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A tetragonal crystal structure with sixfold cation and threefold anion coordination numbers. A common fractional-coordinate description has A at and , and B at and , interpreted modulo integer lattice translations. The cation coordination is a distorted octahedron and the anion coordination is a planar triangle. Titanium dioxide in its rutile polymorph is an example.
A crystal system with mutually perpendicular conventional cell axes and lengths . The physical length of the direction is proportional to ; crystallographic indices are coefficients in a lattice basis, not necessarily Cartesian components of equal scale.
An crystal structure with A on a face-centered cubic lattice and B occupying all eight tetrahedral sites of its conventional cubic unit cell. The coordination numbers are eight for A and four for B. The cubic cell contains four formula units.
A binary crystal structure with one species at the corners of a primitive cubic unit cell and the other at its body centre. Each species has coordination number eight. Distinct chemical labels mean that the body-centre translation is not a translation symmetry; its Bravais lattice is primitive cubic, not body-centred cubic.
An ordered cubic structure with B at cube corners and A at face centres. The chemically labelled Bravais lattice is primitive cubic; its superlattice reflections distinguish it from a chemically disordered face-centered cubic lattice.
The orientation of a crystal structure relative to a specimen or instrument coordinate frame. It determines which Bragg diffraction conditions are excited.
An orientation relationship between adjacent crystalline regions related by a specific crystallographic symmetry operation. A multiply twinned particle is not one perfect lattice with the composite particle symmetry.
A local interruption of the normal sequence of close-packed or other crystallographic layers. It can change local symmetry and influence nanocrystal growth.
A nonuniform distribution of crystallographic orientations among grains in a polycrystal. It can turn directional single-crystal properties into directional bulk behavior.
An ordered, anion-deficient fluorite-related structure often written . It can accommodate compositions and cation sizes outside the stability range of zirconolite polytypes.
A crystal system with three mutually perpendicular axes that are not constrained by symmetry to have equal lengths.
A close-packed structure with hexagonal symmetry. Its basal and c-axis directions need not have equal thermal or irradiation response.
The arrangement of atoms or other constituents attached identically to every lattice point of a Bravais lattice. The lattice specifies translations; the motif specifies the contents repeated by those translations. A multi-atom motif does not make its atoms separate lattice points.
An FCC Bravais lattice with a two-atom basis at fractional positions and . Its conventional cubic cell contains eight atoms. Equal scattering amplitudes at the two basis sites produce additional systematic absences beyond the FCC parity selection rule.
Pinned article: Introduction to the OurBigBook Project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 2. You can publish local OurBigBook lightweight markup files to either OurBigBook.com or as a static website.
Figure 3. Visual Studio Code extension installation.
Figure 5. . You can also edit articles on the Web editor without installing anything locally. Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension. 
- Infinitely deep tables of contents:
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