Infrared studies of matrix isolated sodium and potassium chloride and cyanide dimers

The infrared spectra of matrix isolated sodium and potassium chlorides and cyanides in different inert gas matrices were examined over the range 4000 cm^?1 to 33 cm^?1. A study of the effect of superheating the vapor species on the spectra has been carried out. Temperature cycling experiments have been pursued in an attempt to differentiate between bands due to monomers, dimers, and higher polymers. Isotopic frequency shifts were measured for a carbon-13 enriched sample of sodium cyanide and carbon-13 and nitrogen-15 enriched samples of potassium cyanide in the CN region. Symmetry force constants were calculated assuming a cyclic rhombic structure for the dimers. In the case of the cyanide dimer, the CN group of the molecule was considered as a halide atom. Finally a comparison is given between the symmetry force constants of the dimers of the alkali metal fluorides, cyanides and chlorides.     

Mn2+doping-induced-effects on commensuration and incommensuration of potassium zinc chloride crystal

Undoped and Mn²⁺-doped with different concentrations of potassium zinc chloride (KZC) crystals were grown from aqueous solutions by slow evaporation. The dielectric constant (ε), dielectric losses (tan?δ) and ac conductivity (σ_ac) of the crystals in the ferroelectric-commensurate, incommensurate and normal phases have been measured as a function of frequency, in the range 1–100?kHz, and temperature, in the range 300–580?K. Virgin samples were subjected to measurements of the frequency dependence at selected temperatures and measurements of the temperature dependence was then followed using the same samples. The increase of ε with T could be due to a combination of conductivity, structural variations and discommensuration (DC) formation and pinning as well. The increase of tan?δ with temperature was attributed to relaxation loss in addition to conduction loss, which increases more rapidly with temperature. The ac conductivity (σ_ac) and tan?δ along the polar axis of KZC increased significantly with increasing Mn²⁺ content while ε decreased. σ_ac changed with frequency according to a power law of the form σ_ac?=?f? ^s where 0.15<s<1.27. A linear decrease of ε and tan?δ with increasing the frequency was also found. The obtained results were treated by considering the effect of Mn²⁺-doping on stripples nucleation, DC evolution/annihilation, DC-lattice formation and DCs pinning by the crystal lattice and/or structural defects for virgin and thermally treated samples.     

Mechanical characteristics of solution grown potassium zinc chloride crystals doped with lithium ions

Results of indentation-induced hardness testing studies on potassium zinc chloride crystals doped with Li⁺ ions, leading to an understanding of their mechanical behaviour, are presented. The Vickers hardness of these crystals for (1 0 0), (0 1 0) and (0 0 1) planes in the load range 20–160 g were studied. Load-independent values of hardness are estimated for the three crystallographic planes by applying Hays-Kendall’s and Li-Bradt models. The results showed that: (1) for the three crystallographic planes the load-independent hardness obtained by Li-Bradt model is higher than that predicted by Hays-Kendall’s, approach; (2) the load independent hardness of the (0 0 1) plane is higher than that of both (1 0 0) and (0 1 0) planes, (3) the values of load-independent hardness depend on Li⁺ concentrations in the K₂ZnCl₄ crystals, (4) the variations of crack length and crack morphology are described for studied crystal planes.     

The influence of pressure on the electrical conductivity of molten zinc chloride and its Mixtures with potassium chloride

Abstract

The electrical conductivities of molten ZnCl₂ and its mixtures with KCl were measured as functions of pressure, temperature, and composition. The measuremkents were performed in an internally heated pressure vessel in which the melts were contained in open quartz glass cells. The addition of KCl to molten ZnCl₂ causes a large increase of the conductivity at all pressures and temperatures. With increasing pressure the conductivity increases in pure molten ZnCl₂ and in mixtures rich in ZnCl₂ and decreases in mixtures with more than 30 mol% of KCl.     

Infrared absorption of H- - D- pairs impurity in potassium chloride

Localized vibrations due to H^- - D^- pairs impurity in potassium chloride have been computed using Green function method. The theoretical results are found to give fairly good agreement with the experimental measurements.     

Ionic conductivity of potassium chloride

An analysis of new measurements of the ionic conductivity of nominally pure KCl, KCl:Sr²⁺, and KCl:SO₄^2?, has shown that a consistent set of defect parameters can be obtained only if KCl contains Frenkel defects on both sub-lattices in addition to Schottky defects. This set of parameters is not unique in the sense that several of the parameters are defined by ranges rather than by specific values. This means that the fit of the experimental conductivity to the theoretical equations for the above model is not significantly worse if these parameters are given any value in the specified range. This set of parameters was then used to calculate the diffusion coefficients of K⁺in KCl, KCl:Sr²⁺ and KCl:SO₄^2?;of Cl^? in KCl and KCl:Sr²⁺; and of SO₄^2? in KCl:SO₄^2?. These calculations enabled the defect parameters to be refined to a unique set, with the exception of the entropy of formation of a Schottky defect, which is shown to lie between 7.5 and 7.9 K.     

Phonon dispersion relations for potassium thiocyanate

Measurements of some low frequency phonon dispersion curves in potassium thiocyanate have been made using inelastic neutron scattering techniques. The measured phonon frequencies are presented along with ones calculated from a simple model comprising axially-symmetric force constants between nearest neighbour atoms. The applicability of such a model in describing the lattice dynamics of this crystal structure is discussed.     

Millimeter wave dispersion in ethyl chloride

Dispersion of millimeter waves due to ethyl chloride in the range ν=1·34 cm^?1 to 1·44 cm^?1 is computed by means of quantum mechanical formulas. It is found that dispersion is due to (i) contribution of sixR branch rotational lines in the region considered, (ii) contribution ofR branch lines away from the region and (iii) the contribution ofQ branch lines at zero wavenumber. The maximum variation in the susceptibility is 1·9 × 10^?5 and occurs at ν=1·39 cm^?1 due to combined contribution of transitions at 1·3878 cm^?1, 1·3902 cm^?1 and 1·3927 cm^?1.     

A theoretical study of alkaline-earth cations in crystalline sodium chloride,potassium chloride and potassium bromide

Theoretical methods, based on Mott-Littleton techniques are used to investigate the defect structures of alkali-halide crystals doped with divalent ions. The systems studied are those having Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ as impurity ions in NaCl, KCl and KBr crystals. Our calculations find comparable stability of the (110) nearest-neighbour and (200) next-nearest-neighbour complexes whereas the (211) complex is found to be less stable. Significant trends in the variation of binding energy with dopant ion radius are predicted. We also consider the activation energies for the w₁, w₂, w₃ and w₄ type jumps which occur in the vicinity of the impurity ion. The results are, where possible, compared with experimentally determined defect energies and their implications in diffusion processes of M²⁺ impurities in the alkali halides are discussed.     

The repulsive energy in sodium chloride and potassium chloride crystals

The repulsive energy in sodium chloride and potassium chloride crystals has been evaluated and related to the lattice constant. The accuracy aimed at was ±0·2 kcal mole^-1 but owing to some unidentified experimental error the accuracy claimed is only ±0·6 kcal mole^-1 as compared with previous analyses in which the uncertainty is about ±2 kcal mole^-1. The improvement has been achieved by critical evaluation of the experimental data, by the elimination of inaccuracies from the thermodynamic formulae and by carrying out the analysis at several specified temperatures.     

Infrared and Raman spectroscopy of graphite-ferric chloride

We present the first detailed study of the stage dependence of the IR- and Raman-active optic graphitic modes in a graphite acceptor intercalation compound. The general frequency upshift observed with increasing FeCl₃ concentration for all optic modes is interpreted to indicate an in-plane compression within the graphitic layers. An identification of the IR-active modes with bounding and interior graphite layers is made. A lineshape analysis of the IR spectra implies IR dipole moments corresponding to ～70% of the effective charge in the graphite bounding layers, independent of stage, and ～30% distributed among the graphite interior layers for stage n?3 compounds.     

Infrared dispersion of lead phosphate at room temperature

Infrared reflection spectra [15–4000 cm^-1] along the b (binary axis) and c axes (A_u and B_u-type modes) are reported at room temperature as obtained with a Fourier-transform scanning interferometer. The spectra are analyzed with the factorized form of the dielectric function and the infrared-active mode parameters are reported.     

Infrared radiation of zinc selenide single crystals

Long-wave photoluminescence (PL) spectra of both as-grown and Au-doped n-ZnSe single crystals are studied in the temperature range from 81 to 300 K. A narrow band of infrared (IR) radiation centered at 878 nm (1.411 eV) manifests itself in the low-temperature PL spectrum. It is established that this band intensity first increases and then decreases with increasing concentration of doping impurity. With increasing excitation radiation intensity, spectral position of the IR PL band is unchanged and its intensity increases under the linear law. With increasing excitation radiation wavelength, the IR PL band intensity increases, it becomes narrower and shifts towards long wavelengths. It is shown that the observed IR radiation is caused by recombination of free electrons with holes localized on associative acceptors in the ZnSe:Zn:Au crystals or in the undoped crystals.     

Reinvestigation of crystal growth of thiosemicarbazide potassium chloride and thiosemicarbazide lithium chloride

Reinvestigation of the growth of thiosemicarbazide potassium chloride crystal (1) (Chandrasekaran et al. [1]) and thiosemicarbazide lithium chloride crystal (2) (Maadeswaran et al. [2]), unambiguously confirms that compounds 1 and 2 are pure thiosemicarbazide and do not contain any alkali metal or chloride ions. In this paper we demonstrate the use of classical halide test, flame test, as well as infrared (IR) spectra for correct product characterization.