11,174 research outputs found
Thermal expansion studies on low-dimensional frustrated quantum magnets: the case of Kappa-(BEDT-TTF) 2 Cu 2 (CN) 3 and azurite
No full textThermal expansion measurements provide a sensitive tool for exploring a material's thermodynamic
properties in condensed matter physics as they provide useful information
on the electronic, magnetic and lattice properties of a material. In this thesis, thermal
expansion measurements have been carried out both at ambient-pressure and under hydrostatic
pressure conditions. From the materials point of view, the spin-liquid candidate
Kappa-(BEDT-TTF) 2 Cu 2(CN)3 has been studied extensively as a function of temperature and
magnetic field. Azurite, Cu 3 (CO 3) 2 (OH) 2 - a realization of a one-dimensional distorted
Heisenberg chain is also studied both at ambient and hydrostatic pressure to demonstrate
the proper functioning of the newly built setup "thermal expansion under pressure". ..
Uniaxial Negative Thermal Expansion, Negative Linear Compressibility, and Negative Poisson's Ratio Induced by Specific Topology in Zn[Au(CN)(2)](2)
No full textThe well-known idea of "structure determines properties" can be understood profoundly in the case of hexagonal zinc dicyanometalate. Using density functional theory (DFT) calculations, we show the uniaxial negative thermal expansion (NTE) and negative linear compressibility (NLC) properties of Zn[Au(CN)(2)](2). The temperature dependence of phonon frequencies within the quasi harmonic approximation (QHA) is investigated. The abnormal phonon hardening (frequency increase on heating) is detected in the ranges of 0-225, 320-345, and 410-430 cm(-1), which can be indicative of the unusual physical properties of Zn[Au(CN)(2)](2). Due to the significance of low-energy phonon frequencies in Zn[Au(CN)(2)](2), in this work, the corresponding vibrational mode of the lowest-frequency optical phonon at the zone center is analyzed. The specific topology of a springlike framework that will produce the effects of a compressed spring on heating and an extended spring under hydrostatic pressure is identified and leads to the coexistence of uniaxial-NTE and NLC behaviors in Zn[Au(CN)(2)](2). The. distinguishing phonon group velocity along the a axis and c axis facilitates different responses for both the axes under temperature and hydrostatic pressure field. Through an analysis and visualization of the spatial dependence of elastic tensors, it is found that a negative Poisson's ratio (NPR) is presented in all projection planes due to the specific topology
Topological duality on the function space H(CN)
No full textBy a classical theorem, there is an isomorphism between the space of entire functions of exponential type on Cn,ExpCn, and the analytic functions on H(Cn),H′(Cn) [see, for example, F. Trèves, Topological vector spaces, distributions, and kernels, Academic Press, New York, 1967; MR0225131 (37 #726)]. In this note, the author extends this useful theorem to H(CN), the space of analytic functions on the countable product of complex lines. Specifically, he considers H(CN) endowed with the compact-open topology τ0 and the associated bornological topology τδ. For both τ=τ0 and τδ, the author characterizes the strong duals (H(CN),τ)′ as spaces of entire functions of exponential type on CN. {Reviewer's remark: In the meantime the author has shown (private communication) that these dual spaces are different.}Depto. de Análisis Matemático y Matemática AplicadaFac. de Ciencias MatemáticasTRUEpu
Aspects of sexual failure in the reproductive process of a rare bulbiliferous plant in subtropical Asia, Titanotrichum oldhamii (Gesneriaceae).
No full textPreparation, characterization and crystal structure of [Ni(bpy)3][Fe(CN)5(NO)]3H2O and one-dimensional cyano-bridged [Ni(en)2Fe(CN)5(NO)]H2O
No full textTwo new double complexes [Ni(bpy)3][Fe(CN)5(NO)]3H2O (1) and [Ni(en)2Fe(CN)5(NO)]H2O (2) have been isolated from the reactions of the mixture of NiCl2·6H2O and Na2[Fe(CN)5(NO)] in water, with bipyridine (bpy) and ethylenediammine (en) in ethanol, respectively, and have been characterized by X-ray analysis, IR, EPR, Mössbauer spectroscopy and magnetic measurements. Crystallographic data for 1 and 2 areas follows: triclinic, Full-size image (<1 K); 2: triclinic, Full-size image (<1 K). The bond angles of FeNO are nearly linear for 1 (178.3(4)°) and 2 (1i79.4(3)°). The structure of 1 consists of a double complex of a cation [Ni(bpy)3]2+ and an anion [Fe(CN)5(NO)]2−. The structure of 2 consists of a one-dimensional polymeric chain Ni(en)2NCFe(CN)3(NO)CNNi(en)2 in which the Ni(II) and Fe(II) centers are linked by two CN groups. Crymagnetic investigations (4–900 K) reveal a paramagnetic behavior for 1 and the presence of a one-dimensional Heisenberg weak antiferromagnetic chain with J=−0.47 cm−1 for 2. EPR spectra observed at ambient temperature for the Ni(II) ions in both complexes are also reported.補正完畢SC
Structural and transport properties of neutral radical crystals of Co-III(tmp)(CN)(2) (tmp=5,10,15,20-tetramethylporphyrinato) and the CN-bridged polymer [Co-III( tmp)(CN)](n)
Full text linkAn axially ligated Co(tmp) (tmp = 5,10,15,20-tetramethylporphyrinato) anion, [Co-III(tmp)(CN)(2)](-), has been prepared and subjected to electrochemical oxidation to obtain the open shell tmp pi-ligand. With acetone as the solvent, solvent-free neutral radical crystals of Co-III(tmp)(CN)(2) are obtained, whereas solvent-inclusive crystals of Co-III(tmp)(CN)(2)center dot 2CH(3)CN are obtained with CH3CN as the solvent. In both crystals, the open shell tmp ring deforms into a ruffled form, which makes the pi-pi interactions in the crystal weak. Thus, the electrical conductivity is low, and the crystals behave as semiconductors with a room temperature resistivity of 10(6) Omega cm and an activation energy of about 0.3 eV. When the solvent is acetone, non-oxidized crystals of the CN-bridged polymer {[Co-III(tmp)(CN)](acetone)}(n) are obtained as a byproduct. The closed shell tmp ring deforms into a ruffled form, and there pi-pi interactions in the crystal are negligible. The room temperature resistivity is rather high at about 10(8) Omega cm
- …
