Yazar "Capar, M. Ilk" seçeneğine göre listele

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    Dynamic phenomena and viscous properties in a liquid crystal: A theoretical treatment and molecular dynamic simulations
    (Elsevier, 2011) Capar, M. Ilk; Cebe, E.; Zakharov, A. V.
    The molecular dynamics (MD) simulations, based on a realistic atom-atom interaction potentials were performed on 4-heptyloxy-4'-cyanobiphenyl (7OCB) and 4-hexyloxy-benzylidene-4'-amino-benzonitrile (HBAB) in nematic phase. The set of the order parameters (OPs) S-2L (L = 1,2, 3), rotational self-diffusion (RSD) coefficient D-perpendicular to, rotational gamma(i) (i = 1,2) and Leslie alpha(i)(i = 1,...,6) viscosity coefficients, the set of the orientational correlation times tau(i)(j0)(i = 1,2; j = 0,1) for 7OCB and HBAB in the nematic phase are calculated. Reasonable agreement between the calculated and the experimentally obtained data on S-2, tau(1)(00), and gamma(1) has been obtained. (C) 2011 Elsevier B. V. All rights reserved.
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    Flexoelastic properties of polar liquid crystals
    (Maik Nauka/Interperiodica/Springer, 2011) Capar, M. Ilk; Nar, A.; Zakharov, A. V.; Vakulenko, A. A.
    Structural properties of liquid crystals, such as the order parameters and the orientational, radial, and direct correlation distribution functions of polar liquid crystals 4-n-heptyloxy-4'-n-cyanobiphenyl (7OCB) and 4-n-hexyloxy-benzylidene-4'-n-aminobenzonitrile (HBAB) have been calculated using a combination of numerical simulation and statistical mechanics methods. It has been shown that the calculated values of both the Frank elastic coefficients K (i) (i = 1, 2, 3) corresponding to the splay, twist, and bend deformations and the flexoelectric coefficients e (i) (i = 1, 3) agree with the experimental data for 7OCB. The calculated values of the same coefficients for HBAB have been published for the first time.
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    Miscibility and diffusivity of water in organic acids: Molecular dynamics simulations
    (Elsevier, 2019) Cetin, Ayse; Capar, M. Ilk; Zakharov, A., V
    Molecular dynamics simulations were performed to study both the structural and dynamic properties of n-alkyl carboxylic acid/water/n-alkyl carboxylic acid system with different alkyl chain length, such as acetic (CH3COOH) (A/W/A system), butyric (CH3(CH2)(2)COOH) (B/W/B system) and hexanoic (CH3(CH2)(4)COOH) (H/W/H system) acids. the mass density profiles along the interface normal to the organic acid/water system, the difference in the local structure of H2O molecules in bulk and in the vicinity of interface for A/W/A, B/W/B and H/W/H systems, as well as the diffusion behavior of water molecules at the interface with abovementioned organic acids, in the wide range of the temperature changes, have been investigated. Because of the central importance of water to the biology and pharmacology a number of new calculated regimes of miscibility and diffusivity of water molecules in carboxylic acids help us to better analyze such organic systems. (C) 2019 Elsevier B.V. All rights reserved.
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    Molecular dynamics simulation of nCB series
    (Amer Inst Physics, 2007) Capar, M. Ilk; Cebe, E.; Cetin, SA; Hikmet, I
    This study describes the molecular dynamics (MD) simulations of the 4-n-alkyl-4'-cyanobiphenyl (nCB, n=5-9) liquid crystal homologous series at a selected temperature in the nematic phase. The order parameters and the biaxialities for five mesogens were found to be reasonable agreement with experiments. The orientational distributions of C-C bonds in alkyl chain of nCB were calculated and given for 6CB and 7CB. The odd-even effect was also discussed.
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    Molecular structure and elastic properties of thermotropic liquid crystals: Integrated molecular dynamics-Statistical mechanical theory vs molecular field approach
    (Amer Inst Physics, 2013) Capar, M. Ilk; Nar, A.; Ferrarini, A.; Frezza, E.; Greco, C.; Zakharov, A. V.; Vakulenko, A. A.
    The connection between the molecular structure of liquid crystals and their elastic properties, which control the director deformations relevant for electro-optic applications, remains a challenging objective for theories and computations. Here, we compare two methods that have been proposed to this purpose, both characterized by a detailed molecular level description. One is an integrated molecular dynamics-statistical mechanical approach, where the bulk elastic constants of nematics are calculated from the direct correlation function (DCFs) and the single molecule orientational distribution function [D. A. McQuarrie, Statistical Mechanics (Harper & Row, New York, 1973)]. The latter is obtained from atomistic molecular dynamics trajectories, together with the radial distribution function, from which the DCF is then determined by solving the Ornstein-Zernike equation. The other approach is based on a molecular field theory, where the potential of mean torque experienced by a mesogen in the liquid crystal phase is parameterized according to its molecular surface. In this case, the calculation of elastic constants is combined with the Monte Carlo sampling of single molecule conformations. Using these different approaches, but the same description, at the level of molecular geometry and torsional potentials, we have investigated the elastic properties of the nematic phase of two typical mesogens, 4 '-n-pentyloxy-4-cyanobiphenyl and 4 '-n-heptyloxy-4-cyanobiphenyl. Both methods yield K-3(bend) > K-1 (splay) > K-2 (twist), although there are some discrepancies in the average elastic constants and in their anisotropy. These are interpreted in terms of the different approximations and the different ways of accounting for the structural properties of molecules in the two approaches. In general, the results point to the role of the molecular shape, which is modulated by the conformational freedom and cannot be fully accounted for by a single descriptor such as the aspect ratio. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794920]
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    Structural properties of a cyanobiphenyl monolayer on the graphene surface coated with alkane and alcohol molecules as seen from MD simulations
    (Elsevier, 2024) Duven, H. E.; Capar, M. Ilk; Zakharov, A. V.
    Molecular dynamics simulations were carried out to study structural properties of a cyanobiphenyl monolayer composed of pentyl cyano biphenyl (5CB) and pentyloxy cyano biphenyl (5OCB) molecules on a graphene surface coated with alkane and alcohol molecules. The molecules of dodecane, hexadecane, and dodecanol were chosen as orienting surfactant molecules. In order to investigate the structural properties, as well as the alignment of the cyanobiphenyl monolayer on the graphene surface coated with alkane and alcohol molecules, not only the numerical density profiles of these systems, but also the radial distribution functions, and the tilt angle of the liquid crystal molecules, were calculated. In order to understand the effect of the polar hydroxyl functional group on 5CB and 5OCB molecules deposited on the graphene surface, alcohols were chosen as surfactant molecules.