The Study of Birefringence and Orientational Order in Plastic Tert-Butyl Bromide

Akimov, M. N.; Bezrukov, O. F.; Vuks, M. F.; Struts, Andrey V.

doi:10.1080/00268949008035630

Cited by 3 publications

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“…The dominating motion in phase II changes from C 3 ‘ reorientations in the low-temperature region to overall molecular tumbling in the high-temperature region. ,, In addition, incoherent quasielastic neutron-scattering experiments have shown phase II motions consisting of fluctuations of the dipolar axis 19 of about 30−60°, much greater than those for the molecular homologous tert -butyl chloride for which fluctuations cover only some degrees . The results are consistent with the high values of the dielectric permittivity from dielectric measurements. , The birefringence of the uniaxial crystals of phase II was found early 27 and lately measured . As a proof of the orientational disorder of the dipolar axis, an orientational order parameter describing the average over fluctuations of the dipolar axis from a preferred orientation, defined as S = (1/2)〈3 cos ϑ − 1〉, where ϑ stands for the angle between the 3-fold symmetry axis of the molecule and crystal optical axis, was found to vary between 0.038 at 231 K and 0.052 at 210 K 28 or 0.0031−0.0044 in the same temperature range .…”

Section: Introductionsupporting

confidence: 66%

“…tert- Butyl compounds have stimulated a large number of theoretical studies as well as have been the object of considerable experimental efforts to elucidate the nature of the disorder and, more specifically, the hindrance to the orientational disorder. − …”

Section: Introductionmentioning

confidence: 99%

“…As for the tert -butyl bromide dealt with in this paper, polymorphism has been the subject of an intensive work. ,,− ,,,,− , It exists in three solid phases, designated I, II, and III in order of decreasing temperature and is one of the compounds possessing two stable OD phases (I and II). OD phase I is stable between ca.…”

Section: Introductionmentioning

confidence: 99%

“…This result was confirmed by many other X-ray and neutron powder diffraction studies. − Nevertheless, as far as lattice symmetry of phase II is concerned, results obtained from different works do not agree with each other. Some authors indexed the powder diffraction pattern on the basis of an orthorhombic unit cell. ,, Only recently was Rudman 34 able to obtain a single crystal of phase II by cooling a single crystal of isotropic phase I (as Akimov et al did for measurements of birefringence) and to state that phase II displays a rhombohedral unit cell with a = 15.087(13) Å, α = 89.19(7)°. The same author also indicated some possible relationships between phases I and II confirming the structural similarity between this rhombohedral phase II of (CH 3 ) 3 CBr and phase Ib of CCl 4 .…”

Section: Introductionmentioning

confidence: 99%

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Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

et al. 2006

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Phase equilibria involving orientationally disordered (OD) and liquid phases of the two-component system between carbon tetrachloride (CCl4) and 2-methyl-2-bromomethane ((CH3)3CBr) have been determined by means of X-ray powder diffraction and thermal analysis techniques from 210 K up to the liquid state. The isomorphism relation between the OD stable face-centered cubic (FCC) phase of (CH3)3CBr and the metastable FCC phase of CCl4 has been demonstrated throughout the continuous evolution of the lattice parameters and the existence of the two-phase equilibrium [FCC + L] for the whole range of composition, despite the monotropy of the FCC phase for the CCl4 component with respect to its OD rhombohedral (R) stable phase. A continuous series of OD R mixed crystals is found, which confirms the R lattice symmetry of the OD phase II of (CH3)3CBr, for which the crystallographic results have been long-time misinterpreted. X-ray patterns of such a phase were indexed according to the recent single-crystal results obtained by Rudman (Rudman, R. J. Mol. Struct. 2001, 569, 157). In addition, some experimental evidences are given to confirm the number of molecules per unit cell (Z = 21). The thermodynamic assessment reproduces coherently the phase diagram for the stable [R + L] and [R + FCC] two-phase equilibria as well as for the partially metastable [FCC + L] two-phase equilibrium and provides a set of data for the thermodynamic properties of nonexperimentally available phase transitions of pure components. Surprisingly, the phase equilibrium involving R and FCC OD phases appears as one of the very few showing a solid-solid equilibrium with two extremes.

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Section: Introductionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

et al. 2006

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“…If the molecular polarizability anisotropy is known [38,39], the order parameter S can be determined in one-component system and also in two-component crystals [29]. In our treatment regarding the orientationally disordered (OD) parameter (ψ) of the rhombohedral (R) phase and the orientationally ordered (OO) parameter (η) of the FCC phase of the two-component system (CH 3 CCl 3 +CCl 4 ), we considered only the amplitudes of the order parameters (ψ and η).…”

Section: Discussionmentioning

confidence: 99%

Analysis of the Heat Capacity for Pure CH4 and CH4/CCl4 on Graphite Near the Melting Point and Calculation of the T–X Phase Diagram for (CH3)CCl3+CCl4

Yurtseven

Yilmaz

2016

Front. Phys.

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We study the temperature dependence of the heat capacity C p for the pure CH 4 and the coadsorbed CH 4 /CCl 4 on graphite near the melting point. The heat capacity peaks are analyzed using the experimental data from the literature by means of the power-law formula. The critical exponents for the heat capacity are deduced below and above the melting point for CH 4 (T = m 104.8 K) and CH 4 /CCl 4 (T = m 99.2 K). Our exponent values are larger as compared with the predicted values of some theoretical models exhibiting second order transition. Our analyses indicate that the pure methane shows a nearly second order (weak discontinuity in the heat capacity peak), whereas the transition in coadsorbed CH 4 /CCl 4 is of first order (apparent discontinuity in C p ). We also study the T-X phase diagram of a two-component system of CH 3 CCl 3 +CCl 4 using the Landau phenomenological model. Phase lines of the R+L (rhombohedral + liquid) and FCC+L (face-centered cubic + liquid) are calculated using the observed T-X phase diagram of this binary mixture. Our results show that the Landau mean field theory describes the observed behavior of CH 3 CCl 3 +CCl 4 adequately. From the calculated T-X phase diagram, critical behavior of some thermodynamic quantities can be predicted at various temperatures and concentrations (CCl 4 ) for a binary mixture of CH 3 CCl 3 +CCl 4 .

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The Explicitly Quasi-linear Relation Between the Order Parameter and Normalized Birefringence of Aligned Uniaxially Anisotropic Molecules Determined Using a Numerical Method

Kim¹

2016

Korean Journal of Optics and Photonics

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The birefringence of distributed, uniaxially anisotropic molecules like liquid crystals is calculated as the degree of ordering is varied. The relation between the normalized birefringence   and the orientational order parameter  is investigated. The distribution function, which enables one to monitor the degree of ordering of liquid crystals including randomly distributed ones, is introduced. Using this distribution function, a series of distributed liquid crystals with order parameters ranging from 0 to 1 are generated, and   and  of the correspondingly distributed liquid crystals are calculated. Based on the calculated data, it is revealed that   and  satisfy the quasi-linear relation of            , where  can be approximated asThe anisotropy of molecular polarizability is also calculated, using the birefringence, and separately following Vuks' method and Neugebauer's method, and it is shown that the relations between  and the molecular-polarizability anisotropy are also quasi-linear.

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The Study of Birefringence and Orientational Order in Plastic Tert-Butyl Bromide

Cited by 3 publications

References 3 publications

Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

Analysis of the Heat Capacity for Pure CH4 and CH4/CCl4 on Graphite Near the Melting Point and Calculation of the T–X Phase Diagram for (CH3)CCl3+CCl4

The Explicitly Quasi-linear Relation Between the Order Parameter and Normalized Birefringence of Aligned Uniaxially Anisotropic Molecules Determined Using a Numerical Method

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The Study of Birefringence and Orientational Order in Plastic Tert-Butyl Bromide

Cited by 3 publications

References 3 publications

Two-component System CCl4 + (CH3)3CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

Two-component System CCl4 + (CH3)3CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

Analysis of the Heat Capacity for Pure CH4 and CH4/CCl4 on Graphite Near the Melting Point and Calculation of the T–X Phase Diagram for (CH3)CCl3+CCl4

The Explicitly Quasi-linear Relation Between the Order Parameter and Normalized Birefringence of Aligned Uniaxially Anisotropic Molecules Determined Using a Numerical Method

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Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases