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.

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.

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.

Nematogenic Behaviour of a Cyano-Compound Using Quantum Mechanics and Computer Simulations

2001 ◽  
Vol 56 (3-4) ◽  
pp. 319-325 ◽  
Author(s):  
Durga Prasad Ojha
Keyword(s):  
Quantum Mechanics ◽  
Perturbation Method ◽  
Computer Simulations ◽  
Atomic Charge ◽  
Intermolecular Forces ◽  
Relative Order ◽  
Configuration Energy ◽  
Molecular Ordering ◽  
Schrödinger Perturbation ◽  
Atomic Centre

Abstract Using quantum mechanics and intermolecular forces, the molecular ordering of a nematogenic cya-no-compound, 5-(frans-4-ethylcyclohexyl)-2-(4-cyanophenyl)-pyrimidine (ECCPP), has been exam­ ined. The CNDO/2 method has been employed to evaluate the net atomic charge and the dipole mo­ ment components at each atomic centre of the molecule. The configuration energy has been computed using the modified Rayleigh-Schrödinger perturbation method at intervals of 1Ä in translation and 10P in rotations, and corresponding probabilities have been calculated using Maxwell-Boltzmann statistics. The flexibility of various configurations has been studied in terms of the variation of the probability due to small departures from the most probable configuration. All possible geometrical arrangements between a molecular pair have been considered during stacking, in-plane and terminal interactions, and the most favourable configuration of pairing has been obtained. An attempt has been made to under­ stand the behaviour of the molecules in terms of their relative order. The results have been compared with those obtained for other nematogens like DPAB [4,4'-di-n-propoxy-azoxybenzene] and EMBAC [ethyl 4-(4'-methoxybenzylidene amino) cinnamate].

Nematogenic Behaviour of EPPV in a Dielectric Medium. A Theoretical Study

2001 ◽  
Vol 56 (5) ◽  
pp. 371-375
Author(s):  
Durga Prasad Ojha
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Interaction Energy ◽  
Theoretical Study ◽  
Atomic Charge ◽  
Dielectric Medium ◽  
Intermolecular Interaction Energy ◽  
Molecular Pair ◽  
Atomic Dipole ◽  
Schrödinger Perturbation

Abstract 4-(4/-ethoxyphenylazo) phenyl valerate (EPPV) is a nematic liquid crystal, which shows a nematic mesophase at 352 K and becomes an isotropic melt at 401 K. A theoretical study of the molecular order­ ing has been carried out on the basis of intermolecular interaction energy calculations. The CNDO/2 method has been employed to compute the net atomic charge and atomic dipole components at each atom­ ic centre of the molecule. Modified Rayleigh-Schrödinger perturbation treatment has been employed to calculate the interaction energy between a molecular pair. The probability of the occurrence of a partic­ ular configuration in a dielectric medium has been calculated using the Maxwell-Boltzmann formula. The flexibility of various configurations has been studied in terms of the variation of the probability due to a small departure from the most probable configurations. On the basis of stacking, in-plane and terminal interactions, all possible geometrical arrangements between a molecular pair have been considered, and the most favourable configuration of pairing has been obtained. An attempt has been made to explain the nematogenic behaviour of liquid crystals based on the parameters introduced in this paper.

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).

scholarly journals Comparative analysis of the trypanocidal activity and chemical properties of E-lychnophoric acid and its derivatives using theoretical calculations

2005 ◽  
Vol 30 (3) ◽  
pp. 37-45 ◽  
Author(s):  
A. F. C. Alcântara ◽  
D. Silveira ◽  
E. Chiari ◽  
A. B. Oliveira ◽  
J. E. Guimarães ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Geometry Optimization ◽  
Chemical Properties ◽  
Atomic Charge ◽  
Trypanocidal Activity ◽  
Orbital Population ◽  
Theoretical Results ◽  
Conformational Distribution ◽  
And Chemical Properties ◽  
Endocyclic Bond

E-Lychnophoric acid 1, its derivative ester 2 and alcohol 3 killed 100% of trypomastigote blood forms of Trypanosoma cruzi at the concentrations of 13.86, 5.68, and 6.48 µg/mL, respectively. Conformational distribution calculations (AM1) of 1, 2 and 3 gave minimum energies for the conformers a, b, c, and d, which differ from each other only in the cyclononene ring geometry. Calculations (DFT/BLYP/6-31G*) of geometry optimization and chemical properties were performed for conformers of 1, 2, and 3. The theoretical results were numerically compared to the trypanocidal activity. Calculated values of atomic charge, orbital population, and vibrational frequencies showed that the C-4-C-5 pi-endocyclic bond does not affect the trypanocidal activity of the studied compounds. Nevertheless, the structure of the group at C-4 strongly influences the activity. However, the theoretical results indicated that the intra-ring (C-1 and C-9) and pi-exocycle (C-8 and C-14) carbons of caryophyllene-type structures promote the trypanocidal activity of these compounds.

Unsteady Hydrofoils: Theoretical and Computational Analysis

2013 ◽  
Author(s):  
Daniel T. Valentine
Keyword(s):  
Flat Plate ◽  
Computational Analysis ◽  
Vortex Sheet ◽  
Vortex Wake ◽  
Two Dimensional ◽  
Fixed Angle ◽  
Induced Drag ◽  
Wake Model ◽  
Theoretical Results ◽  
Computational Predictions

In this paper the computational problem examined is the impulsive start of a two-dimensional flat-plate hydrofoil at a fixed angle of attack. The method applied is an equally-spaced lumped-vortex panel method. The results from a lumped-vortex wake model and a shed-vortex sheet wake model are reported. Comparisons with the linear theory of Wagner (1925), the theoretical results associated with the single lumped-vortex wake model and the full wake model are presented. In addition, it is shown that the computational predictions are consistent with results reported by Katz and Plotkin (2001); they applied a distribution of vortices to model the wake. In the present paper the importance of resolving the chordwise pressure distribution in unsteady hydrofoil problems is elucidated. New predictions of both the evolution of lift and induced drag are reported for the instantaneously started flat plate. The computational predictions are compared with theorecticalpredictions also discussed in this paper.

scholarly journals Ripples in Graphene: A Variational Approach

2020 ◽  
Vol 379 (3) ◽  
pp. 915-954
Author(s):  
Manuel Friedrich ◽  
Ulisse Stefanelli
Keyword(s):  
Ground State ◽  
Energy Minimization ◽  
Variational Approach ◽  
Nearest Neighbor ◽  
Interaction Energies ◽  
Dimensional Problem ◽  
Neighbor Interaction ◽  
Configurational Energy ◽  
One Dimensional ◽  
Math Phys

Abstract Suspended graphene samples are observed to be gently rippled rather than being flat. In Friedrich et al. (Z Angew Math Phys 69:70, 2018), we have checked that this nonplanarity can be rigorously described within the classical molecular-mechanical frame of configurational-energy minimization. There, we have identified all ground-state configurations with graphene topology with respect to classes of next-to-nearest neighbor interaction energies and classified their fine nonflat geometries. In this second paper on graphene nonflatness, we refine the analysis further and prove the emergence of wave patterning. Moving within the frame of Friedrich et al. (2018), rippling formation in graphene is reduced to a two-dimensional problem for one-dimensional chains. Specifically, we show that almost minimizers of the configurational energy develop waves with specific wavelength, independently of the size of the sample. This corresponds remarkably to experiments and simulations.

Sign in / Sign up

Export Citation Format

Share Document