Transition Properties Research Articles

Spectroscopic and transition properties of strontium chloride

Abstract The spectroscopic and transition properties of strontium chloride (SrCl) are investigated based on a theoretical approach of ab initio quantum chemistry. The calculation accuracy is improved by introducing Davidson correction, core-valence correlation (CV), the scalar relativistic and spin-orbit coupling (SOC) effect. The results show that the spectroscopic constants of X2Σ+ and A2Π states are consistent with the experimental results. The spectroscopic and molecular constants of most highly excited electronic states have been reported for the first time. The permanent dipole moment (PDMs) and the spin orbit (SO) matrix element have a sudden change for the avoidance of crossing. The potential energy curves (PECs) of the 14 Λ-S states split into 30 Ω states. The splitting energy of A2Π is 290.76 cm-1, which has a little difference from the experimental value 295.597 cm-1. Finally, the transition properties are given, including transition dipole moment (TDMs), Franck-Canton factor (FCFs) and radiation lifetime. It is found that the calculated radiation lifetime is in the order of 10ns. The research will provide theoretical reference for the feasibility laser cooling of SrCl molecule.

Analytic calculation of transition dipole moment using four-component relativistic equation-of-motion coupled-cluster expectation value approach.

We have developed an efficient scheme for the calculation of transition properties within the four-component relativistic equation-of-motion coupled cluster (EOM-CC) method using the expectation value approach. The calculation of transition properties within the relativistic EOM-CC framework requires the solution of both right and left eigenvectors. The accuracy of the approach has been investigated by calculating low-lying transitions of a Xe atom, a HI molecule, and spin forbidden 1S0 → 3P1 and spin allowed 1S0 → 1P1 transitions in a few closed shell cations. In addition to the valence spectra, the relativistic EOM-CCSD expectation value approach is particularly suitable for simulating the L-edge x-ray absorption spectrum (XAS). The calculated results show good agreement with the earlier reported theoretical studies and experimental values.

Vacuum Ultraviolet-Enhanced Topotactic Phase Transition and Physical Properties at the Surface of Cobalt Oxide Epitaxial Thin Films

Vacuum Ultraviolet-Enhanced Topotactic Phase Transition and Physical Properties at the Surface of Cobalt Oxide Epitaxial Thin Films

Hydrogen induced phase transition and emergent properties in SrFeOx

Abstract Ionic modulation, in particular that by hydrogen intercalation, has become a powerful method to tune the material’s properties in recent years. Though the SrFeOx system is akin to SrCoOx that can be protonated to the HSrCoO2.5 phase, it remains a challenge for the hydrogenation of SrFeO2.5. In this work, starting from the perovskite SrFeO3-δ, we achieved the hydrogen intercalation and obtained a stable hydrogenated brownmillerite phase HSrFeO2.5 via Pt-catalyzed H-spillover at room temperature. The results indicate that the hydrogenation process is accompanied by the simultaneous oxygen ionic release, i.e., the perovskite SrFeO3-δ is the prerequisite of the hydrogen-induced phase transition. Then, by realization of the hydrogenation, the complete phase transition cycle among the perovskite SrFeO3-δ, brownmillerite SrFeO2.5 and the hydrogenated HSrFeO2.5 phase, are finished. Upon hydrogenation, SrFeO3-δ exhibits a remarkable 9.4% lattice expansion, and its electronic state undergoes a multi-step evolution, transforming from pristine helical antiferromagnetic insulator to a bad metal, and eventually returning to an antiferromagnetic insulator. Moreover, based on the obtained results we also successfully fabricated the microscale patterns with varied surface morphology and electric conductivity that can be used to construct electronic devices. This work provides a different pathway to modulate the properties of correlated and functional materials.

Three-Dimensional Mesomechanical Complex Modulus Prediction for Asphalt Mortar Considering Conjunctive Shell Mechanism of Interface Transition Zones and Properties of Coarse Mastic

Three-Dimensional Mesomechanical Complex Modulus Prediction for Asphalt Mortar Considering Conjunctive Shell Mechanism of Interface Transition Zones and Properties of Coarse Mastic

Phase transition, electrical and dielectric properties of novel ultra-low sintering temperature NaAlMo2O8 ceramic for application in patch antenna

Phase transition, electrical and dielectric properties of novel ultra-low sintering temperature NaAlMo2O8 ceramic for application in patch antenna

Simulation study on ultra-wideband and ultra-narrowband switchable terahertz metamaterial absorbers based on deep neural networks

Supported by deep neural networks (DNNs), a simulation study on an ultra-wideband (UWB) to ultra-narrowband (UNB) switchable terahertz metamaterial absorbers (THz MAs) was designed and optimized. By leveraging the phase transition properties of vanadium dioxide (VO2), the device achieves nearly perfect absorption, switching between UWB and UNB modes. Finite element analysis was used to simulate and analyze the constructed model. Simulation results indicate that when VO2 is in its metallic state, the device functions as a UWB absorber with an absorption bandwidth of 11.54 THz over the 3.88–15.42 THz range, achieving an absorption rate exceeding 90% and a relative bandwidth (RBW) of 119.6%. When VO2 is in its insulating state, the device switches to a UNB absorber, reaching an absorption rate close to 100% at 13.927 THz. In this state, material detection was conducted, revealing that the device has a maximum refractive index sensitivity (S) of 0.33 THz/RIU and a corresponding quality factor (Q) of up to 515.8, enabling high sensing functionality. Its absorption performance is insensitive to TE and TM polarizations. Additionally, the effects of incident and polarization angles on the operating characteristics were studied. The proposed absorber demonstrates excellent polarization insensitivity, angle stability, and UWB and UNB advantages, offering valuable insights for new multifunctional THz device research. It holds significant application potential in short-range wireless THz communication, ultra-fast optical switching, sensing, transient spectroscopy, and electromagnetic stealth.

ROS fueled autonomous sol-gel-sol transitions for on-demand modulation of inflammation in osteoarthritis.

Osteoarthritis is the most prevalent form of arthritis, and a leading cause of pain and long-term disability. Dysregulation of redox homeostasis is a key feature in the pathological progression of osteoarthritis that amplifies the inflammatory response, aggravates synovitis and accelerates cartilage degradation. Herein, a hemin and chitosan-mediated antioxidant gel inducing ROS conversion (hc-MAGIC) was constructed to targeting oxidative stress for osteoarthritis treatment. The optimized hc-MAGIC exhibited autonomous sol-gel-sol transition properties, which enable to be administered via intra-articular injections, prolong retention in the joint cavity, and controlled modulation of inflammation in response to ROS. Notably, with extracellular ROS fueled, hc-MAGIC could address hypoxia in the osteoarthritic joint cavity through spatiotemporally controlled generation of oxygen (O2). Moreover, hc-MAGIC restored the impaired antioxidative capacity of macrophages by upregulating HO-1 on demand, resulting in suppressing excessive intracellular ROS generation. Consequently, by restoring both extracellular and intracellular redox homeostasis in osteoarthritic joints, hc-MAGIC markedly reversed the inflammatory microenvironment to support chondrogenesis, prevented cartilage degradation, and promoted cartilage repair by augmenting cartilage matrix formation. Therefore, featuring its sol-gel-sol transition properties，ROS-to-O2 conversion, and dual-mode redox regulation, hc-MAGIC offers a potent novel therapy for on-demand modulation of inflammation in osteoarthritis.

Computational evaluation on spectroscopic (FT-IR, Raman), electronic and biological, and NLO properties of cirsilineol by DFT, ADMET, and molecular docking method

Cirsilineol is a natural product that has pharmacological characteristics and is used to prevent the growth of cancer. This study aims to investigate the spectroscopic, electronic, and biological properties of drugs and predict their suitability for drug-like candidates to inhibit prostate cancer. The computational evaluation was performed with density functional theory (DFT) at B3LYP/6−311++G(d,p) level of theory and drug-like characteristics rendered from ADMET analysis. Spectral measurement for IR and Raman provided evidence of intra-molecular hydrogen bonding of the OH group in ring R1. The electronic transition properties of the title compound were determined using TD-DFT with a polarized continuum model in solvent ethanol, resulting in a blue shift in absorption wavelength. The electrostatic potential mapped with the van der Wall surface predicted effective electrophiles and nucleophiles, allowing for the layout of intra- and intermolecular hydrogen bonds. The pharmacological properties of cirsilineol determined by ADMED analysis confirmed that it is non-toxic. To assess the biological performance of cirsilineol, molecular docking was performed with protein codes 1E3G and 1GS4, which showed inhibition action with binding affinity −7.7 and −7.8 kcal/mol, respectively.

An ab initio study of the electronic structure and spectroscopy of CO+ and CS+ diatomic cations

In this study, accurate ab initio methods are used to determine the electronic structure and spectroscopic properties of CS + and CO + cations of astrophysical relevance. The core-valence, scalar relativistic and complete basis set extrapolation (CBS) corrections are used in conjunction with the multireference configuration interaction method to obtain accurate properties. The results obtained are very satisfactory in comparison with the experiment. The potential energy curves have been plotted up to reasonable distances, allowing their asymptotes to be adequately described. The ionisation potentials of the neutral molecules were determined. They are 11.26 eV and 14.02 eV for CS and CO respectively. The vibrational energy levels and the rotational constants are also calculated. Our values are in very good agreement compared with the experiment. For instance, we have G ( 0 ) = 686.550 cm − 1 for the ground state X 2 Σ + ( CS + ), while the experimental value is 686.841 cm − 1 . New data for G ( 0 ) and for the rotational constants of the other states are proposed. The Franck-Condon Factors values computed are in perfect agreement with the experimental ones and this implies an accurate description of the transition properties and the radiative lifetimes.

Comprehensively Understanding the Transformation of Paramagnetic Tetramer to Spin-Paired Dimer in an S = ½ Molecular Crystal

In this study, we comparatively analyzed the variable-temperature crystal structures for two isomorphous salts, [1-benzyl-4-aminopyridinium][M(mnt)2] (M = Ni or Cu; mnt2− = maleonitriledithiolate; labeled as APy-Ni or APy-Cu). Both salts crystallize in the triclinic P–1 space group at 296 K, comprising linear [M(mnt)2]− (M = Ni or Cu) tetramers. A magnetostructural phase transition occurs at TC~190 K in S = ½ APy-Ni at ambient pressure, with a conversion of paramagnetic tetramers into nonmagnetic spin-paired dimers. The discontinuous alteration of cell parameters at TC signifies the characteristic of first-order phase transition in APy-Ni. No such transition appears in the nonmagnetic APy-Cu within the same temperature vicinity, demonstrating the magnetic interactions promoting the structural phase transition in APy-Ni, which is further reinforced through a comparison of the lattice formation energy between APy-Ni and APy-Cu. The phase transition may bear a resemblance to the mechanisms typically observed in spin-Peierls systems. We further explored the magnetic and phase transition properties of APy-Ni under varying pressures. Significantly, TC shows a linear increase with rising pressure within the range of 0.003–0.88 GPa, with a rate of 90 K GPa−1, manifesting that the applied pressure promotes the transition from tetramer to dimer.

Hypoxic Cancer Cells-Derived Exosomes Strengthen the Development of Cancer Stem Cell-Like Properties Through Delivering LINC00665 in Thyroid Cancer Cells.

Hypoxia is a common phenomenon for solid tumors due to a lack of effective vascular system, and has been deemed as an important factor that drives the progression of thyroid cancer (TC) via altering the characteristics of tumor cells. The present study suggested that hypoxic TC cells enhanced cancer stem cell properties and progression of TC by delivering long intergenic non-protein coding RNA 665 (LINC00665)-containing exosomes. Specifically, TPC1 cells were exposed to normoxic or hypoxic environment, and it was found that hypoxic TPC1 cells-secreted exosomes (H-exo) were enriched with LINC00665, compared to normoxic TPC1 cells-derived exosomes (N-exo). In addition, by establishing the in vitro exosomes-TC cells coculture system, we found that in contrast to N-exo, H-exo apparently promoted cell proliferation, epithelial mesenchymal transition (EMT) and cancer stem cell properties via delivering LINC00665. This was supported by the in vivo results that H-exo transferred LINC00665 to promote tumorigenesis and the expression of EMT and stemness-associated markers in xenograft tumor-bearing mice models. Further mechanical experiments validated that LINC00665 combined with EPHB4 mRNA to sustain its stability to enhance cancer aggressiveness of TC. Altogether, our findings verified that hypoxic TC cells-secreted exosomes regulated the LINC00665/EPHB4 axis to enhance cancer stem cell properties of TC, providing novel signatures for TC diagnosis and therapy.

A theoretical investigation of spectroscopy properties and transition properties of TlBr+ cation

The potential energy curves, dipole moments and transition dipole moments of the 14 Λ–S states and 30 Ω states of TlBr+ cation were performed using the multi-reference configuration interaction method. The Davidson correction and spin–orbit coupling effects were also considered. The spectroscopic properties and transition properties of TlBr+ cation were reported at the first time. The results show that the X2Π is the ground state and the A2Σ+ is the first excited state, which are both weakly bound states. 14 Λ–S states are all electronically bound except for the 24Π state, which is repulsive. The phenomenon of avoided crossing in the Ω states occurs in the energy region between 30,000 and 50,000 cm−1. The Franck–Condon factors, radiative lifetimes and emission coefficients between the and transitions are both calculated. The results indicated that the radiative lifetimes of the and states are too large to laser cooling TlBr+ cation, laser cooling of TlBr+ cation is not feasible. These results provide a theoretical basis to explore the spectroscopic properties of TlBr+ cation.

Mechanical and Thermal Properties and Moisture Sorption of Puffed Cereals Made from Brown Rice, Barley, Adlay, and Amaranth.

The moisture sorption, rheological, and glass transition properties of puffed cereals, such as brown rice, barley, adlay, and amaranth, were assessed. The puffed cereals were stored in desiccators until their moisture content reached equilibrium. Moisture sorption isotherms were measured, and monomolecular adsorption moisture content was calculated through Brunauer-Emmett-Teller (BET) analysis. The glass transition temperature (Tg) was determined, and the internal structure was observed using a scanning electron microscope. The rupture force and apparent elastic modulus of puffed cereals decreased with increasing relative humidity (RH). The puffed cereals exhibited ductile fracture ,when the moisture content was >8%. The Tg of puffed cereals with 8% moisture content was approximately 40 °C. It was inferred that puffed cereals demonstrated a crispy texture in the glassy state when stored at <40 °C, but transitioned to a rubbery state at >40 °C, resulting in the loss of crispy texture.

How Structure and Hydrostatic Pressure Impact Excited-State Properties of Organic Room-Temperature Phosphorescence Molecules: A Theoretical Perspective.

Organic room-temperature phosphorescence (RTP) emitters with long lifetimes, high exciton utilizations, and tunable emission properties show promising applications in organic light-emitting diodes (OLEDs) and biomedical fields. Their excited-state properties are highly related to single molecular structure, aggregation morphology, and external stimulus (such as hydrostatic pressure effect). To gain a deeper understanding and effectively regulate the key factors of luminescent efficiency and lifetime for RTP emitters, we employ the thermal vibration correlation function (TVCF) theory coupled with quantum mechanics/molecular mechanics (QM/MM) calculations to investigate the photophysical properties of three reported RTP crystals (Bp-OEt, Xan-OEt, and Xan-OMe) with elastic/plastic deformation. By analyzing the geometric structures and stacking modes of these crystals, we observe that the geometric structure variations influence the electronic structures, subsequently modifying the transition properties and the energy consumption processes. Specifically, the presence of strong π-π interactions and hydrogen bonds in the Xan-OEt crystal inhibits a nonradiative decay process, thereby realizing long-lived emission. Additionally, the hybridized local and charge-transfer (HLCT) excited-state feature with the largest charge transfer excitation contributions (57.74%) for Xan-OEt stabilizes the triplet excitons and facilitates the radiative decay process, ultimately achieving high efficiency and long lifetime emissions. Furthermore, by applying high hydrostatic pressure for the Bp-OEt crystal, the RTP emission efficiencies and lifetimes are enhanced and blue-shifted. All of these results demonstrate the crucial role of molecular structure and stacking modes as well as the hydrostatic pressure effect in regulating RTP properties. Thus, our findings reveal the structure-packing-property relationship and highlight the control of molecular packing and the related tunable approaches, which could provide prospective strategies for constructing stimuli-responsive RTP emitters in practical applications.

Phase transition and electric properties of Pb(Zr,Sn,Ti)O3 antiferroelectric ceramics near the tricritical composition point

Phase transition and electric properties of Pb(Zr,Sn,Ti)O3 antiferroelectric ceramics near the tricritical composition point

The influence of temperature induced changes in the composition of MFGM on membrane phase transition and nanomechanical properties.

Biomimetic membrane was investigated as model systems to mimic the structure of milk fat globule membrane (MFGM) and to study the effects of thermal processing-induced changes in MFGM fractions on membrane morphology and physical properties. Molecular docking was utilized to screen xanthine oxidase (XO) as the MFGM protein most likely to bind to phospholipid molecules on MFGM. Fluorescence spectroscopy verified that XO formed stable complexes with DOPE, DPPC, and PS 18:0-18:1, with the strongest binding to DOPE. Two types of artificial fat globule membrane (AFGM) were further constructed using XO with phospholipid molecules, including N-AFGM (simulating MFGM in raw milk) and P-AFGM (mimicking MFGM in ultra-pasteurized milk). The results of atomic force microscopy showed that the P-AFGM had significantly less liquid ordered phase (Lo), more aggregation of XO, smoother surface, higher Young's modulus, and more prone to rupture compared to N-AFGM. These results contribute to a better understanding of the relationship between changes of MFGM composition induced by thermal processing and fat globule stability.

Order phase transition of HIP nickel-based powder superalloy during isothermal aging

Nickel-based powder superalloys have become one of key materials for aerospace turbine engines due to their excellent comprehensive properties. The microstructure stability during long-term isothermal aging is closely related to mechanical properties. The correlation between order phase transition and mechanical properties of a HIP (hot isostatic pressing) nickel-based powder superalloy after long-term isothermal aging treatment was investigated. The results show that the decomposition of MC carbides and precipitation, growth and coarsening of γ' phases occur with duration of isothermal aging. Tertiary γ' phases precipitates by the way of element diffusion with γ' phases coarsening. In addition, strengthening mechanism is quantitatively calculated, and the relative contribution of γ' phases to yield strength is largest, and multi-mode size of γ' phases are favorable to yield strength and hardness of HIP nickel-based powder superalloy.

Evaluation of wave-induced flow through marine porous media accounting for transition of seepage properties across multiple flow regimes

Wave-induced flow through marine porous media has been attracting coastal engineers and researchers because of their strong correlation with scouring, internal erosion, piping and other destructions of marine porous structures. Previous studies chose Darcy-Forchheimer equation for wave-induced seepage behavior analyses because of its simplicity and perceptiveness. However, numerous experiment observations suggested that significant flow regime transition occurred in porous media with high variations in porosity and particle size, while Darcy-Forchheimer equation is only applicable to flow within Forchheimer regime. In this paper, a mathematical model linking the resistance of porous medium to its porosity and particle size is proposed to characterize the seepage properties across Darcy and Forchheimer regime under wave loadings. The proposed seepage model is then incorporated into volume-averaged Reynolds-averaged Navier-Stokes equations, and thus enabling evaluating fluid motions in waves and marine porous media via a unified framework. Through validation against experimental observations, analytical solutions and well accepted computed results in the literature, the proposed model is shown to replicate the characteristics of resistance of porous media with different porosities and particle sizes under different flow regimes. Numerical analyses are conducted to elucidate that seepage velocities of wave-induced flow in marine porous materials can be over- or under-estimated if not considering transitional seepage properties across multiple flow regimes. Such discrepancies can become significant when strong variations occur in porous media with respect to particle size and/or porosity.

An organic-inorganic hybrid ferroelastic with a near-room-temperature phase transition.

Organic-inorganic hybrid metal halides (OIMHs) with ferroelastic phase transition properties have recently attracted great attention due to their widespread application prospects in the fields of energy storage, sensors, switches, etc. However, most of the hybrid ferroelastics exhibit phase transition points (Tc) far beyond room temperature, which may limit their applications in mechanical switches and energy storage for daily working requirements. Herein, we synthesized a new zinc halide OIMH ferroelastic (E,E)-[BPHD]ZnBr4 (BPHD = N1,N6-bis(piperidine-1-yl) hexa-2,4-diene diamide), which experiences a 2/mF1̄ type paraelastic-ferroelastic phase transition at a near-room-temperature Tc of 285 K. It crystallizes in the monoclinic P21/c space group at 298 K, undergoing a change to the triclinic P1̄ space group in the low-temperature phase, with the number of molecules in asymmetric units doubling. Differential scanning calorimetry, variable-temperature electrical resistivity (ρ) and Raman spectrum tests confirm the occurrence of the phase transition, accompanied by a change in ρ of nearly two orders of magnitude, and reversible evolution of ferroelastic domains has been observed. In addition, (E,E)-[BPHD]ZnBr4 also exhibits remarkable compliance and softness within the category of hybrid crystals. This work will inspire further exploration of new hybrid ferroelastic materials with near-room-temperature phase transitions.