Reorientational Dynamics Research Articles

Order-disorder behavior in the ferroelectric nematic phase investigated via Raman spectroscopy

Polar-ordered fluids are of interest both fundamentally and from an application standpoint. The recently discovered ferroelectric nematic phase is an example of a polar-ordered fluid, and while there has been extensive research interest in these materials, some of the fundamental properties are yet to be fully understood. Here, we report the order parameters of one of the first known materials that exhibit a ferroelectric nematic phase, RM734, determined via Raman spectroscopy. Raman spectroscopy been used extensively to determined order parameters in liquid crystals systems but also to probe ferroelectric behavior in solid ferroelectric systems and is therefore a powerful technique to study the ferroelectric nematic phase. A reduction and subsequent recovery of order parameters (Δ〈P2〉≈0.1, Δ〈P4〉≈0.06) is observed near the onset of the to NF transition, a feature that is confirmed via complementary birefringence measurements. This dip in order parameters has been attributed to splay fluctuations, which occur at the onset of the NF transition; here we suggest a different explanation. A broadening of the full-width half-maxima (FWHM), of the order of 1 cm−1, of the selected Raman peak is observed near the to NF phase transition, which we relate to either a change in reorientational dynamics or the onset of polar order. The NF transition is analyzed using standard solid ferroelectric frameworks. An energetic barrier associated with the para- to ferroelectric transition is found to be of the order of 2.5±0.6kJ/mol, which is comparable to solid ferroelectric materials. Published by the American Physical Society 2024

Interactions between ions and water-DMSO mixed solvent

As a classical cryoprotectant, the cryoprotective mechanism of DMSO remains elusive. In this study, we explore the capability of DMSO to hinder the formation of salt hydrates in the water-DMSO-salt ternary system, given that, at low temperatures, salt hydrates are more prone to attach to surfaces than ice, potentially preventing mechanical damage to cell membranes. Using THz-TDS, we validate the ability of DMSO to suppress salt hydrate formation. Combining IR spectroscopy, we conclude that this inhibitory effect partly arises from the interaction between cations and the S=O groups in DMSO molecules. Semi-quantitative DR spectroscopy provides similar insights from the perspective of molecular reorientation dynamics. Taking into account the intensified ion-dipole interactions due to a higher ion surface charge density, we focus our discussion on MgCl2, while NaCl, more akin to biological processes, serves as a reference. Delving into the specific molecular mechanisms, we put forth conjectures regarding the direct interaction between cations and DMSO or the indirect influence of cations on DMSO through the modulation of hydrogen bonds in surrounding water molecules. These research findings contribute to a better understanding and mastery of cryoprotectants.

Gas-Phase Dynamics of Bundle Formation from High-Aspect-Ratio Carbon Nanotubes.

In floating catalyst chemical vapor deposition (FCCVD), high-aspect-ratio carbon nanotubes (CNTs) are produced in the gas phase at high number concentrations and undergo collision and agglomeration, eventually giving rise to a macroscale aerogel, enabling functional material forms such as fibers or mats to be obtained directly from the synthesis process. The self-assembly behavior between high-aspect-ratio CNTs dictates the resulting morphology at the nanoscale and subsequently the bulk properties of the CNT product. Reorientation between CNTs after collision is a critical step that results in bundle formation and precedes aerogel formation. However, it has been challenging to study the phenomenon with existing methods as it spans multiple time and length scales. In this study, a physics-based semi-analytical model was developed to study the gas-phase reorientation dynamics of high-aspect-ratio CNTs and their bundles, with ±10% accuracy compared with mesoscale molecular dynamics simulations, but at <0.1% the computational cost. It was revealed that the reorientation time scale is dictated by the interplay among the van der Waals potential, drag, and the geometric configuration of CNTs upon collision. This then allows the time scale of reorientation (i.e., bundle formation) to be compared with other gas-phase dynamics in a typical FCCVD reactor and offers new insights into the self-assembly behavior of 1D nanoparticles in the gas phase.

Confinement Effects on Reorientation Dynamics of Water Confined within Graphite Nanoslits.

Molecular dynamics simulations were used to investigate the reorientation dynamics of water confined within graphite nanoslits of size less than 2 nm, where molecules formed inner and interfacial layers parallel to the confining walls. Significantly related to molecular reorientations, the hydrogen-bond (HB) network of nanoconfined water therein was scrutinized by HB configuration fractions compared to those of bulk water and the influences on interfacial-molecule orientations relative to a nearby C atom plate. The second-rank orientation time correlation functions (OTCFs) of nanoconfined water were calculated and found to follow stretched-exponential, power-law, and power-law decays in a time series. To understand this naïve behavior of reorientation relaxation, the approach of statistical mechanics was adopted in our studies. In terms of the orientation Van Hove function (OVHF), an alternative meaning was given to the second-rank OTCF, which is a measure of the deviation of the OVHF between a molecular system and free molecules in random orientations. Indicated by the OVHFs at related time scales, the stretched-exponential decay of the second-rank OTCF resulted from molecules evacuating out of HB cages formed by their neighbors. After the evacuations, the inner molecules relaxed at relatively fast rates toward random orientations, but the interfacial molecules reoriented at slow rates due to restrictions by hydrophobic interactions with graphite walls. The first power-law decay of the second-rank OTCF was attributed to the distinct relaxation rates of inner and interfacial molecules within a graphite nanoslit. When the inner molecules were completely random in orientation, the second-rank OTCFs changed to another power law decay with a power smaller than the first one.

The Influence of Reorientational and Vibrational Dynamics on the Mg2+ Conductivity in Mg(BH4)2·CH3NH2.

Reorientational dynamics in solid electrolytes can significantly enhance the ionic conductivity, and understanding these dynamics can facilitate the rational design of improved solid electrolytes. Additionally, recent investigations on metal hydridoborate-based solid electrolytes have shown that the addition of a neutral ligand can also have a positive effect on the ionic conductivity. In this study, we investigate the dynamics in monomethylamine magnesium borohydride (Mg(BH4)2·CH3NH2) with quasielastic and inelastic neutron scattering, density functional theory calculations, and molecular dynamics simulations. The results suggest that the addition of methylamine significantly speeds up the reorientational frequency of the BH4 - anion compared to Mg(BH4)2. This is likely part of the explanation for the high Mg-ion transport observed for Mg(BH4)2·CH3NH2. Furthermore, while the dynamics of both the BH4 - anion and the CH3 group of the methylamine ligand is rapid, the NH2 group of the methylamine ligand exhibits much slower reorientations, as confirmed by both experimental and computational investigations. Notably, molecular dynamics calculations reveal mean square displacements of 0.387 Å2 for NH2, 1.503 Å2 for CH3, and 1.856 Å2 for BH4 - using a trajectory of 10 ps. This study confirms the simultaneous presence of fast dynamics and high ionic conductivity in a metal borohydride-based system and can function as an experimental foundation for future studies on dynamics in hydrogen-rich solid electrolytes.

Insight into properties of sizable glass former from volumetric measurements.

Sizable glass formers feature numerous unique properties and potential applications, but many questions regarding their glass transition dynamics have not been resolved yet. Here, we have analyzed structural relaxation times measured as a function of temperature and pressure in combination with the equation of state obtained from pressure-volume-temperature measurements. Despite evidence from previous dielectric studies indicating a remarkable sensitivity of supercooled dynamics to compression, and contrary to intuition, our results demonstrated the proof for the almost equivalent importance of thermal energy and free volume fluctuations in controlling reorientation dynamics of sizable molecules. The found scaling exponent γ = 3.0 and Ev/Ep ratio of 0.6 were typical for glass-forming materials with relaxation dynamics determined by both effects with a minor advantage of thermal fluctuations involvement. It shows that the high values of key parameters characterizing the sensitivity of the glass transition dynamics to pressure changes, i.e., activation volume ΔV and dTg/dP, are not a valid premise for a remarkable contribution of volume to glass transition dynamics.

Orientational dynamics of the water layer adjacent to Au surface accelerated by polarization effect.

The orientation and rearrangement of water on a gold electrode significantly influences its physicochemical heterogeneous performance. Despite numerous experimental and theoretical studies aimed at uncovering the structural characteristics of interfacial water, the orientational behavior resulting from electrode-induced rearrangements remains a subject of ongoing debate. Here, we employed molecular dynamics simulations to investigate the adaptive structure and dynamics properties of interfacial water on Au(111) and Au(100) surfaces by considering a polarizable model for Au atoms in comparison with the non-polarizable model. Compared to the nonpolarizable systems, the polarization effect can enhance the interaction between water molecules and the gold surface. Unexpectedly, the rotational dynamics directly associated with the orientational behavior of water adjacent to the gold surface is accelerated, thereby reducing the hydrogen bond lifetime. The underlying mechanism for this anomalous phenomenon originates from the polarization effect, which induces the attraction of the positive hydrogen atoms to the surface by the negative image charge. This leads to a change in orientation that disrupts the hydrogen bonds in the first water layer and subsequently accelerates reorientation dynamics of water molecules adjacent to the gold surface. These results shed light on the intricate interplay between polarization effects and water molecule dynamics on metal surfaces, establishing the foundation for the rational regulation of the orientation of interfacial water.

Range and sensitivity of 17O nuclear spin-lattice relaxation as a probe of aqueous electrolyte dynamics.

The study of electrolytic solutions is of relevance in many research fields, ranging from biophysics, materials, and colloid science to catalysis and electrochemistry. The dependence of solution dynamics on the nature of electrolytes and their concentrations has been the subject of many experimental and computational studies, yet it remains challenging to obtain a full understanding of the factors that govern solution behavior. Here, we provide additional insights into the behavior of aqueous solutions of alkali chlorides by combining 17O relaxation data with diffusion and viscosity data and contrast their behavior with 1H nuclear magnetic resonance relaxation data. The main findings are that 17O relaxation correlates well with viscosity data but not with diffusion data, while 1H relaxation correlates with neither. Certain ionic trends match known ion-specific series behavior, especially at high concentrations. Notably, we also examine the ranges of the interactions and conclude that the majority of the effects are tied to local water reorientation dynamics.

Ionic Conductivity of a Lithium-Doped Deep Eutectic Solvent: Glass Formation and Rotation-Translation Coupling.

Deep eutectic solvents with admixed lithium salts are considered as electrolytes in electrochemical devices, such as batteries or supercapacitors. Compared to eutectic mixtures of hydrogen-bond donors and lithium salts, their raw-material costs are significantly lower. Not much is known about glassy freezing and rotational-translation coupling of such systems. Here, we investigate these phenomena by applying dielectric spectroscopy to the widely studied deep eutectic solvent glyceline, to which 1 and 5 mol % LiCl were added. Our study covers a wide temperature range, including a deeply supercooled state. The temperature dependences of the detected dipolar reorientation dynamics and ionic direct current (dc) conductivity reveal the signatures of glassy freezing. In comparison to pure glyceline, the lithium admixture leads to a reduction of ionic conductivity, which is accompanied by a reduction of the rotational dipolar mobility. However, this reduction is much smaller than that for deep eutectic solvents (DESs), where one main component is lithium salt, which we trace back to the lower glass-transition temperatures of lithium-doped DESs. In contrast to pure glyceline, the ionic and dipolar dynamics become increasingly decoupled at low temperatures and obey a fractional Debye-Stokes-Einstein relation, as previously found in other glass-forming liquids. The obtained results demonstrate the relevance of decoupling effects and glass transition to the enhancement of the technically relevant ionic conductivity in such lithium-doped DESs.

Reorientational Dynamics in Y(BH4)3·xNH3 (x = 0, 3, and 7): The Impact of NH3 on BH4- Dynamics.

The reorientational dynamics of Y(BH4)3·xNH3 (x = 0, 3, and 7) was studied using quasielastic neutron scattering (QENS) and neutron spin echo (NSE). The results showed that changing the number of NH3 ligands drastically alters the reorientational mobility of the BH4- anion. From the QENS experiments, it was determined that the BH4- anion performs 2-fold reorientations around the C2 axis in Y(BH4)3, 3-fold reorientations around the C3 axis in Y(BH4)3·3NH3, and either 2-fold reorientations around the C2 axis or 3-fold reorientations around the C3 axis in Y(BH4)3·7NH3. The relaxation time of the BH4- anion at 300 K decreases from 2 × 10-7 s for x = 0 to 1 × 10-12 s for x = 3 and to 7 × 10-13 s for x = 7. In addition to the reorientational dynamics of the BH4- anion, it was shown that the NH3 ligands exhibit 3-fold reorientations around the C3 axis in Y(BH4)3·3NH3 and Y(BH4)3·7NH3 as well as 3-fold quantum mechanical rotational tunneling around the same axis at 5 K. The new insights constitute a significant step toward understanding the relationship between the addition of ligands and the enhanced ionic conductivity observed in systems such as LiBH4·xNH3 and Mg(BH4)2·xCH3NH2.

Dynamics of Formamide-Water Mixtures Investigated by Linear and Nonlinear Infrared Spectroscopy.

Formamide (FA) exhibits complete miscibility with water, offering a simplified model for exploring the solvation dynamics of peptide linkages in biophysical processes. Its liquid state demonstrates a three-dimensional hydrogen bonding network akin to water, reflecting solvent-like behavior. Analyzing the microscopic structure and dynamics of FA-water mixtures is expected to provide crucial insights into hydrogen bonding dynamics─a key aspect of various biophysical phenomena. This study is focused on the dynamics of FA-water mixtures using linear and femtosecond infrared spectroscopies. By using the intrinsic OD stretch and extrinsic probe SCN-, the local vibrational behaviors across various FA-water compositions were systematically investigated. The vibrational relaxation of OD stretch revealed a negligible impact of FA addition on the vibrational lifetime of water molecules, underscoring the mixture's water-like behavior. However, the reorientational dynamics of OD stretch slowed with increasing FA mole fraction (XFA), plateauing beyond XFA > 0.5. This suggests a correlation between OD's reorientational time and the strength of the hydrogen bond network, likely tied to the solution's changing dielectric constant. Conversely, the vibrational relaxation dynamics of SCN- was strongly correlated with XFA, highlighting a competition between water and FA molecules in solvating SCN-. Moreover, a linear relationship between rising viscosity and the prolonged correlation time of SCN-'s slow dynamics indicates that the solution's macroscopic viscosity is dictated by the extended structures formed between FA and water molecules. The relation between the reorientation dynamics of the SCN- and the macroscopic viscosity in aqueous FA-water mixture solutions was analyzed by using the Stokes-Einstein-Debye equations. The direct viscosity-diffusion coupling is observed, which can be attributed to the homogeneous dynamics feature in FA-water mixture solutions. The inclusion of these intrinsic and extrinsic probes not only enhances the comprehensiveness of our analysis but also provides valuable insights into various aspects of the dynamics within the FA-water system. This investigation sheds light on the fundamental dynamics of FA-water mixtures, emphasizing their molecular-level homogeneity in this binary mixture solution.

Shear rheology senses the electrical room-temperature conductivity optimum in highly Li doped dinitrile electrolytes.

Glutaronitrile (GN) doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) at concentrations below and above the room-temperature conductivity optimum near 1M of Li salt is investigated using dielectric spectroscopy and shear rheology. The experiments are carried out from ambient down to the glass transition temperature Tg, which increases considerably as LiTFSI is admixed to GN. As the temperature is lowered, the conductivity optimum shifts to lower salt concentrations, while the power-law exponents connecting resistivity and molecular reorientation time remain smallest for the 1M composition. By contrast, the rheologically detected time constants, as well as those obtained using dielectric spectroscopy, increase monotonically with increasing Li salt concentration for all temperatures. It is demonstrated that the shear mechanical measurements are, nevertheless, sensitive to the 1M conductivity optimum, thus elucidating the interplay of the dinitrile matrix with the mobile species. The data for the Li doped GN and other nitrile solvents all follow about the same Walden line, in harmony with their highly conductive character. The composition dependent relation between the ionic and the reorientational dynamics is also elucidated.

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents.

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.

The Signature of Fluctuations of the Hydrogen Bond Network Formed by Water Molecules in the Interfacial Layer of Anionic Lipids

As the water molecules found at the interface of lipid bilayers exhibit distinct structural and reorientation dynamics compared to water molecules found in bulk, the fluctuations in their hydrogen bond (HB) network are expected to be different from those generated by the bulk water molecules. The research presented here aims to gain an insight into temperature-dependent fluctuations of a HB network of water molecules found in an interfacial layer of multilamellar liposomes (MLVs) composed of anionic 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine (DMPS) lipids. Besides suspending DMPS lipids in phosphate buffer saline (PBS) of different pH values (6.0, 7.4, and 8.0), the changes in HB network fluctuations were altered by the incorporation of a non-polar flavonoid molecule myricetin (MCE) within the hydrocarbon chain region. By performing a multivariate analysis on the water combination band observed in temperature-dependent FTIR spectra, the results of which were further mathematically analyzed, the temperature-dependent fluctuations of interfacial water molecules were captured; the latter were the greatest for DMPS in PBS with a pH value of 7.4 and in general were greater for DMPS multibilayers in the absence of MCE. The presence of MCE made DMPS lipids more separated, allowing deeper penetration of water molecules towards the non-polar region and their restricted motion that resulted in decreased fluctuations. The experimentally observed results were supported by MD simulations of DMPS (+MCE) lipid bilayers.

In Situ Heterodyne-Detected Second-Harmonic Generation Study of the Influence of Cholesterol on Dye Molecule Adsorption on Lipid Membrane.

Cholesterol plays an essential role in regulating the functionality of biomembranes. This study employed in situ second-harmonic generation (SHG) to investigate the adsorption behavior of the dye molecule 4-(4-(diethylamino)styryl)-N-methyl-pyridinium iodide (D289) on a biomimic membrane composed of 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (DPPG) and cholesterol. The time-dependent polarization SHG intensity exhibited an initial rapid increase, followed by a subsequent decline. The initial increased SHG intensity is responsible for the electrostatic interaction-driven adsorption of D289 onto the membrane, while the decrease in the SHG signal results from the broadening of the orientation distribution within the membrane. Heterodyne-detected SHG (HD-SHG) measurements demonstrated that the adsorption of dye molecules influenced the phase of the induced electric field. The interfacial potential Φ(0) as a function of time was measured, and we found that even after reaching a stable Stern layer state, the diffusion layer continued to exhibit a dynamic change. This study offers a comprehensive understanding of the influence of cholesterol on adsorption, reorientation dynamics, and dynamic changes in the reorientation of water in the diffusion layer.

A comparative study of deep eutectic solvents based on fatty acids and the effect of water on their intermolecular interactions

In this work, intermolecular interactions among the species of fatty acids-based DESs with different hydrogen bond acceptors (HBA) in the adjacent water have been investigated using molecular dynamics (MD) simulation. The results of this work provide deep insights into understanding the water stability of the DESs based on thymol and the eutectic mixtures of choline chloride and fatty acids at a temperature of 353.15 K and atmospheric pressure. Stability, hydrogen bond occupancy analysis, and the distribution of the HBA and HBD around each other were attributed to the alkyl chain length of FAs and the type of HBA. Assessed structural properties include the combined distribution functions (CDFs), the radial distribution functions (RDFs), the angular distribution functions (ADFs), and the Hydrogen bonding network between species and Spatial distribution functions (SDF). The reported results show the remarkable role of the strength of the hydrogen bond between THY molecules and fatty acids on the stability of DES in water. The transport properties of molecules in water–eutectic mixtures were analyzed by using the mean square displacement (MSD) of the centers of mass of the species, self-diffusion coefficients, vector reorientation dynamics (VRD) of bonds and the velocity autocorrelation function (VACF) for the center of the mass of species.

Home field advantage: examining incumbency reorientation dynamics in low-carbon transitions

Recent work has offered a more nuanced view of incumbent actors' roles in transitions, yet a comprehensive understanding of how reorientation activities and subsequent interaction patterns among different incumbent actor types shape the direction of system reconfigurations remains underexplored. This paper proposes a framework for empirically assessing actors' relational dynamics in response to low-carbon transitions and conceptualises actor interaction types and the nature of their interaction. Through a case study of the low-carbon transition of road freight transport in Sweden, we examine how reorientation dynamics, e.g., coalitions, competition, and contestations, can facilitate and hinder system reconfigurations by creating regime tensions. Our study highlights that incumbency reorientations are multi-dimensional, with actor involvement and strategies varying, leading to divergent actor positions and role constellations as actors attempt to reconfigure the focal regime. Extending beyond the Swedish case, five avenues for future research are outlined.

The influence of molecular shape on reorientation dynamics of sizable glass-forming isomers at ambient and elevated pressure

We used dielectric spectroscopy to access the molecular dynamics of three isomers with a structure based on a sizable, partially rigid, and non-polar core connected to a polar phenylene unit differing in the position of the polar group, and, consequently, the direction and magnitude of the dipole moment to address the question how unique molecular properties, in particular large size and elongated shape, affect the dynamics. The position of the polar group differentiates the molecular shape and isomer’s anisotropy and leads to different thermal and dynamic properties of the isomers. The shape of permittivity loss spectra was governed by magnitudes of the longitudinal and transverse components of dipole moment to a large extent. For para isomer with negligible traverse component of dipole moment, the narrowest loss peak was found while for meta isomer, the bimodal loss peak was observed at high temperatures. Its shape evolved on cooling limiting the possibility of individual mode separation near glass transition where the dynamics were more cooperative. High-pressure dielectric studies showed that sizable isomers were characterized by the pronounced sensitivity of glass transition temperature, Tg, to compression. Observed high activation volumes, such as 735 cm3/mol at Tg for para isomer, were found to correlate with the length scale of dynamic cooperativity. The number of dynamically correlated molecules depended on molecular shape and varied among isomers while the determined values were much smaller than that reported for other glass-forming liquids. We discussed here the obtained results in the context of the specific properties of the systems studied showing the overriding role of anisotropy.

Atomic Structure and Dynamics of Organic-Inorganic Hybrid Perovskite Formamidinium Lead Iodide.

The atomic dynamic behaviors of formamidinium lead iodide [HC(NH2)2PbI3] are critical for understanding and improving photovoltaic performances. However, they remain unclear. Here, we investigate the structural phase transitions and the reorientation dynamics of the formamidinium cation [HC(NH2)2+, FA+] of FAPbI3 using neutron scattering techniques. Two structural phase transitions occur with decreasing temperature, from cubic to tetragonal phase at 285 K and then to another tetragonal at 140 K, accompanied by gradually frozen reorientation of FA cations. The nearly isotropic reorientation in the cubic phase is suppressed to reorientation motions involving a two-fold (C2) rotation along the N···N axis and a four-fold (C4) rotation along the C-H axis in the tetragonal phase, and eventually to local disordered motion as a partial C4 along the C-H axis in another tetragonal phase, thereby indicating an intimate interplay between lattice and orientation degrees of freedom in the hybrid perovskite materials. The present complete atomic structure and dynamics provide a solid standing point to understand and then improve photovoltaic properties of organic-inorganic hybrid perovskites in the future.

Pathway dynamics to double-cell premixed flames in lean hydrogen–air mixtures

The propagation of premixed flames over lean hydrogen–air mixtures have been found to be bistable in recent studies, considering slender channels with non-negligible conductive heat losses. In particular, two stable configurations conformed by either a circular or a double-cell flame front arise for the same combination of controlling parameters (fuel mixture, channel size and thermal conductivity). Nevertheless, this multiplicity of solutions lacks a satisfactory explanation to predict the formation of either one structure or the other during a particular ignition transient. In this work, detailed analyses are performed over the unsteady evolution of a set of numerical simulations. Specifically, the initial temperature profiles (distribution and peak value) and subsequent expansion of the flow field prescribe the early growth of the flame front leading to different curvatures and sizes of the kernel that control the evolution into each of the canonical structures. This study explores the underlying physics controlling the final-stage bistable behavior. In particular, the local convective effects and interactions between fronts have been identified as the key causes to produce each of the two stably propagating flames. Frequently found division of kernels cannot ensure the formation of double cells, which require additional reorientation dynamics and merging events due to asymmetric seeding of flame fragments or to interaction with neighboring structures.