The glass transition in rapidly quenched Li17Pb83 remains a fundamental puzzle, particularly regarding the coupling among structural, dynamic and electronic properties in binary asymmetric alloy systems. Here, we perform ab initio molecular dynamics simulations during quenching to characterize its multi-scale evolution. A kinetic glass transition temperature Tking = 386.0 K is determined from the two-stage Arrhenius dependence of Li diffusion. Structural analysis reveals progressive enhancement of Pb short/medium-range order upon cooling, with the Pb–Pb coordination number increasing from 5.09 to 5.33 and the formation of Pb cage-like structures. Concurrently, Li dynamics transition from long-range hopping to localized rattling motions within these cages, as evidenced by van Hove correlation functions and phonon density of states. Electronic structure evolves synchronously. Pb-6p-dominated electron localization intensifies within the Pb cage network, accompanied by slight charge redistribution (Li: +0.136e to +0.130e, Pb −0.028e to −0.027e) and a marginal decrease in Pb–Pb bond order. These electronic changes are intimately linked to structural ordering and dynamic slowdown, providing atomic-scale evidence for the correlated nature of the glass transition. We propose a synergistic structure-dynamics-electron mechanism, Pb cage densification as the structural foundation, Li mobility arrest as the dynamic signature, and Pb-6p localization as the electronic feature that collectively accompanies the dynamic freezing of interstitial Li atoms. This work complements classical glass transition theories with atomic-scale electronic evidence and offers a multi-dimensional characterization approach for asymmetric binary amorphous alloys.
High-entropy engineering has emerged as an effective strategy for tailoring structural disorder and functional responses in tetragonal tungsten bronze (TTB) ferroelectrics. However, how configurational entropy, crystal structure, modulation characteristics, and relaxor dynamics govern the macroscopic electrical response remains insufficiently understood. Here, K(NaPr)1-x(SrBa)xNb5O15 ceramics with continuously varying configurational entropy were designed to investigate the origin of relaxor-ferroelectric evolution. With increasing Sr/Ba substitution, the electrical response evolves from an ergodic-relaxor state with slim hysteresis loops and four current peaks to a ferroelectric-like state with double current peaks, fatter loops, and increased remanent and maximum polarizations. This evolution is accompanied by increased lattice parameter c and tetragonality (c/a), indicating a structural evolution toward a more stable polar state. The dielectric anomalies and Vogel-Fulcher analysis further reveal an increase in freezing temperature and a decrease in activation energy, indicating strengthened coupling among polar nanoregions and a gradual evolution from the relaxor state toward a non-ergodic relaxor or ferroelectric state. Notably, this trend is opposite to the commonly expected enhancement of relaxor behavior in high-entropy systems, suggesting that configurational entropy does not simply strengthen relaxor characteristics through increased compositional disorder. Instead, configurational entropy modulates the order-disorder state of A-site occupation, thereby changing the octahedral tilting patterns and the modulation structure, which affects the diffuseness of the phase transition. These results demonstrate that the macroscopic electrical response in the high-entropy K(NaPr)1-x(SrBa)xNb5O15 system is regulated by crystal structure, modulation structure, and polar nanoregion dynamics, providing new insight into the relaxor behavior of TTB ferroelectrics.
Chongyang Zhang, Weijia Guo, Xingchen Zhang et al.· Journal of Advanced Ceramics· 1 citation
Chemical short-range order (CSRO), the non-random local arrangement of atoms in solid solutions, strongly affects the phase stability and performance of medium- and high-entropy alloys (M/HEAs). Despite its importance, the fundamental nature of CSRO formation remains contested: is it a formal thermodynamic transition? Here, investigating CoCrNi as a model system, we indicate that the main CSRO transformations observed in alloys might not be classical thermodynamic transitions, but instead a kinetic arrest phenomenon analogous to the glass transition. Combining atomistic simulations and in situ synchrotron dilatometry experiments enabled the study of CSRO evolution and its structural impact across multiple length scales. For example, CSRO-driven changes in bond lengths and bond distribution significantly impact the observed lattice parameter and volume, allowing Warren-Cowley parameter values to be determined over a full experimental temperature range. We demonstrate that the degree of CSRO and the apparent transition temperatures, defined here as the komplex reaction temperatures (Tkr), are not intrinsic material constants. Rather, they are path-dependent quantities governed by thermal history and diffusional constraints, directly reflecting the frozen CSRO state. Our findings clarify the thermodynamic and kinetic mechanisms underlying CSRO evolution and establish a framework to distinguish thermodynamic transitions under kinetic constraints from genuine kinetically arrested phenomena. Understanding this distinction is crucial for controlling CSRO during alloy design and processing and provides a foundation for future investigations exploring the implications of CSRO in advanced materials. In situ synchrotron dilatometry and atomistic simulations indicate that changes between chemical short-range order states (evolving local chemical distributions) are governed by a kinetic arrest phenomenon rather than a thermodynamic transition.
G. C. Stumpf, Yifan Cao, V. Bacurau et al.· Nature Communications· 0 citations
Layered two-dimensional halide perovskites (2D HPs) have emerged as a versatile platform for studying strongly bound excitons in the presence of spin–orbit coupling, structural symmetry breaking, and pronounced coupling to lattice vibrations. In this Mini-Review, we focus on the monolayer limit of this class of materials and highlight recent progress in understanding excitonic fine structure and optical selection rules, chiral and spin-dependent optical response, exciton–phonon coupling and exciton relaxation pathways, and the breakdown of simple band-edge pictures in 2D HPs in which organic and inorganic electronic states hybridize or more complex band structures emerge as a consequence of metal-cation chemistry. Throughout, we emphasize the role of atomistic theoretical and computational frameworks in interpreting the rapidly growing experimental literature. Together, these developments highlight 2D HPs as an unusually rich class of low-dimensional materials for studying spin-optical and excitonic quantum phenomena.
Fabian Lie, L. Leppert· Nano letters (Print)· 0 citations
Understanding how heterometal substitution regulates excited-state dynamics is essential for designing atomically precise nanoclusters. Here, we combine time-dependent density functional theory and nonadiabatic molecular dynamics to investigate Au3M2 (M = Cu, Ag) nanoclusters. Despite nearly identical geometries, Ag-to-Cu substitution markedly alters their electronic structures and vibrational properties. Au3Ag2 maintains a symmetric superatomic electronic structure with a closed-shell 1S2 configuration, whereas Au3Cu2 exhibits reduced symmetry and more localized frontier orbitals. Consequently, the two clusters display distinct relaxation pathways. Au3Cu2 undergoes faster ultrafast relaxation from the higher excited state to the intermediate state (71 fs), while Au3Ag2 exhibits more rapid relaxation to the LUMO (4.6 ps) and a longer electron–hole recombination lifetime (53 ns). Analysis of energy-gap fluctuations indicates that these differences originate from distinct electron–vibration coupling associated with core and ligand motions. These results clarify how heterometal substitution governs carrier dynamics in atomically precise nanoclusters.
Hong-Mei Che, Yu Chen, Wei Pei et al.· Journal of Physical Chemistr...· 0 citations
The recent discovery of high-temperature superconductivity in pressurized bilayer La3Ni2O7 has sparked intense research interest, yet the microscopic mechanism governing its pressure-dependent superconducting transition temperature (Tc) remains elusive. In this work, we investigate the electronic and magnetic correlations of La3Ni2O7 under high pressure using a combination of density-functional theory (DFT), constrained random phase approximation (cRPA), and dynamical mean-field theory (DMFT). We find that while hydrostatic pressure enhances the interlayer hopping and the bare superexchange energy scale (4t2/U), it simultaneously drives the system toward a more itinerant regime by reducing the relative correlation strength (U/W). Crucially, our results reveal a distinct orbital-selective evolution: the Ni dx2-y2 states become increasingly itinerant, whereas the Ni dz2 orbitals retain a more localized character. This pressure-induced itinerancy significantly enhances the hybridization between the two, leading to a dramatic amplification of the Kondo-like screening of the local dz2 moments by the itinerant dx2-y2 electrons. Consequently, the effective magnetic exchange coupling (Jeff), which serves as the pairing glue, is suppressed in the high-pressure regime. Our findings suggest that the monotonic decrease of Tc at high pressures is driven by the dominance of Kondo screening over superexchange interactions, providing a coherent microscopic explanation for the dome-shaped superconducting phase diagram in La3Ni2O7.
Group-VA elements readily undergo intricate structural reconstruction and electronic-state evolution under high pressure, exhibiting abundant phase-transition behaviours and exotic superconducting properties, which makes them ideal model systems for investigating the microscopic mechanisms of high-pressure superconductivity. Bismuth undergoes successive structural phase transitions upon compression. Nevertheless, systematic studies on the electron-phonon coupling and superconducting behaviour of its final stable body-centered-cubic Bi-V phase are still lacking. In this work, first-principles density-functional theory and density-functional perturbation theory are adopted to explore the coupled structural-electronic evolution and tunable superconductivity of Bi-V across the range from metastable to high-pressure stable states. Electronic-structure results demonstrate that compression enhances the degree of electron delocalization of the system. In the Bi-IV phase, the Bi-p and Bi-d orbitals contribute comparably to the density of states at the Fermi level. Further investigations on bcc Bi-V reveal that the system at the 15 GPa phase-transition boundary possesses a high Fermi-level density of states and a large logarithmic-mean phonon frequency, corresponding to a superconducting critical temperature (T
c
=5.58 K). By contrast, prominent phonon softening under the metastable condition of 10 GPa substantially strengthens electron-phonon coupling and yields a higher superconducting transition temperature. By comparing the superconducting behaviours of Bi-V at 10 GPa, 15 GPa and higher pressures, this work reveals the physical picture of superconductivity modulated by metastability-driven phonon softening. These findings clarify the intrinsic correlation among structural evolution, electronic states and superconductivity in high-pressure bismuth, deepen the understanding of high-pressure superconducting mechanisms in group VA-element systems, and provide theoretical references for exploring the mechanisms of high-pressure superconductivity.
Lan-Xi Luo, Wen-Guang Li, Zheng-Tang Liu et al.· Modern physics letters B· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
