Narrow Results

Few-nucleon systems can be used as fundamental laboratories for studying details of the nuclear force effects. We performed a series of deuteron-deuteron scattering experiments at intermediate energies. The experiments exploited BINA and BBS experimental setups and polarized deuteron beams with kinetic energies of 65 and 90 MeV/nucleon. These experiments aim to measure differential cross sections, vector and tensor analyzing powers of all available reaction channels in deuteron-deuteron scattering. With these data we will provide a systematic database, which will be used to test present theoretical approximations and upcoming ab-initio calculations in four-nucleon system.

The LHC energies are those at which the asymptotic regime in hadron–hadron diffractive collisions (pp, πp, ππ) might be switched on. Based on results of the Dakhno–Nikonov eikonal model which is a generalization of the Good–Walker eikonal approach for a continuous set of channels, we present a picture for transformation of the constituent quark mode to the black disk one. In the black disk mode , we have a growth of the logarithm squared type for total and elastic cross-sections, σ_tot ~ ln² s and σ_el ~ ln² s and -scaling for diffractive scattering and diffractive dissociation of hadrons. The diffractive dissociation cross-section grows as σ_D ~ ln s, σ_DD ~ ln s, and their relative contribution tends to zero: σ_D/σ_tot → 0, σ_DD/σ_tot → 0. Asymptotic characteristics of diffractive and total cross-sections are universal, and this results in the asymptotical equality of cross-sections for all types of hadrons (the Gribov universality). The energy scale for switching on the asymptotic mode is estimated for different processes.

Bismuth telluride (Bi₂Te₃) is one of the most intricate materials with its semiconducting, insulating and pressure-induced superconducting properties. Although different theoretical works have been carried out to understand the confusing properties of Bi₂Te₃, information about the high pressure structural, elastic, mechanical and phonon properties of this significant material is still rare. Unlike earlier theoretical approaches, two-body interatomic potentials in the Morse potential form have been employed for the first time to predict the density, phase transition pressure, elastic constants, bulk, shear and Young moduli and elastic wave velocities of Bi₂Te₃ under pressures up to 12 GPa. $\alpha \to \beta$ phase transition pressure of Bi₂Te₃ was found to be 10 GPa. The results of above elastic quantities agree well with experiments and are better than some of the published theoretical data. In addition, the effect of pressure on the phonon dispersion and density of states (DOS) were also evaluated with the same potential and their results are satisfactory, especially for the low-frequency acoustic portions of phonons.

The structural, elastic and thermal properties of $\gamma$-TiAl and ${\alpha }_2$-Ti₃Al phases in the TiAl-based alloy under pressure were reported using CASTEP program based on the density functional theory. The calculated equilibrium parameters and elastic constants are in good agreement with experimental and the available theoretical data. The results indicate that under the same pressure, the ${\alpha }_2$ phase in the direction along $a$-axis is easier to be compressed than the $\gamma$ phase, while the compression along $c$-axis of $\gamma$ phase is larger than that of ${\alpha }_2$ phase; when the pressure is below 20 GPa, both the two phases are elastically stable, but the $\gamma$ phase have higher shear modulus and Young’s modulus, and the ${\alpha }_2$ phase has better ductility and plasticity. Debye temperature, bulk modulus, thermal expansion coefficient and heat capacity of the $\gamma$ phase and ${\alpha }_2$ phase under high pressure and high temperature were also successfully calculated and compared using the quasi-harmonic Debye model in the present work.

The structural stability, elastic, mechanical, optical characteristics and Debye temperature of single crystalline superconductors MPd₂P₂ (M = Y, La) were investigated by using the ab initio technique. We have carried out the plane wave pseudopotential within the generalized gradient approximation (GGA) implemented in the CASTEP computer code. Our investigated results of structural data are in well consistent with the previous experimental data. The bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio v, hardness H, and anisotropic factor A of MPd₂P₂ (M = Y, La) compounds were evaluated from the calculated elastic constants. The analysis of ratio B/G shows that the MPd₂P₂ superconductors are in ductile behavior. The Debye temperatures are also investigated from the elastic constants. Finally, the optical functions including reflectivity, absorption coefficient, loss function, conductivity, refractive index, dielectric function are calculated and analyzed.

The elastic and photocatalytic properties of multiferroic material InFeO₃ under strain are calculated through density functional theory. The calculated results indicate that the intrinsic InFeO₃ and the strained InFeO₃ meet the mechanical stability conditions and hold a relatively larger elastic coefficient than popular multiferroic material BiFeO₃. The calculated bandgap and band edge of InFeO₃ under tensile strain show that InFeO₃ could be a high-efficiency photocatalytic hydrogen production material. InFeO₃ under tensile strain holds the ability of photocatalytic water splitting to produce hydrogen with excellent ferroelectric, mechanical properties and absorption of visible light.

Since crystal structure dictates the resultant physical properties of materials, titled physical features of the P2₁ monoclinic SiGe semiconductors, which are still unclear, have been revealed by density functional theory (DFT). The electronic band gap value with 0.49eV was found to be in the order of previously published cubic and hexagonal closed-packed SiGe semiconductors. Surprisingly, P2₁ monoclinic SiGe has a room temperature Seebeck coefficient of 1500$\mu$V/K which is higher than the reported data of both cubic and hexagonal SiGe alloys. Further, the mechanically stable P2₁ monoclinic phase of the SiGe displays a brittle mechanical character with clear elastic anisotropy has also been deduced. The P2₁ monoclinic phase of the SiGe can be also considered a good high-dielectric material and beneficial for practical applications of IR or UV goals due to its high refractive index.

In this paper, the electronic, optical, elastic, mechanical, and vibrational properties of glass B₂O₃ have been investigated. Simulations have been carried out including the P3₁21 structure. Our nonlocal empirical hybrid has accurately described the electronic band structure and band gap energy $E_g$ of the material. Our optical absorption plot has correctly identified the type of the glass B₂O₃ structure. The absorption plot also shows the interband indirect transitions from the valance O 2p¹ to conduction B 2p⁴ orbitals. We have also included the elastic constants and phonon dispersions to test the dynamic stability of the systems. Our theoretical findings bear fundamental interests in the development of complicated amorphous nanostructures.

Based on the framework of density functional theory (DFT), the structure, elastic, optical, Debye temperature and piezoelectric properties of tetragonal ${\mathrm{\text{BaTiO}}}_3$ (BT) individually doped with calcium (Ca) at barium (Ba) and zirconium (Zr) at titanium (Ti) site have been investigated by a first-principles technique. These properties of Ca and Zr (Ca/Zr) co-doped BT (BCZT) also have been investigated by the same calculation method. The effects of exchange and correlation functional on these properties are also investigated. The structural studies have demonstrated that the Ca-doped BT (BCT) exhibits the reduced volume due to radius of Ca smaller than that of Ba, while Zr-doped BT (BZT) presents the enlarged volume due to radius of Zr being larger than that of Ti. The as-calculated lattice parameters have verified the consistency of well-designed crystal structure with the experimental results. The investigations of the band structure demonstrated that the doping of Ca, Zr and Ca/Zr enlarges the band gap ($E_B$) of BT in sequence. Furthermore, the $E_B$ values obtained via HSE06 matched well with experimental values, while those obtained by generalized gradient approximation (GGA) and local density approximation (LDA) are significantly lower. The studies of optical, Debye temperature and elastic properties show that the BCZT displays a decreased refractive index, reduced thermal conductivity and an enhanced anisotropy index. Most importantly, after the co-doping of Ca and Zr, the piezoelectric strain tensor $d_{33}$ of BCZT increases by $\sim 125$% compared to that of BT. This work provides a theoretical guidance for improving the piezoelectric performance of BT via the doping strategy.

Using ab initio first-principles calculations, we investigate the structural, electronic, optical, and vibrational properties of Silver Sulphide Ag₃S and Selenide Ag₃Se with nonlocal hybrids exchange-correlation functional. With our computational predictions, we manage to classify the material to be Fermi-Dirac semi-metal, rather than Weyl metal. Our calculated results show that the electronic band in between the Fermi-Dirac cone shifts downward when we replace the element Sulphide S with Selenide Se. The obtained optical results such as absorption coefficients and dielectric functions (conductivity, reflectivity, etc.) are similar for both Ag₃S and Ag₃Se. A high absorption coefficient of $2\times 10^5$ cm${}^{-1}$ has been reported, and about 50% of light is reflected. In Raman spectra, the A${}_{\mathrm{\text{g}}}^{\mathrm{\text{X}}\text{-}\mathrm{\text{X}}}$ managed to shift downward when replacing the element X, sulphide S with selenide Se, while the A${}_{\mathrm{\text{g}}}^{\mathrm{\text{rigid}}}$ shifts upward (to higher wavelength). The rotation and vibration of the bonding between atoms have also been explained. The calculated results of Silver-VI compounds provide useful information in the exploitation of more complicated structures.

Ab Initio density functional theory (DFT) simulations have been employed to systematically explore the electronic, optical, elastic, mechanical and vibrational properties. In this study, we revealed that $\gamma$-CuI has a wide direct bandgap energy of 3.21 eV, is pure covalent and brittle. We also found that the core level is made up of I s electron orbitals, the valence band is constructed with I p orbitals, and the Cu s orbital states mainly contribute to the conduction band minimum (CBM). The reflectivity of CuI is reported to be low (35.9% for the light reflected), showing high material absorption. A high absorption coefficient of $2.31\times 10^5{\mathrm{\text{cm}}}^{-1}$ is also reported. The elastic and mechanical properties can further confirm the mechanical stability of the CuI system, derived from DFT-calculated elastic constants and phonon dispersion from density functional perturbation theory (DFPT) calculations.

In this paper, we will investigate the structural, electronic, mechanical, magnetic and optical properties of Heusler Mn₂NiAl (MNA) compound using the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) of the full potential linearized augmented plane-wave method for exchange and use correlations, modified Becke–Johnson and GGA+U Hubbard parameter. The calculated band structure (BS) and density of states (DOS) of MNA showed a metallic (GGA), nearly half-metallic (mBJ) and half metallic (GGA+U) behavior. Moreover, the magnetic computed magnetic moments by GGA+U are higher compared to GGA and mBJ results. Bulk modulus, shear modulus, Voigt and Reuss polycrystalline elastic modulus, Debye temperature, sound velocities, the melting temperatures, $B/G$ ratio, Young’s modulus and Poisson’s ratio were obtained. The elastic anisotropy of MNA alloy was analyzed using 2D and 3D figures of directional dependence of Poisson’s ratio, shear modulus, linear compressibility and Young’s modulus. Studies have shown that the Heusler material MNA has magnetic and anisotropic properties and is mechanically stable.

The anti/de-icing methods are mainly divided into two types: active method and passive method. The passive method generally adopts three ideas: reducing water contact, inhibiting water icing and reducing ice adhesion. Silica aerogels, which have adjustable surface wettability, thermal conductivity and porosity, would be designed to satisfy the requirement for passive anti/de-icing methods. In this work, the organic–inorganic hybrid aerogels based on organosilicon were facilely prepared in a sol–gel procedure, which showed hydrophobic and elastic properties. It could be seen that the thermal insulation effect originating from aerogel-like porous network endowed the efficient anti-icing property. Moreover, the lowest ice adhesion strengths of the above silica aerogels and the related oil-based lubricant-filled aerogels were 7.1kPa and 5kPa, respectively, which belonged to the icephobic surface. Besides, the ice adhesion strength only increased to 15.6kPa after 30 icing–deicing cycles, showing that hydrophobic and elastic silica aerogels had efficient deicing durability.

Research Highlights

• •Electronic, magnetic, elastic and thermoelectric properties of RbCrC alloy are investigated.
• •Material is half-metallic, ductile and anisotropic in nature.
• •The total magnetic moment (3$\mu$B) obeys the Slater–Pauling rule.
• •The HM RbCrC compound is identified as potential candidate for spintronic applications.
• •ZT calculated values of 0.89 and 0.94 make RbCrC a promising thermoelectric material candidate for use in future devices.

The aim of this work is to investigate the half-metallicity behavior, elastic, thermodynamic and thermoelectric (TE) properties of the Heusler compound RbCrC using the generalized gradient approximation (GGA-PBE96) and the modified Becke–Johnson (mBJ) approach. The electronic band structures and density of states reveal that RbCrC is a half-metallic ferromagnet (HMF). The calculated total magnetic moment of 3$\mu$B follows the Slater–Pauling rule ($M_{\mathrm{\text{tot}}}=Z_{\mathrm{\text{tot}}}-8$). The half-metallicity character can be maintained in the 5.4–7.4 Å lattice constants range and the 0.8–1.2 $c$/$a$ ratio range. Existence of half-metallic ferromagnetism in RbCrC makes it a promising material for practical applications in the spintronic field. Also, the RbCrC exhibits a ductile and anisotropic behavior. The quasi-harmonic Debye model (QHDM) is used to calculate the thermodynamic properties. The BoltzTraP code which is based on semi-classical Boltzmann theory (SCBT) is applied for calculating TE properties. According to the obtained figure of merit values (ZT between 0.89 and 0.94 from 50 K to 800 K), the RbCrC alloy remains a good candidate for thermoelectric applications.