Reorientation Energy Research Articles

First TPymT-Ln complexes (TPymT = 2,4,6-Tris(2-pyrimidyl)-1,3,5-triazine; Ln = Eu, Gd, Tb, Dy): Solvothermal synthesis, structure, magnetic and photoluminescent properties

Four novel mononuclear lanthanide complexes, [Ln(TPymT)(NO3)3(H2O)2] (Ln: Eu3+ (1), Gd3+ (2), Tb3+ (3) and Dy3+ (4)), have been solvothermally synthesized using multidentate 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (TPymT). Compounds 1–3 have been characterized by means of elemental analysis, FT-IR, and single-crystal/powder X-ray diffraction analysis. Compound 4 was structurally characterized. The Ln3+ ion in 1–4 is ten-coordinated, where TPymT serves as an N3 donor in an isostructural series. The alternating-current magnetic studies showed frequency dependence below ca. 10 K for 3, as an indication of a single-ion magnet. The activation energy for the magnetization reorientation was estimated as Ueff/kB = 95(9) K after applying a dc bias field 2000 Oe for 3. The photoluminescent studies clarified that 1 and 3 behaved as red and green light emitters with quantum yields as high as 17 and 39 %, respectively. The TD-DFT calculation supports the energy level scheme of ground and excited states of TPymT together with the reference compound 4′-phenyl-2,2’:6′,2″-terpyridine. The present work suggests a broad chance and motivation to apply TPymT to the field of 4f coordination chemistry.

Terrylene on monolayer WS2: coverage-dependent molecular re-orientation and interfacial electronic energy levels

The electronic, optical, and functional properties of van der Waals heterostructures comprising organic and two-dimensional inorganic semiconductors depend on the molecular assembly's structure at and near the interface. Despite the...

First-principles investigation on twin-related lattice reorientation in hexagonal metals and alloys

High-throughput ab initio calculations were employed to study the lattice reorientation process accompanying twinning under plastic deformation in hexagonal metals, as well as in alloyed Mg and Ti. The results indicate that, in unalloyed hexagonal metals, reorientation consumes the highest and lowest energies in Be and Mg, respectively, with intermediate energies in Sc, Co, Ti, Zr and Dy. The shuffle component always contributes a significant part of the reorientation energy in Mg, whereas in Ti with sufficient shear strain, subsequent reorientation process becomes energy downhill. In alloyed Mg and Ti, appropriate alloying significantly reduces the reorientation energy, and especially in alloyed Ti, there is significant negative correlation between the reorientation energy and certain properties of the alloying elements. The results are consistent with the fact that reorientation has been experimentally observed in compressed Mg nanopillars, but only in atomic scale simulations under high strain rate in Ti.

Investigating the Probability of the Charging Transition Rate in Cu Contact to P6 System Devices

In this paper, we investigate the probability of the charge transfer interaction process from Cu metal to P6 molecule systems using charge transfer rate calculations. The charge transfer rate from donor Cu metal to an acceptor P6 molecule dye is presented with reorientation energy, electronic drive force, and barrier height emphasis on the effects of transfer processes in the Cu/P6 system. Charge transfer flow probability from Cu metal contacts to P6 dye molecule has recently been considered within the perturbation theory method, where the charge transfer rates have been found to be affected by strength coupling and reorientation energy. The charge transfer could be occurred even at large reorientation energy, less driving force energy, and low potential barrier. It requires to reorientation the donor to acceptor energy levels to start the charge transfer. It has been found that the rate of charge transfer processes enhance the flow rate yield of the transfer cross interface dependent on the potential barrier.

Factors influencing the structure of the complex-defects in AF2: RE3+ (A= Ca, Sr and Ba): A first-principles study

As aliovalent doping materials, RE3+ doped AF2 (A = Ca, Sr and Ba), which show not only high thermal conductivity and low nonlinear refractive index ascribed to fluorides, but also unique spectroscopic properties related to the RE3+ ions, are promising ultra-strong and ultra-fast laser crystal candidates. It is noted that the stability of the C3v complex-defect, in which Fi− compensates at the next-nearest interstitial site of RE3+, increases with the ratio of the lattice parameter to the dopant ionic radius. In this work, systematic first-principles calculations are performed to resolve factors influencing the structure of the RE-Fi monomers. The formation energy, the reorientation energy and the local structure of the monomers are obtained, and the Coulomb interaction and the sub-lattice distortion are quantified. It is concluded that the sub-lattice distortion determines the defect structure even though the Coulomb interaction is the fundamental basis for the complex-defect formation in aliovalent doping materials. On this basis, the cluster aggregation process in AF2: RE3+ are elucidated and the octahedral arrangement of the hexamer is specially explained. Our calculation results and analytical methods not only provide new insights for the defect formation mechanism in AF2: RE3+, but also guide the improvement of aliovalent doping materials.

Calculation of the spin-lattice relaxation time and the activation energy near the IV–III phase transition in pyridinium fluorosulfonate (C5NH6)FSO3

The spin-lattice relaxation time T1 H for protons nuclei is calculated in term of the pseudospin–phonon (PS) coupled and the energy fluctuation (EF) models close to the IV–III solid–solid phase transition of in (C5NH6)FSO3. This calculation was performed by associating the observed second moment of the 1H as the order parameter below T C and the disorder parameter above T C. Values of the activation energy for the cation reorientation in this crystal are also deduced by using both models. In addition, the observed dielectric permittivity of this crystal is analyzed within the framework of the Landau theory and values of the spontaneous polarization (P S) are determined as a function of temperature. The normalized values of P S are used in the PS and EF models to extract the activation energy for the reorientation of the dipole moment of this compound arising from cation–anion interaction. Our results show that the PS and EF models can describe the observed behavior of the spin-lattice relaxation time adequately for the IV–III solid–solid transition in (C5NH6)FSO3.

Phase field-finite element analysis of magnetic-induced deformation in ferromagnetic shape memory alloy

A phase field theory based model considering non-uniform demagnetizing field within ferromagnetic shape memory alloy and free space is established and realized by finite element method in a two-dimensional setting to save huge storage spaces and computational times. The martensite reorientation (contain nucleation and growth) from the stress field-favored martensite variant to magnetic field-favored martensite variant is numerically simulated. The simulation reasonably depicts the essence of magnetic-induced martensite reorientation and magnetization change for NiMnGa ferromagnetic shape memory alloy and their dependence on the loading level. Furthermore, the evolution and interaction of martensite domain structure, magnetic domain structure, magnetic potential and demagnetizing field are analyzed. And the dominant driving force generated by minimization of total Helmholtz free energy for loading level dependent martensite reorientation and magnetization change are revealed by addressing the influence of loading level. The simulation results show that the local demagnetizing field within ferromagnetic shape memory alloy and free space is the key to the local nucleation of new martensite variant. The dominant driving force of local nucleation and growth of new martensite variant are completely different: the local nucleation of new martensite variant is driven by local high magnetocrystalline anisotropy energy caused by local demagnetizing field; the local high Landau-type double well potential energy caused by local nucleation of new martensite variant has the largest impact on growth of the new martensite variant. The local high magnetocrystalline anisotropy energy caused by local nucleation and growth of new martensite variant has the largest impact on local rapid magnetization change within new martensite variant domain. When it comes to high loading level, the inhibition of martensite reorientation is attributed to the elastic strain energy, and the approximately uniform magnetization change is driven by Zeeman energy.

Ab Initio Molecular Dynamics Assessment on the Mixed Ionic–Electronic Transport for Crystalline Poly(3-Hexylthiophene) Using Full Explicit Lithium-Based Dopants and Additives

Here, we report ab initio molecular dynamics calculations dealing with mixed ionic–electronic transport in a poly(3-hexylthiophene) crystalline supercell, including the use of full explicit lithium-based dopants and additives. Up to now and to the best of our knowledge, the use of full explicit dopants and additives for both ionic and electronic transport calculations has remained practically unexplored probably due to their high computational cost. The use of fewer artifacts and other common assumptions in our calculations allowed us to reveal some interesting behavior associated with the presence of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) dopants and dimethoxyethane (DME) additives on the mixed ionic–electronic transport in a wide temperature range. Our ionic and electronic conductivity calculations show a good correlation with the experimental reports of similar mixed ionic–electronic conductors in the very recent literature. For the electronic transport, our transfer integral (J) and reorientation energies (λ) values showed increment respect to typical unexplicit-doped calculations. Furthermore, we also introduce the role of the explicit dopant in the interchain, intrachain, “effective” doping, and charge-transfer complex bonding distances, and their associated static and dynamic disorder effects on electronic transport. These new insights can be extremely helpful to unravel not only the doping mechanism but also, and simultaneously, the mixed ionic–electronic transport mechanism for organic semiconductors. Advancing in the fundamental understanding of mixed ionic–electronic organic conductors is a key to boosting their properties for different applications going from energy storage to bioelectronic devices.

Solid-State Supramolecular Inclusion Complexes of β-Cyclodextrin with Carboxyphenyl Viologens Showing Photochromic Properties

β-Cyclodextrins (β-CDs) are shown to form 1:1 and 2:1 host–guest inclusion complexes with two carboxyphenyl viologens, 1-(4-carboxyphenyl)-4,4′-bipyridinium chloride (1+·Cl–) and 1,1′-bis(4-carboxyphenyl)-4,4′-bipyridinium dichloride (22+·Cl2–), in an aqueous solution. The solid-state supramolecular host–guest inclusion complexes 1+@β-CD and 22+@β-CD2 demonstrate excellent photochromic properties. The results of the electron-spin resonance (ESR) spectroscopy suggest that their photochromic behaviors are caused by the generation of free radicals (V•+). The energy-minimized structure and the calculated reorientation energy of the inclusion complex 1+@β-CD support the electron transfer from the host β-CD to the guest 1+. The practical applications of the inclusion complex 1+@β-CD as erasable inkless printing media and an anticounterfeiting material were also studied. The present study provides a supramolecular method for the construction of photochromic materials.

Nonphotocatalytic Water Splitting Process to Generate Green Electricity in Alkali Doped Zinc Oxide Based Hydroelectric Cell

Efficient nonphotocatalytic water molecule splitting and electricity generation has been obtained from alkali (Li, Na, K) doped zinc oxide (ZnO) hydroelectric cells (HECs) at room temperature. The existence of defect centers including zinc and oxygen vacancies in pure and alkali-doped ZnO has been observed by optical spectroscopy. Broadband dielectric spectroscopy has been carried out to investigate the charge transfer mechanism in the physisorbed layer of water molecules on the surface of porous ZnO HEC. Temperature dependence of dielectric relaxation was also determined to identify the reorientation dynamics of water molecules near the defect site in ZnO. Minimum activation energy for dipolar reorientation, Eₐ ∼ 128.54 kJ/mol, was calculated for the K-ZnO sample depicting easy hopping of H⁺ ions near the defect site. Maximum lattice strain induced by K doping in ZnO led to faster dipolar reorientation and easy hopping of the proton over the physisorbed layer of water molecules on the cell surface. Maximum output power, Pₒᵤₜ ∼ 5.71 mW/cm², has been delivered by K doped ZnO HEC, which is comparable to the best achieved power density by a ZnO nanoparticle-based dye-sensitized solar cell, ∼9.17 mW/cm². Zinc oxide based hydroelectric cells are a low cost, environmentally friendly solution for energy generation scarcity for the masses living in remote locations without the use of any harmful chemicals.

Ferromagnetic strain glass and its physical properties

Ferromagnetic strain glass is a glassy phenomenon reported in the defects of doped Ni-Mn-Ga, Fe-Pd, and Fe-Ni-Cr ferromagnetic martensitic alloy systems recently. It is essentially a frozen state with coexisting short-range lattice strain order and long-range magnetic order. The basic structural unit of the ferromagnetic strain glass is the magnetic martensitic nanodomain. The reorientation energy barrier of these nanodomains is insignificant. They grow slowly across a wide temperature region in the parent phase matrix, and the modulus of the parent phase matrix and nanodomains shows an opposite temperature-dependent tendency. These transforming properties lead to the low-field-driven large magnetostriction and Elinvar effect. Therefore, ferromagnetic strain glass alloys have potentially important applications in microactuators or sensors and precision apparatuses. This paper introduces the macroscopic physical properties, microstructural characteristics, and functional effects of ferromagnetic strain glass. Through the phase diagram of the Ni- X -Mn-Ga ( X =Co, Fe) system, the formation of a ferromagnetic strain glass and its relationship with martensitic and premartensitic phases are clarified. Furthermore, the novel transformation behavior, i.e., the spontaneous martensitic transition of ferromagnetic strain glass in the phase boundary region between ferromagnetic martensite and ferromagnetic strain glass, is also introduced. The material design based on ferromagnetic strain glass is expected to bring new opportunities for the performance breakthrough and functionality development of magnetic materials.

Chromic Properties of Carboxyphenyl Viologen Induced by Complexation in Cucurbit[7]uril

AbstractUpon encapsulation in cucurbit[7]uril, carboxyphenyl viologen exhibited dramatically enhanced photochromism, while its alkaline form exhibited enhanced thermochromism. ESR experiments and reorientation energy calculation indicate that these chromic behaviors are caused by the electron transfer from the host to the guest.

The activation energy for water reorientation differs between IR pump-probe and NMR measurements.

Molecular reorientation dynamics in liquid water are typically probed using either infrared (IR) pump-probe anisotropy experiments or the NMR spin-echo technique. While it is widely appreciated that the two yield different reorientation times based on the nature of the measurements, little attention has been paid to the implications for the corresponding activation energies. Here, the activation energies associated with reorientation of the OH bond vector in liquid water are calculated to high accuracy directly from simulations at a single temperature using a recently developed method [Z. A. Piskulich et al., J. Chem. Phys. 147, 134103 (2017)]. The results indicate that the reorientation times obtained from IR anisotropy and NMR measurements have different activation energies that, with improved accuracy, should be experimentally distinguishable. The origins of the differences in the two activation energies are examined in detail, including by a decomposition into the contributions to the activation energies due to the kinetic energy and the intermolecular interactions.

Frustration and Glasslike Character in RIn1- xMn xO3 (R = Tb, Dy, Gd).

We bring together ac susceptibility and dc magnetization to uncover the rich magnetic field-temperature behavior of a series of rare earth indium oxides, RInO3 (R = Tb, Dy, and Gd). The degree of frustration is much larger than expected, particularly in TbInO3, and the ground states are glasslike with antiferromagnetic tendencies. The activation energy for spin reorientation is low. Chemical substitution with Mn3+ ions to form TbIn1- xMn xO3 ( x ≤ 0.01) relieves much of the frustration that characterizes the parent compound and slightly enhances the short-range antiferromagnetic order. The phase diagrams developed from this work reveal the rich competition between spin orders and provide an opportunity to compare the dynamics in the RInO3 and Mn-substituted systems. These structure-property relations may be useful for understanding magnetism in other geometrically frustrated multiferroics.

Температурно-фазовая зависимость колебательного спектра и ориентационная подвижность тетрафторборат иона в органической соли н-Bu-=SUB=-4-=/SUB=-NBF-=SUB=-4-=/SUB=-

AbstractThe structural and dynamic properties of a tetrafluoroborate ion in n -Bu_4NBF_4 organic salt at different temperatures and phase states were studied by oscillation spectroscopy methods. The results of calculations of the energy and relaxation parameters have shown that in the plastic phase, a $${\text{BF}}_{4}^{ - }$$ ion is characterized by a low reorientation energy as compared with that of the crystalline phase.

Energy paths of twin-related lattice reorientation in hexagonal metals via ab initio calculations

Employing ab initio calculations, we systematically investigated the energy paths of [101¯2]twin-related lattice reorientation in hexagonal metals Be, Mg, Sc, Ti, Co, Y, Zr, Tc, Ru, Gd, Tb, Dy, Ho, Er, Tm, Lu, Hf, Re, and Os. Among the studied systems, lattice reorientation energy increases in the order of Mg, Gd, Tb, Dy, Zr, Tc, Ti, Ho, Y, Co, Er, Sc, Be, Tm, Lu, Hf, Re, Ru and Os. The reorientation process consists of shear and shuffle components. Concerning the significance of shuffle, these hexagonal metals fall into two groups. In the first group, which includes Mg, Co, Ru, Re and Os, regardless of the shear amount, subsequent shuffle is an energy-uphill process, while in the second group, which includes Ti, Tc, Be, Y, Gd, Tb, Dy, Ho, Zr, Er, Sc, Hf, Lu and Tm, shuffle becomes an energy-downhill process if shear component reaches an adequate level (at least 60%). These results qualitatively explain the present observation of lattice reorientation in hexagonal metals, and shed light upon a general understanding on the [101¯2] twinning behavior in the aim of improving materials properties.

Modeling Transfer of Electrons between Energy States of an Electrolyte and CdS thin Films using Gerischer Model

A number of models have been developed to describe electron transfer between electrolytes and group II–VI binary semiconductors. In this report, a study was conducted to describe and model electron transfer between an inorganic semiconductor, (i.e. CdS) and a ferric oxidizing/reducing agent [i.e. K 3 Fe(CN) 6 /K 4 Fe(CN) 6 ]. We describe the interfacial electron transfer using the semi-classical theory approaches as described by Marcus and later developed by Gerischer and therefore called Gerischer model as it is applied to heterogeneous electron transfer in a semiconductor - electrolyte interface. CdS thin films were grown by electro-deposition method on the indium tin oxide (ITO) substrates and were used as electrodes. The data collected was used to determine the kinetic constant rates and re-orientation energies as measured in the solutions with different concentration of redox system, Fe +3 / Fe +2 . Experiments showed that when concentration of oxidized species increased and causing an increase in activity, the kinetic constant rates decreases inversely. Equally light induced current at 0.0V/Ag was higher when the ratio of the oxidant-reductant (i.e. 2/0.02 and 0.2/0.02) was high. EIS studies revealed that for the two ratios of. 2/0.02 and 0.2/0.02, the difference of current density was comparable to the transfer of the charge carriers for the oxidant-reductant electrolyte at 2/0.02 with respect to 0.2/0.02.

First-Principles Insight into the Hydration Ability and Proton Conduction of the Solid State Proton Conductor, Y and Sn Co-Doped BaZrO3

Y and Sn co-doped BaZrO3 (BZSY) has recently been shown to exhibit superior hydration ability and improved power output performance compared to those of the traditional solid oxide fuel cell (SOFC) electrolyte, Y-doped BaZrO3. The fact that BZSY is also chemically stable in both H2O and CO2 atmospheres further illustrates the great potential for BZSY as a future electrolyte material in proton-conducting SOFCs. In this work, we conducted comprehensive density functional theory calculations to analyze the energetics of hydration and proton migration in BZSY. The energy of hydration is calculated at four different locations in the cell to better assess the specific contributions of each defect type. For all locations tested, hydration is found to be strongly exothermic and is most favorable when Y ions are in the vicinity. The calculated energies of hydration (−1.72 to −1.11 eV) are significantly lower than any previously calculated for acceptor-doped BaZrO3-based electrolytes. Nudged elastic band calculations confirm low proton reorientation energies (0.08–0.24 eV) and low intraoctahedral hopping energies (0.21–0.41 eV) and that these diffusion barriers are at minimum when the proton is migrating to an oxygen ion in a YO6 octahedron. Our results show how the synergy of the Sn and Y dopant ions produces the excellent hydration and conduction performance of BZSY and fully support its potential application in next-generation SOFCs.

Modeling Transfer of Electrons between Energy States of an Electrolyte and CdS Thin Films using Gerischer Model

A number of models have been developed to describe electron transfer between electrolytes and group II–VI binary semiconductors. In this report, a study was conducted to describe and model electron transfer between an inorganic semiconductor, (i.e. CdS) and a ferric oxidizing/reducing agent [i.e. K 3 Fe(CN) 6 /K 4 Fe(CN) 6 ]. We describe the interfacial electron transfer using the semi-classical theory approaches as described by Marcus and later developed by Gerischer and therefore called Gerischer model as it is applied to heterogeneous electron transfer in a semiconductor - electrolyte interface. CdS thin films were grown by electro-deposition method on the indium tin oxide (ITO) substrates and were used as electrodes. The data collected was used to determine the kinetic constant rates and re-orientation energies as measured in the solutions with different concentration of redox system, Fe +3 / Fe +2 . Experiments showed that when concentration of oxidized species increased and causing an increase in activity, the kinetic constant rates decreases inversely. Equally light induced current at 0.0V/Ag was higher when the ratio of the oxidant-reductant (i.e. 2/0.02 and 0.2/0.02) was high. EIS studies revealed that for the two ratios of. 2/0.02 and 0.2/0.02, the difference of current density was comparable to the transfer of the charge carriers for the oxidant-reductant electrolyte at 2/0.02 with respect to 0.2/0.02.

Influence of the linkage type between the polymer backbone and side groups on the surface segregation of methyl groups during film formation.

Although poly(vinyl acetate) (PVAc) differs from poly(methyl acrylate) (PMA) only in the reversed position of the ester group, a large difference in the concentration dependence of the casting solution on the corresponding surface structure of the cast films of PVAc, PMA and poly(methyl methacrylate) (PMMA) was observed. The hydrophobicity of both PMA and PMMA films increased with increasing concentration of the corresponding polymer solution, whereas cast PVAc films showed the reverse trend. The surface structure of the cast films prepared with different concentrations of the casting solution, characterized by sum frequency generation (SFG) vibrational spectra, showed that the order of the methylene groups increased while that of the acetyl methyl group decreased on the surface of cast PVAc film with increasing concentration of casting solution. However, the order of the ester methyl group increased and that of methylene groups did not change for cast PMA films with increasing concentration of casting solution. The cast PMMA film showed a reverse trend compared with the corresponding PMA film. It is apparent that well-ordered ester or acetyl methyl groups on the surface, which are oriented away from the polymer film, rather than methylene groups, play an important role in determining surface hydrophobicity, as the latter shield the OC[double bond, length as m-dash]O groups of PVAc, PMA and PMMA film surfaces from being exposed, resulting in low surface free energy. The reason for this difference is attributed to the relatively low energy for ester methyl group reorientation, an ester group structure nearer to the trans state and more regular local configuration of segments in concentrated solutions of PMA and PMMA compared to that of PVAc.