@article {doi:10.1002/cmr.a.21415,
	title = {Evolutionary algorithms and nuclear magnetic resonance of oriented molecules},
	journal = {Concepts in Magnetic Resonance Part A},
	volume = {45A},
	number = {6},
	year = {2016},
	pages = {e21415},
	abstract = {Abstract In this article, we discuss the progress achieved with the use of evolutionary algorithms for the analysis of 1H Nuclear Magnetic Resonance spectra of solutes in orientationally ordered liquids. With these tools the analysis of extremely complex spectra that were hitherto impossible to solve has now become eminently feasible. We discuss applications to 2 molecules of special interest: (a) hexamethylbenzene, which is a text book example of steric hindrance between adjacent rotating methyl groups; and (b) cyclohexane which is the standard example of interconversion between various molecular conformations. New interesting physics is obtained in both cases.},
	keywords = {cyclohexane, evolutionary algorithms, hexamethyl benzene, liquid crystal, orientational order},
	doi = {10.1002/cmr.a.21415},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/cmr.a.21415},
	author = {Burnell, E. Elliott and de Lange, Cornelis A. and Dong, Ronald Y. and Meerts, W. Leo and Weber, Adrian C. J.}
}
@article {2656,
	title = {Solute order parameters in liquid crystals from NMR spectra solved with evolutionary algorithms: Application of double Maier-Saupe Kobayashi-McMillan theory},
	journal = {Chemical Physics Letters},
	volume = {476},
	number = {1-3},
	year = {2009},
	note = {ISI Document Delivery No.: 463YQTimes Cited: 2Cited Reference Count: 25Weber, Adrian C. J. Yang, Xuan Dong, Ronald Y. Meerts, W. Leo Burnell, E. Elliott},
	month = {Jul},
	pages = {116-119},
	type = {Article},
	abstract = {We obtain dipolar couplings via a novel application of evolutionary algorithms solving for multiple spin-systems simultaneously and automatically from the NMR spectra of several solutes in several nematic and smectic liquid crystal solvents. The order parameters obtained from the dipolar couplings are used to test a novel Hamiltonian that includes two Maier-Saupe nematic terms plus Kobayashi-McMillan smectic A terms. It is shown that this Hamiltonian can rationalize the NMR experiments with physically reasonable smectic order parameters and Hamiltonian prefactors. (C) 2009 Elsevier B.V. All rights reserved.},
	keywords = {ELECTRON-DIFFRACTION, MOLECULAR-STRUCTURES, NEMATIC SOLVENTS, orientational order, PHASE, SHAPE},
	isbn = {0009-2614},
	url = {<Go to ISI>://000267470600025},
	author = {Weber, A. C. J. and Yang, X. and Dong, R. Y. and Meerts, W. L. and Burnell, E. E.}
}
@article {1594,
	title = {Dideuterium as solute in nematic liquid crystals},
	journal = {Chemical Physics Letters},
	volume = {426},
	number = {1-3},
	year = {2006},
	note = {ISI Document Delivery No.: 067AMTimes Cited: 6Cited Reference Count: 14ter Beek, Leon C. Burnell, E. Elliott},
	month = {Jul},
	pages = {96-99},
	type = {Article},
	abstract = {Deuteron NMR experiments on dideuterium dissolved in the nematic liquid-crystal solvents 7CB, CCH7, MBBA and PCH7 are reported as a function of temperature. The results are analysed in terms of the average solvent electric field gradient anisotropy (efg) felt by D-2 which is positive with respect to the director in 7CB, CCH7 and PCH7 and negative in MBBA. The order parameter of D-2 is to a large extent rationalized in terms of the interaction between this solvent efg and the solute D-2 molecular quadrupole moment, and its sign is the same as that of the efg. (c) 2006 Elsevier B.V. All rights reserved.},
	keywords = {MOLECULAR-HYDROGEN, NMR, orientational order, SOLVENTS},
	isbn = {0009-2614},
	url = {<Go to ISI>://000239272400020},
	author = {ter Beek, L. C. and Burnell, E. E.}
}
@article {1069,
	title = {Molecules with large-amplitude torsional motion partially oriented in a nematic liquid crystal: Ethane and isotopomers},
	journal = {Journal of Physical Chemistry A},
	volume = {109},
	number = {48},
	year = {2005},
	note = {ISI Document Delivery No.: 990RPTimes Cited: 10Cited Reference Count: 48},
	month = {Dec},
	pages = {11027-11036},
	type = {Article},
	abstract = {An NMR study on ethane and five isotopomers dissolved in the nematic liquid crystal Merck ZLI 1132 is performed. A consistent set of dipolar and quadrupolar couplings is obtained. The dipolar couplings are corrected for harmonic vibrational effects, while the contribution from the torsional motion is incorporated classically. The corrected dipolar couplings cannot be understood in terms of a reasonable molecular structure unless effects of the reorientation-vibration interaction are taken into account. Assuming that the reorientation-vibration contributions that are known for the methyl group in methyl fluoride are transferable to ethane, excellent agreement between observed and calculated dipolar couplings is obtained on the basis of the ethane gas-phase structure. The observed and calculated deuterium quadrupolar couplings show discrepancies supporting the notion that average electric field gradients are important in liquid-crystal solvents. An important consequence of the transferability of the reorientation-vibration correlation is that in other molecules with a methyl group the same procedure as for ethane can be followed. Inclusion of this effect generally removes the need to interpret changes in observed dipolar couplings in terms of elusive chemical effects.},
	keywords = {ANISOTROPIC, ELECTRIC-FIELD GRADIENTS, ENVIRONMENTS, FORCE-FIELDS, H-2 NMR, NUCLEAR-MAGNETIC-RESONANCE, orientational order, POLYATOMIC-MOLECULES, ROTATION, SPECTRA, VIBRATIONS},
	isbn = {1089-5639},
	url = {<Go to ISI>://000233761200026},
	author = {Burnell, E. E. and de Lange, C. A. and Barnhoorn, J. B. S. and Aben, I. and Levelt, P. F.}
}
@article {1068,
	title = {NMR as a tool in the investigation of fundamental problems in ordered liquids},
	journal = {Solid State Nuclear Magnetic Resonance},
	volume = {28},
	number = {2-4},
	year = {2005},
	note = {ISI Document Delivery No.: 998NHTimes Cited: 9Cited Reference Count: 49},
	month = {Sep},
	pages = {73-90},
	type = {Article},
	abstract = {An overview is presented of modern NMR techniques and a variety of experimental and theoretical tools employed in the study of solutes dissolved in liquid crystals. The NMR techniques involve multiple quantum and spectral subtraction methods, In addition, various experimental and theoretical tools are discussed, including: the theoretical background of observed order parameters; the use of,magic mixtures{\textquoteright} to separate orientational contributions; the reorientation-vibration interaction; the use of model calculations based on size and shape of the various solutes; and the use of computer simulations. Applications to the benchmark probe molecules hydrogen, methane, ethane, and butane and their isotopomers are treated. (c) 2005 Elsevier Inc. All rights reserved.},
	keywords = {ANISOTROPIC LIQUIDS, butane, ethane, H-2 NMR, HYDROGEN, INTERNAL-ROTATION, liquid crystal, METHANE, MOLECULES, MOLEKULAR-STATISTISCHE THEORIE, MULTIPLE-QUANTUM NMR, NEMATISCHEN KRISTALLINFLUSSIGEN PHASE, NMR, NUCLEAR-MAGNETIC-RESONANCE, order parameter, orientational order, PROTON DIPOLAR COUPLINGS, SMALL CHAIN},
	isbn = {0926-2040},
	url = {<Go to ISI>://000234325100003},
	author = {Burnell, E. E. and de Lange, C. A.}
}
@article {1044,
	title = {NMR measurement of smectic ordering and nematic-smectic-A coupling in a liquid crystal},
	journal = {Chemical Physics Letters},
	volume = {398},
	number = {4-6},
	year = {2004},
	note = {ISI Document Delivery No.: 867OVTimes Cited: 11Cited Reference Count: 31},
	month = {Nov},
	pages = {517-521},
	type = {Article},
	abstract = {The nuclear magnetic resonance (NMR) spectra of three substituted benzenes as solutes in the liquid crystal 8CB were investigated. The orientational order of all solutes was obtained in the nematic and smectic-A phases. A change in temperature dependence of orientational ordering was observed at the nematic to smectic-A phase transition. We analyzed these results via Kobayashi-McMillan theory applied to solutes, i.e. by incorporating smectic-A layering and nematic smectic-A coupling into a mean-field orientational Hamiltonian. By fitting to experiment, we fully determined Hamiltonian prefactors. The nematic smectic coupling, determined for the first time by NMR, appears solute independent. Solute smectic-A order parameters were self-consistently determined. (C) 2004 Published by Elsevier B.V.},
	keywords = {BINARY-MIXTURES, FIELD, NUCLEAR-MAGNETIC-RESONANCE, orientational order, PHASE-TRANSITION, SHAPE, SOLUTES, TEMPERATURE-DEPENDENCE, TRICRITICAL POINT},
	isbn = {0009-2614},
	url = {<Go to ISI>://000224852800044},
	author = {Yethiraj, A. and Sun, Z. M. and Dong, R. Y. and Burnell, E. E.}
}
@article {515,
	title = {Effects of solute properties and concentrations on liquid crystals: N-(4-ethoxybenzylidene)-2,6-dideutero-4-n-butylaniline},
	journal = {Journal of Chemical Physics},
	volume = {117},
	number = {1},
	year = {2002},
	note = {ISI Document Delivery No.: 563UTTimes Cited: 4Cited Reference Count: 17},
	month = {Jul},
	pages = {376-384},
	type = {Article},
	abstract = {The effects of the nature and concentration of the solutes 1,3,5-trichlorobenzene (TCB), benzene, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene on orientational order in the nematic liquid crystal N-(4-ethoxybenzylidene)-2,6-dideutero-4-n-butylaniline are investigated using NMR spectroscopy. Seven separate samples containing differing concentrations of all solutes are investigated at constant temperature, at constant reduced temperature, at constant TCB orientational order, and at constant liquid crystal orientational order. Various schemes for comparison of orientational order among the samples are examined. For the experiments performed here, the most consistent method to compare solute orientational order in the different samples is to multiply results from the experiments performed at constant temperature by the factor needed to equate the TCB order parameters. (C) 2002 American Institute of Physics.},
	keywords = {MULTIPLE-QUANTUM NMR, orientational order, SHAPE, SHORT-RANGE},
	isbn = {0021-9606},
	url = {<Go to ISI>://000176275700046},
	author = {Syvitski, R. T. and Pau, M. Y. M. and Burnell, E. E.}
}
@article {514,
	title = {Simultaneous selective detection of multiple quantum spectra},
	journal = {Journal of Magnetic Resonance},
	volume = {155},
	number = {2},
	year = {2002},
	note = {ISI Document Delivery No.: 560GETimes Cited: 8Cited Reference Count: 11},
	month = {Apr},
	pages = {251-256},
	type = {Article},
	abstract = {A three-dimensional multiple-quantum NMR experiment that produces individual spectra of all quantum orders is described. The separation of different quantum orders is accomplished via Fourier transformation with respect to the phase of the first two pulses of a generic three-pulse multiple-quantum sequence. This dramatically reduces the time required to obtain several selectively detected spectra and enhances the sensitivity and digital resolution from that obtained using the original two-dimensional technique. The experiment is demonstrated on the protons of para-chlorotoluene dissolved in the nematic liquid crystal Merck ZLI-1132. (C) 2002 Elsevier Science (USA).},
	keywords = {liquid crystal, LIQUID-CRYSTAL SOLVENTS, MQNMR, multiple, nematic, NMR, orientational order, quantum coherence, SPECTROSCOPY},
	isbn = {1090-7807},
	url = {<Go to ISI>://000176073700006},
	author = {Syvitski, R. T. and Burlinson, N. and Burnell, E. E. and Jeener, J.}
}
@article {5104,
	title = {Ferroelectric order in positionally frozen dipolar systems},
	journal = {Journal of Chemical Physics},
	volume = {115},
	number = {10},
	year = {2001},
	note = {ISI Document Delivery No.: 466LTTimes Cited: 13Cited Reference Count: 46},
	month = {Sep},
	pages = {4718-4731},
	type = {Article},
	abstract = {We discuss the possibility of long-range ferroelectric order in an amorphous dipolar system. Our model consists of spheres with frozen positions and freely rotating three-dimensional dipole moments. Correlation functions are calculated by means of the hypernetted-chain integral theory combined with the replica method. Our results suggest that inhomogeneities in the frozen spatial structure induce a gradual local freezing of the dipole axes upon decreasing temperature. However, at sufficiently high densities and dipole moments, the long-range interactions dominate the short-range frustration, resulting in a ferroelectric transition. The estimated transition temperatures depend strongly on the degree of spatial correlation in the underlying system of frozen spheres. For a randomly frozen system, we find that the transition temperature is considerably lower than that predicted by mean field theory, and also lower than the temperature where simulations indicate the onset of glass-like behavior. Strong positional correlations can push the transition toward temperatures higher even than those observed for dipolar fluids. (C) 2001 American Institute of Physics.},
	keywords = {GROUND-STATE, HARD-SPHERES, HYPERNETTED-CHAIN APPROXIMATION, INTEGRAL-EQUATION THEORY, ISING-MODEL, LIQUID-VAPOR INTERFACE, LOCAL-MEAN-FIELD, orientational order, ORNSTEIN-ZERNIKE APPROXIMATION, RANDOM ANISOTROPY},
	isbn = {0021-9606},
	url = {<Go to ISI>://000170647600035},
	author = {Klapp, S. H. L. and Patey, G. N.}
}
@article {4848,
	title = {Crystallization of dipolar spheres: A discussion of second-order density functional theory},
	journal = {Journal of Chemical Physics},
	volume = {112},
	number = {24},
	year = {2000},
	note = {ISI Document Delivery No.: 324HYTimes Cited: 6Cited Reference Count: 43},
	month = {Jun},
	pages = {10949-10956},
	type = {Article},
	abstract = {We investigate the application of second-order density functional theory to the crystallization of dipolar hard and soft spheres. It is shown that the results are highly sensitive to the repulsive part of the pair potential, and to the symmetry of the fluid phase considered in the density functional theory. In general, the theoretical results for dipolar soft spheres (with r(-12) repulsion) are found to be physically more reasonable than those obtained for dipolar hard spheres. In particular, the fluid-solid density gap is greatly reduced and lies in the range expected on physical grounds and from simulations. However, theories constructed by expanding about the isotropic fluid phase overestimate the stability of the ferroelectric solid for both models, and fail to predict the stable ferroelectric fluids found in computer simulations. We have carried out calculations using ferroelectric dipolar fluids with both perfect and fluctuating orientational order as "starting points" in the density functional expansion. The results demonstrate the high sensitivity of the theory to the underlying fluid state, and strongly indicate the existence of stable ferroelectric fluids in accord with computer simulations. (C) 2000 American Institute of Physics. [S0021-9606(00)50924-6].},
	keywords = {FLUIDS, HARD-SPHERES, INTEGRAL-EQUATIONS, LIQUID-VAPOR INTERFACE, NEMATIC PHASE, orientational order, PHASE-TRANSITIONS, SOFT SPHERES, SOLID-PHASES, STABILITY},
	isbn = {0021-9606},
	url = {<Go to ISI>://000087617300033},
	author = {Klapp, S. H. L. and Patey, G. N.}
}
@article {4749,
	title = {Isotropic fluid phases of dipolar hard spheres},
	journal = {Physical Review Letters},
	volume = {84},
	number = {1},
	year = {2000},
	note = {ISI Document Delivery No.: 271HJTimes Cited: 86Cited Reference Count: 28},
	month = {Jan},
	pages = {115-118},
	type = {Article},
	abstract = {Monte Carlo simulations are used to calculate the equation of state and free energy-of dipolar hard sphere fluids at low temperatures and densities. Evidence for the existence of isotropic-fluid-isotropic-fluid phase transitions is presented and discussed. Condensation in the dipolar hard sphere fluid is unusual in that it is not accompanied by large energy or entropy changes. An explanation of this behavior is put forward.},
	keywords = {CLUSTERS, COMPUTER-SIMULATION, CONDENSATION, LIQUID, orientational order, SYSTEMS},
	isbn = {0031-9007},
	url = {<Go to ISI>://000084587900029},
	author = {Camp, P. J. and Shelley, J. C. and Patey, G. N.}
}
@article {4746,
	title = {Monte Carlo simulations of zero electric field gradient liquid crystal mixtures},
	journal = {Chemical Physics Letters},
	volume = {331},
	number = {5-6},
	year = {2000},
	note = {ISI Document Delivery No.: 382YCTimes Cited: 13Cited Reference Count: 14},
	month = {Dec},
	pages = {455-464},
	type = {Article},
	abstract = {We explore with Monte Carlo simulations the NMR finding that solutes in special nematic liquid crystal mixtures {\textquoteright}feel{\textquoteright} zero average electric field gradient F-ZZ. The simulations involve solute-solvent mixtures of 1000 identical Gay-Berne ellipsoidal particles with added electric quadrupoles of varying strengths placed at particle centres. As long as all quadrupoles are sufficiently small, F-ZZ calculated at the particle centres is equal for all particles. For larger quadrupole moments, interactions among quadrupoles alter the interparticle distribution and subsequently F-ZZ depends on both solvent and solute quadrupoles; in general, the quadrupolar interactions produce a negative contribution to energy. (C) 2000 Elsevier Science B.V. All rights reserved.},
	keywords = {NMR, orientational order, SHAPE, SOLUTES},
	isbn = {0009-2614},
	url = {<Go to ISI>://000165854100016},
	author = {Burnell, E. E. and Berardi, R. and Syvitski, R. T. and Zannoni, C.}
}
@article {4945,
	title = {Multiple quantum and high-resolution NMR, molecular structure, and order parameters of partially oriented ortho and meta dimethyl-, dichloro-, and chloromethylbenzenes codissolved in nematic liquid crystals},
	journal = {Journal of Magnetic Resonance},
	volume = {144},
	number = {1},
	year = {2000},
	note = {ISI Document Delivery No.: 313NCTimes Cited: 18Cited Reference Count: 62},
	month = {May},
	pages = {58-73},
	type = {Article},
	abstract = {We develop a strategy for analyzing complex nuclear magnetic resonance (NMR) spectra of several solutes codissolved in liquid-crystal phases. Spectral parameters of solutes m- or o-xylene were estimated by analyzing 2D multiple-quantum NMR spectra using a modified version of a least-squares fitting routine which adjusts chemical shifts, order parameters, structural parameters, and/or dipolar couplings independently. These estimates were used to facilitate analysis of the high-resolution spectra which contain resonances from many solutes. Calculated spectra of m- or o-xylene were subtracted from the experimental high-resolution spectra leaving resonances from the other solutes readily visible, Accurate spectral parameters of all codissolved solutes were determined from the high-resolution spectra. Order parameters and structural parameters (including vibrationally corrected parameters) of m- and o-xylene, m- and o-chlorotoluene, and m- and o-dichlorobenzene were calculated from the dipolar couplings. (C) 2000 Academic Press.},
	keywords = {ELECTRIC-DIPOLE INTERACTIONS, EXCITATION, INTERNAL-ROTATION, NUCLEAR-MAGNETIC-RESONANCE, orientational order, PHASE, POTENTIALS, SELECTIVE, SOLUTES, SOLVENTS, TRANSITIONS},
	isbn = {1090-7807},
	url = {<Go to ISI>://000087004900008},
	author = {Syvitski, R. T. and Burnell, E. E.}
}
@article {4748,
	title = {Structure and scattering in colloidal ferrofluids},
	journal = {Physical Review E},
	volume = {62},
	number = {4},
	year = {2000},
	note = {ISI Document Delivery No.: 365YATimes Cited: 67Cited Reference Count: 32Part B},
	month = {Oct},
	pages = {5403-5408},
	type = {Article},
	abstract = {The structure of a model colloidal ferrofluid, the dipolar hard-sphere fluid, at low temperature has been investigated using Monte Carlo simulations. Extensive particle association into chainlike and ringlike clusters is observed at low density. The structure factors have been calculated, and are analyzed with the aid of simple scaling arguments. We describe the progression of fluid structures from the low-density associated phase, to the high-density liquid phase. This paper may he of help in obtaining an experimental observation of a fluid-fluid transition in colloidal ferrofluids.},
	keywords = {DIPOLAR HARD-SPHERES, FLUIDS, LIQUID, LIVING, LOW-DENSITIES, MODEL POLAR CLUSTERS, MONTE-CARLO, orientational order, PHASES, POLYMERS, SYSTEMS},
	isbn = {1063-651X},
	url = {<Go to ISI>://000089977000025},
	author = {Camp, P. J. and Patey, G. N.}
}
@article {4663,
	title = {Liquid-vapor coexistence in fluids of dipolar hard dumbbells and spherocylinders},
	journal = {Physical Review E},
	volume = {59},
	number = {3},
	year = {1999},
	note = {ISI Document Delivery No.: 177WFTimes Cited: 29Cited Reference Count: 11Part B},
	month = {Mar},
	pages = {3065-3070},
	type = {Article},
	abstract = {Fluids of dipolar hard spheres are thought to have rather unusual phase behavior in that liquid-vapor equilibrium has not been observed in computer simulations. Recently, McGrother and Jackson [Phys. Rev. Lett. 76, 4183 (1996)] have reported Gibbs ensemble Monte Carlo (GEMC) results for dipolar hard spherocylinders. At the reduced temperature T*=0.12 they report liquid-vapor coexistence for aspect ratios L/D greater than or similar to 0.19, bur no coexistence was found for smaller values. In the present paper we investigate the phase behavior of dipolar hard dumbbells and dipolar hard spherocylinders using both GEMC and grand canonical Monte Carlo methods. For both models at the same reduced temperature we find liquid-vapor coexistence for aspect ratios as low as 0.1. For aspect ratios less than or similar to 0.1, the strong dipolar interactions create severe sampling problems and reliable results cannot be obtained. This is particularly true for the GEMC method and possibly accounts for the disagreement we find with the earlier simulations. [S1063-651X(99)08502-5].},
	keywords = {orientational order, SIMULATION, SPHERES, SYSTEMS},
	isbn = {1063-651X},
	url = {<Go to ISI>://000079233500001},
	author = {Shelley, J. C. and Patey, G. N. and Levesque, D. and Weis, J. J.}
}
@article {4198,
	title = {Gas-liquid coexistence and demixing in systems with highly directional pair potentials},
	journal = {Physical Review E},
	volume = {57},
	number = {5},
	year = {1998},
	note = {ISI Document Delivery No.: ZP583Times Cited: 19Cited Reference Count: 21Part B},
	month = {May},
	pages = {5682-5686},
	type = {Article},
	abstract = {Recent computer simulation studies strongly indicate that fluids of dipolar hard spheres do not display gas-isotropic liquid coexistence. In this paper we discuss a second example that also exhibits this rather unexpected behavior. This is a simple liquid-crystal model that we explore employing Gibbs ensemble Monte Carlo (GEMC) methods. It is shown that the system has clear gas-nematic liquid coexistence, but that the gas-isotropic liquid coexistence line is completely missing from the phase diagram. We attribute this to the highly directional nature of the attractive potential and argue that similar considerations are likely of relevance in the dipolar hard-sphere case as well. We also use GEMC techniques to investigate demixing in binary mixtures of neutral and dipolar hard spheres. For similar mixtures of neutral and charged have spheres, it is known that demixing is essentially condensation of the Coulombic fluid weakly influenced by the background of neutral hard spheres. Therefore, given that dipolar hard spheres do not condense, whether or not the present mixtures demix is an interesting question. In fact, demi?ring is observed and, moreover, the transition temperatures are in reasonable agreement with those predicted by the same integral equation theories that incorrectly predict condensation of the pure dipolar fluid. The critical temperature decreases rapidly with decreasing diameter of the neutral species consistent with the lack of gas-isotropic liquid coexistence for pure dipolar hard spheres. Clearly, for the present model demixing and dipolar condensation are not closely related phenomena as they are in the Coulombic systems. The neutral species appears to reduce the formation of dipolar "chains" or "clusters" that inhibit condensation of the purl dipolar hard-sphere fluid.},
	keywords = {COMPUTER-SIMULATION, CRYSTAL MODELS, DIPOLAR HARD-SPHERES, FLUID, GIBBS ENSEMBLE, INSTABILITY, MIXTURE, MONTE-CARLO, orientational order, PHASE},
	isbn = {1063-651X},
	url = {<Go to ISI>://000073768000025},
	author = {Blair, M. J. and Patey, G. N.}
}
@article {4114,
	title = {Analysis of single and multiple quantum NMR spectra of 1,3-dichloro-2-ethenylbenzene in liquid crystal solvents},
	journal = {Molecular Physics},
	volume = {90},
	number = {4},
	year = {1997},
	note = {ISI Document Delivery No.: WN909Times Cited: 10Cited Reference Count: 37},
	month = {Mar},
	pages = {541-551},
	type = {Article},
	abstract = {The single and multiple quantum NMR spectra of 1,3-dichloro-2-ethenylbenzene as solute in two different nematic liquid crystals have been measured and analysed in terms of dipolar couplings and chemical shift differences. Because the single quantum spectra did not yield to straightforward analysis, normal and frequency selective multiple quantum experiments were used to aid the analysis. The results from four spectra were combined to yield structural information and the order matrix in each solution. The structure of the ring is very close to that of 1,3-dichlorobenzene, and that of the ethenyl group very close to that of ethenyl-benzene. The dihedral angle between the ethenyl group and the aromatic ring is found to be 454 +/- 1.0 degrees, and the C-CC=C angle is found to be 127.3 +/- 0.3 degrees.},
	keywords = {EQUILIBRIUM, FIELD, MAGNETIC-RESONANCE, MIXTURES, MOLECULAR-STRUCTURE, orientational order, ROTATION, SHAPE, SOLUTES, SPECTROSCOPY},
	isbn = {0026-8976},
	url = {<Go to ISI>://A1997WN90900005},
	author = {Rendell, J. C. T. and Burnell, E. E.}
}
@article {4141,
	title = {Dipole-induced ordering in nematic liquid crystals fact or fiction?},
	journal = {Chemical Physics Letters},
	volume = {281},
	number = {1-3},
	year = {1997},
	note = {ISI Document Delivery No.: YP239Times Cited: 18Cited Reference Count: 35},
	month = {Dec},
	pages = {199-206},
	type = {Article},
	abstract = {Similar size and shape molecules with different electric multipoles are used to investigate effects of dipole and quadrupole interactions on the average orientation of solutes in nematic liquid crystals. Permanent dipoles have a negligible influence on solute orientation. Order parameters predicted from strong, short-range repulsive forces coupled with interactions between the solute quadrupole and the average electric field gradient felt by the solute [EFG] are consistent with experimental values. Calculated [EFG]{\textquoteright}s are the same sign and similar magnitude to those determined previously from D-2 and HD. For the nematic mixture 55wt\% ZLI 1132 in EBBA, the contribution to solute ordering from long-range electrostatic interactions is negligible. (C) 1997 Elsevier Science B.V.},
	keywords = {deuterium, ELECTRIC-DIPOLE, MECHANISMS, MOLECULAR-HYDROGEN, NMR-SPECTRA, orientational order, POTENTIALS, QUADRUPOLE-MOMENTS, SOLUTES, SOLVENTS},
	isbn = {0009-2614},
	url = {<Go to ISI>://000071256600030},
	author = {Syvitski, R. T. and Burnell, E. E.}
}
@article {3887,
	title = {Liquid crystal phases of dipolar discotic particles},
	journal = {Physical Review E},
	volume = {55},
	number = {1},
	year = {1997},
	note = {ISI Document Delivery No.: WD545Times Cited: 15Cited Reference Count: 21Part A},
	month = {Jan},
	pages = {447-454},
	type = {Article},
	abstract = {Fluids of dipolar oblate ellipsoids of revolution are investigated in detail employing molecular dynamics simulations. For aspect ratios (height-to-breadth) between similar to 1.2 and similar to 3, it is shown that these systems may form two liquid crystal phases. These are a ferroelectric phase which is stable at higher temperatures and an antiferroelectric columnar phase which is stable at lower temperatures. A partial phase diagram is given and the important structural features of these phases are determined and discussed.},
	keywords = {COMPUTER-SIMULATION, ELLIPSOIDS, MODEL, MOLECULES, MONTE-CARLO SIMULATIONS, NEMATIC PHASE, orientational order, SPHERES, SYSTEMS},
	isbn = {1063-651X},
	url = {<Go to ISI>://A1997WD54500056},
	author = {Ayton, G. and Wei, D. Q. and Patey, G. N.}
}
@article {4107,
	title = {Monte Carlo simulations of solute ordering in nematic liquid crystals: Shape anisotropy and quadrupole-quadrupole interactions as orienting mechanisms},
	journal = {Physical Review E},
	volume = {55},
	number = {4},
	year = {1997},
	note = {ISI Document Delivery No.: WV249Times Cited: 17Cited Reference Count: 51},
	month = {Apr},
	pages = {4321-4337},
	type = {Article},
	abstract = {Monte Carlo computer simulations were used to investigate the effects of shape anisotropy and electrostatic interactions as mechanisms for orientational ordering of solutes in nematic liquid crystals. The simulation results were analyzed in terms of two theories of solute ordering which derive mean-field orientational potentials from the intermolecular pair potential. In the calculations, solute and solvent molecular shapes were approximated by hard ellipsoids. Most simulations also incorporated the interaction between point quadrupole moments placed at the centers of the ellipsoids. In the hard-core systems, orientational order parameters and distribution functions were calculated for a collection of different solutes under a variety of conditions. A theory due to Terzis and Photinos [Mol. Phys. 83, 847 (1994)] was found to underestimate the effect of shape anisotropy on orientational ordering drastically. The introduction of an effective solvent packing fraction was unable to improve the predictive power of the theory significantly. The quadrupolar systems were used to investigate a mean-field model for solute ordering which considers an interaction between the solute molecular quadrupole moment with an average electric-field gradient. The simulations indicate that the electric-field gradient sampled by the solute is highly dependent on the properties of the solute, contrary to some experimental evidence. Further, the effects of the intermolecular quadrupolar interactions on orientational ordering and the electric-field gradient were analyzed using a mean-field potential derived here and based on the theory due to Emsley, Palke, and Shilstone [Liq. Cryst. 9, 649 (1991)]. This model was found to provide a qualitatively correct but quantitatively imprecise prediction of orientational ordering.},
	keywords = {acetylene, COMPUTER-SIMULATION, ELECTRIC-DIPOLE INTERACTIONS, HARD ELLIPSOIDS, MEAN TORQUE, MOLECULAR-HYDROGEN, NMR, orientational order, POTENTIALS, SOLVENTS},
	isbn = {1063-651X},
	url = {<Go to ISI>://A1997WV24900067},
	author = {Polson, J. M. and Burnell, E. E.}
}
@article {3930,
	title = {A temperature dependence study of small solutes in zero electric field gradient nematic liquid crystal mixtures},
	journal = {Molecular Physics},
	volume = {90},
	number = {3},
	year = {1997},
	note = {ISI Document Delivery No.: WK754Times Cited: 10Cited Reference Count: 50},
	month = {Feb},
	pages = {303-313},
	type = {Article},
	abstract = {The temperature dependences of the proton nuclear magnetic resonance (NMR) spectra of the solutes 1,3,5-trichlorobenzene, metadichlorobenzene, orthodichlorobenzene, 1,3-bromochlorobenzene, benzene and 2-butyne have been studied in the special {\textquoteright}zero electric field gradient{\textquoteright} mixtures 55wt\% 1132-N-(4-ethoxybenzylidene)-4{\textquoteright}-n-butylaniline (EBBA) and 70wt\% (4-n-pentyl)-4{\textquoteright}-cyanobiphenyl-EBBA. The order parameter matrices obtained for each solute from an analysis of the NMR spectra indicate that the solutes experience a similar anisotropic potential in both mixtures.},
	keywords = {BIAXIAL SOLUTE, CONFORMATIONAL EQUILIBRIUM, INTERNAL-ROTATION, MOLECULES, NORMAL-BUTANE, orientational order, POTENTIAL FUNCTION, RAMAN-SPECTRA, SHAPE, SOLVENTS},
	isbn = {0026-8976},
	url = {<Go to ISI>://A1997WK75400001},
	author = {Chandrakumar, T. and Burnell, E. E.}
}
@article {3919,
	title = {Tritium nuclear magnetic resonance study of T-2, HT, and DT dissolved in nematic solvents},
	journal = {Physical Review E},
	volume = {55},
	number = {1},
	year = {1997},
	note = {ISI Document Delivery No.: WD545Times Cited: 5Cited Reference Count: 25Part A},
	month = {Jan},
	pages = {496-503},
	type = {Article},
	abstract = {A tritium nuclear magnetic resonance study is carried out on the T-2, HT, and DT isotopomers of dihydrogen dissolved in various nematic phases, including a zero-electric-field-gradient mixture. Ab initio calculations are performed to reproduce the observed dipolar couplings. Within the framework of the {\textquoteright}{\textquoteright}mean-field{\textquoteright}{\textquoteright} approximation, the results provide support for a picture in which two independent contributions to the solute orientation can be distinguished. One contribution involves a liquid-crystal-dependent interaction between the mean solvent electric-field gradient and the solute molecular quadrupole moment. The other contribution is of unknown origin; however, it is essentially identical in all liquid crystals and it can be modeled adequately with a phenomenological mean-field interaction. A remarkable feature of this second interaction is that it causes the average orientation of the asymmetrical isotopomers, and especially of HT, to behave differently from the symmetrical species.},
	keywords = {ELECTRIC-FIELD GRADIENTS, ENVIRONMENTS, LIQUID-CRYSTAL MIXTURES, MECHANISMS, METHANES, MOLECULAR-HYDROGEN, NMR, orientational order, SOLUTES},
	isbn = {1063-651X},
	url = {<Go to ISI>://A1997WD54500062},
	author = {Burnell, E. E. and de Lange, C. A. and Segre, A. L. and Capitani, D. and Angelini, G. and Lilla, G. and Barnhoorn, J. B. S.}
}
@article {3596,
	title = {Ferroelectric order in model discotic nematic liquid crystals},
	journal = {Physical Review Letters},
	volume = {76},
	number = {2},
	year = {1996},
	note = {ISI Document Delivery No.: TN761Times Cited: 31Cited Reference Count: 12},
	month = {Jan},
	pages = {239-242},
	type = {Article},
	abstract = {Monte Carlo calculations are used to examine orientational order in fluids of disk-shape particles with embedded dipoles. The dipoles are distributed over a circular {\textquoteright}{\textquoteright}patch{\textquoteright}{\textquoteright} of finite size. It is shown that such systems may undergo spontaneous polarization to form a stable ferroelectric discotic nematic phase.},
	keywords = {COMPUTER-SIMULATION, ELECTROSTATIC SYSTEMS, MONTE-CARLO, orientational order, PERIODIC BOUNDARY-CONDITIONS, PHASE},
	isbn = {0031-9007},
	url = {<Go to ISI>://A1996TN76100021},
	author = {Ayton, G. and Patey, G. N.}
}
@article {2983,
	title = {COMPARISON OF SHORT-RANGE INTERACTIONS IN NEMATIC LIQUID-CRYSTALS - A H-2-NMR STUDY OF 5CB-D(19) AS A SOLUTE},
	journal = {Liquid Crystals},
	volume = {17},
	number = {4},
	year = {1994},
	note = {ISI Document Delivery No.: PH470Times Cited: 4Cited Reference Count: 42},
	month = {Oct},
	pages = {457-485},
	type = {Article},
	abstract = {Previous studies using dideuterium as a solute have demonstrated the importance for orientation of the interaction between the solute molecular quadrupole moment and the average electric field gradient present in liquid crystals. With the aim of learning about additional orientational mechanisms, we have studied the temperature dependence of the H-2-NMR spectra of the liquid crystal 5CB-d(19) as the solute in three liquid crystal mixtures: 55 wt \% 1132/EBBA, 56.5 wt \% 1132/EBBA and 70 wt \% 5CB/EBBA. In these mixtures, the contribution from the environment to the average electric field gradient at the H-2 nucleus of dideuterium is zero. The spectra of 5CB-d(19) in the mixtures 55 wt \% 1132/EBBA and 56.5 wt \% 1132/EBBA are equivalent, but are different from those in 70 wt \% 5CB/EBBA. The spectra of 5CB in 55 wt \% 1132/EBBA and 70 wt \% 5CB/EBBA are analysed using two different models for the short range potential, and parameters of the models are used to compare the potentials in the different mixtures. For a given spectral splitting of the chain C-1 deuteron, the reduced short range potential is the same in all three mixtures studied. The spectral differences observed are a consequence of different nematic-isotropic phase transition temperatures combined with the effect of trans/gauche-isomerization in the hydrocarbon chain.},
	keywords = {BINARY-MIXTURES, EQUILIBRIUM, FLEXIBILITY, MAGNETIC-RESONANCE, MOLECULAR-STRUCTURE, MULTIPLE-QUANTUM NMR, NORMAL-BUTANE, orientational order, RAMAN-SPECTRA, SPECTROSCOPY},
	isbn = {0267-8292},
	url = {<Go to ISI>://A1994PH47000001},
	author = {Chandrakumar, T. and Zimmerman, D. S. and Bates, G. S. and Burnell, E. E.}
}
@article {2983,
	title = {COMPARISON OF SHORT-RANGE INTERACTIONS IN NEMATIC LIQUID-CRYSTALS - A H-2-NMR STUDY OF 5CB-D(19) AS A SOLUTE},
	journal = {Liquid Crystals},
	volume = {17},
	number = {4},
	year = {1994},
	note = {ISI Document Delivery No.: PH470Times Cited: 4Cited Reference Count: 42},
	month = {Oct},
	pages = {457-485},
	type = {Article},
	abstract = {Previous studies using dideuterium as a solute have demonstrated the importance for orientation of the interaction between the solute molecular quadrupole moment and the average electric field gradient present in liquid crystals. With the aim of learning about additional orientational mechanisms, we have studied the temperature dependence of the H-2-NMR spectra of the liquid crystal 5CB-d(19) as the solute in three liquid crystal mixtures: 55 wt \% 1132/EBBA, 56.5 wt \% 1132/EBBA and 70 wt \% 5CB/EBBA. In these mixtures, the contribution from the environment to the average electric field gradient at the H-2 nucleus of dideuterium is zero. The spectra of 5CB-d(19) in the mixtures 55 wt \% 1132/EBBA and 56.5 wt \% 1132/EBBA are equivalent, but are different from those in 70 wt \% 5CB/EBBA. The spectra of 5CB in 55 wt \% 1132/EBBA and 70 wt \% 5CB/EBBA are analysed using two different models for the short range potential, and parameters of the models are used to compare the potentials in the different mixtures. For a given spectral splitting of the chain C-1 deuteron, the reduced short range potential is the same in all three mixtures studied. The spectral differences observed are a consequence of different nematic-isotropic phase transition temperatures combined with the effect of trans/gauche-isomerization in the hydrocarbon chain.},
	keywords = {BINARY-MIXTURES, EQUILIBRIUM, FLEXIBILITY, MAGNETIC-RESONANCE, MOLECULAR-STRUCTURE, MULTIPLE-QUANTUM NMR, NORMAL-BUTANE, orientational order, RAMAN-SPECTRA, SPECTROSCOPY},
	isbn = {0267-8292},
	url = {<Go to ISI>://A1994PH47000001},
	author = {Chandrakumar, T. and Zimmerman, D. S. and Bates, G. S. and Burnell, E. E.}
}
@article {2945,
	title = {ANISOTROPIC SHORT-RANGE POTENTIALS FOR SOLUTES IN NEMATIC LIQUID-CRYSTALS},
	journal = {Molecular Physics},
	volume = {78},
	number = {3},
	year = {1993},
	note = {ISI Document Delivery No.: KQ355Times Cited: 35Cited Reference Count: 12},
	month = {Feb},
	pages = {687-702},
	type = {Article},
	abstract = {Recently, it has been suggested that the orientational order of solutes dissolved in nematic liquid crystals results from short range forces which depend on the size and shape of the solute molecule and from the interaction between the molecular quadrupole moment and the average electric field gradient experienced by the molecule. In this paper, we model the size and shape-dependent short range potential by assuming that the contribution to the potential from each surface element of a cavity representing the molecule depends on the orientation of the surface element with respect to the director. We have tried a variety of potentials based on this assumption, and we report here the ones which yielded the best agreement between theory and experiment. One of the potentials is obtained by integrating, along the director, the circumference of a slice cut through the molecule perpendicular to the director; better fits are obtained by adding a term which depends on a Hooke{\textquoteright}s law elastic distortion of the liquid crystal solvent. Another potential depends on the surface area of a cavity formed from the projections onto a plane perpendicular to the director and onto walls parallel to it. These models are used to fit the experimental order parameters of a collection of 46 molecules dissolved in a special mixture where the ordering is dominated by the size and shape potential. We attribute the superior quality of the resulting fits to the fact that these potentials depend in a more sensitive manner on the details of the geometry of the molecules than previously used ones.},
	keywords = {orientational order, SIZE},
	isbn = {0026-8976},
	url = {<Go to ISI>://A1993KQ35500011},
	author = {Zimmerman, D. S. and Burnell, E. E.}
}
@article {7119,
	title = {THE CONFORMATION OF 2,2{\textquoteright}-DITHIOPHENE IN NEMATIC SOLVENTS DETERMINED BY H-1-NMR},
	journal = {Molecular Physics},
	volume = {74},
	number = {5},
	year = {1991},
	note = {ISI Document Delivery No.: GY085Times Cited: 24Cited Reference Count: 26},
	month = {Dec},
	pages = {1027-1035},
	type = {Article},
	abstract = {In this paper we report a determination of the structure 2,2{\textquoteright}-dithiophene dissolved in different nematic liquid crystal solvents. The H-1-NMR spectra of this molecule dissolved in a 55\% Merck ZLI 1132/45\% N-(4-ethoxybenzylidene)-4{\textquoteright}-n-butylaniline (w/w) mixture are recorded at 300 and 304 K and are analysed. The dipolar coupling constants obtained are used to show that the solute molecule exists in both the s-cis and the s-trans conformations. The s-trans conformer is planar and the absolute value of the dihedral angle-PHI between the two thiophene ring planes for the s-cis conformer is found to be (24 +/- 1)degrees. Using the same method of analysis we reinterpreted two additional independent sets of published dipolar coupling constants from H-1-NMR spectra of 2,2{\textquoteright}-dithiophene dissolved in Merck Phase IV at room temperature and in 80\% N-(4-ethoxybenzylidene)-4{\textquoteright}-n-butylaniline/20\% O-carbobutoxy-4-oxybenzoic acid ethoxy phenyl ester at 301 K. These additional studies yield the same results for the structure of 2,2{\textquoteright}-dithiophene. We also estimate that in each of the three nematic solvents (61 +/- 3)\% of the solute 2,2{\textquoteright}-dithiophene exists in the s-trans state.},
	keywords = {2, 2{\textquoteright}-BITHIENYL, BARRIER, LIQUID-CRYSTALS, MOLECULES, orientational order, PHASE, SIZE, SOLUTES},
	isbn = {0026-8976},
	url = {<Go to ISI>://A1991GY08500007},
	author = {ter Beek, L. C. and Zimmerman, D. S. and Burnell, E. E.}
}
