discriminating phases with similar crystal structures
CrystalStructure Britannica
CrystalCrystalStructure Crystals can be grown under moderate conditions from all 92 naturally occurring elements except helium and helium can be crystallized at low temperatures by using 25 atmospheres of pressure. Binary crystals are composed of two elements. There are thousands of binary crystals some examples are sodium chloride (NaCl) alumina (Al2O3) and ice (H2O).
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Scanning Electron Microscopy (SEM)
May 26 2017 · The SEM is routinely used to generate high-resolution images of shapes of objects (SEI) and to show spatial variations in chemical compositions 1) acquiring elemental maps or spot chemical analyses using EDS 2)discrimination of phases based on mean atomic number (commonly related to relative density) using BSE and 3) compositional maps based on differences in trace element
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Allotropes of plutoniumWikipedia
Overview. Plutonium normally has six allotropes and forms a seventh (zeta ζ) under high temperature and a limited pressure range. These allotropes have very similar energy levels but significantly varying densities and crystal structures.This makes plutonium very sensitive to changes in temperature pressure or chemistry and allows for dramatic volume changes following phase transitions.
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Assessing phase discrimination via the segmentation of an
micro-texture and fractions of individual phases accurate phase discrimination is an essential rst step. However the above close correspondence in the crystal structure and lattice parameters of Bi 2Te 3 and Bi 2Te 2S renders phase discrimination via electron
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Phaser crystallographic software
Phaser is a program for phasing macromolecular crystal structures by both molecular replacement and experimental phasing methods. The novel phasing algorithms implemented in Phaser have been developed using maximum likelihood and multivariate statistics. For
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Differentiate Compounds with Similar Crystal Structures
This means that if different phases within a sample have similar crystal structures it can be difficult to differentiate between them using only EBSD. In these cases it can be useful to combine EBSD with a technique that differentiates based on chemical differences such as
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(IUCr) Introduction to the calculation of structure factors
Introduction to the calculation of structure factors S. C. Wallwork. In X-ray crystallography the structure factor F(hkl) of any X-ray reflection (diffracted beam) hkl is the quantity that expresses both the amplitude and the phase of that reflection. It plays a central role in the solution and refinement of crystal structures because it represents the quantity related to the intensity of the
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Discriminating β α and α″ phases in metastable β titanium
Apr 01 2020 · On the other hand the similarity in the crystal structures of martensite and possible tertiary phases such as body-centred-cubic (bcc) ferrite and/or tempered martensite (bcc or bct) renders diffraction-based phase segmentation difficult.
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Allotropes of plutoniumWikipedia
Overview. Plutonium normally has six allotropes and forms a seventh (zeta ζ) under high temperature and a limited pressure range. These allotropes have very similar energy levels but significantly varying densities and crystal structures.This makes plutonium very sensitive to changes in temperature pressure or chemistry and allows for dramatic volume changes following phase transitions.
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Phase TransitionsUniversity College London
Not all phase transitions are of this type e.g. ice changing to water. Solid-solid phase transformations may be broadly classified into two classes first-order which tend to be of a reconstructive nature in terms of the crystal structure and second-order which tend to be more of a displacive nature.
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Ni-based superalloy crystalline orientation mapping and
Because of the identical geometry of acquisition for the iCHORD orientation maps and the secondary ion images both information can be easily superimposed. It allows discriminating between the two phases and giving their crystallographic orientations (see figure 3).
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10.6 Lattice Structures in Crystalline SolidsChemistry
The entire structure then consists of this unit cell repeating in three dimensions as illustrated in Figure 1. Figure 1. A unit cell shows the locations of lattice points repeating in all directions. Let us begin our investigation of crystal lattice structure and unit cells with the most straightforward structure and the most basic unit cell.
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Component Phase and phase boundaries
Phase diagramis a graphical representation of all the equilibrium phases as a function of temperature pressure and composition. crystal structure FCC similar radii and electronegativity). 4 MSE 2090 Introduction to Materials Science Chapter 9 Phase Diagrams 13
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X-ray CrystallographyChemistry LibreTexts
Aug 15 2020 · This equation is known as Bragg s Law named after W. H. Bragg and his son W. L. Bragg who discovered this geometric relationship in 1912. C C Bragg s Law relates the distance between two planes in a crystal and the angle of reflection to the x-ray wavelength. The x-rays that are diffracted off the crystal have to be in-phase in order to
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Draw Explain Isomorphous and Eutectoid phase diagram.
i. Same Crystal structure. ii. Valency. iii. Similar atomic radius. iv. Similar electronegativity. The diagram is very useful in finding the amount phase and composition of solutions. Most common example of this type of alloying is Copper-Nickel alloy as both have BCC crystal structure and atomic radii are same with same valences and
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(PDF) Discrimination between biologically relevant calcium
phases. Due to the improvement of the lateral resolution of modern The crystal structures of all powders were verified by XRD anal- surface analytical methods like ToF-SIMS or XPS within the last ysis prior to the surface analysis.
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Structural discrimination via density functional theory
Two distinct crystal structures for the monoclinic low-temperature phase of Mg 2 NiH 4 which we designate as LTI and LTII are available in the published literature. We demonstrate that density functional theory and lattice dynamics can easily identify LTII as the preferable structure at two levels of inquiry. First enthalpies of formation ∆H calculated using three different forms for
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Phase TransitionsUniversity College London
Not all phase transitions are of this type e.g. ice changing to water. Solid-solid phase transformations may be broadly classified into two classes first-order which tend to be of a reconstructive nature in terms of the crystal structure and second-order which tend to be more of a displacive nature.
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Types of Crystals Shapes and Structures
Nov 07 2019 · Combining the 7 crystal systems with the 2 lattice types yields the 14 Bravais Lattices (named after Auguste Bravais who worked out lattice structures in 1850). Crystals Grouped by Properties There are four main categories of crystals as grouped by
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(IUCr) The phase problem
May 01 2003 · Experimental phases are often only the starting point for phase improvement using a variety of methods of density modification which are also based on some prior knowledge of structure. Solvent flattening histogram matching and non-crystallographic averaging are the main techniques used to modify electron density and improve phases (Fig. 14 ).
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Assessing phase discrimination via the segmentation of an
micro-texture and fractions of individual phases accurate phase discrimination is an essential rst step. However the above close correspondence in the crystal structure and lattice parameters of Bi 2Te 3 and Bi 2Te 2S renders phase discrimination via electron
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PhaserInternational Union of Crystallography
Phaser is a program for phasing macromolecular crystal structures by both molecular replacement and experimental phasing methods. The novel phasing algorithms implemented in Phaser have been developed using maximum likelihood and multivariate statistics. For molecular replacement the new algorithms have proved to be significantly better than traditional methods in discriminating correct
Chat OnlineElectron Diffraction and Crystal Structure
2/9/06 2 Electron Diffraction the unit cell are atoms the size of the unit cell is related to the inter-atomic spacing or lattice constant which is usually called a. This experiment will be done with a graphite (carbon) crystal that has a hexagonal structure.
Chat OnlineAn introduction in crystal structure solution and refinement
•Basic structure solution scheme –0. Take random starting phases compute map with Fobs –1. Square the observed map back transform to get new phases –2. Combine phases with Fobs compute new map –3. Go to 1 Cycle until done –Pick peaks and find model •Multiple random starts are needed •Step 1 can be done more efficiently via a an
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Discrimination of TiO polymorphs in sedimentary and
2 structure) is stable (Withers et al. 2003). Hwang et al. (2000) find this phase included in garnet in the Erzgebirge. In their crystal structures rutile and anatase are the most similar TiO 2 polymorphs both crystallize in the tetragonal crystal system. The brookite crystal structure is orthorhom-bic.
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X-ray CrystallographyChemistry LibreTexts
Aug 15 2020 · This equation is known as Bragg s Law named after W. H. Bragg and his son W. L. Bragg who discovered this geometric relationship in 1912. C C Bragg s Law relates the distance between two planes in a crystal and the angle of reflection to the x-ray wavelength. The x-rays that are diffracted off the crystal have to be in-phase in order to
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Component Phase and phase boundaries
Phase diagramis a graphical representation of all the equilibrium phases as a function of temperature pressure and composition. crystal structure FCC similar radii and electronegativity). 4 MSE 2090 Introduction to Materials Science Chapter 9 Phase Diagrams 13
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(PDF) Structural aspects of diastereomeric discrimination
The crystal structure of the 1 1 complex of strychnine N-benzoyl-L-alanine·2H2O (a=10.751 b=30.366 c=8.608 Å space group P212121) provides an insight into the mechanism of Pasteur s method
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Phase TransitionsUniversity College London
Not all phase transitions are of this type e.g. ice changing to water. Solid-solid phase transformations may be broadly classified into two classes first-order which tend to be of a reconstructive nature in terms of the crystal structure and second-order which tend to be more of a displacive nature.
Chat OnlineCHAPTER 4 IMPERFECTIONS IN SOLIDS
2. Crystal structures same for "pure" metals 3. Electronegativity The atoms should have similar electronegativity or compounds will form 4. Valences If (1) -(3) are favorable then the metal of lower valence will dissolve more in crystal structure of the higher valence metal than vice versa.
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