Geometry for self-assembling of spherical hydrocarbon cages with methane thiolates on au(111)

An organodisulfide with a pair of adamantane moieties was synthesized, and its self-assembled monolayer (SAM) was formed on Au(111). The adamantane moieties are almost spherical and much bulkier than alkyl chains. The structure was characterized by scanning tunneling microscopy. Two-dimensional crystals of the SAM were found to be four orientationally different hexagonals with almost the same lattice constant with 4 radical 3a/3 and 7a/3 (a = 0.2884 nm, the Au lattice constant). The structure is assigned to four of the high-order commensurate adlayers. The present study of geometry and energetics for self-assembling of such an organosulfur compound with spherical cages provides a new insight into the probable SAM structure of various thiolate derivatives on Au(111).     

Refractive indices of organo‐metallic and ‐metalloid compounds: A long‐range corrected DFT study

Refractive indices of metal‐ and metalloid‐containing compounds are systematically evaluated using the Lorentz–Lorenz equation with polarizabilities obtained via density functional theory (DFT). Among exchange‐correlation functionals studied, the long‐range corrected (LC) fuctionals yield the lowest errors for the polarizabilities of gaseous compounds and refractive indices of liquids. The LC‐DFT predicts very well the wavelength dependence of refractive indices. A scheme for computing Abbe numbers of organometallic and organometaloid compounds is proposed and a refractive index – Abbe number plot for 80 compounds is constructed. The compounds containing heavier metals tend to have higher refractive index and lower Abbe number, but several outliers, among them Te(CH₃)₂, Ni(PF₃)₄, Sb(C₂F₃)₃, Hg(C₂F₃)₂, are found. For Hg(C₂F₃)₂, also the effect of intramolecular and intermolecular degrees of freedom on polarizability is investigated. The absolute relative error in polarizability decreases from 5.7% for monomer model to 1.7% when a dimer model (derived from the available experimental crystal data) is employed. © 2016 Wiley Periodicals, Inc.     

Data-driven exploration for pressure-induced superconductors using diamond anvil cell with boron-doped diamond electrodes and undoped diamond insulating layer

ABSTRACT

Data-driven exploration for pressure-induced superconductors was performed based on the high-throughput first-principles screening of electronic band structures. In the screening conditions, we focused on the characteristics including a narrow band gap, flat band feature, and possibility of metallization under high pressure. The 27 promising compounds were screened out from the database of Atomwork for the candidates of new pressure-induced superconductors. Among the candidates, we actually synthesized three compounds in a single crystal, and all candidates exhibited the pressure-induced superconductivity. For the in-situ electrical transport measurements, we developed a novel configuration of diamond anvil cell with boron-doped diamond electrodes and an undoped diamond insulating layer. The discovered new pressure-induced superconductors via the data-driven approach and the developed diamond anvil cell were summarized in this paper.     

Quadrupolar susceptibility and magnetic phase diagram of PrNi2Cd20 with non-Kramers doublet ground state

ABSTRACT

In this study, ultrasonic measurements were performed on a single crystal of cubic PrNi₂Cd₂₀, down to a temperature of 0.02?K, to investigate the crystalline electric field ground state and search for possible phase transitions at low temperatures. The elastic constant (C₁₁?C₁₂)/2, which is related to the Γ₃-symmetry quadrupolar response, exhibits the Curie-type softening at temperatures below ～30?K, which indicates that the present system has a Γ₃ non-Kramers doublet ground state. A leveling-off of the elastic response appears below ～0.1?K toward the lowest temperatures, which implies the presence of level splitting owing to a long-range order in a finite-volume fraction associated with Γ₃-symmetry multipoles. A magnetic field–temperature phase diagram of the present compound is constructed up to 28?T for H || [110]. A clear acoustic de Haas–van Alphen signal and a possible magnetic-field-induced phase transition at H ～26?T are also detected by high-magnetic-field measurements.     

Dialkylboryl-Substituted Cyclic Disilenes Synthesized by Desilylation-Borylation of Trimethylsilyl-Substituted Disilenes

π-Electron systems of silicon have attracted attention because of their narrow HOMO-LUMO gap and high reactivity, but the structural diversity remains limited. Herein, new dialkylboryl-substituted disilenes were synthesized by the selective desilylation-borylation of the corresponding trimethylsilyl-substituted disilenes. The dialkylboryl-substituted disilenes were fully characterized by a combination of NMR spectroscopy, MS spectrometry, single-crystal X-ray diffraction analysis, and theoretical calculations. The longest-wavelength absorption bands of boryldisilenes were bathochromically shifted compared to the corresponding silyl-substituted disilenes, indicating a substantial conjugation between π(Si=Si) and vacant 2p(B) orbitals. In the presence of 4-(dimethylamino)pyridine (DMAP), the dialkylboryl groups in the boryl-substituted disilenes were easily converted to trimethylsilyl groups, suggesting the dialkylboryl-substituted disilenes in the presence of a base serve as the surrogates of disilenyl anions (disilenides).     

Synthesis of l-α-phosphatidyl-d-myo-inositol 3,5-bisphosphate from d-glucose

Efficient synthesis of l-α-phosphatidyl-d-myo-inositol 3,5-bisphosphate was achieved from 1,2,5,6-diisopropylidene-d-glucose by utilizing ring-closing metathesis and catalytic OsO₄ dihydroxylation.     

Dynamic moderation of an electric field using a SiO2 switching layer in TaOx ‐based ReRAM

ReRAMs using oxygen vacancy drift in their resistive switching are promising candidates as next generation memory devices. One remaining issue is degradation of the on/off ratio down to 10² or less with an increased number of switching cycles. Such degradation is caused by a local hard breakdown in a set process due to a very high electric field formed just before the completion of a conductive filament formation. We found that introducing an ultra‐thin SiO₂ layer prevents the hard breakdown by dynamical moderation of the electric field formed in the TaO_x matrix, resulting in repeated switching while retaining a higher on/off ratio of about 10⁵. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)