Showing papers on "Valency published in 1996"
TL;DR: In this paper, the variation of hardness, polarizability, and valency of molecules during the course of a chemical reaction was studied using the Kohn-Kohn method.
Abstract: We have studied the variation of hardness, polarizability, and valency of molecules during the course of a chemical reaction. For isomerization reactions, the quantities are calculated through Kohn...
179 citations
TL;DR: In this article, the role of superexchange interaction among 3D and 4d orbitals of transition metal ions via oxygen ions was investigated and the 1:1 ordered perovskite type compounds Sr2MMoO6 (M = Mn.Fe.Co) were prepared and their structures and properties were examined.
Abstract: In order to investigate the role of superexchange interaction among 3d and 4d orbitals of transition metal ions via oxygen ions. 1:1 ordered perovskite-type compounds Sr2MMoO6 (M = Mn.Fe.Co) were prepared and their structures and properties were examined. Structural analysis using the powder X-ray diffraction data revealed that all of these compounds have a 1:1 ordered arrangement in their B-sites. Measurements of electrical resistivity and magnetic susceptibility revealed that these compounds have the valency pairs of Mn2+ (3d5:t2g3eg2), Mo6+ (4d0). Fe3+ (3d5:t2g3eg2), Mo5+ (4d1:t2g1) and Co2+ (3d7:t2g5eg2), Mo6+ (4d0). The properties of these compounds are summarized as follows: Sr2MnMoO6, semiconductive and antiferromagnetic: Sr2FeMoO6, metallic and ferrimagnetic: Sr2CoMoO6, semiconductive and antiferromagnetic.
119 citations
Book•
01 Jan 1996
TL;DR: This chapter discusses Classical Phrase Structure Grammar, modern PSG and Other Frameworks, and some further structures, as well as some of the techniques used in developing these frameworks.
Abstract: Preface. 1. Preliminaries. 2. Classical Phrase Structure Grammar. 3. Syntactic Categories. 4. Rules and Principles. 5. Semantics. 6. Some Basic Structures. 7. Some Further Structures. 8. Raising and Control. 9. Unbounded Dependencies. 10. Anaphora. 11. Valency Alternations. 12. Some Further Phenomena. 13. Modern PSG and Other Frameworks. References. Index.
50 citations
TL;DR: The crystal structure of bismuth compounds was established by Aurivillius and the general formula (Bi2O2)2+(Mn−1RnO3n+1)2− indicates that n (1 to 6) perovskite-like layers.
Abstract: The crystal structure of bismuth compounds was established by Aurivillius and the general formula (Bi2O2)2+(Mn−1RnO3n+1)2− indicates that n (1 to 6) perovskite-like layers. M is a cation of 1, 2 or 3 valency and R is a smaller cation of 3, 4, 5 or 6 valency. The properties of a large number of compounds of this family (lattice parameters, ferroelectric Curie temperature, etc.) are correlated with composition, ionic size, value of n, etc. Attention is drawn to their low values of lattice distorition, coercive field and electric fatigue, while possessing high Curie temperatures. The recently discovered cuprate superconductors have compositional (R = Cu) and structural similarity to bismuth layer ferroelectrics.
48 citations
TL;DR: The off-stoichiometric manganite has formally the same mixed manganese valency as compounds such as (, there is no resistivity peak at and no giant magnetoresistance).
Abstract: Treating off-stoichiometric in hydrogen transforms its electrical and magnetic properties. The untreated material is a ferromagnetic narrow-gap semiconductor () whereas the near-stoichiometric reduced material is an antiferromagnetic insulator ). Although the off-stoichiometric manganite has formally the same mixed manganese valency as compounds such as (, there is no resistivity peak at and no giant magnetoresistance. The difference may be due to potential fluctuations associated with cation vacancies.
25 citations
TL;DR: In this article, the Tb{sub 1-x}Bi{sub x}SrO{sub 3} type was investigated under oxidizing sintering conditions.
14 citations
TL;DR: In this paper, the formula CuxGayCrzSe4 (x + y + z ≈ 3) for the investigated single crystals was determined from X-ray photoelectron spectroscopy data and Xray microprobe analysis.
13 citations
TL;DR: In this paper, the 141 Pr Mossbauer isomer shift and hyperfine field of PrBa 2 Cu 3 O 7 and some other praseodymium oxides were measured.
Abstract: The 141 Pr Mossbauer isomer shift and hyperfine field of PrBa 2 Cu 3 O 7 and some other praseodymium oxides were measured. When we put the isomer shift of these oxides on a linear scale, we find for PrBa 2 Cu 3 O 7 the mean valency 3.4(1). This value corresponds to the number of holes which goes into the Pr-2(Cu(2)-O 2 ) layers. The spectra below T N ≈ 17 K are broadened, but no well resolved hyperfine field split pattern is observed. We surmise that these spectra are due to relaxation. In the discussion we ascribe the different results on the valency of Pr in PrBa 2 Cu 3 O 7 reported in the literature to a different use of the term valency. A model is furthermore proposed in which we suggest that the correlation of the Pr4f shell introduced into the O 2p wave functions is responsible for the anomalous properties of PrBa 2 Cu 3 O 7
11 citations
TL;DR: In this paper, the electrosorption valency for the adsorption of parabonic acid has been determined on single crystal gold electrodes and mercury near the point of zero charge.
7 citations
24 May 1996
TL;DR: In this article, the average d-occupancy of transition metal compounds was determined with sufficient accuracy from core level photoemission spectra, though different interaction strengths, like U, Δ and t individually have a very wide range of uncertainties.
Abstract: With extensive calculations based on cluster and impurity models, we analyse core level photoemission spectra of several transition metal compounds. Our results show that the average d-occupancy is determined with sufficient accuracy from these spectra, though different interaction strengths, like U, Δ and t individually have a very wide range of uncertainties. It is also found that an analysis of core level spectra of a stoichiometric compound can provide a good estimate even for the character of doped holes in such systems.
TL;DR: In this article, the role of double exchange, a non-Heisenberg spin-spin interaction between the magnetic ions of identical chemical nature but different charge states, in the mixed-valency diluted magnetic semiconductors is discussed.
Abstract: The role of double-exchange, a non-Heisenberg spin-spin interaction between the magnetic ions of identical chemical nature but different charge states, in the mixed-valency diluted magnetic semiconductors is discussed. The mechanism correlates the spins of magnetic ions by virtual hopping of a d-electron from one ion to the other via the p-band states. We calculate the energy spectrum for pairs of magnetic ions within the charged ionic clusters stabilized by the charge—charge correlations, taking into account simultaneously both the double and the superexchange. The ferromagnetic, non-Heisenberg double exchange might compete with the Heisenberg-like, ferrimagnetic superexchange, thus resulting in canted alignments of ionic spins. PACS numbers: 71.70.Gm, 75.30.Εt
Patent•
31 May 1996
TL;DR: In this paper, a redox-flow cell with a positive active material is operated so that when charge is finished, the positive active materials in the first valency state is left in the electrolyte, and preferably the negative active material in the second valency states is 90% or less.
Abstract: PURPOSE: To prevent deterioration of an electrode and lengthen the life of a cell by operating under a specified condition in a operating method for a redox-flow cell containing a specified positive active material. CONSTITUTION: A redox-flow cell 1 contains a positive active material which changes from a first valency state (example: V ) to a second valency state (example: V ) in charge, and conducts reverse reaction in discharge, in a positive electrode. The cell 1 is operated so that when charge is finished, the positive active material in the first valency state is left in the electrolyte, and preferably the positive active material in the second valency state is 90% or less.
TL;DR: In this paper, a comparative study on the doping effects of 3D elements in Bi(1.5), Pb(0.2), Sr(2), Ca(2)Cu(2.8), M(0,2)O(y) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn) has been carried out.
Abstract: With XRD, R-T, and ac chi measurements a comparative study on the doping effects of 3d elements in Bi(1.5)Pb(0.2)Sr(2)Ca(2)Cu(2.8)M(0.2)O(y) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn) has been carried out. The effects of the former five members are significantly different, both on phase formed and on T-c, from the latter four. It seems that the effect on phase stabilization correlates with the valency of the doped cation. In connection with the instability of the 2223 phase, the correlation has been discussed.
Patent•
20 Apr 1996
TL;DR: In this paper, it was claimed that the oxide of the metal of lower valency is present in the spinel lattice and dissolved in this in more than the stoichiometric ratio 1:1.
Abstract: Ceramic material contg. oxides of at least 2 metals of different valency has a spinel as main phase. The oxide of the metal of lower valency is present in the spinel lattice and dissolved in this in more than the stoichiometric ratio 1:1. Also claimed is a method of producing the material.
Patent•
04 Jan 1996
TL;DR: An aromatic copolyamide contains repeating units of formulae (I), (II) -(OC-Ar-CO-NH-Ar -NH)- (III) as mentioned in this paper.
Abstract: An aromatic copolyamide contains repeating units of formulae (I), (II) -(OC-Ar -CO-NH-Ar -NH)- (II) and -(OC-Ar -CO-NH-Ar -NH)- (III). Ar , Ar , Ar , Ar = divalent aromatic gps. with their valency bonds in p-position or in a coaxial or parallel position comparable to this; Ar = divalent aromatic gp., different from Ar , with valency bonds in p-position or in a comparable coaxial or parallel position to each other, or is a divalent aromatic gp. with valency bonds in m-position to each other or in a comparably angled position; Y = -O-, -S- or -NR -; R = monovalent organic gp., or esp. H; the Ar gps. may be substituted with 1 or 2 gps. inert to carboxylic acid chlorides.
TL;DR: The CONTRAGRAM Contrastive Verb Valency Dictionary of Dutch, French and English not only describes interlingual differences between different types of verb complementation exhaustively, it also provides a semantic picture of the entry verbs that offers a suitable basis for describing conceptual differences between various languages.
TL;DR: In this article, the authors test the possibility that liquid mixtures in general may show anomalies when 2•4 the pressure, bond lifetime, network persistence time and the self-diffusion coefficient were measured in mixtures of two-and three-valent saturated square-well molecules in which the mean valency is varied from 2 to 3 in steps of 1/8, the inverse temperature e/kT was varied from 0 to 4.
Abstract: Constraint theory predicts, from topological considerations alone, that covalently bonded glasses change from floppy to rigid when the mean valency increases through a threshold value = 2•4. There is evidence for extrema in several properties of liquid mixtures of Ge, As,and Se when the mean valency is 2•4. To test the possibility that liquid mixtures in generalmay show anomalies when 2•4 the pressure, bond lifetime, network persistence time and the self-diffusion coefficient were measured in mixtures of two- and three-valent saturated square-well molecules in which the mean valency is varied from 2 to 3 in steps of 1/8, the inverse temperature e/kT is varied from 0 to 4, and the density is varied from a gas-like value to near the glass transition. The measured properties are insensitive to , they vary monotonically with and there are no indications of special effects near = 2•4.