Showing papers by "Indian Association for the Cultivation of Science published in 1983"
TL;DR: In this article, the refractive indices and densities of six liquid crystals (two alkylcyanobiphenyls, three alkoxycyclaneobipenyls and one mixture of two alkylancyanogenobiphensyls) have been reported as a function of temperature.
Abstract: The refractive indices and densities of six liquid crystals—two alkylcyanobiphenyls, three alkoxycyanobiphenyls and one mixture of two alkylcyanobiphenyls have been reported as a function of temperature. The effective polarizabilities αeand αo in the nematic phase calculated using the methods due to Neugebauer, Vuks and Saupe and Maier, are found to be appreciably different, though the order parameter S evaluated with those values of (αe - αo) are in good agreement. The preference of one method over the other two is discussed.
72 citations
TL;DR: In this paper, a variational determination of the cluster components using Euler's principle for the energy functional was proposed, in spirit to the Varied Portion Approach (VPA) of Sinanoglu and conventional coupled-cluster theory.
Abstract: If the ground state wave-function ψgr is written as ψgr = Φo+X, withX as the correlation part satisfying (φo¦x) = 0, andx expressed as an expansion in terms of pair, pair-pair etc. cluster functions, then the expectation value of the energyE = (ψgr¦H¦ψgr)/(ψgr¦ψgr) has the property that the normalization term in the denominator completely cancels the unlinked part of the numerator, as noted by Sinanoglu. We use Cizek's coupled-pair ansatz ψgr = exp(T2)Φ0 for transcribing Sinanoglu's expansion in a many-body language to study the behaviour of the size-consistent (linked) energy functional thus generated. For calculating the matrix-elements of the cluster components ofT, we use two recipes: (1) a variational determination of the cluster components using Euler's principle for the energy functional akin in spirit to the Varied Portion Approach (VPA) of Sinanoglu and (ii) a nonvariational determination of the cluster components using the conventional coupled-cluster theory. Results are presented for model test systems and are compared with variational CI and nonvariational coupled-cluster values. It has been observed that the values obtained from the size-consistent energy functional from the cluster components obtained from methods (i) and (ii) are quite close and both compare well with the nonvariational coupled-cluster results. Some useful simplifications afforded by the VPA are also indicated. A brief perspective of the method vis-a-vis other related theories is also given.
56 citations
TL;DR: In this article, principal electrical conductivities and seebeck coefficients, as well as Hall effect, in p-type single crystals of natural molybdenite (MoS2) have been investigated within the temperature range 100°K to 850°K.
40 citations
TL;DR: In this paper, the positronium-formation cross sections in positron-helium scattering have been calculated with the use of a distorted-wave polarizedorbital method from the threshold to 100 eV.
Abstract: The positronium-formation cross sections in positron-helium scattering have been calculated with the use of a distorted-wave polarized-orbital method from the threshold to 100 eV. The results with and without the matrix elements involving the distorted target wave functions are found to differ appreciably. The results of the first Born approximation are not expected to be correct even at the incident-positron energy 100 eV. The measured values at 20 eV are found to be less than (1/2) of the present predicted values. The sharp rise of the formation cross section within the ore-gap region as observed by Charlton et al. has also been noticed by us. The minimum in the differential cross section has been found at all energies as in the case of hydrogen atom.
26 citations
TL;DR: The positronium-formation cross section in positron-hydrogen scattering has been calculated by using the distorted-wave approximation in which the total incident wave function is obtained by the method of polarized orbitals.
Abstract: The positronium-formation cross section in positron-hydrogen scattering has been calculated by using the distorted-wave approximation in which the total incident wave function is obtained by the method of polarized orbitals The two variants of the polarized-orbital method, one due to Temkin and Lamkin and the other due to Callaway et al, have been employed to estimate their relative importance The present results have been compared with those obtained by elaborate variational methods The results obtained by using the potential of Temkin and Lamkin have been found to be encouraging
22 citations
TL;DR: In this paper, the triply differential cross sections (TDCS) for electron-impact ionization of helium in the Glauber approximation in the incident energy range 224.58-2824.58 eV were presented.
Abstract: We report numerical results for the triply differential cross sections (TDCS) for electron-impact ionization of helium in the Glauber approximation in the incident energy range 224.58--2824.58 eV. The present calculation is based upon the technique of Roy et al., which has an advantage over the conventional partial-wave method in calculating TDCS in that the latter requires substantial computer time where many partial waves are involved. A comparison is made of the present TDCS with the results of available theoretical calculations and absolute measurements.
19 citations
TL;DR: In this article, the cloud points for the co-nonsolvent systems (i) pyridine (PY) + formic acid (FA) towards poly(ϵ-caprolactone) (PCL) or poly(methyl methacrylate) (PMMA) were experimentally determined as a function of solvent composition at fixed polymer concentrations.
18 citations
TL;DR: In this paper, a simple experimental technique for the investigation of structural phase transitions in molecular crystals in the temperature range 77-300 K has been developed and applied to a wide variety of organic molecular crystals.
Abstract: A simple experimental technique for the investigation of structural phase transitions in molecular crystals in the temperature range 77-300 K has been developed and applied to a wide variety of organic molecular crystals. The ‘Photokinematical Approach’, as the method has been termed, utilizes the responsiveness of photoluminescence of guest aromatic ketone molecules to the changes in crystalline structure of host molecular crystals as sensitive probe for the identification of structural phase transformations in host molecular crystals. In this method the prediction of the number of distinct polymorphs a given molecular crystal may exist, their corresponding optimum temperatures of existence and the transition temperatures is based on the observation of characteristic changes in the luminescence intensity of the guest ketone molecules that occur in response to host crystalline modifications. The reliability of the method has been established from the conformity and reproducibility of the results ...
18 citations
TL;DR: In this article, the authors investigated the electrical transport properties of some two-dimensional isostructural compounds and a one dimensional conductor in the temperature range 300 to 150 K, and found that the observed trend in conductivities among these compounds may be rationalized either on the basis of shortest CuCu distances or on the carrier charge concentrations per unit volume.
15 citations
01 Jan 1983
TL;DR: In this paper, the relativistic Hartree-Fock-Roothaan formalism has been reviewed in the case of molecules with an arbitrary symmetry and for crystals with translational symmetry and different coefficients have been introduced for all the four sets of basis functions which constitute the four component Dirac spinors of a molecule or of a crystal.
Abstract: The relativistic Hartree-Fock-Roothaan formalism (ab initio relativistic SCF LCAO method) has been reviewed in the case of molecules with an arbitrary symmetry and for crystals with translational symmetry In the derivation different coefficients have been introduced for all the four sets of basis functions which constitute the four component Dirac spinor of a molecule or of a crystal (full variation in the framework of the relativistic Hartree-Fock theory) and also for crystals the non local exchange has been applied The problems of admixture of negative energy states and of the choice of the basis sets are discussed
15 citations
TL;DR: In this article, the authors used a Shimadzu DT-30 thermal analyzer to investigate the thermochemical reactions of [Nien3]X2·n H2O, where en = ethylenediamine, X = 1 2 SO2−4, CHCl2COO− and CCl3COO+ and n = 0 or 1.
TL;DR: In this article, the water-soluble polysaccharide from Mahua flowers gave two homogeneous fractions with molar ratios of ∼21:5:1:1/1:6.
TL;DR: In this paper, the authors investigated the thermal properties of NiL 2 X 2 ]· n H 2 O, where L = N, N -diethylethylenediamine, X = Cl −, SCN − or CCl 3 COO − and n = 2 or 0, [NiL 2 (H 2 O) 2 ]Br 2 and [NiLiX 2 (NiLX 2(H 2O) 2 ], where X = CH 3 CPO −.
TL;DR: In this paper, the electrical resistivity, temperature coefficient of resistivity and Hall constant and thermoelectric power of antimony films were measured in situ and it was shown that holes were the majority carriers in these films.
TL;DR: In this article, the composite-wave variational version of the augmented plane wave method was used to calculate the crystal potentials of LaH2 and NdH2 for both the hydrides.
Abstract: Electronic energy bands of LaH2 and NdH2 have been calculated by the composite-wave variational version of the augmented plane wave method. Crystal potentials for both the hydrides were constructed by the superposition of the atomic potentials of Herman and Skillman (1963). From the band structure data, density of states, joint density of states, optical absorption spectra and Fermi surfaces of these two hydrides have been calculated. The results of the optical studies have been successfully compared with the experimental results of Weaver et al. (1977, 1978). From the theoretical point of view the present results for LaH2 have been satisfactorily compared with the results of Gupta et al. (1978, 1980). Since no theoretical calculation exists for NdH2, theoretical comparison, in this case, was not possible for NdH2.
TL;DR: In this article, the electronic and ir absorption spectra of some fluoro alcohols in binary and ternary solution in cyclohexane and dioxane were reported.
TL;DR: In this article, the temperature dependences of the three independent adiabatic elastic stiffness coefficients c 11, C 12 and C 44 of four Ni-Fe single crystal alloys with compositions from 50 to 90 wt.
TL;DR: The results of X-ray crystallographic studies of the molecular structure of mesitil are presented in this article, where the two carbonyl planes make an angle of 177.77° and the mesityl groups are forced out of the carbonyls by 75.82° and 78.02°.
TL;DR: In this paper, the photodetachment cross section of the H/sup -/ ion has been obtained with the use of two variants of the polarized-orbital method, taking into account the matrix elements involving a distorted-target wave function that has been neglected by Bell and Kingston.
Abstract: The photodetachment cross section of the H/sup -/ ion has been obtained with the use of two variants of the polarized-orbital method. Calculation takes into account the matrix elements involving a distorted-target wave function that has been neglected by Bell and Kingston. The results have been compared with other theoretical results.
TL;DR: In this article, the authors show that the a → α transition is not discernible in conductivity measurements or thermal analysis; therefore the line of a-α transitions is presently unknown.
TL;DR: In this article, the change in semiconductivity of a series of naphthyl polyenes of the type R-(CHCH) n - R, where R stands for the naphthy group and n = 1-6, on adsorption of vapours of some organic solvents at a constant sample temperature was examined.
TL;DR: In this paper, the fluorescence intensity of 5,6,7,8-tetrahydronaphtols in cyclohexane is enhanced due to hydrogen bonding with ethanol and dioxane.
TL;DR: Detailed information was obtained regarding the partial structure of the lipopolysaccharide (LPS), containing glucose, glucuronic acid, 2-amino-2-deoxy-glucose, L-glycero-D-gluco-heptose, and small proportions of L- glucose, D-manno-hePTose, mannose,
TL;DR: In this article, an extrinsic surface optical polaron bound to an impurity atom near the surface is investigated for the first time in the framework of a recently developed canonical transformation method.
Abstract: The problem of an extrinsic surface optical polaron, bound to an impurity atom, near the surface is investigated for the first time in the framework of a recently developed canonical transformation method. Energy and wave function for all ranges of the coupling constant (α) and the impurity parameter (β) are obtained numerically following the canonical transformation method. For a strong impurity the relatively unimportant effect due to the image potential is neglected. The dependence of the energy, the wave function, and the induced potential on α, β are obtained and shown graphically.
Das Problem eines an ein Fremdatom gebundenen optischen Oberflachen-Storstellenpolarons in der Nahe der Oberflache wird zum ersten Mal im Rahmen der kurzlich entwickelten Methode der kanonischen Transformation untersucht. Energie und Wellenfunktion werden in allen Bereichen der Kopplungskonstanten α und des Storstellenparameters β numerisch erhalten. Fur eine starke Storstelle wird der relativ unwesentliche Effekt des Bildpotentials vernachlassigt. Die Abhangig-keiten der Energie, der Wellenfunktion und des induzierten Potentials von α und β werden berechnet und graphisch dargestellt.
TL;DR: The use of binary systems as accelerators in the vulcanization of rubber has received considerable attention, since many of them in suitable combinations, have been shown to provide efficient vulcanisation systems.
Abstract: The use of binary systems as accelerators in the vulcanization of rubber has received considerable attention, since many of them in suitable combinations, have been shown to provide efficient vulcanization systems. Dogadkin and co-workers and Skinner and Watson reported mutual activation with a number of popular accelerator combinations. It was suggested that the mutual activation occurs by the interaction of the accelerators to form intermediate complexes which decompose to produce free radicals responsible for initiating the various reactions involved in the vulcanization process. Recently Krymowski and Taylor studied the reaction between N-oxydiethylenethiocarbamyl-N′-oxydiethylenesulfenamide (OTOS) and N-oxydiethylene-2-benzothiazylsulfenamide (OBTS), a synergistic accelerator system, in tetrachloroethane at 142°C, and identified the various products formed. Many of these reaction products themselves are familiar as vulcanization accelerators and thus may contribute to the synergistic activit...
TL;DR: In this paper, the reduction of 1-carbomethoxy-4, 6-dimethoxynaphthalene in anhydrous ammonia gave 1-methyl-1-caromethox-6-methoxy-1, 4-dihydronaphthalenes in good yield.
TL;DR: In this article, the synthesis and characterization of CdL n X 2 · m H 2 O, where L = N 2 H 4 ; n = 3, 2, 1.75 and 1; X = Cl −, Br − and 1 2 SO 2− 4 ; and m = 0 or 0.5, have been done and their thermal studies have been carried out using a Shimadzu DT-30 thermal analyzer.
TL;DR: In this paper, the Coulomb-Born matrix element between arbitrary initial and final Slater orbitals is evaluated for the electron-impact excitation of a complex ion from an arbitrary initial state to an arbitrary final state.
Abstract: We have presented a method for the evaluation of the Coulomb-Born matrix element between arbitrary initial and final Slater orbitals. Since for the two- or more-electron ionic target the wave functions may be constructed by the combination of the Slater orbitals of various angular momenta, one can easily apply this method to calculate the cross sections for the electron-impact excitation of a complex ion from an arbitrary initial state to an arbitrary final state. As an example we have calculated the excitation cross sections of the ${\mathrm{He}}^{+}$ ion from the ground state to the $4f$ state at several energies.