scholarly journals Identification of Local Structure in 2-D and 3-D Atomic Systems through Crystallographic Analysis

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1008
Author(s):  
Pablo Miguel Ramos ◽  
Miguel Herranz ◽  
Katerina Foteinopoulou ◽  
Nikos Ch. Karayiannis ◽  
Manuel Laso
Keyword(s):  
Local Structure ◽  
Point Group ◽  
Local Symmetry ◽  
Crystallographic Analysis ◽  
Three Dimensions ◽  
Group Symmetry ◽  
Spherical Particles ◽  
Specific Reference ◽  
Face Centered Cubic ◽  
Face Centered

In the present work, we revise and extend the Characteristic Crystallographic Element (CCE) norm, an algorithm used to simultaneously detect radial and orientational similarity of computer-generated structures with respect to specific reference crystals and local symmetries. Based on the identification of point group symmetry elements, the CCE descriptor is able to gauge local structure with high precision and finely distinguish between competing morphologies. As test cases we use computer-generated monomeric and polymer systems of spherical particles interacting with the hard-sphere and square-well attractive potentials. We demonstrate that the CCE norm is able to detect and differentiate, between others, among: hexagonal close packed (HCP), face centered cubic (FCC), hexagonal (HEX) and body centered cubic (BCC) crystals as well as non-crystallographic fivefold (FIV) local symmetry in bulk 3-D systems; triangular (TRI), square (SQU) and honeycomb (HON) crystals, as well as pentagonal (PEN) local symmetry in thin films of one-layer thickness (2-D systems). The descriptor is general and can be applied to identify the symmetry elements of any point group for arbitrary atomic or particulate system in two or three dimensions, in the bulk or under confinement.

scholarly journals Identification of Local Structure in 2-D and 3-D Atomic Systems through Crystallographic Analysis

2020 ◽  
Author(s):  
Pablo Miguel Ramos ◽  
Miguel Herranz ◽  
Katerina Foteinopoulou ◽  
Nikos Ch. Karayiannis ◽  
Manuel Laso
Keyword(s):  
Local Structure ◽  
Point Group ◽  
Local Symmetry ◽  
Crystallographic Analysis ◽  
Three Dimensions ◽  
Group Symmetry ◽  
Spherical Particles ◽  
Specific Reference ◽  
Face Centered Cubic ◽  
Face Centered

In the present work we revise and extend the Characteristic Crystallographic Element (CCE) norm, an algorithm used to simultaneously detect radial and orientational similarity of computer-generated structures with respect to specific reference crystals and local symmetries. Based on the identification of point group symmetry elements, the CCE descriptor is able to gauge local structure with high precision and finely distinguish between competing morphologies. As test cases we use computer-generated monomeric and polymer systems of spherical particles interacting with the hard-sphere and square-well attractive potentials. We demonstrate that the CCE norm is able to detect and differentiate, between others, among: hexagonal close packed (HCP), face centered cubic (FCC), hexagonal (HEX) and body centered cubic (BCC) crystals as well as non-crystallographic fivefold (FIV) local symmetry in bulk 3-D systems; triangular (TRI), square (SQU) and honeycomb (HON) crystals, as well as pentagonal (PEN) local symmetry in thin films of one-layer thickness (2-D systems). The descriptor is general and can be applied to identify the symmetry elements of any point group for arbitrary atomic or particulate system in two or three dimensions, in the bulk or under confinement.

Towards a Virtual Laboratory for Grain Boundaries and Dislocations

2009 ◽  
Vol 1224 ◽  
Author(s):  
Sebastián Echeverri Restrepo ◽  
Barend J. Thijsse
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundaries ◽  
Systematic Study ◽  
Degrees Of Freedom ◽  
Minimum Energy ◽  
Local Symmetry ◽  
Virtual Laboratory ◽  
Face Centered Cubic ◽  
Face Centered ◽  
Edge Dislocations

AbstractIn order to perform a systematic study of the interaction between grain boundaries (GBs) and dislocations using molecular dynamics (MD), several tools need to be available. A combination of computational geometry and MD was used to build the foundations of what we call a virtual laboratory. First, an algorithm to generate GBs on face-centered cubic bicrystals was developed. Two crystals with different orientations are placed together. Then, by applying “microscopic” rigid body translations along the GB plane to one of the crystals and removing overlapping atoms, a set of initial configurations is sampled and a minimum energy configuration is found. Second, to classify the geometry of the GBs a local symmetry type (LST) describing the angular environment of each atom is calculated. It is found that for a given relaxed GB the number of atoms with different LSTs is not very large and that it is possible to find unique geometrical patterns in each GB. For instance, the LSTs of two GBs having the same “macroscopic” configuration but different “microscopic” degrees of freedom can be dissimilar: the configurations with higher GB energy tend to have a higher number of atoms with different LSTs. Third, edge dislocations are introduced into the bicrystals. We see that full edge dislocations split into Shockley partials. Finally, by loading the bicrystals with tensile stresses the edge dislocations are put into motion. Various examples of dislocation-GB interactions in Cu are presented.

scholarly journals Close-packed block copolymer micelles induced by temperature quenching

2018 ◽  
Vol 115 (28) ◽  
pp. 7218-7223 ◽  
Author(s):  
Liwen Chen ◽  
Han Seung Lee ◽  
Sangwoo Lee
Keyword(s):  
Block Copolymer ◽  
Spherical Particles ◽  
Face Centered Cubic ◽  
Time Resolved ◽  
Hexagonal Close Packed ◽  
Block Copolymer Micelles ◽  
Copolymer Micelles ◽  
Crystal Grains ◽  
Self Assembled ◽  
Face Centered

Close-packed structures of uniformly sized spheres are ubiquitous across diverse material systems including elements, micelles, and colloidal assemblies. However, the controlled access to a specific symmetry of self-assembled close-packed spherical particles has not been well established. We investigated the ordering of spherical block copolymer micelles in aqueous solutions that was induced by rapid temperature changes referred to as quenching. As a function of quench depth, the quenched self-assembled block copolymer micelles formed three different close-packed structures: face-centered cubic (fcc), random stacking of hexagonal-close-packed layers (rhcp), and hexagonal-close-packed (hcp). The induced hcp and rhcp structures were stable for at least a few weeks when maintained at their quench temperatures, but heating or cooling these hcp and rhcp structures transformed both structures to fcc crystallites with coarsening of the crystal grains, which suggests that these noncubic close-packed structures are intermediate states. Time-resolved scattering experiments prove that the micellar rhcp structures do not originate from the rapid growth of competing close-packed structures. We speculate that the long-lived metastable hcp and rhcp structures originate from the small size of crystal grains, which introduces a nonnegligible Laplace pressure to the crystal domains. The reported transitions from the less stable hcp to the more stable rhcp and fcc are experimental observations of Ostwald’s rule manifesting the transition order of the key close-packed structures in the crystallization of close-packed uniform spheres.

Utilization of Aquatic Weed for Environmental and Rapid Synthesis of Silver Nanoparticles

2013 ◽  
Vol 662 ◽  
pp. 80-83 ◽  
Author(s):  
Mana Intarasawang ◽  
Kheamrutai Thamaphat
Keyword(s):  
Silver Nanoparticles ◽  
Water Hyacinth ◽  
Cell Structure ◽  
Silver Ions ◽  
Spherical Particles ◽  
Aquatic Weed ◽  
Face Centered Cubic ◽  
X Ray ◽  
Light Yellow ◽  
Face Centered

In the present study, we demonstrated an effective cost and environmentally benign method to synthesize the silver nanoparticles (AgNPs) using aquatic weed namely water hyacinth as a reducing agent. Ultraviolet irradiation was also combined in the process to enhance the reaction rate. The aqueous silver ions mixed with water hyacinth leaf extract under UV irradiation were reduced to AgNPs. The mixture color was changed from light yellow to yellowish-brown color within 5 min due to excitation of surface plasmon vibrations in AgNPs. The formation of AgNPs was confirmed by UV-visible spectroscopy, X-ray diffraction (XRD) spectrometry, energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM). The AgNPs were found to be polycrystalline in nature and spherical particles with mean diameter of 12.54 ± 0.19 nm. The XRD pattern peaked at different diffraction angles corresponding to the (111), (200), (220), and (311) planes indicated that AgNPs have face-centered cubic (fcc) unit cell structure. This proposed method revealed that unwanted plant can utilize in nano-manufacturing as well.

scholarly journals NONCOLLINEAR MAGNETIC ORDER IN THE DOUBLE PEROVSKITES: DOUBLE EXCHANGE ON A GEOMETRICALLY FRUSTRATED LATTICE

2013 ◽  
Vol 27 (06) ◽  
pp. 1350018 ◽  
Author(s):  
RAJARSHI TIWARI ◽  
PINAKI MAJUMDAR
Keyword(s):  
Metal Ion ◽  
Double Exchange ◽  
Three Dimensions ◽  
Density Level ◽  
Face Centered Cubic ◽  
Double Perovskites ◽  
Magnetic Ground State ◽  
Geometrically Frustrated ◽  
Variational Calculations ◽  
Face Centered

Double perovskites (DPs) of the form A 2 BB ′ O 6 usually involve a transition metal ion, B, with a large magnetic moment, and a nonmagnetic ion B ′. While many DPs are ferromagnetic, studies on the underlying model reveal the possibility of antiferromagnetic (AF) phases as well driven by electron delocalization. In this paper we present a comprehensive study of the magnetic ground state and Tc scales of the minimal DP model in three dimensions using a combination of spin-fermion Monte Carlo and variational calculations. The effective magnetic lattice in three dimensions is face centered cubic (FCC) and so geometrically frustrated. This promotes noncollinear spiral states and "flux" like phases in addition to collinear AF order. We map out the possible magnetic phases for varying electron density, "level separation" ϵB - ϵB', and the crucial B ′ B ′ (next neighbour) hopping t′.

scholarly journals Structural building principles of complex face-centered cubic intermetallics

2011 ◽  
Vol 67 (4) ◽  
pp. 269-292 ◽  
Author(s):  
Julia Dshemuchadse ◽  
Daniel Y. Jung ◽  
Walter Steurer
Keyword(s):  
Chemical Composition ◽  
Crystal Structures ◽  
Electronic Band Structure ◽  
Layer Structure ◽  
Repeat Unit ◽  
Basic Structure ◽  
Group Symmetry ◽  
Face Centered Cubic ◽  
Electronic Band ◽  
Face Centered

Fundamental structural building principles are discussed for all 56 known intermetallic phases with approximately 400 or more atoms per unit cell and space-group symmetry F\bar{4}3m, Fd\bar{3}m, Fd\bar{3}, Fm\bar{3}m or Fm\bar{3}c. Despite fundamental differences in chemical composition, bonding and electronic band structure, their complex crystal structures show striking similarities indicating common building principles. We demonstrate that the structure-determining elements are flat and puckered atomic {110} layers stacked with periodicities 2p. The atoms on this set of layers, which intersect each other, form pentagon face-sharing endohedral fullerene-like clusters arranged in a face-centered cubic packing (f.c.c.). Due to their topological layer structure, all these crystal structures can be described as (p × p × p) = p 3-fold superstructures of a common basic structure of the double-diamond type. The parameter p, with p = 3, 4, 7 or 11, is determined by the number of layers per repeat unit and the type of cluster packing, which in turn are controlled by chemical composition.

Structure of Self-assembled Magnetic FePtCu Nanoparticles Arrays

2003 ◽  
Vol 775 ◽  
Author(s):  
Xiangcheng Sun ◽  
J.W. Harrell ◽  
D. E. Nikles ◽  
K. Sun ◽  
L. M. Wang ◽  
...  
Keyword(s):  
Average Diameter ◽  
Iron Pentacarbonyl ◽  
Particle Packing ◽  
Three Dimensions ◽  
Face Centered Cubic ◽  
Oleyl Amine ◽  
Organic Surfactant ◽  
Self Assembled ◽  
Face Centered ◽  
Organic Capping

AbstractIn this study, a series of FexPtyCu100-x-y nanoparticles were chemically synthesized by solution-phase reduction of platinum and copper reagents and thermal decomposition of iron pentacarbonyl in the presence of stabilizers oleic acid and oleyl amine. As-prepared particles had a chemically disordered face-centered cubic (fcc) lattice with an average diameter of 3.5 nm. The particle size, and the corresponding size distribution were controlled by varying the organic surfactant (oleic acids, etc.), its concentration, and the reaction temperature. These particles were well dispersed in hydrocarbon solvents and self-assembled into two or three dimensions particles arrays with a variety of closepacking arrangements. Domain of monolayers, bilayers and multilayers of particles arrays were frequently detected in TEM specimens. Both cubic close-packed (ccp) and honeycomb arrays were also uniquely observed. It was also demonstrated that the controlled organic surfactant layer (organic capping) play a crucial role in determining assembly dimensions and symmetry as well as particle packing arrays.

Green Synthesis of Starch-Stabilized Silver Nanoparticles and their Antibacterial Properties

2011 ◽  
Vol 236-238 ◽  
pp. 1945-1948 ◽  
Author(s):  
Xiang Hua Gao ◽  
Li Qiao Wei ◽  
Jing Wang ◽  
Bing She Xu
Keyword(s):  
Silver Nanoparticles ◽  
Antibacterial Properties ◽  
Spherical Particles ◽  
Ring Test ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Green Route ◽  
Vis Spectroscopy ◽  
Face Centered ◽  
20 Nm

Stable silver nanoparticles were synthesized from AgNO3through a simple green route using biodegradable and renewable starch as stabilizing agent. Nanoparticles have been studied for their formation, structure, morphology and size using UV–vis spectroscopy, X-ray diffraction (XRD) and HRTEM analysis. XRD showed that the nanoparticles were of face centered cubic structure. UV–Vis and HRTEM revealed that the spherical particles having radius 5-20 nm are mostly stabilized by starch. Further, antibacterial properties of these starch-stabilized nanoparticles show promising results for S.aureus in growth inhibition ring test.

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