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Durga P. Ojha - One of the best experts on this subject based on the ideXlab platform.

  • Phase stability and ordering of nematogen at molecular level: A computer-aided modeling
    Molecular Crystals and Liquid Crystals, 2016
    Co-Authors: Durga P. Ojha
    Abstract:

    ABSTRACTThe present article deals with the phase stability and ordering of nematogen, viz., 6-octyloxy-2-naphthylyl-4-octoxybenzoate (ONOB) at molecular level. A comparative picture has been given between molecular charge distribution, and phase stability based on AM1, PM3, CNDO, and MNDO methods. The modified Rayleigh–Schrodinger perturbation method along with multicentered-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a “6-exp” potential function has been assumed for the short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature, nematic-isotropic transition temperature, and above transition temperature using the Maxwell–Boltzmann Formula. Further, the entropy of each configuration has been computed during the different modes of interactions. An effort has been made to develop a computational model at molecular level bas...

  • Ordering and Nematic Phase Behavior of a Naphthyl Ester: A Computational Model Based on Semiempirical Approach
    Molecular Crystals and Liquid Crystals, 2015
    Co-Authors: Durga P. Ojha
    Abstract:

    The present article deals with the ordering and nematic phase behavior of naphthyl-ester, viz., 4-octylphenyl-6-octyloxy-2-naphthoate based on semiempirical approach at a molecular level. The atomic net charge and dipole moment at each atomic centre has been evaluated using the complete neglect differential overlap method. The modified Rayleigh–Schrodinger perturbation method along with multicentered-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a “6-exp” potential function has been assumed for the short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature, nematic-isotropic transition temperature, and above transition temperature using the Maxwell–Boltzmann Formula. Further, the entropy of each configuration has been computed during the different modes of interactions. An effort has been made to develop a computational mo...

  • The Influence of Alkyl Chain Length and Solvents on Configurational Probability of Liquid Crystalline Materials: A Computational Approach
    Molecular Crystals and Liquid Crystals, 2015
    Co-Authors: P. Lakshmi Praveen, Durga P. Ojha
    Abstract:

    The influence of alkyl chain length and solvents on two liquid crystalline materials, p-n-butylbenzoic acid (4BAC), and p-n-pentylbenzoic acid (5BAC) has been carried out with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger Perturbation theory with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann Formula in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4), and chloroform (CHCl3) at room temperature 300 K. It has been observed that the increase of alkyl chain length causes a minim...

  • order disorder phenomenon of nematogens at molecular level a computational approach
    Molecular Crystals and Liquid Crystals, 2014
    Co-Authors: Durga P. Ojha
    Abstract:

    The phase behavior of nematogenic p-n-Alkoxy cinamic acids (nOCAC) with alkyl chain carbon atoms (n = 2,4) has been reported with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger Perturbation theory with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann Formula in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4), and chloroform (CHCl3) at room temperature 300 K. Further, entropy of each configuration has been computed. It has been observed that the molecules show the remarkable beh...

  • Conformational Behavior and Influence of Organic Solvents on a Strong Polar Group Nematogen at Room Temperature—A Computational Model
    Molecular Crystals and Liquid Crystals, 2014
    Co-Authors: Durga P. Ojha
    Abstract:

    The conformational behavior and influence of organic solvents on a nematogen, 4’-n-alkyl-4-cyanobiphenyl, with strong polar group propyl (3CB) that is of commercial and application interest has been studied with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh-Schrodinger Perturbation theory with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann Formula in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4), and chloroform (CHCl3) at room temperature 300 K. It has been observed that the molecules...

V. G. K. M. Pisipati - One of the best experts on this subject based on the ideXlab platform.

  • Ordering of p–n-alkoxybenzoic acids at phase transition temperatures: a comparative computational analysis
    Journal of Molecular Modeling, 2006
    Co-Authors: N. Ajeetha, D. P. Ojha, V. G. K. M. Pisipati
    Abstract:

    A comparative analysis of molecular ordering of nematogenic p–n -alkoxybenzoic acids has been carried out with respect to translatory and orientational motions for the acids with seven (7OBAC), eight (8OBAC), nine (9OBAC) and 10 (10OBAC) carbon atoms in the alkyl chain. The CNDO/2 method has been used to compute the net atomic charge and dipole moment components at each atomic center. Modified Rayleigh–Schrodinger perturbation theory with multicentered–multipole expansion method has been used 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 by these computations were used to calculate the probability of each configuration at the phase-transition temperature using the Maxwell–Boltzmann Formula. The flexibility of various configurations has been studied in terms of variation of probability due to small departures from the most probable configuration. A comparative picture of molecular parameters like total energy, binding energy and total dipole moment has been given. An attempt has been made to explain the nematogenicity of these acids in terms of their relative order with the molecular parameter introduced in this paper.

  • Computer simulations of ordering in homologous series of p-n-alkoxybenzoic acids (nOBAC) at nematic-isotropic transition temperature role of dielectric medium
    Journal of Molecular Liquids, 2005
    Co-Authors: Durga P. Ojha, V. G. K. M. Pisipati
    Abstract:

    Abstract Computer simulations of molecular ordering in nematogenic p - n -alkoxybenzoic acids has been carried out with respect to translatory and orientational motions for the acids having 7 (7OBAC); 8 (8OBAC) and 9 (9OBAC) carbon atoms in the alkyl chain. The net atomic charge and atomic dipole components at each atomic centre of the molecule has been evaluated using the CNDO/2 method. The configurational energy has been computed using the Rayleigh–Schrodinger perturbation method. The total interaction energy values obtained by these computations were used to calculate the probability of each configuration in a dielectric medium (i.e., non-interacting and non-mesogenic solvent, benzene) at phase transition temperature using the Maxwell–Boltzmann Formula. The flexibility of various configurations has been studied in terms of variation of probability due to small departures from the most probable configuration. The various possible geometrical arrangements between a molecular pair during the different modes of interactions have been considered. An attempt has been made to develop a new and interesting model of nematogens in dielectric medium.

  • COMPUTER SIMULATIONS OF ORDERING IN A HOMOLOGOUS SERIES OF p-n-ALKOXYCINNAMIC ACIDS (nOCAC) AT PHASE TRANSITION TEMPERATURE---ROLE OF DIELECTRIC MEDIUM
    Molecular Crystals and Liquid Crystals, 2004
    Co-Authors: Durga P. Ojha, V. G. K. M. Pisipati
    Abstract:

    Computer simulations of ordering in three nematogenic acids (nOCAC) having two, four, and six carbon atoms in the alkyl chain was carried out on the basis of quantum mechanics and intermolecular forces. The evaluation of atomic charges and dipole moment at each atomic center was carried out through an all-valence electron (CNDO/2) method. The configurational energy has been computed using the Rayleigh-Schrodinger perturbation method. The total interaction energy values obtained through these computations were used to calculate the probability of each configuration in a dielectric medium (i.e., noninteracting and nonmesogenic solvent, benzene) at phase transition temperature using the Maxwell-Boltzmann Formula. It was observed that in dielectric medium the energies/probabilities are redistributed and there is considerable rise in the probability of interactions, although the order of preference remains the same. An attempt has been made to develop a new and interesting model of nematogenic acids in dielect...

  • Computer Simulations of Ordering in 4Cb at Phase Transition Temperature
    Molecular Crystals and Liquid Crystals, 2004
    Co-Authors: Durga P. Ojha, V. G. K. M. Pisipati
    Abstract:

    The molecular ordering of 4′-n-butyl-4-cyanobiphenyl (4CB), a monotropic nematic liquid crystal, has been carried out at phase transition temperature with respect to translatory and orientational motions. The CNDO/2 method has been employed to compute the net atomic charge and atomic dipole moment at each atomic center. The modified Rayleigh-Schrodinger perturbation theory along with multicentered-multipole expansion method have been employed to evaluate long-range intermolecular interactions, while a 6-exp potential function has been assumed for short-range interactions. The interaction energy values obtained through these computations were used to calculate the probability of each configuration at 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. The results are correlated with molecular parameter introduced in this article, a...

  • Ordering of fluoro-mesogens: a statistical approach based on quantum mechanics and computer simulation
    Liquid Crystals, 2003
    Co-Authors: Durga P. Ojha, V. G. K. M. Pisipati
    Abstract:

    Computational analysis of the molecular ordering of nematic p-phenylene-4-methoxy benzoyl 4-trifluoromethylbenzoate (FLUORO1) and smectic 4-propyloxyphenyl 4-(4-trifluoromethylbenzoyloxy) benzoate (FLUORO2) mesogens has been carried out with respect to translatory and orientational motions. The net atomic charge and atomic dipole components at each atomic centre of the molecule have been evaluated using the CNDO/2 method. Rayleigh-Schrodinger perturbation theory, along with the multicentred-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 the phase transition temperature using the Maxwell-Boltzmann Formula. The flexibility of various configurations has been studied in terms of the variation of probability due to small departures from the most p...

Hiromi Saida - One of the best experts on this subject based on the ideXlab platform.

  • Universal property of quantum gravity implied by uniqueness theorem of Bekenstein-Hawking entropy
    Journal of Physics: Conference Series, 2014
    Co-Authors: Hiromi Saida
    Abstract:

    We have searched for a universal property of quantum gravity, where "universal" means to be independent of any existing model of quantum gravity (such as the super string theory, loop quantum gravity, causal dynamical triangulation, and so on). To do so, we have investigated carefully the basis of black hole thermodynamics. The uniqueness of Bekenstein-Hawking entropy lets us extract a reasonable universal property of quantum gravity from the conditions justifying Boltzmann Formula. The universal property indicates a repulsive gravity at Planck length scale, otherwise stationary black holes can not be regarded as thermal equilibrium states of gravity.

  • Universal Property of Quantum Gravity implied by Bekenstein-Hawking Entropy and Boltzmann Formula
    Journal of Physics: Conference Series, 2013
    Co-Authors: Hiromi Saida
    Abstract:

    We search for a universal property of quantum gravity. By "universal", we mean the independence from any existing model of quantum gravity (such as the super string theory, loop quantum gravity, causal dynamical triangulation, and so on). To do so, we try to put the basis of our discussion on theories established by some experiments. Thus, we focus our attention on thermodynamical and statistical-mechanical basis of the black hole thermodynamics: Let us assume that the Bekenstein-Hawking entropy is given by the Boltzmann Formula applied to the underlying theory of quantum gravity. Under this assumption, the conditions justifying Boltzmann Formula together with uniqueness of Bekenstein-Hawking entropy imply a reasonable universal property of quantum gravity. The universal property indicates a repulsive gravity at Planck length scale, otherwise stationary black holes can not be regarded as thermal equilibrium states of gravity. Further, in semi-classical level, we discuss a possible correction of Einstein equation which generates repulsive gravity at Planck length scale.

  • universal property of quantum gravity implied by bekenstein hawking entropy and Boltzmann Formula
    arXiv: General Relativity and Quantum Cosmology, 2013
    Co-Authors: Hiromi Saida
    Abstract:

    We search for a universal property of quantum gravity. By "universal", we mean the independence from any existing model of quantum gravity (such as the super string theory, loop quantum gravity, causal dynamical triangulation, and so on). To do so, we try to put the basis of our discussion on theories established by some experiments. Thus, we focus our attention on thermodynamical and statistical-mechanical basis of the black hole thermodynamics: Let us assume that the Bekenstein-Hawking entropy is given by the Boltzmann Formula applied to the underlying theory of quantum gravity. Under this assumption, the conditions justifying Boltzmann Formula together with uniqueness of Bekenstein-Hawking entropy imply a reasonable universal property of quantum gravity. The universal property indicates a repulsive gravity at Planck length scale, otherwise stationary black holes can not be regarded as thermal equilibrium states of gravity. Further, in semi-classical level, we discuss a possible correction of Einstein equation which generates repulsive gravity at Planck length scale. (This article is bease on ref.[4] (Entropy 13(2011)1611-1647), but the conclusion in sec.4 is modified from ref.[4].)

  • Universal Property of Quantum Gravity implied by Uniqueness Theorem of Bekenstein-Hawking Entropy
    Entropy, 2011
    Co-Authors: Hiromi Saida
    Abstract:

    This paper consists of three parts. In the first part, we prove that the Bekenstein-Hawking entropy is the unique expression of black hole entropy. Our proof is constructed in the framework of thermodynamics without any statistical discussion. In the second part, intrinsic properties of quantum mechanics are shown, which justify the Boltzmann Formula to yield a unique entropy in statistical mechanics. These properties clarify three conditions, one of which is necessary and others are sufficient for the validity of Boltzmann Formula. In the third part, by combining the above results, we find a reasonable suggestion from the sufficient conditions that the potential of gravitational interaction among microstates of underlying quantum gravity may not diverge to negative infinity (such as Newtonian gravity) but is bounded below at a finite length scale. In addition to that, from the necessary condition, the interaction has to be repulsive within the finite length scale. The length scale should be Planck size. Thus, quantum gravity may become repulsive at Planck length. Also, a relation of these suggestions with action integral of gravity at semi-classical level is given. These suggestions about quantum gravity are universal in the sense that they are independent of any existing model of quantum gravity.

I. Sakalli - One of the best experts on this subject based on the ideXlab platform.

  • Hawking Radiation of Relativistic Particles from Black Strings
    Theoretical and Mathematical Physics, 2019
    Co-Authors: F. S. Mirekhtiary, I. Sakalli
    Abstract:

    We study Hawking radiation of relativistic particles from uncharged and charged black strings in 3+1 dimensions in detail. We use the method of quantum tunneling in the framework of the Hamilton–Jacobi approach. We show that the radial function of the action allows calculating the tunneling rate of the emitted relativistic particles. Using the Boltzmann Formula, we derive the Hawking temperatures of uncharged and charged black strings. We discuss the influence of the temporal contribution to the tunneling rate.

  • Hawking Radiation of Mass Generating Particles from Dyonic Reissner–Nordström Black Hole
    Journal of Astrophysics and Astronomy, 2016
    Co-Authors: I. Sakalli, A. Övgün
    Abstract:

    The Hawking radiation is considered as a quantum tunneling process, which can be studied in the framework of the Hamilton–Jacobi method. In this study, we present the wave equation for a mass generating massive and charged scalar particle (boson). In sequel, we analyse the quantum tunneling of these bosons from a generic 4-dimensional spherically symmetric black hole. We apply the Hamilton–Jacobi formalism to derive the radial integral solution for the classically forbidden action which leads to the tunneling probability. To support our arguments, we take the dyonic Reissner–Nordström black hole as a test background. Comparing the tunneling probability obtained with the Boltzmann Formula, we succeed in reading the standard Hawking temperature of the dyonic Reissner–Nordström black hole.

  • Hawking Radiation of Mass Generating Particles From Dyonic Reissner Nordström Black Hole
    Journal of Astrophysics and Astronomy, 2016
    Co-Authors: I. Sakalli, A. Övgün
    Abstract:

    The Hawking radiation is considered as a quantum tunneling process, which can be studied in the framework of the Hamilton–Jacobi method. In this study, we present the wave equation for a mass generating massive and charged scalar particle (boson). In sequel, we analyse the quantum tunneling of these bosons from a generic 4-dimensional spherically symmetric black hole. We apply the Hamilton–Jacobi formalism to derive the radial integral solution for the classically forbidden action which leads to the tunneling probability. To support our arguments, we take the dyonic Reissner–Nordstrom black hole as a test background. Comparing the tunneling probability obtained with the Boltzmann Formula, we succeed in reading the standard Hawking temperature of the dyonic Reissner–Nordstrom black hole.

  • Quantum tunneling from rotating black holes with scalar hair in three dimensions
    The European Physical Journal C, 2016
    Co-Authors: I. Sakalli, H. Gursel
    Abstract:

    We study the Hawking radiation of scalar and Dirac particles (fermions) emitted from a rotating scalar hair black hole (RSHBH) within the context of three dimensional (3 D ) Einstein gravity using non-minimally coupled scalar field theory. Amalgamating the quantum tunneling approach with the Wentzel–Kramers–Brillouin approximation, we obtain the tunneling rates of the outgoing particles across the event horizon. Inserting the resultant tunneling rates into the Boltzmann Formula, we then obtain the Hawking temperature ( $$T_\mathrm{H}$$ T H ) of the 3 D RSHBH.

P. Lakshmi Praveen - One of the best experts on this subject based on the ideXlab platform.

  • The Influence of Alkyl Chain Length and Solvents on Configurational Probability of Liquid Crystalline Materials: A Computational Approach
    Molecular Crystals and Liquid Crystals, 2015
    Co-Authors: P. Lakshmi Praveen, Durga P. Ojha
    Abstract:

    The influence of alkyl chain length and solvents on two liquid crystalline materials, p-n-butylbenzoic acid (4BAC), and p-n-pentylbenzoic acid (5BAC) has been carried out with respect to the translational and orientational motions. The atomic net charge and dipole moment components at each atomic center have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger Perturbation theory with the multicentered-multipole expansion method has been employed to evaluate the long-range interactions, and a “6-exp.” potential function has been assumed for the short-range interactions. The minimum energy configurations obtained during the different modes of interactions have been taken as input to calculate the configurational probability using the Maxwell–Boltzmann Formula in nonpolar organic solvents, i.e., carbon tetrachloride (CCl4), and chloroform (CHCl3) at room temperature 300 K. It has been observed that the increase of alkyl chain length causes a minim...

  • Molecular Structure and Ordering in a Fluorinated Smectogenic Compound—A Statistical Thermodynamic Approach
    Molecular Crystals and Liquid Crystals, 2013
    Co-Authors: P. Lakshmi Praveen, Durga P. Ojha
    Abstract:

    In the present paper, molecular structure and ordering in a fluorinated smectogenic compound 4-propyloxyphenyl 4-(4-trifluoromethyl-benzoyloxy) benzoate (FLUORO) with respect to translatory and orientational motions have been reported. The evaluation of net atomic charges and dipole moments at each atomic center has been carried out through the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger perturbation method along with multicentered-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a “6-exp” potential function has been assumed for the short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature (300 K), smectic–isotropic transition temperature (488 K), and above transition temperature (550 K) using the Maxwell–Boltzmann Formula. Further, thermodynamic parameters such as Helmholtz free ...

  • Thermodynamic stability and phase behaviour of a liquid crystalline material: a theoretical model at molecular level
    Phase Transitions, 2013
    Co-Authors: P. Lakshmi Praveen, Durga P. Ojha
    Abstract:

    This article describes the thermodynamic stability and phase behaviour of a liquid crystalline material p-n-hexyloxybenzylidene-p-toluidine (6OBT) at a molecular level. The atomic net charge and dipole moment at each atomic centre have been evaluated using the complete neglect differential overlap (CNDO/2) method. The modified Rayleigh–Schrodinger perturbation method along with multicentred-multipole expansion method has been employed to evaluate the long-range intermolecular interactions, while a ‘6-exp’ potential function has been assumed for the short-range interactions. The total interaction energy values obtained through these computations have been used to calculate the probability of each configuration at room temperature (300 K), nematic–isotropic transition temperature (346.9 K) and above transition temperature (400 K) using the Maxwell–Boltzmann Formula. Further, the Helmholtz free energy and entropy of each configuration has been computed during the different modes of interactions. An attempt h...

  • Estimation of Configurational Probability and Phase Behaviour of N-n-undecyl-D-gluconamide having V-Shaped Conformation – A Molecular Simulation Approach
    Zeitschrift für Naturforschung A, 2012
    Co-Authors: P. Lakshmi Praveen, Durga P. Ojha
    Abstract:

    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–Schrodinger 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.

  • Phase organization in laterally substituted dicyclohexylethane derivatives—A molecular model for smectogens
    Journal of Molecular Liquids, 2011
    Co-Authors: P. Lakshmi Praveen, Durga P. Ojha
    Abstract:

    Abstract The present article deals with the configurational probabilities of smectogens 1, 2-bis (4-pentylcyclohexyl) ethan-1-ol (PCHE1) and 1, 2-bis (4-pentylcyclohexyl) ethan-1-one (PCHE2) with respect to translational and orientational motions. 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–Schrodinger perturbation theory along with 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 through these computations have been used to calculate the configurational probability at smectic B-isotropic transition temperature using the Maxwell–Boltzmann Formula. Molecular arrangements inside a bulk of materials and smectic behavior of the compounds in terms of their relative order have been discussed. Further, a model has been developed at molecular level to understand the effect of translational/rotational rigidity on phase organization and relative flexibility of one configuration over the other.