperature, the phase of elastic displacement decreases. This effect is explained within the multiband model, in which the potential is attributed to the ballistic quasiwave, while the elastic component…
MV$_2$Ga$_4$ (M = Sc, Zr, Hf) compounds belong to an emerging class of materials showing a unique combination of unusual superconducting behavior with extended linear chains in the crystal structure. In order to gain insights {into} its mechanical and thermal properties, we have performed first-principles electronic-structure calculations in the framework of the Density Functional Theory (DFT). From the calculated second-order elastic constants, we have systematically shown that the extended linear vanadium chain substructures indeed give rise to an anisotropic regime in the elastic and mechan…
Hot Isostatic Pressing was applied to synthesize bulk samples with diameter up to 30 mm starting with Alfa Aesar magnesium diboride powder. HIPing at 2 kbar, 1000 C with cooling under pressure (DMCUP cycle) resulted in a fully dense (or low porosity) material with a sharp superconducting transition and critical current comparable with the best reported. Elastic constants were measured using method of resonant ultrasound spectroscopy. Their values for most dense samples (bulk modulus 142.5 GPa and Young's modulus 272.5 GPa) are close to theoretically predicted values for solid magnesium diborid…
For the first time, we have reported in this study an ab initio investigation on elastic properties, Debye temperature, Mulliken population, Vickers hardness, and charge density of superconducting ScRhP and ScIrP phosphides. The optimized cell parameters show fair agreement with experimental results. The elastic constants and moduli, Poisson's as well as Pugh's ratio and elastic anisotropy factors have also been calculated to understand the mechanical behavior of these ternary compounds. Their mechanical stability is confirmed via the calculated elastic constants. The calculated values for Poi…
NaSn2P2 is a recently discovered superconducting system belonging to a particular class of materials with van der Waals structure. There is enormous interest in such compounds because of their intriguing electrical, optical, chemical, thermal, and superconducting state properties. We have studied the pressure dependent structural, thermo-physical, electronic band structure, and superconducting state properties of this quasi-two dimensional system in details for the first time via ab initio technique. The optical The optical properties are also investigated for different electric field polariza…
Spatial dependence of the magnetic field and the superconducting current in a flux line pinned by a screw dislocation are computed. Interaction of a superconducting vortex with the chiral-symmetry breaking elastic strain of a screw dislocation results in a helical current along the axis of the dislocation. It is argued that screw dislocations make impossible a force-free arrangement of flux lines in the presence of a transport current.
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 …
DFT based investigation of structural, elastic, optoelectronic, thermophysical and superconducting state properties of binary Mo3P at different pressures
In this work, a question is tackled concerning the formation of a superconducting condensate in an earlier proposed model of "elastic jelly", in which phonons of the valent skeleton play the part of initiating ones. It was shown that in distinction from the BCS theory, the momenta of forming electron couples are different from zero. This fact changes the pattern of the description of the superconductivity phenomenon in the proposed model. First, the gap in the one-electron spectrum appears due to the effect of a "mean field" on the energy of one-electron state from the side of occupied states,…
The effects of long-range anisotropic elastic deformations on electronic structure in superconductors are analyzed within the framework of the Bogoliubov-de Gennes equations. Cases of twin boundaries and isolated defects are considered as illustrations. We find that the superconducting order parameter is depressed in the regions where pronounced lattice deformation occurs. The calculated local density of states suggests that the electronic structure is strongly modulated in response to lattice deformations, and propagates to longer distances. In particular, this allows the trapping of low-lyin…
A first-principles calculation has been performed to study elastic, electronic, thermodynamic, transport and superconducting properties of recently reported osmium based two superconductors, XOsSi (X=Nb, Ta). We have calculated elastic constants and elastic moduli of XOsSi for the first time. The calculated values of bulk, Youngs, shear moduli are reasonably larger than the average value obtained from the rule of mixtures of the constituents. NbOsSi and TaOsSi both compounds are found to be relatively hard material, elastically stable and ductile in nature. The obtained directional bulk modulu…
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 sup…
Very recently (November, 2010, PRB, 82, 180520R), the first ThCr2Si2-type ternary superconductor K0.8Fe2Se2 with enhanced TC ~ 31 K has been discovered. This finding has stimulated much activity in search for related materials and triggered intense studies of their properties. Indeed, very soon superconductivity (TC ~ 28-32 K) was also found in the series of related ternary systems (so-called 122 phases) such as CsxFe2-ySe2, RbxFe2-ySe2, (TlK)xFeySe2, (TlRb)xFeySe2 etc., which formed a new group of superconducting iron-based materials without toxic As. In this paper the recent progress in synt…
Very recently carbon-rich NaC6 with sodalite-like structure has been predicted to show superconducting transition temperature above 100 K at relatively low applied (compared to high-Tc hydrides) hydrostatic pressures. We have investigated the pressure dependent structural, elastic, electronic, superconducting state, and optoelectronic properties of NaC6 in this study. Some important thermophysical properties have also been explored. The elastic properties along with Poisson's and Pugh's ratios and optoelectronic parameters are investigated for the first time. NaC6 was found to be structurally …
The elasticity, dynamic properties, and superconductivity of $α$, $ω$, and $β$ Zr are investigated by using first-principles methods. Our calculated elastic constants, elastic moduli, and Debye temperatures of $α$ and $ω$ phases are in excellent agreement with experiments. Electron-phonon coupling constant $λ$ and electronic density of states at the Fermi level $N$(\emph{E}$_{\rm{F}}$) are found to increase with pressure for these two hexagonal structures. For cubic $β$ phase, the critical pressure for mechanical stability is predicted to be 3.13 GPa and at \emph{P}=4 GPa the low elastic modul…
In this work, we expand the set of known layered compounds to include ionic layered materials, which are well known for superconducting, thermoelectric, and battery applications. Focusing on known ternary compounds from the ICSD, we screen for ionic layered structures by expanding upon our previously developed algorithm for identification of van der Waals (vdW) layered structures, thus identifying over 1,500 ionic layered compounds. Since vdW layered structures can be chemically mutated to form ionic layered structures, we have developed a methodology to structurally link binary vdW to ternary…
Very recently (November, 2010, PRB, 82, 180520R) the first 122-like ternary superconductor KxFe2Se2 with enhanced TC ~ 31K has been discovered. This finding has stimulated much activity in search of related materials and triggered the intense studies of their properties. Indeed already in 2010-2011 the superconductivity (TC ~ 27-33K) was also found in the series of new synthesized 122 phases such as CsxFe2Se2, RbxFe2Se2, (TlK)xFeySe2 etc. which have formed today the new family of superconducting iron-based materials without toxic As. Here, using the ab initio FLAPW-GGA method we have predicted…
Three new phases of ternary transitional metal carbides, namely MAX phases, Nb4SiC3, Nb4GeC3 and Nb4GaC3 were proposed by means of density functional theory, and they were all predicted to be mechanically stable. It was figured out that the alpha type crystal structures of the hypothesized nanolaminates are energetically favored than beta type. Together with the known Nb4AlC3, the role of A group elements in Nb4AC3 (A= Al, Si, Ga, Ge) on various properties were systematically investigated. Not only bulk moduli, compressibility, shear moduli, and Youngs moduli, but the approach to the ductility…
The present paper deals with the analysis of experimental results taking into account mechanisms brought by the bulk elastic energy transformed by the thermodynamic parameters, temperature, magnetic fields, high hydrostatic pressure (T-H-P). An effect of the external parameters is considered through the separation of critical lines and points of the cooling-heating effect in the course of analysis of linear elastic evolution of properties in sign alternating and crossing effects of elastic stress energy as well as their value for structural reorganizations at reversible volume changes (structu…
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, LaR…
Titanium nitride halides, TiNX (X = F, Cl, Br, I) in the α-phase (orthorhombic) are exciting quasi two-dimensional (2D) electronic systems exhibiting a fascinating series of electronic ground states under different conditions. Pristine TiNX are semiconductors with varying energy gaps and possess attractive properties for potential applications in the fields of optoelectronics, photovoltaics, and thermoelectrics. Alkali metal intercalated TiNCl becomes superconducting at reasonably high temperature in the α-phase. We have revisited the electronic band structure of these compounds using density …
This work reports on the elastic and electronic properties of the newly discovered superconductor Th2NiC2 (A .Machado, et al., Supercond. Sci. Technol. 25 (2012) 045010) as obtained within ab initio calculations. We found that Th2NiC2 is mechanically stable and it will behave as a ductile material exhibiting enhanced elastic anisotropy in shear and a rather low hardness Our data reveal that for Th2NiC2 the Fermi level is located in a deep DOS minimum and the experimentally observed increase in TC in the sequence Th2NiC2 -> Th1.8Sc0.2NiC2 may be explained by the growth of N(EF). We also specula…
The Fe K X-ray absorption near edge structure (XANES) of BaFe2-xCoxAs2 superconductors was investigated. No appreciable alteration in shape or energy position of this edge was observed with Co substitution. This result provides experimental support to previous ab initio calculations in which the extra Co electron is concentrated at the substitute site and do not change the electronic occupation of the Fe ions. Superconductivity may emerge due to bonding modifications induced by the substitute atom that weakens the spin-density-wave ground state by reducing the Fe local moments and/or increasin…
Crystal structure searching and ab initio calculations have been used here to explore low-energy structures of boron carbides under high pressure. Under pressures of 85-110 GPa, a metastable B6C with R-3m symmetry is found to be energetically more stable than the mixture of previous B4C and elemental boron. This B6C is a rhombohedral structure and contains mooncake-like B24 clusters with stuffing of C2 pairs. The mechanical and dynamical stabilities of this structure at ambient pressure are confirmed by its elastic constants and phonon dispersions. The bulk modulus and shear modulus of this ne…
Physical properties of transition metal hydride superconductors Mg2TmH6 (Tm = Rh, Pd, Ir, Pt) by first-principles calculations
Mawlana Bhashani Science and Technology University（毛拉纳·巴沙尼科技大学）；University of Rajshahi（拉杰沙希大学）；Rajshahi University of Engineering and Technology（拉杰沙希工程与技术大学）
