R. N. V. Ranga Reddy

A study on the Moss relation

Abstract A simple empirical relationship has been established for the estimation of refractive indices for various materials directly from their energy gaps. Its validity is tested in various classes of materials such as semiconductors, insulators and oxides. There has been no report in the literature which explains the dependence of energy gap and refractive index in a variety class of solids. Its performance is compared with Moss and Ravindras relations. A simple analysis on the average percentage deviation for low and high n value materials is also presented. The average percentage deviation in the present approach reveals that the modified Moss relation proves its identity and soundness compared to that of Moss and Ravindras relations. Good agreement is observed between the computed and literature values of refractive indices. The present proposed empirical relation cannot be applied when Eg ⩽ 0.36 and therefore cannot be applied to some classes of semiconductors such as lead salts, InSb etc.

Variation of magnetic susceptibility with electronic polarizability in compound semiconductors and alkali halides

Abstract Valence electron plasma energies have been evaluated from the interionic distances for II–VI and III–V group semiconductors and alkali halides based on the assumption that a linear relationship exists between them within a molecular group of compounds. The estimated valence electron plasma energy values are used in the evaluation of electronic polarizability in the above group of solids. Different new relations are proposed between the magnetic susceptibility and electronic polarizability. Good agreement is observed between the computed and literature values of magnetic susceptibility.

Coefficient of Volume Expansion and Thermoacoustic Parameters of Alkyl-Cyano-Biphenyl Liquid Crystals

Dilatometric studies were performed on the nematic and isotropic phases of the homologous series of alkyl-cyano-biphenyl liquid crystals CnH2n+1C6H4C6H4. CN for n = 5 to 9. From these studies the coefficient of volume expansion (a) of the liquid crystal is estimated. Using this data a number of thermoacoustic and an harmonic parameters of the liquid crystal are evaluated. The temperature dependence of these parameters have also been investigated. All these thermoacoustic and an harmonic parameters evaluated in this case show characteristic change in the immediate vicinity of the phase transition temperature.

Polarizabilities of a Few Nematic Liquid Crystals

Abstract The parallel, perpendicular and the mean polarizabilities of two series of nematogenic homologous series have been evaluated using modified method of Lippincot-δ-function potential model. The results are discussed in relation to reported values. The fair agreement between calculated and reported value of α lends support to the applicability of Lippincot-δ-function model to liquid crystals.

Absorption and photoluminescence spectra of some rare earth doped B2O3TeO2BaOR2O (R = Li, Na, Li + Na) glasses

Abstract This paper reports the preparation and optical characterisation of certain rare earth (Sm3+, Dy3+, Eu3+) doped borotellurite glasses of the following composition: B2O3ue5f8TeO2ue5f8BaOue5f8R2Oue5f8REF3 where R = Li, Na and Li + Na; RE = Sm3+, Dy3+ and Eu3+. From the measured spectra, absorption band intensity parametrisation and luminescence characteristic parameters have been evaluated for the glasses investigated. Under a UV source, it was observed that Sm3+ doped glasses have been luminescing in greenish-yellow, Dy3+ glasses in yellowish-blue and Eu3+ glasses in red colours. These optical glasses are found to be IR-transmitting (up to 4.5 μm) with good transparency and sufficient hardness.

The correlation between average nuclear effective charge, refractive index, standard heat of atomization and melting point in tetrahedral semiconductors

Abstract Simple correlations between the average nuclear effective charge, standard heat of formation, refractive index and melting point have been given for some tetrahedral semiconductors. Refractive indices and melting points are evaluated. Results are in fair agreement with the experimental values.

Relation between energy gap and electronic polarizability of ternary chalcopyrites

Abstract A simple relation between energy gap and electronic polarizability is given. The estimated electronic polarizability values are in good agreement with the values obtained using the Clausius-Mossotti relation. These values are considered better than than values obtained using the dielectric theory of Phillips, Van Vechten and the bond charge model of Levine.

DISSOCIATION ENERGIES OF PH AND PH

Abstract Dissociation energies for the ground electronic states of diatomic PH and PH + are determined by fitting empirical potential functions to the respective RKRV curves using correlation coefficients. The estimated ground state dissociation energies of PH and PH + are 3.10 and 3.20 eV respectively by the curve fitting procedure using Lippincott potential function. The computed values are in good agreement with experimental values.

Physical Studies of Homologous 4-Cyanophenyl Esters of 4′- n-Alkylcinnamic Acids

Abstract The mean polarizabilities of homologous series of nematic liquid crystals of 4-cyanophenyl esters of 4′- n-alkylcinnamic acids are evaluated by using the MLδP method. From these polarizabilities the mean diamagnetic susceptibilities of the liquid crystals are also calculated. The orientational order parameters of these compounds are also estimated using the Vuks and Neugebauer methods. The variation of the order parameter with temperature is discussed.

Simple expressions for the electronegativity and physico-chemical parameters of alkali halides

Abstract Formulae relating Martynov and Bastsanov electronegativities and some physico-chemical parameters of alkali halides are proposed. The estimated heat of atomization, energy gap, bond energy, refractive index, interionic distance, plasma energy, ionization potential and lattice energy values are in good agreement with the values cited in the literature. The proposed equations are simple and have the advantage over others that less computational work is involved in the calculations of physico-chemical parameters of alkali halides.