computer science

SHELX

SHELX is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand SHELX rather than just read about it. In short: SHELX is a suite of programs created by George M. Sheldrick for the determination of crystal structures from single-crystal X-ray and neutron diffraction data.

Key takeaways

SHELX belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SHELX to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SHELX from memory before moving on to harder problems.

Reference excerpt

SHELX is a suite of programs created by George M. Sheldrick for the determination of crystal structures from single-crystal X-ray and neutron diffraction data. The suite consists of several stand-alone executables that are compatible with modern versions of Linux, Windows, and macOS. The software is available free of charge for academic institutions, while commercial entities are required to pay for a license. The significance of the software is highlighted by its high citation rate; a primary publication describing the program is the fifth most-cited research paper of the 21st century across all scientific fields.

Overview The individual programs can be run from graphical user interfaces such as shelXle, Olex2, Oscail, or WinGX. Alternatively, the programs can be run from the command line. SHELX-2019 includes the following programs:

SHELXT – For solving crystal structures. SHELXS – Contains the classic direct methods for solving crystal structures. SHELXL – For the refinement of crystal structures. PDB2INS – Generates input files for the refinement of macromolecules with SHELXL. CIFTAB and ShredCIF – Allow editing and processing of CIF files. SHELXC, SHELXD, and SHELXE – Process structural data from macromolecules. AnoDe – Enables the analysis of density maps of macromolecules.

Program architecture The programs are written in Fortran. Since 2000, parallelized versions of the programs have been developed for multi-CPU computers.

Further reading Sheldrick, G. M. (2008). "A short history of SHELX". Acta Cryst. A64, 112–122. doi:10.1107/S0108767307043930. Müller, P., Herbst-Irmer, R., Spek, A. L., Schneider, T. R. (2006). Crystal Structure Refinement: A Crystallographer's Guide to SHELXL. (International Union of Crystallography Texts on Crystallography, Vol. 19). Oxford University Press. ISBN 978-0-19-857076-9.

References

Worked examples

Example 1 — a first encounter with SHELX

Start with the simplest possible case. Write down what SHELX claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to SHELX before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about SHELX ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of SHELX

In research: SHELX appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses SHELX in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: SHELX is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computational chemistry software, Software programmed in Fortran, so understanding it makes those chapters shorter.
In everyday life: Look for SHELX outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study SHELX in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SHELX means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain SHELX out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SHELX in simple terms?

SHELX is a suite of programs created by George M. Sheldrick for the determination of crystal structures from single-crystal X-ray and neutron diffraction data.

Why does SHELX matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study SHELX?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on SHELX.