Surface alignment of ferroelectric nematic liquid crystals

Caimi, Federico; Nava, Giovanni; Barboza, Raouf; Clark, Noel A.; Körblová, Eva; Walba, David M.; Bellini, Tommaso; Lucchetti, L.

doi:10.1039/d1sm00734c

Cited by 54 publications

(63 citation statements)

References 10 publications

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“…Recent synthesis and evaluation [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] of new mesogens with large molecular dipoles led to a demonstration of a fluid ferroelectric nematic liquid crystal (NF) with a uniaxial polar ordering of the molecules 13,14 . The ferroelectric nature of NF has been established by polarizing optical microscopy observations of domains with opposite orientations of the polarization density vector P and their response to a direct current (dc) electric field 𝐄 13,14 .…”

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confidence: 99%

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

et al. 2022

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Surface interactions are responsible for many properties of condensed matter, ranging from crystal faceting to the kinetics of phase transitions. Usually, these interactions are polar along the normal to the interface and apolar within the interface. Here we demonstrate that polar in-plane surface interactions of a ferroelectric nematic NF produce polar monodomains in micron-thin planar cells and stripes of an alternating electric polarization, separated by $${180}^{{{{{{\rm{o}}}}}}}$$ 180 o domain walls, in thicker slabs. The surface polarity binds together pairs of these walls, yielding a total polarization rotation by $${360}^{{{{{{\rm{o}}}}}}}$$ 360 o . The polar contribution to the total surface anchoring strength is on the order of 10%. The domain walls involve splay, bend, and twist of the polarization. The structure suggests that the splay elastic constant is larger than the bend modulus. The $${360}^{{{{{{\rm{o}}}}}}}$$ 360 o pairs resemble domain walls in cosmology models with biased vacuums and ferromagnets in an external magnetic field.

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confidence: 99%

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

et al. 2022

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“…27 Polar nematic order gives rise to extremely large ferroelectric polarisations, 25 which are of interest to both fundamental and applied science. [28][29][30][31] We simulated a polar nematic configuration of the NF material RM554 (Figure 3a) 32 by taking an isotropic configuration of 680 molecules with liquid-like density of 1.1 g cm 3 and applying a static electric field (0.1 V nm -1 ) along the y-axis; this gives a large polar order parameter (<P1>) of ~ 0.9 and an orientational order parameter (<P2>) of ~ 0.65. Following this, a production MD simulation (without biasing field) of 250 ns was performed from this polar configuration at a temperature of 375 K with anisotropic pressure coupling; note that, as with prior simulations, the polar order is essentially constant over the entire production run.…”

Section: Resultsmentioning

confidence: 99%

Implementation of a cylindrical distribution function for the analysis of anisotropic molecular dynamics simulations.

Mandle

2022

Preprint

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The cylindrical distribution function (CDF) is a convenient anisotropic analogue of the radial distribution function, the difference being the use of cylindrical shells for binning. As such, CDF analysis can be a powerful tool for the analysis of positional correlations within anisotropic systems, such as liquid crystals. Here we describe a lightweight Python tool, cylindr, for the calculation of cylindrical distribution function, which is compatible with the output of a number of popular MD engines. We demonstrate the use of cylindr in computing the CDF of a number of exemplar materials: classical and ferroelectric nematics; lamellar and columnar liquid crystals.

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“…When the two surfaces are rubbed in parallel we get a non-twisted state (just as in the N phase). The possible twisted states and electrooptic effects in the polar nematic phase are further discussed by Caimi et al 10 and Sebastián et al 11 .…”

Section: Introductionmentioning

confidence: 95%

“…In the N F -phase ( b ) the polarization (red) aligns with the rubbing direction. In the case of anti-parallel rubbing the structure has to make a right-handed (R) or left-handed (L) twist of 180° to match the in-plane polar boundary conditions 9 , 10 . …”

Section: Introductionmentioning

confidence: 99%

Revealing the polar nature of a ferroelectric nematic by means of circular alignment

Rudquist

2021

Sci Rep

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The recent discovery of spontaneously polar nematic liquid crystals—so-called ferroelectric nematics—more than a century after the first discussions about their possible existence—has attracted large interest, both from fundamental scientific and applicational points of view. However, the experimental demonstration of such a phase has, so-far, been non-trivial. Here I present a direct method for the experimental verification of a ferroelectric nematic liquid crystal phase. The method utilizes a single sample cell where the two substrates are linearly and circularly rubbed, respectively, and the ferroelectric nematic phase (NF) is revealed by the orientation of the resulting disclination lines in the cell.

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Surface alignment of ferroelectric nematic liquid crystals

Abstract: The success of nematic liquid crystals in displays and optical applications is due to the combination of their optical uniaxiality, fluidity, elasticity, responsiveness to electric fields and controllable coupling of...

Cited by 54 publications

References 10 publications

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

Soliton walls paired by polar surface interactions in a ferroelectric nematic liquid crystal

Implementation of a cylindrical distribution function for the analysis of anisotropic molecular dynamics simulations.

Revealing the polar nature of a ferroelectric nematic by means of circular alignment

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