scholarly journals Molecular Organization in a Nematogen: PBPCN -A Computational Analysis Based on Quantum Mechanics

2001 ◽  
Vol 56 (11) ◽  
pp. 730-734
Author(s):  
Durga Prasad Ojha ◽  
Devesh Kumar ◽  
V. G. K. M. Pisipati
Keyword(s):  
Computational Analysis ◽  
Atomic Charge ◽  
Expansion Method ◽  
Multipole Expansion ◽  
The Other ◽  
Molecular Organization ◽  
Multipole Expansion Method ◽  
Atomic Dipole ◽  
Schrödinger Perturbation ◽  
Atomic Centre

Abstract A computational analysis has been carried out to determine the configurational preference of a pair of 4'-n-pentyloxy-4-biphenylcarbonitrile (PBPCN) molecules with respect to translatory and orientational motions. The CNDO/2 method has been employed to evaluate the net atomic charge and atomic dipole components at each atomic centre of the molecule. Modified Rayleigh-Schrödinger perturbation theory along with 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. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible geometrical arrangements of molecular pair have been considered. It has been observed that the molecule has a strong preference for stacking through a particular face, while the other configurations, such as stacking through the other face, in-plane and terminal interactions show, in general, an aligned structure along molecular axis. The results are discussed in the light of experimental as well as other theoretical observations.

ORDERING IN HIGHER HOMOLOGOUS SERIES OF nBAC — A COMPARATIVE COMPUTATIONAL ANALYSIS

2005 ◽  
Vol 04 (04) ◽  
pp. 1015-1028 ◽  
Author(s):  
DURGA PRASAD OJHA
Keyword(s):  
Dipole Moment ◽  
Transition Temperature ◽  
Homologous Series ◽  
Computational Analysis ◽  
Atomic Charge ◽  
Expansion Method ◽  
Multipole Expansion ◽  
Intermolecular Forces ◽  
Multipole Expansion Method ◽  
Schrödinger Perturbation

A Comparative computational analysis of ordering in higher homologous series of p-n-alkylbenzoic acids (nBAC), having 7(7BAC); 8(8BAC) and 9(9BAC) carbon atoms in the alkyl chain, has been carried out based on quantum mechanics and intermolecular forces. The evaluation of atomic charge and dipole moment at each atomic centre has been carried out through an all-valence electron (CNDO/2) method. The modified Rayleigh-Schrodinger perturbation theory, along with 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. The total interaction energy values obtained through these computations were used to calculate the probability of each configuration at room temperature, nematic-isotropic transition temperature and above transition temperature using the Maxwell-Boltzmann formula. A comparative picture of molecular parameters such as total energy, binding energy and total dipole moment has been given. A model has been developed to describe the nematogenicity of these acids in terms of their relative order with molecular parameter introduced in this paper.

Molecular Ordering in Non-Liquid Crystalline versus Liquid Crystalline Materials with Special Reference to DADMBP – A Computational Analysis

2002 ◽  
Vol 57 (3-4) ◽  
pp. 194-198 ◽  
Author(s):  
Durga Prasad Ojha
Keyword(s):  
Long Range ◽  
Liquid Crystalline ◽  
Computational Analysis ◽  
Atomic Charge ◽  
Expansion Method ◽  
Multipole Expansion ◽  
Molecular Ordering ◽  
Multipole Expansion Method ◽  
Schrödinger Perturbation ◽  
Liquid Crystalline Materials

DADMBPA computational analysis of the molecular ordering of the non-liquid crystalline biphenyl derivative 4,4ʹ-diamino-3,3ʹ-dimethylbiphenyl () has been performed. The CNDO/2 method has been employed to compute the net atomic charge and atomic dipole components at each atomic centre. The modified Rayleigh-Schrödinger perturbation theory along with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, while a “6-exp” potential function has been assumed for short-range interactions. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible arrangements of a molecular pair have been considered. It is found that, if a suitable functional group is attached to DADMBP, so that the length to breadth ratio is increased, the molecule will show a change in the long-range order, the phase transition temperature and other liquid crystalline properties. The results are compared with those for the liquid crystalline compounds 4-(4ʹ-ethoxyphenylazo)phenyl valerate (EPPV) and 4,4ʹ-di-n-propoxy-azoxybenzene (DPAB).

Nematic Behaviour of a Compound EBBA – A Compuational Analysis

2002 ◽  
Vol 57 (12) ◽  
pp. 977-981 ◽  
Author(s):  
V. G. K. M. Pisipati ◽  
Durga Prasad Ojha
Keyword(s):  
Perturbation Method ◽  
Computational Analysis ◽  
Atomic Charge ◽  
Interaction Energies ◽  
Configurational Energy ◽  
Molecular Pair ◽  
Atomic Dipole ◽  
Schrödinger Perturbation ◽  
Atomic Centre ◽  
Theoretical Results

EBBAA computational analysis has been carried out to determine the configurational preferences of a pair of p-ethoxybenzylidine-p-n-butylaniline () molecules with respect to translatory and orientational motions. The CNDO/2 method has been employed to evaluate the net atomic charge and atomic dipole components at each atomic centre of the molecule. The configurational energy has been computed using the Rayleigh-Schrödinger perturbation method. The interaction energies obtained through these computations were used to calculate the probability of each configuration at 300 K. The energy of a molecular pair during stacking, in-plane, and terminal interaction has been calculated. The results are discussed in the light of other experimental and theoretical results.

scholarly journals Molecular Ordering of 4-Acetyl-2'-Nitrobiphenyl - A Computational Analysis

2000 ◽  
Vol 55 (11-12) ◽  
pp. 918-922 ◽  
Author(s):  
Durga Prasad Ojha
Keyword(s):  
Liquid Crystalline ◽  
Molecular Model ◽  
Atomic Charge ◽  
Expansion Method ◽  
Multipole Expansion ◽  
Intermolecular Forces ◽  
Molecular Ordering ◽  
Multipole Expansion Method ◽  
Plane Interaction ◽  
Schrödinger Perturbation

Abstract The molecular ordering of some biphenyl derivatives like 4-acetyl-2'-nitrobiphenyl (ANBP), 4-nitro-2-biphenylamine (NBPA) and 4-acetyl-3'-chlorobiphenyl (ACBP) has been examined using basic con-cepts of quantum mechanics and intermolecular forces. The CNDO/2 method has been employed to compute the net atomic charge and atomic dipole components at each atomic centre. The modified Ray-leigh-Schrödinger perturbation theory along with the multicentred-multipole expansion method has been employed to evaluate long-range interactions while a '6-exp' potential function has been assumed for short-range interactions. Accuracies upto 0.1 A in translation and 1° in rotation have been achieved. Probability of occurrence of a particular configuration has been calculated using MB-statistics. On the basis of stacking and in-plane interaction energy calculations, all possible geometrical arrangements between molecular pairs have been considered and a most favorable configuration of pairing has been obtained. A comparative picture of molecular parameters like total energy, binding energy, total dipole moment etc. has been given. An attempt has been made to develop a molecular model correlated with the liquid crystalline property exhibited by this class of molecules.

Molecular Ordering of a Nematic Liquid Crystal in a Dielectric Medium

2000 ◽  
Vol 55 (11-12) ◽  
pp. 929-935
Author(s):  
Durga Prasad Ojha ◽  
B. Raja Rajeswari ◽  
V. G. K. M. Pisipati
Keyword(s):  
Molecular Model ◽  
Atomic Charge ◽  
Expansion Method ◽  
Multipole Expansion ◽  
Dielectric Medium ◽  
Intermolecular Interaction Energy ◽  
Molecular Ordering ◽  
Multipole Expansion Method ◽  
Atomic Dipole Moment ◽  
Schrödinger Perturbation

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 corresponding 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 variations of the probability due to departure from the most probable configuration. All possible geometrical 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],

Estimation of Configurational Probability and Phase Behaviour of N-n-undecyl-D-gluconamide having V-Shaped Conformation – A Molecular Simulation Approach

2012 ◽  
Vol 67 (3-4) ◽  
pp. 210-216 ◽  
Author(s):  
P. Lakshmi Praveen ◽  
Durga P. Ojha
Keyword(s):  
Room Temperature ◽  
Atomic Charge ◽  
Expansion Method ◽  
Multipole Expansion ◽  
Phase Behaviour ◽  
Multipole Expansion Method ◽  
Complete Neglect ◽  
Atomic Dipole ◽  
Total Interaction ◽  
Atomic Dipole Moment

The present article deals with the configurational probabilities of a smectogen N-n-undecyl-Dgluconamide (GAM11). The complete neglect differential overlap (CNDO/2) method has been employed to compute the net atomic charge and atomic dipole moment components at each atomic center. The modified Rayleigh-Schr¨odinger perturbation theory along with the multicentered-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a ‘6-exp’ potential function has been assumed for short-range interactions. The total interaction energy values obtained during different modes of molecular interactions have been used as input to calculate the configurational probability at room temperature (300 K), and smectic-isotropic transition temperature (429:7 K) using the Maxwell-Boltzmann formula. The various possible geometrical arrangements of molecular pairs have been considered. Further, an attempt has been made to explain the smectic behaviour of GAM11 in terms of their relative order based on the molecular parameters introduced in this paper

Smectogenic Behaviour of 7O.6 at it's Phase Transition Temperature: A Computational Analysis Reprint request to

2001 ◽  
Vol 56 (12) ◽  
pp. 873-878
Author(s):  
Durga Prasad Ojha ◽  
Devesh Kumar ◽  
V. G. K. M. Pisipati
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Perturbation Method ◽  
Phase Transition Temperature ◽  
Computational Analysis ◽  
Atomic Charge ◽  
Configurational Energy ◽  
Schrödinger Perturbation ◽  
Atomic Centre

Abstract A computational analysis has been carried out to determine the configurational preference of a pair of Ar-(4-n-heptyloxybenzylidine)-4-hexylaniline (70.6) molecules with respect to translatory and orien­ tational motions. The CNDO/2 method has been employed to evaluate the net atomic charge and atom ic dipole components at each atomic centre of the molecule. The configurational energy has been com­ puted using the modified Rayleigh-Schrödinger perturbation method. The obtained energies were used to calculate the probability of each configuration at phase transition temperature, using Maxwell-Boltz-mann's formula. The flexibility of various configurations has been studied in terms of variations of the probability due to small departures from the most probable configuration. The results are discussed in the light of experimental as well as other theoretical observations. The smectogenic character of the molecule has been correlated with the parameters introduced in this paper.

Role of Dielectric Medium on a Nematogen. A Statistical Approach Based on Quantum Mechanics and Computer Aided Modelling

2002 ◽  
Vol 57 (8) ◽  
pp. 645-649
Author(s):  
Durga Prasad Ojha ◽  
V. G. K. M. Pisipati
Keyword(s):  
Molecular Model ◽  
Atomic Charge ◽  
Dielectric Medium ◽  
Liquid Crystallinity ◽  
Configurational Energy ◽  
Atomic Dipole ◽  
Total Interaction ◽  
Schrödinger Perturbation ◽  
Atomic Centre

ECCPA statistical analysis has been carried out to determine the configurational preferences of a pair of 5-(4-ethylcyclohexyl)-2-(4-cyanophenyl) pyrimidine () molecules. The CNDO/2 method has been employed to evaluate the net atomic charge and atomic dipole components at each atomic centre of the molecule. The configurational energy has been computed using the Rayleigh-Schrödinger perturbation theory. The total interaction energies obtained by these computations were used to calculate the probability of each configuration in vacuum and in a dielectric medium (benzene) at the phase transition temperature using the Maxwell-Boltzmann formula. On the basis of stacking, in-plane and terminal interaction energy calculations, all possible geometrical arrangements of the molecular pair have been considered. An attempt has been made to explain the nematogenic behavior of liquid crystals and thereby develop a molecular model for liquid crystallinity.

Molecular Ordering in Liquid Crystalline EMBAC. A Quantum Mechanical Study

2000 ◽  
Vol 55 (11-12) ◽  
pp. 923-928 ◽  
Author(s):  
Durga Prasad Ojha
Keyword(s):  
Interaction Energy ◽  
Liquid Crystalline ◽  
Molecular Model ◽  
Atomic Charge ◽  
Expansion Method ◽  
Multipole Expansion ◽  
Intermolecular Interaction Energy ◽  
Energy Calculations ◽  
Molecular Ordering ◽  
Multipole Expansion Method

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 interaction 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 energy, 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 crystals and thereby develop a molecular model for liquid crystallinity.

scholarly journals On the Convergence of the Multipole Expansion Method

2021 ◽  
Vol 59 (5) ◽  
pp. 2473-2499
Author(s):  
Brian Fitzpatrick ◽  
Enzo De Sena ◽  
Toon van Waterschoot
Keyword(s):  
Expansion Method ◽  
Multipole Expansion ◽  
Multipole Expansion Method
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