Site controlled nucleation of ferroelectric crystals: a step towards lithography modulated self-assembly

2003 ◽  
Vol 784 ◽  
Author(s):  
P. Muralt ◽  
S. Bühlmann ◽  
S. Von Allmen
Keyword(s):  
Single Crystal ◽  
Self Assembly ◽  
Nucleation Theory ◽  
Piezoelectric Response ◽  
Classical Nucleation Theory ◽  
Narrow Size Distribution ◽  
Controlled Nucleation ◽  
Additive Technique ◽  
Nm Range ◽  
Ferroelectric Switching

ABSTRACTAn additive technique for the growth of PZT crystallites in the sub-200 nm range on predefined sites is presented. The method is based on nucleation promotion by TiO2 seeds. Epitaxial (111)-oriented Pt on a SrTiO3 single crystal served as substrate. TiO2 seed sites have been defined by an e-beam lithographic process. The initial Pb flux determines whether (100) or (111) crystallites are obtained. Best results have been obtained with PZT(100) yielding one square grain per site with a narrow size distribution (120 to 150 nm). In this case, the seed collected additional PbO adatoms reaching the seed by diffusion. The sidewalls consist mostly of {110} facets. A model in the frame of classical nucleation theory describes well experimental observations. The piezoelectric response and the ferroelectric switching of the structures have been verified.

A simple model of burst nucleation

2015 ◽  
Vol 17 (32) ◽  
pp. 20846-20852 ◽  
Author(s):  
Alexandr Baronov ◽  
Kevin Bufkin ◽  
Dan W. Shaw ◽  
Brad L. Johnson ◽  
David L. Patrick
Keyword(s):  
Simple Model ◽  
Induction Period ◽  
Rate Equation ◽  
Self Assembly ◽  
Mean Field ◽  
Equation Model ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Rate Equation Model ◽  
Quantitative Treatment

We introduce a comprehensive quantitative treatment for burst nucleation (BN), a kinetic pathway toward self-assembly or crystallization defined by an extended post-supersaturation induction period, followed by a burst of nucleation, and finally the growth of existing stable assemblages absent the formation of new ones, based on a hybrid mean field rate equation model incorporating thermodynamic treatment of the saturated solvent from classical nucleation theory.

scholarly journals Robust nonequilibrium pathways to microcompartment assembly

2018 ◽  
Vol 115 (25) ◽  
pp. 6341-6346 ◽  
Author(s):  
Grant M. Rotskoff ◽  
Phillip L. Geissler
Keyword(s):  
Mathematical Model ◽  
Stable Equilibrium ◽  
Molecular Model ◽  
Elastic Shell ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Narrow Size Distribution ◽  
Viral Capsids ◽  
Size And Shape ◽  
Self Assembling

Cyanobacteria sequester photosynthetic enzymes into microcompartments which facilitate the conversion of carbon dioxide into sugars. Geometric similarities between these structures and self-assembling viral capsids have inspired models that posit microcompartments as stable equilibrium arrangements of the constituent proteins. Here we describe a different mechanism for microcompartment assembly, one that is fundamentally nonequilibrium and yet highly reliable. This pathway is revealed by simulations of a molecular model resolving the size and shape of a cargo droplet and the extent and topography of an elastic shell. The resulting metastable microcompartment structures closely resemble those of carboxysomes, with a narrow size distribution and faceted shells. The essence of their assembly dynamics can be understood from a simpler mathematical model that combines elements of classical nucleation theory with continuum elasticity. These results highlight important control variables for achieving nanoscale encapsulation in general and for modulating the size and shape of carboxysomes in particular.

scholarly journals Consistency and variability of cocrystals containing positional isomers: the self-assembly evolution mechanism of supramolecular synthons of cresol–piperazine

IUCrJ ◽  
2019 ◽  
Vol 6 (6) ◽  
pp. 1064-1073 ◽  
Author(s):  
Na Wang ◽  
Xin Huang ◽  
Lihang Chen ◽  
Jinyue Yang ◽  
Xin Li ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Functional Groups ◽  
Self Assembly ◽  
Weak Interactions ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Positional Isomers ◽  
Supramolecular Synthon ◽  
Supramolecular Synthons ◽  
Assembly Mechanism

The disposition of functional groups can induce variations in the nature and type of interactions and hence affect the molecular recognition and self-assembly mechanism in cocrystals. To better understand the formation of cocrystals on a molecular level, the effects of disposition of functional groups on the formation of cocrystals were systematically and comprehensively investigated using cresol isomers (o-, m-, p-cresol) as model compounds. Consistency and variability in these cocrystals containing positional isomers were found and analyzed. The structures, molecular recognition and self-assembly mechanism of supramolecular synthons in solution and in their corresponding cocrystals were verified by a combined experimental and theoretical calculation approach. It was found that the heterosynthons (heterotrimer or heterodimer) combined with O—H...N hydrogen bonding played a significant role. Hirshfeld surface analysis and computed interaction energy values were used to determine the hierarchical ordering of the weak interactions. The quantitative analyses of charge transfers and molecular electrostatic potential were also applied to reveal and verify the reasons for consistency and variability. Finally, the molecular recognition, self-assembly and evolution process of the supramolecular synthons in solution were investigated. The results confirm that the supramolecular synthon structures formed initially in solution would be carried over to the final cocrystals, and the supramolecular synthon structures are the precursors of cocrystals and the information memory of the cocrystallization process, which is evidence for classical nucleation theory.

scholarly journals Exploiting classical nucleation theory for reverse self-assembly

2010 ◽  
Vol 133 (23) ◽  
pp. 234108 ◽  
Author(s):  
William L. Miller ◽  
Angelo Cacciuto
Keyword(s):  
Self Assembly ◽  
Nucleation Theory ◽  
Classical Nucleation Theory

scholarly journals On the mechanism of solid-state phase transitions in molecular crystals – the role of cooperative motion in (quasi)racemic linear amino acids

IUCrJ ◽  
2020 ◽  
Vol 7 (2) ◽  
pp. 331-341 ◽  
Author(s):  
M. M. H. Smets ◽  
E. Kalkman ◽  
A. Krieger ◽  
P. Tinnemans ◽  
H. Meekes ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Solid State ◽  
Single Crystal ◽  
Linear Chain ◽  
Molecular Crystals ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Stable Form ◽  
Extensive Literature ◽  
Cooperative Motion

During single-crystal-to-single-crystal (SCSC) phase transitions, a polymorph of a compound can transform to a more stable form while remaining in the solid state. By understanding the mechanism of these transitions, strategies can be developed to control this phenomenon. This is particularly important in the pharmaceutical industry, but also relevant for other industries such as the food and agrochemical industries. Although extensive literature exists on SCSC phase transitions in inorganic crystals, it is unclear whether their classications and mechanisms translate to molecular crystals, with weaker interactions and more steric hindrance. A comparitive study of SCSC phase transitions in aliphatic linear-chain amino acid crystals, both racemates and quasi-racemates, is presented. A total of 34 transitions are considered and most are classified according to their structural change during the transition. Transitions without torsional changes show very different characteristics, such as transition temperature, enthalpy and free energy, compared with transitions that involve torsional changes. These differences can be rationalized using classical nucleation theory and in terms of a difference in mechanism; torsional changes occur in a molecule-by-molecule fashion, whereas transitions without torsional changes involve cooperative motion with multiple molecules at the same time.

scholarly journals Phase-field modeling of grain evolutions in additive manufacturing from nucleation, growth, to coarsening

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Min Yang ◽  
Lu Wang ◽  
Wentao Yan
Keyword(s):  
Additive Manufacturing ◽  
Phase Field ◽  
Field Model ◽  
Three Dimensional ◽  
Phase Field Model ◽  
Nucleation Theory ◽  
Experimental Result ◽  
Classical Nucleation Theory ◽  
Validation Experiment ◽  
Powder Particles

AbstractA three-dimensional phase-field model is developed to simulate grain evolutions during powder-bed-fusion (PBF) additive manufacturing, while the physically-informed temperature profile is implemented from a thermal-fluid flow model. The phase-field model incorporates a nucleation model based on classical nucleation theory, as well as the initial grain structures of powder particles and substrate. The grain evolutions during the three-layer three-track PBF process are comprehensively reproduced, including grain nucleation and growth in molten pools, epitaxial growth from powder particles, substrate and previous tracks, grain re-melting and re-growth in overlapping zones, and grain coarsening in heat-affected zones. A validation experiment has been carried out, showing that the simulation results are consistent with the experimental results in the molten pool and grain morphologies. Furthermore, the grain refinement by adding nanoparticles is preliminarily reproduced and compared against the experimental result in literature.

scholarly journals On the Role of Poly-Glutamic Acid in the Early Stages of Iron(III) (Oxy)(hydr)oxide Formation

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 715
Author(s):  
Miodrag J. Lukić ◽  
Felix Lücke ◽  
Teodora Ilić ◽  
Katharina Petrović ◽  
Denis Gebauer
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Phase Separation ◽  
Fourier Transform Infrared Spectroscopy ◽  
Fourier Transform Infrared ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Oxide Formation ◽  
Early Stages ◽  
Titration Assay

Nucleation of minerals in the presence of additives is critical for achieving control over the formation of solids in biomineralization processes or during syntheses of advanced hybrid materials. Herein, we investigated the early stages of Fe(III) (oxy)(hydr)oxide formation with/without polyglutamic acid (pGlu) at low driving force for phase separation (pH 2.0 to 3.0). We employed an advanced pH-constant titration assay, X-ray diffraction, thermal analysis with mass spectrometry, Fourier Transform infrared spectroscopy, and scanning electron microscopy. Three stages were observed: initial binding, stabilization of Fe(III) pre-nucleation clusters (PNCs), and phase separation, yielding Fe(III) (oxy)(hydr)oxide. The data suggest that organic–inorganic interactions occurred via binding of olation Fe(III) PNC species. Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed a plausible interaction motif and a conformational adaptation of the polypeptide. The stabilization of the aqueous Fe(III) system against nucleation by pGlu contrasts with the previously reported influence of poly-aspartic acid (pAsp). While this is difficult to explain based on classical nucleation theory, alternative notions such as the so-called PNC pathway provide a possible rationale. Developing a nucleation theory that successfully explains and predicts distinct influences for chemically similar additives like pAsp and pGlu is the Holy Grail toward advancing the knowledge of nucleation, early growth, and structure formation.

scholarly journals An Analysis of Acoustic Cavitation Thresholds of Water Based on the Incubation Time Criterion Approach

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 134
Author(s):  
Ivan Smirnov ◽  
Natalia Mikhailova
Keyword(s):  
Incubation Time ◽  
Dynamic Strength ◽  
Acoustic Cavitation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Accurate Estimation ◽  
Ultrasound Frequency ◽  
Time Criterion ◽  
Good Potential ◽  
Cavitation Threshold

Researchers are still working on the development of models that facilitate the accurate estimation of acoustic cavitation threshold. In this paper, we have analyzed the possibility of using the incubation time criterion to calculate the threshold of the onset of acoustic cavitation depending on the ultrasound frequency, hydrostatic pressure, and temperature of a liquid. This criterion has been successfully used by earlier studies to calculate the dynamic strength of solids and has recently been proposed in an adapted version for calculating the cavitation threshold. The analysis is carried out for various experimental data for water presented in the literature. Although the criterion assumes the use of macroparameters of a liquid, we also considered the possibility of taking into account the size of cavitation nuclei and its influence on the calculation result. We compared the results of cavitation threshold calculations done using the incubation time criterion of cavitation and the classical nucleation theory. Our results showed that the incubation time criterion more qualitatively models the results of experiments using only three parameters of the liquid. We then discussed a possible relationship between the parameters of the two approaches. The results of our study showed that the criterion under consideration has a good potential and can be conveniently used for applications where there are special requirements for ultrasound parameters, maximum negative pressure, and liquid temperature.

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