Molecular Constants of MnF6 −2 Anion

Abstract

The normal coordinate analysis of XY₆ type of anions and molecules employing different force fields is well established.^1,2 Recently, the vibrational spectra and complete frequency assignment of MnF₆ ^?2 has been reported by Flint.³ Using the available vibrational data the force constants have been evaluated employing three potential models viz. general valence force field (GVFF), Urey-Bradley force field (UBFF) and orbital valence force field (OVFF). The mean amplitudes of vibration and Bastiansen-Morino shrinkages have also been computed at two temperatures.     

Molecular constants of XeO3F2

The force constants of XeO₃F₂ have been evaluated using the general valence force field. The mean square amplitudes of vibration, the generalised mean square amplitudes and shrinkage constants, Coriolis coupling coefficients and centrifugal distortion constants have also been calculated for the first time using the vibrational frequencies and the structural parameters. The thermodynamic properties have been computed for the ideal gaseous state at 1 atmospheric pressure for 11 temperatures from 100° to 1000°K using a rigid rotor harmonic oscillator approximation.     

Force Constants and Mean Amplitudes of Vibration of the Thiazyl Halides Cisn and BrSN

The force constants have been calculated for thiazylnalides CISN and BrSN employing general valence force field and Urey-Dradley force field. The computed results show some interesting features. The mean amplitudes of vibration have also been calculated at temperatures, O°K, 298.15°K and 500°K. These results will be helpful for the interpretation of the electron diffraction data whenever available.     

Intramolecular Force Fields and Vibrational Amplitudes of Disulfur Monoxide Isotopes

The force constants of S₂O have been calculated smploying GVFF and UBFF models. The reliability of the set of force constants have been examined. The mean amplitudes of vibration have also been evaluated at three temperatures, viz., 0°K, 298·15°K and 500°K. The results have been briefly discussed. The mean amplitude values will be helpful in interpretation of the electron diffraction data whenever available.     

Force Constants,Coriolis Coupling Constants,and Mean Amplitudes of Vibration of InCl6 3-

Abstract

The general quadratic force constants, coriolis coupling constants and mean amplitudes of vibration have been evaluated for InCl₆ ^3- using recent vibrational data. The results are employed to study the trend of variation in the isoelectronic sequences e.g. InCl₆ ^3-, SnCl₆ ^2- and SbCl₆ ^?.

In the present communication we report the force constants, coriolis coupling constants and mean amplitudes of vibration for InCl₆ ^3- which have not been reported so far. The results are used to study the trend of variation of the molecular parameters in the isoelectronic sequence e.g. InCl₆ ^3-, SnCl₆ ^2- and SbCl₆ ^?. The fundamental frequencies of InCl₆ ^3-, employed in this computation, have been reported on the basis of octahedral symmetry, from infrared and Raman Spectral Studies¹.     

The GVFT Force Constants for PO4 3-/Td/

The force constants for the tetrahedral PO₄ ^3- ion have been calculated on the basis of the general valence force field with the application of the Wilson FG matrix method^1,2.     

Vibrational Parameters of Some Mixed Tetracoordinate Halogenomercurate(II) Complexes

Abstract

The normal coordinate analysis has been performed for the mercury(II) halogeno complexes HgX₃Y²? (X≠Y=C1, Br, I) using latest Raman spectral data for the first time. The general quadratic valence force field has been used in this study. The results in turn are utilized to investigate the useful vibrational parameters such as compliance constants and mean amplitudes of vibration. The trends among the vibrational parameters are discussed and the bond properties of the mercury(II) and related complexes are examined.     

Vibrational Mean Amplitudes of XY3 Pyramidal Molecules

The vibrational mean amplitudes for bonded as well as for nonbonded distances have been evaluated for AsP₃, SbP₃, and PAs₃ at temperatures : T = 0^oK, T = 298.15^oK and T=500 ^oK using recent vibrational data. The results have been briefly discussed.     

The Vibrational Spectra and Normal Coordinate Analysis of 6Li- and 7Li-Substituted Lithium Disilicate Phases

Infrared and Raman spectra were measured for crystalline ⁶Li- and ⁷Li-substituted lithium disilicate. The spectra were analysed by normal coordinate analysis (NCA) using a modified valence force field. The resulting force constants were consistent with those calculated for related SiO₂-containing phases. The Raman spectral results for related glasses were interpreted with respect to the spectral data for the crystalline phase.     

Normal coordinate analyses for trimethylantimony(V) dihalides: A comparison of three force fields

Approximate normal coordinate analyses have been carried out for the series (CH₃)₃SbX₂ (X = F, Cl, Br, and I) assuming a molecular symmetry of D_3h and that the methyl groups behave as single atoms. Sets of seven force constants have been evaluated for each molecule using each of the following force fields: general valence, modified Urey-Bradley, and orbital valence. The fundamental vibrational frequencies have been evaluated using these force constants and have been compared with the experimentally observed values published previously. The orbital valence force constants generally led to better agreement between calculated and observed frequencies. Trends in the force constant values are discussed briefly.     

Vibrational Behaviour of the CrO3- 4 Anion in Different Crystalline Environments

The powder-infrared spectra of different crystalline compounds containing the tetrahedral Cro^3- ₄, anion have been recorded and analyzed with the aid of the site symmetry rules. In some cases Raman data are also reported. The effect of the different crystalline environments is discussed in detail and comparisons with isostructural phases are also made. A definitive assignment for the internal vibrations of the CrO^3- ₄, ion is proposed and a new set of force constants has been calculated fron a modified valence force field.     

Effect of local cationic environment on the valence state of <Superscript>119</Superscript>Sn probe atoms on the surface of antiferromagnet MnTiO<Subscript>3</Subscript> with ilmenite structure

Annealing in argon of MnTiO₃ impregnated with a SnCl₄ solution leads to the distribution of Sn⁴⁺ ions over sites with different cationic environments in the surface layers of crystallites. The chemical behavior of Sn⁴⁺ ions emerging on the surface upon subsequent annealing in hydrogen depends on the tendency of the neighboring cations to retain the octahedral coordination by O^2? anions. The absence of spin polarization of the Sn²⁺ cations formed on the surface shows that their specific valence state is stabilized by the nearby Ti⁴⁺ cations.     

Ground state rotational spectrum,K = 3 splittings,ab initio anharmonic force field and equilibrium structure of trifluoroamine

The submillimetre-wave spectrum of ¹⁴NF₃ has been measured and the ground state rotational spectrum has been reanalysed, including the K=3 splittings. The quadratic, cubic and semidiagonal quartic force field has been calculated at the CCSD(T) level of theory employing a basis set of at least polarized valence triple-zeta quality. This force field has been used to predict the spectroscopic constants, including the parameters specific to the doubly degenerate vibrational states. The calculated values are found to be in good agreement with the available experimental data. The equilibrium structure has been derived from the experimental ground state rotational constants and either the ab initio or the experimental rovibrational interaction parameters. These experimental and semiexperimental structures are in excellent agreement with the ab initio equilibrium geometry.     

Magnetic characterization of Bi2FeMnO6 film grown on (100) SrTiO3 substrate

Single phase Bi₂FeMnO₆ films on (100) SrTiO₃ substrate were fabricated using a pulsed laser deposition method through optimization of the preparation conditions. The magnetic moment is 0.30μ_B at 5 K in the magnetic field of 1 T, indicating that B site cations of Fe and Mn are disordered in the sample. The zero‐field‐cooling (ZFC) and field‐cooling (FC) magnetization curves measured from 2 K to 400 K coincide at 360 K. This is consistent with the observation that hysteresis disappears at 360 K, revealing the antiferromagnetic transition at this temperature. A spin‐glass‐like behaviour was observed at low temperature (～100 K) with a cusp of 25 K. Mn shows multiple valence states in the film. It is possibly because Mn²⁺ and Mn⁴⁺ could decrease the Jahn–Teller effect from Mn³⁺ in the film which results in less lattice distortion. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Lattice vibration analysis of cryolite A3B′X6 and elpasolite A3BB′X6 compounds. A force constant calculation of Sr2ZnTeO6

A normal coordinate treatment of crystals with general formula A₃B′X₆ and A₂BB′X₆ with cubic structure (space group F_m3m) is made with the G-F matrix method. A modified valence force field is assumed to give a set of ten force constants for calculating all fundamental vibrations in the k = 0 approximation.     

Effect of Cr on hyperfine parameters in a-Fe-Cr-Si-B alloys

Mössbauer studies on a-Fe_80–xCr_xSi₈B₁₂ (x = 0,2,...12) at 5K have been reported. The average hyperfine field and width of P(H) distribution have been analysed by a model which assumes a random distribution of Cr atoms. On assumption that the hyperfine field distribution of Fe atom with r number of Cr nearest neighbours is given by a gaussian with a mean field H_r =H_o - rC₁ + r²C₂; C and C₂ being constants; broad features of Mössbauer spectra are explained.     

Ordre a courte distance et energie interne des composes Sr2TaFeO6 et Sr2TaCrO6 de type perovskite

The disordered samples of the perovskite compounds Sr₂TaFeO₆ and Sr₂TaCrO₆ have been studied using powder X-ray diffuse scattering techniques. The short range order parameters show that on Sr₂TaFeO₆ the Ta⁵⁺ and Fe³⁺ cations are almost completely disordered while high short range order is found between Ta⁵⁺ and Cr³⁺ in Sr₂TaCrO₆. Local displacements of all the ions have been found. In particular the anions move largely toward the positive Ta⁵⁺ ions.The electrostatic energies (order, polarization, displacements) between a “NaCl” order structure-type and the fully disordered perovskite-structure are compared.The existence of the disordered structure can be completely explained by the polarization energy of the anions and Sr²⁺ cations.Qualitatively the displacement energy increases as the radius of the 5+ cations decreases. This allows us to explain the fact that some of these phases are ordered.     

Force field calculations of acetonitrile using CNDO/force method

The redundancy-free internal valence force field (RFIVFF) of acetonitrile is reported using CNDO/force method. The initial force field is set up by taking the interaction and bending force constants from CNDO force field and transferring stretching force constants from the force fields of chemically related molecules. The final force field is obtained by refining the initial force field using vibrational harmonic frequencies of CH₃CN,¹³CH₃CN, CH₃ ¹³CN, CH₃C¹⁵N, CD₃CN and CD₃ ¹³CN. The final force field thus obtained is found to be excellent on the basis of frequency fit and potential energy distribution.     

Anharmonic force field for methanol

An ab initio quartic anharmonic force field for methanol has been calculated at the equilibrium position using the CCSD(T) method for the structure and the harmonic potential energy surface, and the MP4(SDQ) method for the anharmonic part of the surface. A triple zeta basis set was employed with symmetrized curvilinear internal valence coordinates in all calculations. The internal coordinate force field constants have been transformed into force constants in the dimensionless normal coordinate representation for various isotopomers. Vibrational term values for CH₃OH, CH₃OD, CD₃OH, and CD₃OD have been obtained using second order perturbation theory. Particular care has been devoted to the inclusion of Fermi resonance interactions between different vibrational states. A good accuracy has been achieved in the calculation of the fundamentals for all the isotopomers, the mean absolute error being 5.8 cm^?1.     

Effects of increasing number of rings on the ion sensing ability of CdSe quantum dots: a theoretical study

A computational study on the structural and electronic properties of a special class of artificial atoms, known as quantum dots, has been carried out. These are semiconductors with unique optical and electronic properties and have been widely used in various applications, such as bio-sensing, bio-imaging, and so on. We have considered quantum dots belonging to II–VI types of semiconductors, due to their wide band gap, possession of large exciton binding energies and unique optical and electronic properties. We have studied their applications as chemical ion sensors by beginning with the study of the ion sensing ability of (CdSe) _n (n?=?3, 6, 9 which are in the size range of ~?0.24, 0.49, 0.74 nm, respectively) quantum dots for cations of the zinc triad, namely Zn²⁺, Cd²⁺, Hg²⁺, and various anions of biological and environmental importance, and studied the effect of increasing number of rings on their ion sensing ability. The various structural, electronic, and optical properties, their interaction energies, and charge transfer on interaction with metal ions and anions have been calculated and reported. Our studies indicate that the CdSe quantum dots can be employed as sensors for both divalent cations and anions, but they can sense cations better than anions.