Building a Library of Simulated Atom Probe Data for Different Crystal Structures and Tip Orientations Using TAPSim

2019 ◽  
Vol 25 (2) ◽  
pp. 320-330 ◽  
Author(s):  
Markus Kühbach ◽  
Andrew Breen ◽  
Michael Herbig ◽  
Baptiste Gault
Keyword(s):  
Open Source ◽  
Crystal Structures ◽  
Atom Probe ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
Computational Performance ◽  
The Face ◽  
Simulated Field ◽  
Face Centered ◽  
Density Zone

AbstractThe process of building an open source library of simulated field desorption maps for differently oriented synthetic tips of the face-centered cubic, body-centered cubic, and hexagonal-close-packed crystal structures using the open source software TAPSim is reported. Specifically, the field evaporation of a total set of 4 × 101 single-crystalline tips was simulated. Their lattices were oriented randomly to sample economically the fundamental zone of crystal orientations. Such data are intended to facilitate the interpretation of low-density zone lines and poles that are observed on detector hit maps during Atom Probe Tomography (APT) experiments. The datasets and corresponding tools have been made publicly available to the APT community in an effort to provide better access to simulated atom probe datasets. In addition, a computational performance analysis was conducted, from which recommendations are made as to which key tasks should be optimized in the future to improve the parallel efficiency of TAPSim.

Graphite encapsulated nanocrystals produced using a low carbon : metal ratio

1997 ◽  
Vol 12 (5) ◽  
pp. 1268-1273 ◽  
Author(s):  
Jonathon J. Host ◽  
Mao H. Teng ◽  
Brian R. Elliott ◽  
Jin-Ha Hwang ◽  
Thomas O. Mason ◽  
...  
Keyword(s):  
Analytical Techniques ◽  
Pure Metal ◽  
Face Centered Cubic ◽  
Low Carbon ◽  
Hexagonal Close Packed ◽  
The Face ◽  
Metal Ratio ◽  
Face Centered ◽  
Fcc Phase ◽  
Equilibrium Phases

Graphite encapsulated nanocrystals produced by a low carbon tungsten arc were analyzed to determine their chemistry, crystallography, and nanostructural morphology. Metallic nanocrystals of Fe, Co, and Ni are in the face-centered cubic (fcc) phase, and no trace of the bulk equilibrium phases of body-centered cubic (Fe) and hexagonal close-packed (Co) were found. Various analytical techniques have revealed that the encased nanocrystals are pure metal (some carbide was found in the case of Fe), ferromagnetic, and generally spherical. The nanocrystals are protected by turbostratic graphite, regardless of the size of the nanocrystals. The turbostratic graphite coating is usually made up of between 2 and 10 layers. No trace of any unwanted elements (e.g., oxygen) was found. The low carbon: metal ratio arc technique is a relatively clean process for the production of graphite encapsulated nanocrystals.

Noble Metal Nanomaterials with Nontraditional Crystal Structures

2020 ◽  
Vol 50 (1) ◽  
pp. 345-370 ◽  
Author(s):  
Chaitali Sow ◽  
Suchithra P ◽  
Gangaiah Mettela ◽  
Giridhar U. Kulkarni
Keyword(s):  
Crystal Structures ◽  
Noble Metals ◽  
High Symmetry ◽  
Face Centered Cubic ◽  
Fcc Metals ◽  
Hexagonal Close Packed ◽  
The Subject ◽  
Hcp Structure ◽  
Face Centered ◽  
High Degree

Noble metals (Ru, Os, Rh, Ir, Pd, Pt, Ag, and Au) are known for their extraordinary oxidant-resistant behavior, good electrical and thermal conductivity, high work function, and brilliant luster. All occur in close-packed crystal structures: Ru and Os in hexagonal close-packed (hcp) and the rest in face-centered cubic (fcc) structures, both possessing high-symmetry structures and, therefore, a high degree of stabilization. Numerous studies in the literature have attempted to stabilize these metals away from their conventional crystal structures with the aim of realizing new properties. While obtaining conventional fcc metals in hcp structure or vice versa has been the subject of most studies, there are also examples of fcc metals crystallizing in lower-symmetry structures such as monoclinic. The nonnative crystal structures are generally realized during the crystallite growth itself, with a few exceptions in which a posttreatment was required for lattice transformation. In most cases, the new crystal structures pertain to the nanometer-length scale in the form of nanoparticles, nanoplates, nanoribbons, and nanowires, but there are good examples from microcrystallites as well. In this article, we review this active area of research, focusing on ambient stable crystal systems with some account of their interesting properties as reported in recent literature.

Tailoring deformation-induced effects in Co powders by milling them with α–Al2O3

2007 ◽  
Vol 22 (11) ◽  
pp. 2998-3005 ◽  
Author(s):  
E. Menéndez ◽  
J. Sort ◽  
S. Suriñach ◽  
M.D. Baró ◽  
J. Nogués
Keyword(s):  
Magnetic Properties ◽  
Ball Milling ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
The Face ◽  
Face Centered ◽  
Α Al2o3 ◽  
Nanocomposite Powders

The evolution of the structural and magnetic properties of metal-ceramic, cermet, nanocomposite powders, consisting of Co and α–Al2O3 in different proportions, prepared by ball milling has been investigated. The overall microstructure of the system, after long-term milling, is found to be very sensitive to the amount of α–Al2O3, yielding a less refined and faulted hexagonal-close-packed (hcp)-Co structure for the sample with larger α–Al2O3 percentage. The increased presence of the ceramic counterpart also causes a delay of the face-centered-cubic (fcc) to hcp-Co stress-induced transformation during ball milling. The results seem to indicate an evolution of the role of α–Al2O3, from increasing locally the strain rate of the mechanical work for small amounts of ceramic to absorbing milling energy for large amounts of α–Al2O3. The magnetic properties correlate with the obtained microstructure, where the amount of hcp-Co and stacking faults and the isolation of the Co particles by the α–Al2O3 control the coercivity.

Localization of 5f electrons and phase transitions in americium

2005 ◽  
Vol 893 ◽  
Author(s):  
Michel Pénicaud
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Crystal Structures ◽  
Lower Energy ◽  
Density Functional ◽  
Face Centered Cubic ◽  
Hexagonal Close Packed ◽  
5F Electrons ◽  
Face Centered ◽  
Complex Crystal

AbstractDensity-functional electronic calculations have been used to investigate the high-pressure behavior of americium.The phase transitions calculated agree with the recent sequence obtained experimentally under pressure: double hexagonal close packed → face centered cubic → face centered orthorhombic, primitive orthorhombic. In the first three phases the 5f electrons are found localized, only in the fourth phase (Am IV) the 5f electrons are found delocalized. The localization of the 5f electrons is modelled by an anti-ferromagnetic configuration which has a lower energy than the ferromagnetic ones. In this study the complex crystal structures have been fully relaxed.

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