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Infrared Spectra of the HAnX and H <sub/>2</sub> AnX <sub/>2</sub> Molecules (An=Th and U, X=Cl and Br) in Argon Matrices Supported by Electronic Structure Calculations
摘要： Uranium and thorium hydrides are known as functional groups for ligand stabilized complexes and as isolated molecules under matrix isolation conditions. Here, the new molecular products of the reactions of laser-ablated U and Th atoms with HCl and with HBr, namely HUCl, HUBr and HThCl, HThBr, based on their mid and far infrared spectra in solid argon, are reported. The assignment of these species is based on the close agreement between observed and calculated vibrational frequencies. The H–U and U–35Cl stretching modes of HUCl were observed at 1404.6 and 323.8 cm?1, respectively. Using DCl instead to form DUCl gives absorption bands at 1003.1 and 314.7 cm?1. The corresponding bands of HThCl are 1483.8 (H–Th) and 1058.0 (D–Th), as well as 340.3 and 335.8 cm?1 (Th–35Cl), respectively. HUBr is observed at 1410.6 cm?1 and the BP86 computed shift from HUCl is 6.2 cm?1 in excellent agreement. The U–H stretching frequency increases from 1383.1 (HUF), 1404.6 (HUCl), 1410.6 (HUBr) to 1423.6 cm?1 (UH) as less electronic charge is removed from the U–H bond by the less electronegative substituent. These U–H stretching frequencies follow the Mayer bond orders calculated for the three HUX molecules. A similar trend is found for the Th counterparts. Additional absorptions are assigned to the H2AnX2 molecules (An = U, Th, X = Cl, Br) formed by the exothermic reaction of a second HX molecule with the above primary products.
关键词： infrared,matrix isolation,thorium,uranium,density functional calculations
更新于2025-09-23 15:22:29
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Ce(IO3)2F2·H2O: The First Rare Earth Iodate Fluoride with Large Second Harmonic Generation Response
摘要： The first rare earth iodate fluoride, Ce(IO3)2F2·H2O, has been synthesized via hydrothermal method. In the structure, the CeO5F4 polyhedra connect with isolated IO3 groups to form one-dimensional infinite 1∞[Ce(IO3)2F2] chains, which interconnect with each other by weak hydrogen bond to construct the whole structure. Ce(IO3)2F2·H2O produces a large second harmonic generation response, which is 3 times that of KDP. Theoretical calculations using density functional theory and dipole moments were executed to illustrate the relationships between the structure and the properties. The results show that Ce(IO3)2F2·H2O is a new iodate fluoride with novel structure and has potential applications in the field of nonlinear optics.
关键词： crystal structure,iodate fluorides,density functional calculations,cerium iodates,1∞[Ce(IO3)2F2] chain
更新于2025-09-23 15:21:21
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Truly Concomitant and Independently Expressed Short- and Long-Term Plasticity in a Bi <sub/>2</sub> O <sub/>2</sub> Se-Based Three-Terminal Memristor
摘要： Concomitance of diverse synaptic plasticity across different timescales produces complex cognitive processes. To achieve comparable cognitive complexity in memristive neuromorphic systems, devices that are capable of emulating short-term (STP) and long-term plasticity (LTP) concomitantly are essential. In existing memristors, however, STP and LTP can only be induced selectively because of the inability to be decoupled using different loci and mechanisms. In this work, the first demonstration of truly concomitant STP and LTP is reported in a three-terminal memristor that uses independent physical phenomena to represent each form of plasticity. The emerging layered material Bi2O2Se is used for memristors for the first time, opening up the prospects for ultrathin, high-speed, and low-power neuromorphic devices. The concerted action of STP and LTP allows full-range modulation of the transient synaptic efficacy, from depression to facilitation, by stimulus frequency or intensity, providing a versatile device platform for neuromorphic function implementation. A heuristic recurrent neural circuitry model is developed to simulate the intricate “sleep–wake cycle autoregulation” process, in which the concomitance of STP and LTP is posited as a key factor in enabling this neural homeostasis. This work sheds new light on the development of generic memristor platforms for highly dynamic neuromorphic computing.
关键词： Bi2O2Se,hybrid density functional calculations,long-term plasticity,short-term plasticity,three-terminal memristors
更新于2025-09-23 15:21:01
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Charge Transfer Complex of Thioxanthonephenacyl Sulfonium Salt as Visible Light Photoinitiator for Free Radical and Cationic Polymerizations.
摘要： A new double chromophoric sulfonium salt photoinitiator possessing both thioxanthone and phenacyl groups, namely 2-isopropylthioxanthonium phenacyl hexafluoroantimonate (ITXPhenS) was synthesized and characterized. ITXPhenS can form charge transfer complex (CTC) with the donor N, N-dimethyl aniline (DMA) with absorption characteristics in the visible range as confirmed by spectral analysis, cyclic voltammetry (CV) and density functional theory (DFT). The extension of the absorbance shift can be controlled by the ITXPhenS to DMA ratio. The ability of the CTC to initiate free radical and cationic polymerization reactions of various monomers under visible and natural sunlight is demonstrated. The proposed mechanism assumes the generation of radical and ionic species by the heterolytic and/or homolytic cleavage of ITXPhenS within the CTC followed by electron transfer reactions.
关键词： photochemistry,density functional calculations,cyclic voltammetry,polymerization,charge transfer
更新于2025-09-23 15:21:01
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InP Quantum Dots-Based Electroluminescent Devices
摘要： A metal-free, intermolecular syn-addition of hexamethyldisilane across simple alkenes is reported. The catalytic cycle is initiated and propagated by the transfer of a methyl group from the disilane to a silylium-ion-like intermediate, corresponding to the (re)generation of the silylium-ion catalyst. The key feature of the reaction sequence is the cleavage of the Si–Si bond in a 1,3-silyl shift from silicon to carbon. A central intermediate of the catalysis was structurally characterized by X-ray diffraction, and the computed reaction mechanism is fully consistent with the experimental findings.
关键词： silylium ions,density functional calculations,homogeneous catalysis,alkenes,Si–Si activation
更新于2025-09-23 15:19:57
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Controlled switching of a single CuPc molecule on Cu(111) at low temperature
摘要： Low temperature measurements of the tunneling current as a function of the applied bias voltage have been performed on a dense constant-height grid above individual copper phthalocyanine molecules adsorbed on a Cu(111) surface. By appropriate tuning of the applied bias, the molecule can be reversibly switched between two configurations in which pairs of opposite maxima appear rotated by 90? in the tunneling current map. The underlying conformations are revealed by density functional calculations including van der Waals interactions: a C2v symmetric ground state and two energetically equivalent states, in which the molecule is twisted and rotated around its center by ±7?. For tip biases above 200 mV position-dependent current switching is observed, as in previous measurements of telegraph noise [Schaffert et al., Nat. Mater. 12, 223 (2013)]. In a small voltage interval around zero the measured current becomes bistable. Switching to a particular state can be initiated by sweeping the voltage past well-defined positive and negative thresholds at certain positions above the molecule or by scanning at constant current and a reduced reverse bias.
关键词： density functional calculations,van der Waals interactions,tunneling current,copper phthalocyanine,Cu(111) surface,bistable current
更新于2025-09-23 15:19:57
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Building Blocks for High‐Efficiency Organic Photovoltaics: Interplay of Molecular, Crystal, and Electronic Properties in Post‐Fullerene ITIC Ensembles
摘要： Accurate single-crystal X-ray diffraction data offer a unique opportunity to compare and contrast the atomistic details of bulk heterojunction photovoltaic small-molecule acceptor structure and packing, as well as provide an essential starting point for computational electronic structure and charge transport analysis. Herein, we report diffraction-derived crystal structures and computational analyses on the n-type semiconductors which enable some of the highest efficiency organic solar cells produced to date, 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2’,3’-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (ITIC) and seven derivatives (including three new crystal structures: 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-propylphenyl)-dithieno[2,3-d:2’,3’-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (ITIC-C3), 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(3-hexylphenyl)-dithieno[2,3-d:2’,3’-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (m-ITIC-C6), and 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6,7-difluoro)-indanone))-5,5,11,11-tetrakis(4-butylphenyl)-dithieno[2,3-d:2’,3’-d’]-s-indaceno[1,2-b:5,6-b’]dithiophene (ITIC-C4-4F). IDTT acceptors typically pack in a face-to-face fashion with π–π distances ranging from 3.28–3.95 ?. Additionally, edge-to-face packing is observed with S?π interactions as short as 3.21–3.24 ?. Moreover, ITIC end group identities and side chain substituents influence the nature and strength of noncovalent interactions (e.g. H-bonding, π–π) and thus correlate with the observed packing motif, electronic structure, and charge transport properties of the crystals. Density functional theory (DFT) calculations reveal relatively large nearest-neighbor intermolecular π-π electronic couplings (5.85–56.8 meV) and correlate the nature of the band structure with the dispersion interactions in the single crystals and core–end group polarization effects. Overall, this combined experimental and theoretical work reveals key insights into crystal engineering strategies for indacenodithienothiophene (IDTT) acceptors, as well as general design rules for high-efficiency post-fullerene small molecule acceptors.
关键词： density functional calculations,crystal structure,non-fullerene,molecular modelling,solar cells
更新于2025-09-11 14:15:04
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Higher amounts of loophole-free Bell violation using a heralded entangled source
摘要： Benzene, the prototype of aromatics, has six equivalent C-C bonds (1.397 ?), which are intermediate between a C-C double bond and a C-C single bond. For over 80 years, chemists have spent much effort on freezing a localized structure to obtain a distorted bond-length alternating benzene ring in the ground state, leading to various localized trisannelated benzene rings. However, most of the central benzene rings are still aromatic or nonaromatic. Here we report an antiaromatic benzene ring caused by hyperconjugation. Specifically, symmetric annulation of 5,5-difluorocyclopentadiene results in an antiaromatic benzene ring, which is supported by various aromaticity indices, including nucleus independent chemical shift, anisotropy of the induced current density, π-separated electron-localization function and heat of hydrogenation. Our findings highlight a strong power of hyperconjugation, a “weak” interaction in organic chemistry, paving the way for designing and realizing more novel (anti)aromatics.
关键词： Benzene,Antiaromaticity,Hyperconjugation,Density Functional Calculations
更新于2025-09-11 14:15:04
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Oxygen vacancies in the bulk and at neutral domain walls in hexagonal
摘要： We use density functional calculations to investigate the accommodation and migration of oxygen vacancies in bulk hexagonal YMnO3, and to study interactions between neutral ferroelectric domain walls and oxygen vacancies. Our calculations show that oxygen vacancies in bulk YMnO3 are more stable in the Mn-O layers than in the Y-O layers. Migration barriers of the planar oxygen vacancies are high compared to oxygen vacancies in perovskites, and to previously reported values for oxygen interstitials in h-YMnO3. The calculated polarization decreases linearly with vacancy concentration, while the out-of-plane lattice parameter expands in agreement with previous experiments. In contrast to ferroelectric perovskites, oxygen vacancies are found to be more stable in bulk than at domain walls. The tendency of oxygen vacancies to segregate away from neutral domain walls is explained by unfavorable Y-O bond lengths caused by the local strain field at the domain walls.
关键词： oxygen vacancies,ferroelectric domain walls,hexagonal YMnO3,density functional calculations,migration barriers
更新于2025-09-11 14:15:04
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pH-Dependent Degradation of Layered Black Phosphorus: Essential Role of Hydroxide Ions
摘要： The practical application of layered black phosphorus (LBP) was challenged by fast decomposition in the presence of H2O and/or O2, and the role of H2O was highly controversial. Herein, we proposed a hydroxide ion (OH-)-initiated degradation mechanism for LBP to elucidate the role of H2O. We found that LBP degraded faster in alkaline solutions than in neutral or acidic solutions with or without O2. Degradation rates of LBP increased linearly from pH 4 to 10. Density functional theory calculations showed that OH- initiated the decomposition of LBP through breaking the P–P bond and forming a P–O bond. The detection of hypophosphite, generated from OH- reacting with P atoms, confirmed the hypothesis. Protons acted in a way distinctive from OH-, by inducing deposition/aggregation or forming a cation-π layer to protect LBP from degradation. This work revealed the exact degradation mechanism of LBP to facilitate the development of effective stabilization technologies.
关键词： Degradation mechanism,Hydroxide ion,Nanostructures,Density functional calculations,Black phosphorus
更新于2025-09-10 09:29:36