We report the properties of two new isostructural compounds, U3Bi4Ni3 and U3Bi4Rh3. The first of these compounds is non-metallic, and the second is a nearly ferromagnetic metal, both as anticipated from their electron count relative to other U-based members of the larger 3-4-3 family. For U3Bi4Rh3, a logarithmic increase of C/T below 3 K, a resistivity proportional to T^4/3, and the recovery of Fermi-liquid behavior in both properties with applied fields greater than 3T, suggest that U3Bi4Rh3 may be a new example of a material displaying ferromagnetic quantum criticality.
A double-exchange mechanism for the emergence of ferromagnetism in cubic uranium compounds is proposed on the basis of a $j$-$j$ coupling scheme. The idea is {\it orbital-dependent duality} of $5f$ electrons concerning itinerant $Γ_8^-$ and localized $Γ_7^-$ states in the cubic structure. Since orbital degree of freedom is still active in the ferromagnetic phase, orbital-related quantum critical phenomenon is expected to appear. In fact, odd-parity p-wave pairing compatible with ferromagnetism is found in the vicinity of an orbital ordered phase. Furthermore, even-parity d-wave pairing with si…
We study the spin-dependent electronic structure of UTe and UT_{2}Si_{2} (T=Cu and Mn) compounds with a combination of x-ray magnetic circular dichroism measurements and first principle calculations. By exploiting the presence of sizable quadrupolar and dipolar contributions to the U L_{2,3}-edge x-ray absorption cross section we are able to provide unique information on the extent of hybridization between 5f and 6d/3d electronic states, a key parameter regulating the physical properties of all actinide materials. Since this information is hardly accessible to other probes, the new methodology…
Graphite intercalation compounds (GICs) with the geometrical anisotropy and strong electron-phonon coupling are in full swing and have shown their great potential for applications in nanodevices. I selected representative three elements in actinide group with valence electron arrangement: Thorium (Th) ([Rn]6d27s2), Uranium (U) ([Rn]5f36d17s2), Plutonium (Pu) ([Rn]5f67s2). I calculated their phonon spectra and demonstrated the atomic-scale microstructure identification of actinide graphite intercalation compounds by angle-resolved polarized Raman spectroscopy.
We present theoretical results for the underscreened Kondo lattice model with localized S=1 spins coupled to a conduction band through a Kondo coupling, $J_K$, and interacting among them ferromagnetically. We use a fermionic representation for the spin operators and expand the Hamiltonian in terms of bosonic fields. For large values of $J_K$, we obtain a ferromagnetically ordered solution and a Kondo regime with a Kondo temperature, $T_K$, larger than the Curie temperature, $T_C$. This finding suggests a scenario for a coexistence of Kondo effect and ferromagnetic order. In some uranium compou…
The technological settings of a modified sol-gel method for preparation of highly fine homogeneous powder Ca2CuO3 doped with uranium 238 (x=0-0.05) is presented. The analysis of structure, purity of phases and the justification for the role of uranium in the given compounds are provided together with almost complete classification of observed optical phonons by means of the Raman, IR measurements and ab initio calculation. The significant reduction in particle size was achieved by doping and the strong correlation between resistivity and doping concentration was observed and explained using th…
The electronic structures of cerium-based ternary 122 compounds Ce$M_{2}$Si$_{2}$, where $M =$ Ru, Rh, Pd, and Ag, are investigated systematically by using the density functional theory in combination with the single-site dynamical mean-field theory. The momentum-resolved spectral functions, total and 4$f$ partial density of states, self-energy functions, and valence state fluctuations are calculated. The obtained results are in good accord with the available experimental data. It is suggested that, upon increasing atomic number from Ru to Ag, the 4$f$ electrons should become increasingly loca…
The magnetic properties of RNi4Ga (R = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm and Lu) compounds have been investigated. These compounds form in a hexagonal CaCu5 type structure with a space group P6/mmm. Compounds with the magnetic rare earths, R = Nd, Sm, Gd, Tb, Dy, Ho, Er and Tm, undergo a ferromagnetic transition at 5 K, 17 K, 20 K, 19 K, 12 K, 3.5 K, 8 K and 6.5 K, respectively. The transition temperatures are smaller compared to their respective parent compounds RNi5. PrNi4Ga is paramagnetic down to 2 K. LaNi4Ga and LuNi4Ga are Pauli paramagnets. All the compounds show thermomagnetic irr…
Higher-fold chiral fermions that go beyond two-fold Weyl fermions have recently been reported in crystalline systems. Here, we focus on such excitations in several binary, ternary and quaternary alloys/compounds with CoGe, BiSbPt and KMgBO3 as the representative examples that belong to the crystal space group (SG) 198. We found distinct three-fold, four-fold and six-fold chiral fermions in the bulk via Density Functional computations. We provide general symmetry arguments for the protection of these degeneracies with special emphasis on the four-fold fermions. Our surface spectra simulations s…
Only several compounds bearing Ag(II) cation and other transition metal cation have been known. Herein, we predict stability and crystal structures of hypothetical ternary silver(II) fluorides with copper, nickel and cobalt in 1:1 stoichiometry at pressure range from 0 GPa up to 20 GPa within the frame of Density Functional Theory. Calculations show that AgCoF4 could be synthesized already at ambient conditions but this compound would host diamagnetic Ag(I) and high-spin Co(III). However, at increased pressure ternary fluorides of Ag(II) featuring Cu and Ni could be synthesized, in the pressur…
Based on crystal chemistry rationale and calculations within the density functional theory DFT, the U:B system is complemented with additional binary compounds UB3, U2B6, and UB6 possessing two-dimensional 2D and 3D boron substructures. Observations are supported quantitatively with the trends of cohesive energies, charge transfers onto the boron sub-lattice and geometry optimized structures. The results point out to a structure crossover from hexagonal (layer B network) to 3D boron network at compositions above UB3 found to be connected with a threshold amount of charge onto boron which is ~0…
Ternary C_{x}N_{y}O_{z} compounds are actively researched as novel high energy density and ultrahard materials. Although some synthesis work has been performed at ambient conditions, very little is known about the high pressure chemistry of of C_{x}N_{y}O_{z} compounds. In this work, first principles variable-composition evolutionary structure prediction calculations are performed with the goal of discovering novel mixed C_{x}N_{y}O_{z} materials at ambient and high pressure conditions. By systematically searching ternary variable composition crystalline materials, the full ternary phase diagr…
We present the magnetic and transport behavior of some Tb compounds, viz., TbIrGe2, TbFe(0.4)Ge2, and TbCo(0.4)Ge2. The stoichoometric germanide TbIrGe2 exhibits at least two distinct magnetic transitions in a close temperature interval around 10 K. The non-stoichiometric compounds, TbFe(0.4)Ge2 and TbCo(0.4)Ge2, undergo magnetic ordering around 17 and 19 K respectively. The magnetic state of these compouds appears to be antiferromagnetic-like. Qualitatively, there is a correlation between the field response of the magnetization (M), the magnetoresistance (MR) and the entropy change curve in a…
GICs doped with elements containing d and f orbitals have been studied rarely. We control the distribution and density of intercalated actinide metals (Th, U and Pu), and consider the effect of changing the distance of two adjacent carbon layers on the electronic structure so as to infer the physical properties of such materials under high pressure or high temperature - which is of great significance in fundamental research. According to band schemas, those GICs are all metallic. The projected density of states (PDOS) indicates that the metal atoms first undergo hybridization of its s, p, d, a…
Ternary tetradymites Bi2Te2S, Bi2Te2Se and Bi2Se2Te are found to be stable, bulk topological insulators via theory, showing band inversion between group V and VI pz orbitals. We identify Bi2Se2Te as a good candidate to study massive Dirac Fermions, with a (111) cleavage-surface-derived Dirac point (DP) isolated in the bulk band gap at the Fermi energy Ef like Bi2Se3 but with a spin texture alterable by layer chemistry. In contrast, Bi2Te2S and Bi2Te2Se (111) behave like Bi2Te3, with a DP below Ef buried in bulk bands. Bi2Te2S offers large bulk resistivity needed for devices.
Ordered intermetallics are long believed to be the final products of the aging of U-Nb solid solutions at low temperatures, a crucial property for the practical applications of this alloy in engineering and industry. However, such conjectured ordered compounds have not been experimentally or theoretically established. Herein, numerical evidence for ordered intermetallic U-Nb compounds is presented using thorough first-principles structure predictions up to 500 GPa. Two stable U2Nb compounds and one metastable U2Nb and one metastable U3Nb were discovered. A unique hybridized transition driven b…
We review topological properties of two series of ternary compounds AMgBi (A=K, RB, Cs) and ABC with a hexagonal ZrBeSi type structure. The first series of materials AMgBi are predicted to be topological critical Dirac semimetals. The second series of ternary compounds, such as KZnP, BaAgAs, NaAuTe and KHgSb, can be used to realize various topological insulating states and semimetal states. The states are highly tunable as the realization of these topological states depends on the competition between several energy scales, including the energy of atomic orbitals, the energy of crystal splittin…
An interesting class of tetrahedrally coordinated ternary compounds have attracted considerable interest because of their potential as good thermoelectrics. These compounds, denoted as I$_3$-V-VI$_4$, contain three monovalent-I (Cu, Ag), one nominally pentavalent-V (P, As, Sb, Bi), and four hexavalent-VI (S, Se, Te) atoms; and can be visualized as ternary derivatives of the II-VI zincblende or wurtzite semiconductors, obtained by starting from four unit cells of (II-VI) and replacing four type II atoms by three type I and one type V atoms. In trying to understand their electronic structures an…
Using an ab-initio density functional theory based electronic structure method with a semi-local density approximation, we study thin-film electronic properties of two topological insulators based on ternary compounds of Tl (Thallium) and Bi (Bismuth). We consider TlBiX$_2$ (X=Se, Te) and Bi$_2$$X$_2$Y (X,Y= Se,Te) compounds which provide better Dirac cones, compared to the model binary compounds Bi$_2$X$_3$ (X=Se, Te). With this property in combination with a structurally perfect bulk crystal, the latter ternary compound has been found to have improved surface electronic transport in recent e…
The fundamental principles underlying the arrangement of elements into solid compounds with an enormous variety of crystal structures are still largely unknown. This study presents a general overview of the structure types appearing in an important subset of the solid compounds, i.e., binary and ternary compounds of the 6A column oxides, sulfides and selenides. It contains an analysis of these compounds, including the prevalence of various structure types, their symmetry properties, compositions, stoichiometries and unit cell sizes. It is found that these compound families include preferred st…
Discovering new materials with ultrahigh thermal conductivity has been a critical research frontier and driven by many important technological applications ranging from thermal management to energy science. Here we have rigorously investigated the fundamental lattice vibrational spectra in ternary compounds and determined the thermal conductivity using a predictive ab initio approach. Phonon transport in B-X-C (X = N, P, As) groups is systematically quantified with different crystal structures and high-order anharmonicity involving a four-phonon process. Our calculation found an ultrahigh room…
We propose a new layered-ternary Ta4SiC3 with two different stacking sequences (α- and β-phases) of the metal atoms along c axis and study their structural stability. The mechanical, electronic and optical properties are then calculated and compared with those of other compounds M4AX3 (M = V, Nb, Ta; A = Al, Si and X = C). The predicted compound in the α-phase is found to possess higher hardness than any of these compounds. The independent elastic constants of the two phases are also evaluated and the results discussed. The electronic band structures for α- and β-Ta4SiC3 show metallic conducti…
The electronic structure of crystalline CdTe, CdO, $α$-TeO$_2$, CdTeO$_3$ and Cd$_3$TeO$_6$ is studied by means of first principles calculations. The band structure, total and partial density of states, and charge densities are presented. For $α$-TeO$_2$ and CdTeO$_3$, Density Functional Theory within the Local Density Approximation (LDA) correctly describes the insulating character of these compounds. In the first four compounds, LDA underestimates the optical bandgap by roughly 1 eV. Based on this trend, we predict an optical bandgap of 1.7 eV for Cd$_3$TeO$_6$. This material shows an isolat…
We present anisotropic, zero applied magnetic field, temperature dependent resistivity measurements on hexagonal, non-magnetic, YPtIn and LuAgGe single crystals. For these materials the in-plane resistivity, $ρ_{ab}$, is significantly higher than the $c$ - axis one, $ρ_c$, with $ρ_{ab}/ρ_c \approx 1.4$ for YPtIn and $\approx 4.2 - 4.7$ for LuAgGe. The connection between the electronic structure and the anisotropic transport properties is discussed using density functional calculations that link the observed anisotropy with a specific shape of Fermi surface and anisotropy of the Fermi velocitie…
We have extended the search for topological insulators to the ternary tetradymite-like compounds M2X2Y (M = Bi or Sb; X and Y = S, Se or Te), which are variations of the well-known binary compounds Bi2Se3 and Bi2Te3. Our first-principles computations suggest that five existing compounds are strong topological insulators with a single Dirac cone on the surface. In particular, stoichiometric Bi2Se2S, Sb2Te2Se and Sb2Te2S are predicted to have an isolated Dirac cone on their naturally cleaved surface. This finding paves the way for the realization of the topological transport regime.
We report a new family of ternary 111 hexagonal LnAuSb (Ln = La-Nd, Sm) compounds that, with a 19 valence electron count, has one extra electron compared to all other known LnAuZ compound. The "19th" electron is accommodated by Au-Au bonding between the layers; this Au-Au interaction drives the phases to crystallize in the YPtAs-type structure rather than the more common LiGaGe-type. This is critical, as the YPtAs structure type has the symmetry-allowed band crossing necessary for the formation of Dirac semimetals. Band structure, density of stats, and crystal orbital calculations confirm this…
Employing {\it ab initio} electronic structure calculations we extensively study ternary Heusler compounds having the chemical formula X$_2$X$^\prime$Z, where X = Mn, Fe or Co; Z = Al or Si; and X$^\prime$ changes along the row of 4$d$ transition metals. A comprehensive overview of these compounds, addressing the trends in structural, electronic, magnetic properties and Curie temperature is presented here along with the search for new materials for spintronics applications. A simple picture of hybridization of the $d$ orbitals of the neighboring atoms is used to explain the origin of the half-…
We demonstrate that first-principles based adiabatic continuation approach is a very powerful and efficient tool for constructing topological phase diagrams and locating non-trivial topological insulator materials. Using this technique, we predict that the ternary intermetallic series Li$_2M'X$ where $M'$=Cu, Ag, Au, or Cd, and $X$=Sb, Bi, or Sn, hosts a number of topological insulators with remarkable functional variants and tunability. We also predict that several III-V semimetallic compounds are topologically non-trivial. We construct a topological phase diagram in the parameter space of th…
The structural stability and electronic properties of the ternary intermetallic compounds NiSnM (M = Ti, Zr, Hf) and the closely related Heusler compounds Ni$_2$SnM are discussed using the results of ab initio pseudopotential total energy and band-structure calculations performed with a plane wave basis set using the conjugate gradients algorithm. The results characterize the lowest energy phase of NiSnM compounds, with a SnM rocksalt structure sublattice, as narrow gap semiconductors with indirect gaps near 0.5 eV. Two other atomic arrangements for NiSnM in the MgAgAs structure result in ener…
We present a comprehensive investigation of semi-classical transport properties of n-type ternary compound AlGaAs2, using Rode's iterative method. Four scattering mechanisms, have been included in our transport calculation, namely, ionized impurity, piezoelectric, acoustic deformation and polar optical phonon (POP). The scattering rates have been calculated in terms of ab-initio parameters. We consider AlGaAs2 to have two distinct crystal geometries, one in tetragonal phase (space group: ), while the other one having body centered tetragonal crystal structure (space group:). We have observed h…
We study a newly predicted layered-ternary compound Ti4SiN3 in its α- and β-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 α- and β-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…
One of the most exciting subjects in solid state physics is a single layer of graphite which exhibits a variety of unconventional novel properties. The key feature of its electronic structure are linear dispersive bands which cross in a single point at the Fermi energy. This so-called Dirac cone is closely related to the surface states of the recently discovered topological insulators. The ternary compounds, such as LiAuSe and KHgSb with a honeycomb structure of their Au-Se and Hg-Sb layers feature band inversion very similar to HgTe which is a strong precondition for existence of the topologi…
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…
We have synthesized and investigated the magnetic and transport properties of a series of compounds, R2CoIn8 (R = rare earth). Compounds form in single phase with a tetragonal structure (space group P4/mmm, no. 162). The Ce compound shows heavy fermion behavior. The magnetic susceptibility of Pr2CoIn8 shows a marked deviation from the Curie-Weiss behavior at low temperatures, which is attributed to the crystalline electric field effects. Heat capacity and magnetization measurements show that Dy2CoIn8 undergoes a magnetic transition at 17 K and a second transition near 5 K, the latter of which …
Computational searches for new materials are naturally turning from binary systems, to ternary and other multicomponent systems, and beyond. Here, we select the industrially-relevant metals titanium and aluminium and report the results of an extensive structure prediction study on the ternary titanium-carbon-oxygen (Ti-C-O) and aluminium-carbon-oxygen (Al-C-O) systems. We map out for the first time the full phase stability of Ti-C-O and Al-C-O compounds using first-principles calculations, through simple, efficient and highly parallel random structure searching in conjunction with techniques b…
Various ternary chalcogenide systems and their properties are one of the hot topics for researchers nowadays. In this article, one of the ternary chalcogenide compounds, CdTl2Te4 is studied including its electronic structures and optical properties via first principles calculations using SIESTA code. The structure of the compound has a tetragonal crystal system and the unit cell is periodic in all directions. The band structure showed it is a direct band gap semiconductor which is explained by the density of states. The energy gap obtained is seen to increase on employing external electric fie…
Magnetic skyrmions, topologically protected chiral spin swirling quasiparticles, have attracted great attention in fundamental physics and applications. Recently, the discovery of two-dimensional (2D) van der Waals (vdW) magnets has aroused great interest due to their appealing physical properties. Moreover, both experimental and theoretical works have revealed that isotropic Dzyaloshinskii Moriya interaction (DMI) can be achieved in 2D magnets or ferromagnet-based heterostructures. However, 2D magnets with anisotropic DMI haven't been reported yet. Here, via using first-principles calculation…
Density functional calculations have performed to study the band structures of $Bi_2Te_3$-related binary ($Bi_2Te_3$, $Sb_2Te_3$, $Bi_2Se_3$, and $Sb_2Se_3$) and $Sb$/$Se$ doped ternary compounds [$(Bi_{1-x}Sb_x)_2Te_3$ and $Bi_2(Te_{1-y}Se_y)_3$]. It is found that the band gap can be increased by $Sb$ doping and it is monotonically increased by $Se$ doping. In ternary compounds, the change of the conduction band structure is more significant, as compared to the change of valence band. The band degeneracy of valence band maximum is maintained to be 6 in binaries and ternaries. However, as goin…
Here we report the discovery of superconductivity in the ternary LaRu2As2 compound. The polycrystalline LaRu2As2 samples were synthesized by the conventional solid state reaction method. Powder X-ray diffraction analysis indicates that LaRu2As2 crystallizes in the ThCr2Si2-type crystal structure with the space group I4/mmm (No. 139), and the refined lattice parameters are a = 4.182(6) Å and c = 10.590(3) Å. The temperature dependent resistivity measurement shows a clear superconducting transition with the onset Tc (critical temperature) at 7.8 K, and zero resistivity happens at 6.8 K. The uppe…
Crystallographic data, Seebeck coefficient, electrical resistance and thermal conductivity are reported for a large number of rare-earth compounds, manifestations of the Kondo effect being discussed. In more detail, thermoelectric properties of Yb3Co4Ge13 and Yb3Co4Sn13 compounds and Yb2CeCo4Ge13 and Yb2.3La0.7Co4Ge13 solid solutions are presented.
The recent discovery of room temperature superconductivity (283 K) in carbonaceous sulfur hydride (C-S-H) has attracted lots of interests in ternary hydrogen rich materials. In this report, ternary hydride P-S-H has been synthesized through photochemical reaction from elemental sulfur (S), phosphorus (P) and molecular hydrogen (H2) at high pressures and room temperature. The Raman spectroscopy under pressure shows that H2S and PH3 compounds are synthesized after laser heating at 0.9 GPa and a ternary van der Waals compound P-S-H is synthesized with a further compression to 4.6 GPa. The P-S-H c…
We report the computational investigation of a series of ternary X$_4$Y$_2$Z and X$_5$Y$_2$Z$_2$ compounds with X={Mg, Ca, Sr, Ba}, Y={P, As, Sb, Bi}, and Z={S, Se, Te}. The compositions for these materials were predicted through a search guided by machine learning, while the structures were resolved using the minima hopping crystal structure prediction method. Based on $\textit{ab initio}$ calculations, we predict that many of these compounds are thermodynamically stable. In particular, 21 of the X$_4$Y$_2$Z compounds crystallize in a tetragonal structure with $\textit{I-42d}$ symmetry, and e…
8K superconductivity was observed in the metal rich Li-Pd-B ternary system. Structural, microstructural, electrical and magnetic investigations for various compositions proved that Li2Pd3B compound, which has a cubic structure composed of distorted Pd6B octahedrons, is responsible for the superconductivity. This is the first observation of superconductivity in metal rich ternary borides containing alkaline metal and Pd as a late transition metal. The compound prepared by arc melting has high density, is stable in the air and has an upper critical field, Hc2(0), of 6T.
Recently the Quantum Spin Hall effect (QSH) was theoretically predicted and experimentally realized in a quantum wells based on binary semiconductor HgTe[1-3]. QSH state and topological insulators are the new states of quantum matter interesting both for fundamental condensed matter physics and material science[1-11]. Many of Heusler compounds with C1b structure are ternary semiconductors which are structurally and electronically related to the binary semiconductors. The diversity of Heusler materials opens wide possibilities for tuning the band gap and setting the desired band inversion by ch…
The data on the electronic and magnetic properties of the ternary ytterbium-based alloy YbPd$_2 $Ge$_{1.7}$ are presented and compared with those for YbPd$_2 $Ge$_{2}$ and YbPd$_2 $Ge compounds. YbPd$_2 $Ge$_{1.7}$ demonstrates a moderate heavy-fermion behavior with linear specific heat coefficient $γ\simeq $ 100 mJ/mol K$^2$. Magnetic susceptibility is large and demonstrates nearly Curie behavior. Resistivity shows a power-law $T^{1.2}$-dependence at not too low temperatures $T$. Thermoelectric power has non-monotonous behavior and changes its sign at low $T$.
Predicting a new Dirac semimetal (DSM), as well as other topological materials, is quite challenging, since the relationship between crystal structure, composing atoms and the band topology is complex and elusive. Here, we demonstrate an approach to design DSMs via exploring the chemical degree of freedom. Based on the understanding of the well-known DSM Na$_3$Bi, three compounds in one family, namely Na$_2$MgSn, Na$_2$MgPb and Na$_2$CdSn, have been exactly located. Further hybrid-functional calculations with improved estimation of band inversion show that two of them, Na$_2$MgPb and Na$_2$CdS…
Superconducting ternary compounds Li-X-B (X=Mo, W) within the mild pressure range: First-principles predictions
State Key Laboratory of Quantum Functional Materials, School of Physical Science and Technology, ShanghaiTech University（上海科技大学物理科学与技术学院量子功能材料国家重点实验室）；School of Physics, Hangzhou Normal University（杭州师范大学物理学院）；ShanghaiTech Laboratory for Topological Physics, ShanghaiTech University（上海科技大学拓扑物理实验室）；National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学物理学院固体微结构物理国家重点实验室先进微结构协同创新中心）；Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学先进微结构协同创新中心）；Shanghai Key Laboratory of High-resolution Electron Microscopy, ShanghaiTech University（上海科技大学高分辨电子显微镜上海市重点实验室）
The outer crust of a cold nonaccreting neutron star has been generally assumed to be stratified into different layers, each of which consists of a pure body-centered cubic ionic crystal in a charge compensating background of highly degenerate electrons. The validity of this assumption is examined by analyzing the stability of multinary ionic compounds in dense stellar matter. It is thus shown that their stability against phase separation is uniquely determined by their structure and their composition irrespective of the stellar conditions. However, equilibrium with respect to weak and strong n…
We explore the stability of structure exhibiting hybridization gaps across a broad range of binary and ternary intermetallic compositions by means of band structure and total energy calculations. This search reveals previously unknown metal-based insulators, some with large gaps exceeding 1 eV, such as Al2Fe and Al4IrRe. We confirm large gaps using a hybrid density functional including exact exchange, and predict a gap of 2.2 eV for AlMnSi in the Pearson type tP6 structure, which is a chemically ordered ternary variant of the prototype MoSi2 (Pearson type tI6) structure.
We studied the magnetoresistivity of the AM2B2 and A3Rh8B6 (A = Ca, Sr; M = Rh, Ir) compounds within the ranges 1.8<=T<=300 K and 0<=H<=50 kOe. The zero-field resistivity ρ0(T) is metallic and follows closely the Bloch-Grüneisen description. A positive, nonsaturating, and dominantly linear-in-H magnetoresistivity was observed in all samples, including the ones with a superconducting ground state. Such ΔρT(H)/ρT(0), reaching 1200% in favorable cases, was found to be much stronger for the AM2B2 compounds and to decrease with temperature as well as when Ca is replaced by Sr, or Rh is replaced by …
We predicted a new ternary hydride Li$_2$SiH$_6$ at high pressures. A systematic structure search in Li$_2$SiH$_6$ compound reveals novel stable phases with intriguing electronic and phonon properties. It is found that Li$_2$SiH$_6$ is dynamically stable from ambient pressure up to 400 GPa with three novel phases: P312, P$\bar{3}$, and P$\bar{6}$2m. The calculation of electron-phonon coupling combined with Bardeen-Cooper-Schrieffer's argument indicates that this compound may be a candidate for high $T_c$ superconductors under high pressures. In particular, the maximum $T_c$ of $P\bar{6}2m$-Li$…
