ZfN: Search Results

1	Author	Prasad Durga, B. Ojha, V.G K M Raja Rajeswari, Pisipati	Requires cookie*
	Title	Molecular Ordering of a Nematic Liquid Crystal in a Dielectric Medium
	Abstract	A computational analysis of the molecular ordering of 4-(4'-ethoxyphenylazo) phenyl hexanoate (EPPH) has ben carried out on the basis of intermolecular interaction energy calculations. The CNDO/2 method has been employed to evaluate the net atomic charge ad atomic dipole moment components at each atomic centre of the molecule. A modified Rayleigh-Schrödinger perturbation theory alongwith a multicentered-multipole expansion method has been employed to evaluate long-range intermolecular interactions, while a "6-exp" potential function has been assumed for short-range interactions, and cor-responding probabilities have been calculated in a dielectric medium (benzene) using the Maxwell-Boltzmann formula. Further, the flexibility of various configurations has been studied in terms of vari-ations of the probability due to departure from the most probable configuration. All possible geometri-cal arrangements between molecular pairs have been considered during stacking, in-plane and terminal interactions, and the most favourable configuration of the paring has been obtained. It has been observed that in a dielectric medium the probabilities are redistributed and there is a considerable rise in the prob-ability of interactions although the order of preference remains the same. An attempt has been made to explain the nematogenic behaviour of liquid crystals and thereby develop a molecular model for liquid crystallinity. Results have been discussed in the light of those obtained for other nematogens like EPPV [4-(4'-ethoxyphenylazo) phenyl valerate] and DPAB [4-4'-di-n-propoxy-azoxybenzene],
	Reference	Z. Naturforsch. 55a, 929—935 (2000); received November 3 2000
	Published	2000
	Keywords	CNDO/2 Method, Intermolecular Interactions, Statistical Analysis, Computer Simulation
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	TEI-XML for	default:Reihe_A/55/ZNA-2000-55a-0929.pdf
	Identifier	ZNA-2000-55a-0929
	Volume	55

2	Author	D. Schiel, W. Richter, G. Döge	Requires cookie*
	Title	CH3F/CD3F System
	Abstract	It has been proved with the aid of CH3F/CD3F mixtures that the remarkably large non-coincidence effect in the Raman scattering spectrum of the v 3 mode of liquid methyl fluoride is due to intermolecular vibrational coupling medi-ated mainly by transition dipole interaction. The amount of the effect and its temperature and mole fraction dependence are -at least qualitatively -in agreement with Logan's theoretical concept. The rather different behaviour of the isotopic species and the asymmetry and narrow width of the isotropic band, however, raise new questions which require further investigations.
	Reference	Z. Naturforsch. 45a, 1381—1382 (1990); received September 26 1990
	Published	1990
	Keywords	Raman spectroscopy, Liquids, Intermolecular interactions, Isotopic dilution, Band shift
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	TEI-XML for	default:Reihe_A/45/ZNA-1990-45a-1381_n.pdf
	Identifier	ZNA-1990-45a-1381_n
	Volume	45

3	Author	DurgaPrasad Ojha	Requires cookie*
	Title	Molecular Ordering in Liquid Crystalline EMBAC. A Quantum Mechanical Study
	Abstract	Molecular ordering in a liquid crystal, ethyl 4-(4'-methoxybenzylidene amino) cinnamate (EMBAC) has been studied by intermolecular interaction energy calculations. The CNDO/2 method has been employed to compute the atomic charge and atomic dipole at each atomic centre. The modified Rayleigh-Schrödinger perturbation theory along with the multicentered-multipole expansion method have been employed to evaluate the long-range intermolecular interactions, while a '6-exp' potential function has been assumed for the short-range interactions. On the basis of stacking, in-plane, and terminal interac-tion energy calculations all possible geometrical arrangements of a molecular pair have been considered, and the most favourable configuration of the pair has been obtained. Molecular parameters like total ener-gy, binding energy and total dipole moment have been given. Results are discussed in the light of those obtained for the nematogens 4-(4'-ethoxyphenylazo) phenyl valerate (EPPV) and 4,4'-di-n-propoxy-azoxybenzene (DPAB). An attempt is made to explain the liquid crystalline behavior of these liquid crys-tals and thereby develop a molecular model for liquid crystallinity.
	Reference	Z. Naturforsch. 55a, 923—928 (2000); received September 28 2000
	Published	2000
	Keywords	Liquid Crystal, Multicentered-multipole, CNDO/2 Method, Intermolecular Interactions, EMBAC
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	TEI-XML for	default:Reihe_A/55/ZNA-2000-55a-0923.pdf
	Identifier	ZNA-2000-55a-0923
	Volume	55