Theory of the photoelastic effect in ZnO,ZnS and CdS crystals

It has been a general opinion that the Clausius-Mossotti dielectric theory is not capable of explaining the observed photoelastic behaviour of partially ionic crystals.However in the present communication we show that by making account of the variation of polarizabilities under compressive stress within the framework of the Clausius-Mossotti theory it is possible to obtain a reasonable agreement with experimental data on the photoelastic behaviour of ZnO, ZnS and CdS crystals.     

Analysis of polarizabilities of alkali halides using Narayan-Ramaseshan repulsive potential

The repulsive potential in ionic crystals recently proposed by Narayan and Ramaseshan (NR) can be expressed as the sum of the contributions from the individual ions. In the present paper we show that using this repulsive potential it is possible to divide the polarizability arising from the relative displacement of ions into its ionic constituents. NR have also derived the ionic radii in alkali halides which we have used to estimate the electronic polarizabilities of ions with the help of polarizability-radius cube relation. The electronic polarizabilities of alkali and halogen ions thus evaluated show a good agreement with those deduced from the experimental refraction data.     

A new expression for the Anderson-Grüneisen parameter δ for ionic crystals

The Anderson-Grüneisen parameter δ has been computed theoretically from a general expression developed by Sharma and Tripathi[6]. The δ-γ (Grüneisen parameter) curves have been plotted to find a relation for the best fitted yielding curves by the method of least squares. The relation developed can be put as δ = AγB and it can be inferred that chang's[3] relation is a particular case of this general equation.     

Positron annihilation in solid krypton and xenon

A computation of the life time of positrons as well as the angular distribution of the resulting gamma pair for polycrystalline krypton and xenon has been made. The calculations are based on the technique employed by Salvadori and Carbotte for the case of solid argon. The field seen by the positrons is constructed from the charge densities derived from Herman-Skillman wave functions. The positron wave functions are obtained using the Wigner-Seitz approximation. For electrons Herman-Skillman wave functions have been used. The computed distributions, when the effects of correlation are ignored, are wider than the experimental ones. The calculated values for the mean lives of positrons for krypton and xenon are 2.2×10⁻⁹ sec and 2.7×10⁻⁹ sec, respectively, and that for xenon is, as usual, longer than the measured value of 0.43×10⁻⁹ sec. Effects of electronpositron correlations on the angular distribution and the life time have been calculated for the case of krypton. When these corrections are taken into account, the life time of positrons in krypton is reduced by a factor of about eight and the angular distribution shows a slight narrowing. Paper A24 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973).     

A new flavone C-glucoside from Glycosmis arborea (Rutaceae)

<正>A new C-glycosyl flavone 7,4'-dihydroxy-5-methoxyflavone-6-C-β-D-glucopyranoside 1 has been isolated and characterized form ethanolic extract of leaves part of Glycosmis arborea.The structure of compound was verified by means of high field 1D and 2D NMR(DEFT,COSY,DQF-HSQC,HMBC) and HRMS spectral analysis,respectively.     

Synthesis and Characterization of Dichlorotin(IV)trithiophosphates and Their Adducts with Nitrogen Donor Bases

Abstract

Dichlorotin(IV)trithiophosphates [(RO)P(S)S ₂ ]SnCl ₂ were prepared by the reaction of methanolic solution of SnCl ₄ and dipotassium salt of trithiophosphates in a 1:1 molar ratio and their adducts [(RO)P(S)S ₂ ]SnCl _2.N ₂ C ₁₂ H ₈ and [(RO)P(S)S ₂ ]SnCl _2.N ₂ C ₁₀ H ₈ were prepared by the reaction of methanolic solution of [(RO)P(S)S ₂ ]SnCl ₂ and N-donor bases in a 1:1 molar ratio. These newly synthesised derivatives have been characterized by elemental analysis; molecular weight measurements; and IR, ¹³ C, ³¹ p and ¹¹⁹ Sn NMR spectral studies. Coordination number of four and six was suggested for dichlorotin (IV)trithiophosphates and their adducts with N-donor bases respectively.     

Magnesium ion transport in poly(ethylene oxide)-based polymer electrolyte containing plastic-crystalline succinonitrile

A new composition of magnesium (Mg)-ion-conducting polymer electrolyte comprising poly(ethylene oxide) (PEO) complexed with Mg trifluoromethanesulfonate (Mg triflate or Mg(Tf)₂) containing different amounts of a nonionic plastic crystal succinonitrile (SN) has been prepared and characterized. High polarity and rotational disorder of the SN molecules in the plastic-crystalline phase, supports the enhancement of ionic conductivity of the PEO-Mg(Tf)₂ complex system, showing a maximum room temperature ionic conductivity of ～6?×?10^-4 S cm^?1 observed with the addition of 50 wt.% of SN. X-ray diffraction, optical microscopy, and differential scanning calorimetry suggest a substantial structural modification, decrease in crystallinity, and various interactions in the polymer electrolyte components due to addition of SN. The cyclic voltammetry, impedance, and dc polarization studies confirm the Mg-ion conduction in the PEO complex. The electrochemical potential window of the electrolyte, observed from the linear sweep voltammetry, is determined to be ～4.1 V. The performance characteristics of the SN-incorporated polymer electrolyte system indicate their potential applicability as electrolytes in ionic devices including Mg batteries.     

Synthesis of new conjugated copolymers containing 4,8-bis(dodecyloxy)benzo[1,2-b:4,5-b′]dithiophene/5,7-bis(3,4-diethylthien-2-yl)-2,3-diphenylthieno[3,4-b]pyrazine and 4,8-bis(dodecyloxy)benzo[1,2-b:4,5-b′]dithiophene/4,6-di(3,4-diethylthien-2-yl)-thieno[3,4-c][1,2,5]thiadiazole derivatives for photovoltaic applications

Two new donor-acceptor narrow-band-gap photovoltaic copolymers containing various electron-acceptor functional groups, such as thienopyrazine and thienodithiazole derivatives, are synthesized under the conditions of the Suzuki polycondensation reaction and characterized via ¹H NMR spectroscopy and GPC. The optical, electrochemical, and photovoltaic properties of the polymers are examined in detail. Both copolymers have good solubilities, high thermal stabilities, broad absorption regions (350–950 nm), relatively low levels of the highest occupied molecular orbital (?5.01 and ?5.02 eV for polymers I and II, respectively), and narrow band gaps (1.31 and 1.41 eV, respectively). Photovoltaic devices based on a polymer-II-PC₆₀BM (1: 3, wt/wt) mixture under AM 1.5 irradiation of 100 mV/cm² exhibit a power-conversion efficiency of ～0.29%, a short-circuit current of 1.45 mA/cm², an open-circuit voltage of V _oc = 0.67 V, and a fill factor of 0.30. These results are evidence that thienopyrazine functional groups are attractive as electron-acceptor building blocks in organic electronics.