Questions tagged [crystallography]

For questions concerning crystalline structures and their properties.

Filter by
Sorted by
Tagged with
0 votes
0 answers
18 views

How is the cubic d-spacing formula derived from the Miller indices of a standard plane? [duplicate]

I just had a question about deriving the cubic structure d spacing formula. Just trying to work through the logic so I understand it better. If I start with the standard plane: • The plane ...
user avatar
0 votes
2 answers
73 views

Two atoms exist in the same coordinate position in the lattice?

I am trying to simulate the properties of FeF3(H2O)3, so I download its crystal structure file from Crystallography Open Database, but it seems that in the lattice, ...
user avatar
  • 111
0 votes
0 answers
14 views

How to find the standard deviations of lattice parameters after Rietveld refinement with GSASII?

I am trying to learn how to use GSASII. It is different from GSAS/EXPGUI, so I feel hard to find some information from GSASII interface. I want to find what are the values for the standard deviations ...
user avatar
-1 votes
1 answer
30 views

A problem with Miller indices [closed]

I know how to calculate Miller indices (hkl), but I have found a weird one I can not work out could you please help, I know your you have to expand the plane but after that I’m lost.
user avatar
6 votes
1 answer
361 views

Why does Samarium have such a large c-axis lattice constant? (>26 Å) Are there significantly larger lattice constants of the elements?

Figure 1.2 on page 12 of The Structure of Rare-earth Metal Surfaces linked below shows a repeating stack of hexagonal layers arranged as A B A B C B C A C... and several sources give the c-axis ...
user avatar
  • 6,220
5 votes
4 answers
750 views

Given a CIF (crystallographic interchange format) file (and thus cartesian atomic coordinates), how can you find the bonds between atoms?

Applications like Vesta show bonds when viewing a CIF file; how could one algorithmically find all bond pairs? Here is an example CIF file: ...
user avatar
6 votes
3 answers
592 views

What material properties are unpredictable (not reproducible) but can be measured consistently and at a low cost?

I'm looking for a process to create a material which has some easy to measure properties. These properties should be consistent over a long period. It should be very hard (expensive) to predict/...
user avatar
  • 79
3 votes
2 answers
104 views

A good lab demonstration of this particular optical transform pair?

At about 1:11 the video linked below shows what think is the optical Fourier transform of a sine wave as approximated by a saw blade. https://www.youtube.com/watch?v=jzmqeRp_tmk The set-up appears to ...
user avatar
  • 964
5 votes
1 answer
72 views

What do sequence numbers in PDB files actually mean and why don't they match the sequence?

I am studying the 3D structure of the LDH from x-ray crystallographic imaging I was pointed to from Is there any stereospecific enzyme in PDB that catalyzes an anabolic reaction and has an entry ...
user avatar
2 votes
0 answers
31 views

Appearance of drying hemoglobin-and-salt droplets

I initially posted these or similar images at the bio site because they looked to me like organic/mold contamination in a slide (low power) containing hemoglobin and salt. As the slide dried these ...
user avatar
  • 964
2 votes
1 answer
79 views

How to identify 'water' mistakes in protein crystal structures: Are B-factors and occupancy good indicators?

When solving the structure of a protein from diffraction data (x-ray crystallography), it can sometimes be difficult know what should be modelled into small spheres of electron density that are not ...
user avatar
5 votes
0 answers
155 views

What determines the kind of Bravais lattice structure (body-centred cubic, hexagonal, etc) a transition metal shows?

With the exception of Zn, Hg, Cd and Mn transition metals most transition metals have only one kind of lattice structure at room temperature. Another trend I noticed was that Groups 3 and 4 have ...
user avatar
  • 287
5 votes
2 answers
577 views

Why are there only 14 types of Bravais lattices and not 28 when there are 7 types of unit cells and each can have four variations?

As the title suggests, I can't understand why certain kinds of variations (like Face-centred or Body-centred) are restricted to certain types of unit cells. An orthorhombic unit cell has Primitive, ...
user avatar
  • 287
-1 votes
1 answer
364 views

How many 4th nearest neighbours are there in an hcp lattice?

My teacher told us that there are 18 4th nearest neighbors in an hcp lattice, at a distance of √3a . I have only been able to identify 12. Can you help me find all the 4th nearest neighbors?
user avatar
  • 25
1 vote
0 answers
26 views

What does “Average Width” mean in crystallography?

Mathematician G. Polya noted (the solution for Problem 8, Axes of a Cube) in his book How to Solve it: ... there are three kinds of axes: (1) 4 axes, each through two opposite vertices ... (2) 6 axes,...
user avatar
2 votes
1 answer
70 views

In crystallography, how does the real space R factor relate to the atomic B factor?

In assessing the quality of different parts of an atomic model derived from diffraction data, you can look at the real space R factor or at the atomic B factor. Do these give the same information or ...
user avatar
1 vote
1 answer
799 views

Radius ratio of octahedral interstitial site in BCC lithium

Problem Determine the minimum radius of an atom that will just fit into (a) the tetrahedral interstitial site in FCC nickel and (b) the octahedral interstitial site in BCC lithium. Solution (a) For ...
user avatar
  • 284
1 vote
0 answers
32 views

HCP and hexagonal primitive cell [duplicate]

There are 14 types of Bravais lattices one of them is hexagonal which is just present as primitive cell ie the basis are at its corners , now when I read about hexagonal closed packing I came to know ...
user avatar
2 votes
1 answer
381 views

Whats the difference between unit cell and motif?

The definition in my material is that motif and unit cells are both a repeating unit, but whereas motif is with respect to 2D lattice the unit cell is with respect to 3D lattice. But I can't find ...
user avatar
3 votes
0 answers
33 views

Debye–Waller factors for tin(IV) oxide

How I could find the bulk Debye–Waller factor for tetragonal rutile type $\ce{SnO2}$ at room temperature? I have been doing some online digging with no luck. If anyone has a reference I could use that ...
user avatar
  • 31
4 votes
1 answer
105 views

Getting an “index” of 7 for a set of powder diffraction data

I tried to index powder diffractogram from the following problem: A metal (of density $\pu{0.862 g cm^-3})$ gives the following powder X-ray diffraction data $(\lambda = \pu{1.5418 Å}).$ $$2\theta \...
user avatar
0 votes
0 answers
64 views

Find the Linear Packing factor of FCC [-1 -2 1]

I have been trying to figure out this question, and essentially if I assume that the only atoms that the vector touches are the starting and ending atoms, then I get 0.58. I am trying to find a more ...
user avatar
7 votes
2 answers
135 views

$P 4_{2} 22$ tetragonal group choice of origin for symmetry of special projections

I was looking at the description of the tetragonal group $$P 4_{2} 2 2$$ (No 93 in the International Tables of Crystallography) and there is one aspect that I do not understand. Namely, what is the ...
user avatar
0 votes
0 answers
45 views

octahedral interstitial sites located entirely within a full hexagonal HCP unit cell at a height of $c/4$ up from the bottom of the unit cell

I have been trying to visualize and find the number of them for a while, through the image attached. I can't tell whether the c/4 part includes the octahedral site or not...how should I go about ...
user avatar
5 votes
2 answers
512 views

Why is the base-centered orthorhombic crystal lattice a unique crystal system?

I'm having difficulty understanding why the base-centered orthorhombic crystal system is a unique crystal system. When I draw two base-centered orthorhombic unit cells next to each other there appears ...
user avatar
2 votes
0 answers
352 views

Why is U the symbol for lattice energy?

I often see $U$ or even $\Delta U$ being the symbol for lattice energy. Why is that? Does it refer to internal energy?
user avatar
0 votes
1 answer
45 views

Miller Indices of Goldnanoparticles from Turkevich and Frens method

I need the miller indices of gold nanoparticles that were synthesized after the route of Turkevich and Frens. I during my research I found a lot of publications, but it looks like no one measured it ...
user avatar
  • 261
2 votes
1 answer
2k views

Finding the atomic packing factor (APF) of Sodium Chloride and other FCC ionic compounds

For a piece of coursework I am doing, I need to calculate the atomic packing factor of some ionic compounds. I have had no formal teaching in this area, so what I know comes from information I have ...
user avatar
1 vote
1 answer
41 views

What is meant by "basis" in "... its basis in particles leads to a material comprising crystallites or grains tightly bound together, ..."?

I am currently studying Ultrasonic transducers – Materials and design for sensors, actuators and medical applications by Kentaro Nakamura. In chapter 1.2.1 Ferroelectricity, the author says the ...
user avatar
  • 1,035
5 votes
1 answer
139 views

What is the precision of intensity data in XRD measurement?

I made some relative crystallinity measurements on a zeolite (crystalline aluminosilicate). Which is measured for a specific peak area and compared with a reference sample. The XRD of powder patterns ...
user avatar
-1 votes
1 answer
97 views

Can a crystal structure of a substance appear or disappear?

I read somewhere before that some substances no longer crystallize naturally in some specific structures, although it do that readily before. Instead, new structures that never happen before become ...
user avatar
  • 117
0 votes
0 answers
40 views

Could someone advise me on sources for crystallography and surface sciences?

I'm a physicist learning crystallography and surface science on the side of my research and I came across the concepts: surface reconstruction in hexagonal materials, unit mesh of surfaces, etc. I was ...
user avatar
1 vote
2 answers
138 views

Conventional unit cell for a hexagonal crystal system

The figure shows a unit cell of a hexagonal crystal system. Drawn in bold, is the unit cell. The lightly shaded one is a unit cell as well and has a six fold symmetry along an axis, hence is more ...
user avatar
  • 287
3 votes
2 answers
458 views

Trouble understanding interplanar spacing using miller indices

We know that two parallel planes have the same Miller indices, this implies that we can have an infinite number of parallel planes close to one another all of which have the same Miller indices. But ...
user avatar
  • 287
0 votes
1 answer
176 views

How to differentiate hydrous and anhydrous compound? [closed]

For an experiment, my teacher gave me containers of hydrates and their corresponding anhydrous compounds, but I have a feeling that for one of the compounds she switched the hydrate and anhydrous ...
user avatar
1 vote
2 answers
276 views

If stirring negatively affects crystal purity, why is it so?

My Intellectual Expectations Intuitively, I would expect strong stirring to improve crystal purity during the process of crystalization. My rationale is that strong stirring would increase contact ...
user avatar
  • 889
0 votes
1 answer
63 views

The formation of ice crystals on/in frozen food that has been defrosted and then frozen again

I made a mistake. I put my ice cream in the refrigerator instead of the freezer and left it there for a night. I realized my folly the next day. I put it in the freezer. When I took it out, I noticed ...
user avatar
  • 195
2 votes
0 answers
180 views

What does the order of a class mean in a character table?

I am not from a chemistry background. I am trying to see how the symmetry operations affect the stiffness tensor which led me in the path of understanding character tables. I am looking at the ...
user avatar
2 votes
3 answers
652 views

Are crystallographic omit maps only used with molecular replacement?

(This is in the context of macromolecular X-ray crystallography.) From Lamb et al. 2015: Model bias is the result of how maps are calculated: because the phase estimates [of the structure factor] for ...
user avatar
  • 161
8 votes
3 answers
393 views

If you accumulate 100 identical spheres how many will end up on the surface?

So far I have asked this question in physics, engineering and math sections but have not gotten an answer in three years. If you have 100 identical spheres and group them into A sphere shape, how many ...
user avatar
0 votes
1 answer
82 views

Change of ionic packing upon crystals are pressurized

When rock salt crystal is pressurized, its FCC structure changes to BCC structure whereby coordination ratio changes from 6:6 to 8:8. At the same time packing efficiency of the crystal decreases from ...
user avatar
1 vote
1 answer
90 views

Will these K-alum crystals combine into a "cohesive/well-glued" mass?

The attempt to make a single solid mass of K-alum, using over 125 grams of McCormick K-alum powder, has resulted, in less than 2 hours, in: So besides the growth around the loop of the seed "...
user avatar
1 vote
1 answer
734 views

How do I find miller indices for a plane whose intercepts are fractions of the lattice constant?

[I'm talking with respect to cubic lattices alone.] For instance, if a plane has $x,y,z$ intercepts $a/2,a/2,a/2$ (where $a$ is the lattice constant) the miller index would be $[2\space2\space2]$. The ...
user avatar
4 votes
2 answers
167 views

Is there a standard scholarly reference for lattice constants of crystals of the elements?

I need to discuss the lattice constants of bulk crystals of several metal and semiconductor elements. I can find plenty of tables and numbers that are probably "close enough" but for a paper ...
user avatar
  • 6,220
1 vote
0 answers
54 views

Any open-source to animate 2D materials in 3D. (e.g. van der Waals heterostructures, 2D crystal layers etc.)

I want to model different 2D nano-structures, layered materials in 3D (animated version). Is there any open source where I can build these structures. Like this:
user avatar
  • 11
3 votes
1 answer
88 views

Why should the scalar product of the components along two axes remain unchanged after transformation?

A couple of proofs from Chapter 2 of "Space Groups for Solid State Scientists" are giving me a hard time (see attached image). So what I understand is: "r" was the original ...
user avatar
3 votes
3 answers
3k views

Converting fractional coordinates into cartesian coordinates for crystallography

So let's say for a given molecule I have the volume of a unit cell, the shape of the unit cell (monoclinic, cubic, etc), the cell angles alpha, beta, and gamma, the cell lengths a,b, and c, and a list ...
user avatar
0 votes
0 answers
1k views

How to find bond lengths from .cif files of crystal structure

I am confused about how to calculate the bond lengths within a given structure given its .cif file. I have highlighted the bond of interest in the image below. The atom coordinates are shown in the ...
user avatar
  • 11
0 votes
0 answers
44 views

What is meant by "rotation about an axis that passes through a lattice point"?

I am currently studying Introduction to Solid State Physics, 8th edition, by Charles Kittel. In the section Fundamental Types of Lattices of chapter 1, the author says the following: Crystal lattices ...
user avatar
  • 1,035
1 vote
0 answers
25 views

Crystmet or alternative metals/alloys/intermetallics powder diffraction database

Does anyone know what happened to Crystmet, the metals structure database? The website seems to have disappeared. Is there any way to access the database or is there a recommended powder diffraction ...
user avatar