Twist renormalization in molecular crystals driven by geometric frustration

Soft Matter ◽  
2019 ◽  
Vol 15 (1) ◽  
pp. 116-126 ◽  
Author(s):  
Asaf Haddad ◽  
Hillel Aharoni ◽  
Eran Sharon ◽  
Alexander G. Shtukenberg ◽  
Bart Kahr ◽  
...  
Keyword(s):  
Molecular Crystals ◽  
Length Scales ◽  
Size Dependent ◽  
Geometric Frustration

Geometric frustration provides a path for conveying twist across length scales and for producing size dependent twist in macroscopic assemblies, thus shining a light on the formation of twisted molecular crystals.

scholarly journals Size-dependent elastic/inelastic behavior of enamel over millimeter and nanometer length scales

Biomaterials ◽  
2010 ◽  
Vol 31 (7) ◽  
pp. 1955-1963 ◽  
Author(s):  
Siang Fung Ang ◽  
Emely L. Bortel ◽  
Michael V. Swain ◽  
Arndt Klocke ◽  
Gerold A. Schneider
Keyword(s):  
Inelastic Behavior ◽  
Length Scales ◽  
Size Dependent

scholarly journals Recognition-Control and Host-Guest Interactions in High-Symmetry Cocrystals of Fullerenes with Cubane and Mesitylene

2020 ◽  
Author(s):  
Gábor Bortel ◽  
Éva Kováts ◽  
Dávid Földes ◽  
Emma Jakab ◽  
Gábor Durkó ◽  
...  
Keyword(s):  
Structure Determination ◽  
Molecular Crystals ◽  
High Symmetry ◽  
New Materials ◽  
Size Dependent ◽  
Limited Success ◽  
Global Phase Diagrams ◽  
Molecule Interactions ◽  
The Stability

The limited success in the prediction of structure is one of the most serious problems in the engineering of molecular crystals. Here we show that the packing of high-symmetry molecules such as ball-shaped rotating fullerenes, cube-shaped cubane and octahedral-shaped mesitylene dimers give rise to the formation of cubic cocrystals with easily predictable lattice parameters. We present the synthesis and structure determination of Sc3N@C80-Ih cocrystals with cubane (C8H8) and mesitylene (C9H12) and compare the new materials with related C60 and C70 based structures. In this family of materials, most atom-to-atom interactions are averaged out by the symmetry and the crystal structures can be described in terms of classical molecule-to-molecule interactions. Size-dependent homo- and heteromolecular contacts control the stability of the ball-cube and ball-octahedron systems creating several host-guest and recognition-controlled regions. The analysis of the global phase diagrams explains not only the stability of the observed materials, but also the instability of a missing derivative.

scholarly journals Recognition-Control and Host-Guest Interactions in High-Symmetry Cocrystals of Fullerenes with Cubane and Mesitylene

2020 ◽  
Author(s):  
Gábor Bortel ◽  
Éva Kováts ◽  
Dávid Földes ◽  
Emma Jakab ◽  
Gábor Durkó ◽  
...  
Keyword(s):  
Structure Determination ◽  
Molecular Crystals ◽  
High Symmetry ◽  
New Materials ◽  
Size Dependent ◽  
Limited Success ◽  
Global Phase Diagrams ◽  
Molecule Interactions ◽  
The Stability

The limited success in the prediction of structure is one of the most serious problems in the engineering of molecular crystals. Here we show that the packing of high-symmetry molecules such as ball-shaped rotating fullerenes, cube-shaped cubane and octahedral-shaped mesitylene dimers give rise to the formation of cubic cocrystals with easily predictable lattice parameters. We present the synthesis and structure determination of Sc3N@C80-Ih cocrystals with cubane (C8H8) and mesitylene (C9H12) and compare the new materials with related C60 and C70 based structures. In this family of materials, most atom-to-atom interactions are averaged out by the symmetry and the crystal structures can be described in terms of classical molecule-to-molecule interactions. Size-dependent homo- and heteromolecular contacts control the stability of the ball-cube and ball-octahedron systems creating several host-guest and recognition-controlled regions. The analysis of the global phase diagrams explains not only the stability of the observed materials, but also the instability of a missing derivative.

A micromechanics-based constitutive model for nanocrystalline shape memory alloys incorporating grain size effects

2021 ◽  
pp. 1045389X2110282
Author(s):  
Xiang Zhu ◽  
Guansuo Dui ◽  
Yicong Zheng
Keyword(s):  
Grain Size ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Size Effects ◽  
Boundary Phase ◽  
Length Scale ◽  
Internal Length ◽  
Length Scales ◽  
Size Dependent ◽  
Grain Size Effects

A micromechanics-based model is developed to capture the grain-size dependent superelasticity of nanocrystalline shape memory alloys (SMAs). Grain-size effects are incorporated in the proposed model through definition of dissipative length scale and energetic length scale parameters. In this paper, nanocrystalline SMAs are considered as two-phase composites consisting of the grain-core phase and the grain-boundary phase. Based on the Gibbs free energy including the spatial gradient of the martensite volume fraction, a new transformation function determining the evolution law for transformation strain is derived. Using micromechanical averaging techniques, the grain-size-dependent superelastic behavior of nanocrystalline SMAs can be described. The internal length scales are calibrated using experimental results from published literature. In addition, model validation is performed by comparing the model predictions with the corresponding experimental data on nanostructured NiTi polycrystalline SMA. Finally, effects of the internal length scales on the critical stresses for forward and reverse transformations, the hysteresis loop area (transformation dissipation energy), and the strain hardening are investigated.

A Hierarchical Framework for Thermal Modelling of Electronic Devices: From Atoms to Chips

2013 ◽  
Author(s):  
David A. Romero ◽  
Elham Pakseresht ◽  
Daniel Sellan ◽  
Aydin Nabovati ◽  
Cristina Amon
Keyword(s):  
Thermal Transport ◽  
Electronic Devices ◽  
Thermal Conductance ◽  
Logic Gates ◽  
Silicon Films ◽  
Thermal Modelling ◽  
Length Scales ◽  
Energy Carriers ◽  
Size Dependent ◽  
Functional Block

In this work, we provide an overview of a hierarchical computational framework to predict thermal transport in electronic devices through integration of physics-based models at different length scales. Information from atomistic simulations at the smallest length scales are transferred to upper levels of the hierarchy, up to thermal models for the chip. The proposed methodology includes five levels of length scales in electronic devices, namely (i) atomistic level, (ii) thin film and nanowire level, (iii) transistor and logic gate level, (iv) functional block level, and (v) chip level. At the first level of the hierarchy, properties of energy carriers in a semiconductor material (e.g., phonons) are obtained from atomistic level simulations, such as Molecular Dynamics (MD) and Lattice Dynamics (LD) calculations. At the second level, thermal transport in thin silicon films is modelled using a Lattice Boltzmann Method (LBM) for phonons. The outcome of these simulations is a size-dependent thermal conductivity for silicon films. At the third level of the hierarchy, these effective thermal conductivities are used in thermal modelling of logic gates. Detailed structures of different types of logic gates are reconstructed based on different manufacturing technologies (MOSFET and FinFET) at different technology nodes. Since the characteristic sizes of different parts of the logic gates are comparable to the mean free path of energy carriers, we use the size-dependent, effective thermal conductivities that were calculated at lower levels of the hierarchy to build simulation models for the logic gates. Based on these models, we calculate an equivalent thermal conductance for the logic gates, which would then be used in the upper level simulations to determine an equivalent thermal conductance for different functional blocks of the die based on their internal structure and the number and type of logic gates found in each functional block. Overall, the proposed hierarchical model enables us to include the effect of atomistic-level physics into package-level simulations, and thus, have an accurate prediction of thermal transport in an electronic device.

scholarly journals Self-Assembly in Materials Synthesis

MRS Bulletin ◽  
2005 ◽  
Vol 30 (10) ◽  
pp. 700-704 ◽  
Author(s):  
Matthew V. Tirrell ◽  
Alexander Katz
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
Molecular Crystals ◽  
Building Blocks ◽  
Materials Synthesis ◽  
Length Scales ◽  
Organic Molecular Crystals ◽  
Introductory Article ◽  
Small Building ◽  
Synthesis Of Materials

AbstractThe synthesis of materials via self-assembly typically involves the spontaneous and reversible organization of small building blocks for the purpose of creating conglomerate structures over larger length scales. This introductory article describes self-assembly processes on several length scales, from subnanometer up to millimeter scales, and briefly summarizes some of the incredible diversity of materials that exhibit selfassembly. Articles in this issue cover self-assembly using zeolitic structures, organic molecular crystals, block copolymers, surfactants, mesoscale templates, and soluble crystallization additives. Keywords: block copolymers, materials synthesis, self-assembly, surfactants, templates, zeolites.

Production and STEM examination of controlled-size silver clusters

1983 ◽  
Vol 41 ◽  
pp. 338-339
Author(s):  
M. A. Listvan ◽  
R. P. Andres
Keyword(s):  
Cluster Size ◽  
Metal Clusters ◽  
Experimental Parameter ◽  
Carbon Films ◽  
Metal Species ◽  
Silver Clusters ◽  
Free Jet ◽  
Size Dependent ◽  
Cluster Properties ◽  
Controllable Size

Knowledge of the function and structure of small metal clusters is one goal of research in catalysis. One important experimental parameter is cluster size. Ideally, one would like to produce metal clusters of regulated size in order to characterize size-dependent cluster properties.A source has been developed which is capable of producing microscopic metal clusters of controllable size (in the range 5-500 atoms) This source, the Multiple Expansion Cluster Source, with a Free Jet Deceleration Filter (MECS/FJDF) operates as follows. The bulk metal is heated in an oven to give controlled concentrations of monomer and dimer which were expanded sonically. These metal species were quenched and condensed in He and filtered to produce areosol particles of a controlled size as verified by mass spectrometer measurements. The clusters were caught on pre-mounted, clean carbon films. The grids were then transferred in air for microscopic examination. MECS/FJDF was used to produce two different sizes of silver clusters for this study: nominally Ag6 and Ag50.

Transfer Technique for Electron Microscopy of Membrance Filter Samples

1974 ◽  
Vol 32 ◽  
pp. 554-555
Author(s):  
Lawrence W. Ortiz ◽  
Bonnie L. Isom
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Pore Size ◽  
Membrane Filters ◽  
Size Dependent

A procedure is described for the quantitative transfer of fibers and particulates collected on membrane filters to electron microscope (EM) grids. Various Millipore MF filters (Millipore AA, HA, GS, and VM; 0.8, 0.45, 0.22 and 0.05 μm mean pore size) have been used with success. Observed particle losses have not been size dependent and have not exceeded 10%. With fibers (glass or asbestos) as the collected media this observed loss is approximately 3%.

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