scholarly journals The entropic bond in colloidal crystals

2019 ◽  
Vol 116 (34) ◽  
pp. 16703-16710 ◽  
Author(s):  
Eric S. Harper ◽  
Greg van Anders ◽  
Sharon C. Glotzer
Keyword(s):  
Chemical Bonding ◽  
Minimal Model ◽  
Colloidal Crystals ◽  
Particle Systems ◽  
Chemical Bonds ◽  
Hard Particle ◽  
Natural Phenomena ◽  
Vast Array ◽  
Colloidal Crystallization ◽  
Hexagonal Nanoplates

A vast array of natural phenomena can be understood through the long-established schema of chemical bonding. Conventional chemical bonds arise through local gradients resulting from the rearrangement of electrons; however, it is possible that the hallmark features of chemical bonding could arise through local gradients resulting from nonelectronic forms of mediation. If other forms of mediation give rise to “bonds” that act like conventional ones, recognizing them as bonds could open new forms of supramolecular descriptions of phenomena at the nano- and microscales. Here, we show via a minimal model that crowded hard-particle systems governed solely by entropy exhibit the hallmark features of bonding despite the absence of chemical interactions. We quantitatively characterize these features and compare them to those exhibited by chemical bonds to argue for the existence of entropic bonds. As an example of the utility of the entropic bond classification, we demonstrate the nearly equivalent tradeoff between chemical bonds and entropic bonds in the colloidal crystallization of hard hexagonal nanoplates.

GROWTH OF COLLOIDAL CRYSTALS UNDER MICROGRAVITY

2002 ◽  
Vol 16 (01n02) ◽  
pp. 338-345 ◽  
Author(s):  
M. ISHIKAWA ◽  
H. MORIMOTO ◽  
T. OKUBO ◽  
T. MAEKAWA
Keyword(s):  
Fractal Dimension ◽  
Power Law ◽  
Brownian Dynamics ◽  
Normal Gravity ◽  
Colloidal Crystals ◽  
Growth Dynamics ◽  
Sounding Rocket ◽  
Microgravity Experiment ◽  
Colloidal Crystallization ◽  
Number Of Particles

The growth dynamics of colloidal crystallization was evaluated under sedimentation free conditions using sounding rocket and Brownian Dynamics (BD) simulation. The Bragg's reflections of colloidal crystals were measured during microgravity flight and average sizes of crystallites were obtained by the Sherrer's method. Results showed a power-law relationship between size and time, L ∝ tα where L is the size of crystallites and t is time. The obtained α s were 0.33 ± 0.03 in microgravity and 0.25 ± 0.02 in normal gravity, respectively. Browninan Dynamics (BD) simulation showed the time evolution of ordered domains that consisted of connected structures of crystalline clusters. The power law relationship n ∝ t0.5 in post-nucleation period was confirmed between the number of particles (n) in clusters and time. The calculated power was related to α using the fractal dimension of crystalline clusters and α = 0.31 was obtained. The value was matched well with that of the microgravity experiment.

scholarly journals Convenient and Efficient Fabrication of Colloidal Crystals Based on Solidification-Induced Colloidal Assembly

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 575 ◽  
Author(s):  
Ting Shao ◽  
Laixi Sun ◽  
Chun Yang ◽  
Xin Ye ◽  
Shufan Chen ◽  
...  
Keyword(s):  
Driving Force ◽  
Crystallization Process ◽  
Colloidal Crystal ◽  
Colloidal Crystals ◽  
Magnetic Interaction ◽  
Colloidal Assembly ◽  
Water Suspension ◽  
Colloidal Crystallization ◽  
New Strategy ◽  
Crystal Grains

The simple yet efficient and versatile fabrication of colloidal crystals was investigated based on the solidification-induced colloidal crystallization process with particle/water suspension as precursor. The resulting colloidal crystals were constituted by crystal grains with sizes ranging from several tens of micrometers to a few millimeters. Each of the grains had a close-hexagonal array of colloids, which endowed the bulk colloidal crystal powders with some specific optical properties. The freezing of water was shown as the major driving force to form colloidal crystal grains, which supersaturated the solution with nanoparticles and thus induced the formation and growth of colloidal crystal seeds. This process is intrinsically different from those conventional methods based on shearing force, surface tension, columbic interaction or magnetic interaction, revealing a new strategy to fabricate colloidal crystals in a convenient and efficient way.

scholarly journals Relevance of packing to colloidal self-assembly

2018 ◽  
Vol 115 (7) ◽  
pp. 1439-1444 ◽  
Author(s):  
Rose K. Cersonsky ◽  
Greg van Anders ◽  
Paul M. Dodd ◽  
Sharon C. Glotzer
Keyword(s):  
Crystal Structures ◽  
Self Assembly ◽  
Colloidal Crystals ◽  
Causal Mechanism ◽  
Hard Particle ◽  
Self Assembled ◽  
Particle Shapes ◽  
The Ideal

Since the 1920s, packing arguments have been used to rationalize crystal structures in systems ranging from atomic mixtures to colloidal crystals. Packing arguments have recently been applied to complex nanoparticle structures, where they often, but not always, work. We examine when, if ever, packing is a causal mechanism in hard particle approximations of colloidal crystals. We investigate three crystal structures composed of their ideal packing shapes. We show that, contrary to expectations, the ordering mechanism cannot be packing, even when the thermodynamically self-assembled structure is the same as that of the densest packing. We also show that the best particle shapes for hard particle colloidal crystals at any finite pressure are imperfect versions of the ideal packing shape.

CHEMICAL BONDS AND ELECTRONIC STRUCTURES OF THE METHONIUM CATIONS ${\rm CH}_{6}^{2+}$ AND ${\rm CH}_{7}^{3+}$

2008 ◽  
Vol 07 (01) ◽  
pp. 139-156 ◽  
Author(s):  
HAI BEI LI ◽  
SHAN XI TIAN
Keyword(s):  
Chemical Bonding ◽  
Electronic Structures ◽  
Natural Bond Orbital ◽  
Chemical Bonds ◽  
Global Minima ◽  
Resonance Theory ◽  
Resonance Structures ◽  
The Common ◽  
High Possibility ◽  
Hydrogen Scrambling

Six isomers with C2v, D3h, C5v, D2d, Oh, and C4v symmetries of [Formula: see text] and two isomers with C3v and C2v symmetries of [Formula: see text] are investigated at the high ab initio level combined with the natural bond orbital and the atoms-in-molecules theorems. The hyperconjugative interaction and the electron topological analyses indicate that the multiple three-center two-electron (3c-2e) hyperbond is the common chemical-bonding basis for [Formula: see text] and [Formula: see text] species. In contrast to the planar 3c-2e (triangle structure) and planar four-center four-electron (4c-4e) hyperbonds in [Formula: see text] isomeric species, the 3c-2e hyperbond in [Formula: see text] (C4v) is linear while the 4c-4e hyperbonds in [Formula: see text] (C5v, D2d, Oh) are unplanar. [Formula: see text] (C2v) and [Formula: see text] (C3v) as the global minima have many resonance structures predicted by the natural bond resonance theory, indicating the high possibility of the hydrogen scrambling which is similar to the scenario of [Formula: see text].

scholarly journals Interaction Region Indicator (IRI): A Very Simple Real Space Function Clearly Revealing Both Chemical Bonds and Weak Interactions

2021 ◽  
Author(s):  
Tian Lu ◽  
qinxue chen
Keyword(s):  
Weak Interaction ◽  
Chemical Bonding ◽  
Computational Cost ◽  
Interaction Strength ◽  
Real Space ◽  
Interaction Region ◽  
Chemical System ◽  
Chemical Bonds ◽  
Space Function ◽  
Interaction Regions

Graphically revealing interaction regions in a chemical system enables chemists to notice the areas at a glance where significant interactions have formed, it is very helpful in studying chemical bonds, intermolecular and intramolecular interactions. Reduced density gradient (RDG) has already been widely employed in literatures to visually exhibit weak interaction regions, in fact it also has the ability of revealing chemical bonding regions. Unfortunately, RDG cannot clearly show both types of the interactions at the same time. In this paper, we propose a new real space function named interaction region indicator (IRI), which is a slight modification on RDG. We found IRI can reveal chemical bonding and weak interaction regions equally well, this brings great convenience in the study of various chemical systems as well as chemical reactions. It is noteworthy that IRI has simpler definition, lower computational cost and better graphical effect than the density overlap regions indicator (DORI), which has similar purpose to IRI. In this article IRI is also compared with atom-in-molecules (AIM) topology analysis of electron density, we demonstrated that IRI has the ability to reveal additional interactions to provide chemists a more complete picture. In addition, we put forward a variant of IRI named IRI-pi, which is dedicated to reveal interactions of pi electrons. It is found that IRI-pi can not only distinguish type of pi interactions but can also exhibit pi-interaction strength. IRI and IRI-pi have been efficiently implemented in our freely available Multiwfn wavefunction analysis code, it is expected that they will become new useful members of computational chemists' toolbox in studying chemical problems.

An Avoidance Model for Short-Range Order Induced by Soft Repulsions in Systems of Rigid Rods

1996 ◽  
Vol 463 ◽  
Author(s):  
Jining Han ◽  
Judith Herzfeld
Keyword(s):  
Short Range ◽  
Short Range Order ◽  
Mean Field ◽  
Axial Ratio ◽  
Field Approximation ◽  
Particle Systems ◽  
Range Order ◽  
Mean Field Approximation ◽  
Hard Particle ◽  
Rigid Rods

ABSTRACTThe effects of soft repulsions on hard particle systems are calculated using an avoidance model which improves upon the simple mean field approximation. The method not only yields a better free energy, but also gives an estimate for the short-range positional order induced by soft repulsions. The results indicate little short-range order for isotropically oriented rods. However, for parallel rods short-range order increases to significant levels as the particle axial ratio increases.

scholarly journals Simulations of Transport in Hard Particle Systems

2020 ◽  
Vol 180 (1-6) ◽  
pp. 474-533
Author(s):  
Pablo I. Hurtado ◽  
Pedro L. Garrido
Keyword(s):  
Particle Systems ◽  
Hard Particle
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