Journal of Physics: Condensed Matter最新文献

The evolution of an ensemble of spherical crystals in a supersaturated solution is considered with allowance for fluctuations in crystal growth rates and initial crystal-size distribution. Two approaches for constructing the analytical solutions based on the saddle-point method and separation of radial and time functions are developed. Both methods yield similar desupersaturation dynamics, which agree well with the experimental data. The first method gives a crystal-size distribution function decaying with time, consistent with a decrease in solution supersaturation. The second method results in a distribution function with opposite dynamics and works only in the case of exponentially decaying initial crystal-size distribution. Therefore, the first method can be used to determine any characteristics of an ensemble of crystals based on calculating the moments of the distribution function. The use of the second, mathematically simpler method, is suitable only for describing the kinetics of supersaturation removal.

The physics of charge transport across the interface in an inorganic Si/organic conducting polymer junction diode has received little attention compared to the inorganicp-nsilicon diode. One reason is the amorphous nature of the organic polymer and the polymer chain orientation which introduces disorder and barriers to charge flow. Herein we first present an easy technique to fabricate an inorganic/organic,p-Si/n-poly(benzimidazobenzophenanthroline-BBL) junction diode. The physics of charge transport across the heterojunction, and in the BBL film is then analyzed from the device current-voltage characteristics as a function of temperature in the range 150 K <T< 370 K. The temperature dependence of the diode ideality parameter and of the saturation current density demonstrate that tunneling enhanced charge recombination via exponential trap distributions in the depletion region was responsible for charge transport across the junction. Furthermore, the temperature dependence of the diode conductance revealed that thermal activation and hopping both contributed to charge transport in the BBL film away from the junction. BBL is a ladder polymer with a discrete layered crystal structure that is oriented perpendicular to the substrate. Such polymer chain orientation, combined with a distribution of bond lengths and numerous conjugation paths available for charge delocalization result in the multiple charge transport mechanisms as observed in the diode.

NaNiO₂is a Ni³⁺-containing layered material consisting of alternating triangular networks of Ni and Na cations, separated by octahedrally-coordinated O anions. At ambient pressure, it features a collinear Jahn-Teller distortion belowTonsetJT≈480 K, which disappears in a first-order transition on heating toTendJT≈500 K, corresponding to the increase in symmetry from monoclinic to rhombohedral. It was previously studied by variable-pressure neutron diffraction (Nagle-Coccoet al2022ACS Inorg. Chem.614312) and found to exhibit an increasingTonsetJTwith pressure up to ∼5 GPa. In this work, powdered NaNiO₂was studied via variable-pressure synchrotron x-ray diffraction up to pressures of ∼67 GPa at 294 K and 403 K. Suppression of the collinear Jahn-Teller ordering is observed via the emergence of a high-symmetry rhombohedral phase, with the onset pressure occurring at ∼18 GPa at both studied temperatures. Further, a discontinuous decrease in unit cell volume is observed on transitioning from the monoclinic to the rhombohedral phase. These results taken together suggest that in the vicinity of the transition, application of pressure causes the Jahn-Teller transition temperature,TonsetJT, to decrease rapidly. We conclude that the pressure-temperature phase diagram of the cooperative Jahn-Teller distortion in NaNiO₂is dome-like.

Silica-binding peptides (SBPs) are increasingly recognized as versatile tools for various applications spanning biosensing, biocatalysis, and environmental remediation. This review explores the interaction between these peptides and silica surfaces, offering insights into how variables such as surface silanol density, peptide sequence and composition, and solution conditions influence binding affinity. Key advancements in SBP applications are discussed, including their roles in protein purification, biocatalysis, biosensing, and biomedical engineering. By examining the underlying binding mechanisms and exploring their practical potential, this work provides a comprehensive understanding of how SBPs can drive innovations in materials science and biotechnology.

We show with hybrid density functional theory calculations that chalcogen donors other than oxygen (i.e. SN, SeN, and TeN) give rise to deep donor states in aluminum nitride. These donors trap a localized electron in their neutral charge state, leading to deep (+/0) donor levels that are 0.45 eV or more from the conduction-band edge. As such, this behavior is distinct from theDXbehavior leads to deep (+/-) levels which affects other donors such as ONand SiAl. We highlight how these results hint at the formation of small electron polarons in AlN, which are found to be unstable in the bulk, but metastable when bound to donor dopants like SiAland the chalocogens, with activation energies on the order of 0.2-0.3 eV. These results indicate that S, Se, and Te are not shallow donor dopants in aluminum nitride and identify origins of the experimentally observed ∼200-300 meV activation energies for dopant activation in donor-doped samples.

DiboridesAB2crystallizing in the hexagonal C32 structure exhibit a wide range of magnetic and electronic properties depending on the choice of the elementAand the precise values of the lattice constantsaandc. ErB₂represents a typical rare-earth diboride, exhibiting easy-plane ferromagnetic order below 14 K. We report a study of the evolution of the electrical transport properties of ErB₂when tuning the lattice constants under pressures up to 5.6 GPa. Using Bridgman-type pressure cells with polycrystalline diamond anvils and steatite as the solid pressure medium, quasi-hydrostatic conditions are provided. We find that magnetic order is stabilized under pressure and discuss the influence of uniaxial components by comparing measurements on polycrystalline and single-crystalline samples.

The class of zinc dialkyldithiophosphates (ZDDPs) has been the most widely used anti-wear additive class in the automotive industry for over 60 years, yet the pathway to the generation of the protective tribofilm remains elusive. In this context, density functional theory (DFT) can be utilized to investigate the interactions between ZDDPs and materials surfaces. We employed DFT+Ucalculations to examine the electronic structure of bulk hematite and three relevant (0001) surface terminations: Fe-O-Fe, O-Fe-Fe, and HO-Fe-Fe. Our results demonstrate that, while the Fe-O-Fe and HO-Fe-Fe slabs are insulating, the O-Fe-Fe terminated slab is metallic due to the formation of surface states from O dangling bonds. Additionally, we found that ZDDP binds more strongly on the Fe-O-Fe slab, leading to changes in ZDDP geometry and atomic charges. Minimal changes are observed when bound to the other surfaces. We have provided an in-depth study of the electronic structure of hematite and its surfaces, and their interaction with ZDDP. We include a detailed study of the first-principles Hubbard U and Hund J for Fe 3d orbitals in bulk hematite, finding a negligible self-consistency effect but a significant projector dependence. The new insights from this work provide a new path that can be used to understand the decomposition pathways of ZDDPs on metallic surfaces.

The discovery of two-dimensional (2D) magnetic materials ushers in the engineering of future magnetoelectric nanodevices and spintronics, however, it is limited by the lack of a material platform with simultaneously large magnetic anisotropy and high transition temperature. Using a recently synthesized CrSe₂monolayer as a demonstration, the impact on magnetism and electronics is studied via first-principles calculations by functionalizing the monolayer with electron-donating and electron-withdrawing groups namely NH₂and NO₂. The magnetic ground state of the CrSe₂changes from the stripe antiferromagnetic to the ferromagnetic state after functionalization. The transition temperature of CrSe₂-NO₂and CrSe₂-NH₂enhances to 105 and 70 K, respectively, due to the expansion of the CrSe₂superlattice. Besides, the magnetic anisotropy energy (MAE) of the CrSe₂-NO₂increases to 1.12 meV/Cr along the in-plane direction due to the electron-withdrawing effect of the NO₂group. Oppositely, the electron-donating effect will decrease the MAE. Moreover, robust out-of-plane electric polarization is induced into the functionalized CrSe₂monolayer, relying on the semiconducting nature and asymmetric geometry along thezdirection. These findings demonstrate the critical role of functional groups in regulating the magnetic and electronic properties of 2D multiferroic structures, providing a general approach for controllable 2D spintronic applications.

We performed inelastic neutron scattering experiments on single crystal samples of a linear magnetoelectric material Mn₃Ta₂O₈, which exhibits a collinear antiferromagnetic order, to reveal the spin dynamics. Numerous modes observed in the neutron spectra were reasonably reproduced by linear spin-wave theory on the basis of the spin Hamiltonian including eight Heisenberg interactions and an easy-plane type single-ion anisotropy. The presence of strong frustration was found in the identified spin Hamiltonian.